Thermodynamic studies of the complexation of plutonium(IV) by linear and macrocyclic poly-amino-carboxylate ligands

International Nuclear Information System (INIS)

Burgat, Romain

2007-01-01

In the framework of a collaboration between the CEA (Commissariat a l Energie Atomique) of Valduc and the ICMUB (Institut de Chimie Moleculaire de l Universite de Bourgogne), a study platform of the structural and physico-chemical properties of the radioelements U, Pu and Am complexes has been implemented. The plutonium(IV) complexation has been studied in a molar nitrate medium. The affinity of three linear poly-amino-carboxylates (EDTA, CDTA and DTPA) towards plutonium(IV) has then been estimated. For the three ligands, the formation constants of the monoleptic complexes Pu(EDTA), Pu(CDTA) and [Pu(DTPA)] - have been determined in a (H,K)NO 3 1 M medium and then extrapolated at a zero ionic force with the specific interactions theory (SIT). For the three complexes, mono-hydroxylated monoleptic species have been observed. With the EDTA and the CDTA, protonated dileptic complexes of a general formula [Pu(L) 2 H h ] (4-h)- have been revealed too. Nevertheless, the steric hindrance around the metallic center is too important to allow to a second molecule of DTPA to coordinate the Pu 4+ cation. The exclusive formation of the species [Pu(DTPA)] - and [Pu(DTPA)(OH)] 2- has been confirmed by capillary electrophoresis (EC-ICP-MS). On account of the preliminary results obtained during the titration of the cyclame tetraacetic product (TETRA) in presence of plutonium(IV), the adding of a competitive ligand such as EDTA has been considered for the study of the complexation of this radioelement by macrocyclic ligands. At last, the affinity of different macrocyclic ligands containing either four amide functions (TETAMMe 2 and TETAMMEt 2 ) or carboxylate groups (TETA, DOTPr and TETPr) towards lanthanides(III) has been estimated too. Although the complexation reaction be fast with the two first ligands, these complexes are less stable than those formed with the carboxylic macrocycles. (O.M.)

Synthesis, spectroscopic studies and reactivity of triphenylphosphine ruthenium (II) complexes with N-heterocyclic ligands

International Nuclear Information System (INIS)

Rivera, A.B.

1989-01-01

Reported is the chemistry of triphenylphosphine ruthenium (II) complexes of general formula RuCl 2 (PPh 3 ) 2 L 2 and RuCl 2 (PPh 3 ) 2 A, obtained from the reaction of RuCl 2 (PPh 3 ) 3 with N-heterocyclic ligands L, or A (of ambidentate nature). The electronic spectra exhibit two strong metal-to-ligand charge-transfer bands, ascribed to the b 1 (dxz)->b 1 (pi) and a 2 (dxy)->a 2 (pi) transitions, and a third, weak band ascribed to the b 2 (dyz)->a 2 (pi) transition. The electronic states and the vibrational modes of the complexes were characterized by means of their resonance Raman and infrared absorption spectra. Thermogravimetric and thermodifferential analysis indicated that the melting process is succeeded by an exothermic reaction, and that the weigh loss starts to occur only after this step. The complexes dissociated in CHCl 3 solution, showing preferential labilization of the phosphine ligands, as in the case of the hydrogenation catalyst Ru(PPh 3 ) 3 Cl 2 . In the presence of CO, RuCl 2 (CO) 2 L 2 complexes were gennerated. Several derivatives were isolated and characterized. (author) [pt

Carboxylate ligands drastically enhance the rates of oxo exchange and hydrogen peroxide disproportionation by oxo manganese compounds of potential biological significance.

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Dubois, Lionel; Pécaut, Jacques; Charlot, Marie-France; Baffert, Carole; Collomb, Marie-Noëlle; Deronzier, Alain; Latour, Jean-Marc

2008-01-01

To mimic the carboxylate-rich active site of the manganese catalases more closely we introduced carboxylate groups into dimanganese complexes in place of nitrogen ligands. The series of dimanganese(III,IV) complexes of tripodal ligands [Mn(2)(L)(2)(O)(2)](3+/+/-/3-) was extended from those of tpa (1) and H(bpg) (2) to those of H(2)(pda) (3) and H(3)(nta) (4) (tpa=tris-picolylamine, H(bpg)=bis-picolylglycylamine, H(2)(pda)=picolyldiglycylamine, H(3)(nta)=nitrilotriacetic acid). While 3 [Mn(2)(pda)(2)(O)(2)][Na(H(2)O)(3)] could be synthesized at -20 degrees C and characterized in the solid state, 4 [Mn(2)(nta)(2)(O)(2)](3-) could be obtained and studied only in solution at -60 degrees C. A new synthetic procedure for the dimanganese(III,III) complexes was devised, using stoichiometric reduction of the dimanganese(III,IV) precursor by the benzil radical with EPR monitoring. This enabled the preparation of the parent dimanganese(III,III) complex 5 [Mn(2)(tpa)(2)(O)(2)](ClO(4))(2), which was structurally characterized. The UV/visible, IR, EPR, magnetic, and electrochemical properties of complexes 1-3 and 5 were analyzed to assess the electronic changes brought about by the carboxylate replacement of pyridine ligands. The kinetics of the oxo ligand exchanges with labeled water was examined in acetonitrile solution. A dramatic effect of the number of carboxylates was evidenced. Interestingly, the influence of the second carboxylate substitution differs from that of the first one probably because this substitution occurs on an out-of-plane coordination while the former occurs in the plane of the [Mn(2)O(2)] core. Indeed, on going from 1 to 3 the exchange rate was increased by a factor of 50. Addition of triethylamine caused a rate increase for 1, but not for 3. The abilities of 1-3 to disproportionate H(2)O(2) were assessed volumetrically. The disproportionation exhibited a sensitivity corresponding to the carboxylate substitution. These observations strongly suggest that

Decarboxylative Trifluoromethylation of Aliphatic Carboxylic Acids.

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Kautzky, Jacob A; Wang, Tao; Evans, Ryan W; MacMillan, David W C

2018-05-14

Herein we disclose an efficient method for the conversion of carboxylic acids to trifluoromethyl groups via the combination of photoredox and copper catalysis. This transformation tolerates a wide range of functionality including heterocycles, olefins, alcohols, and strained ring systems. To demonstrate the broad potential of this new methodology for late-stage functionalization, we successfully converted a diverse array of carboxylic acid-bearing natural products and medicinal agents to the corresponding trifluoromethyl analogues.

Phosphorescent emissions of phosphine copper(I) complexes bearing 8-hydroxyquinoline carboxylic acid analogue ligands

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Małecki, Jan G., E-mail: gmalecki@us.edu.pl [Department of Crystallography, Institute of Chemistry, University of Silesia, Szkolna 9 street, 40-006 Katowice (Poland); Łakomska, Iwona, E-mail: iwolak@chem.umk.pl [Department of Chemistry, Nicolaus Copernicus University, Toruń (Poland); Maroń, Anna [Department of Crystallography, Institute of Chemistry, University of Silesia, Szkolna 9 street, 40-006 Katowice (Poland); Szala, Marcin [Institute of Chemistry, University of Silesia, ul. Szkolna 9, 40-006 Katowice (Poland); Fandzloch, Marzena [Department of Chemistry, Nicolaus Copernicus University, Toruń (Poland); Nycz, Jacek E., E-mail: jacek.nycz@us.edu.pl [Institute of Chemistry, University of Silesia, ul. Szkolna 9, 40-006 Katowice (Poland)

2015-05-15

The pseudotetrahedral complexes of [Cu(PPh{sub 3}){sub 2}(L)], where L=8-hydroxy-2-methylquinoline-7-carboxylic acid (1), 8-hydroxy-2,5-dimethylquinoline-7-carboxylic acid (2) or 5-chloro-8-hydroxy-2-methylquinoline-7-carboxylic acid (3) have been synthesized and structurally characterized by X-ray crystallography. Their properties have been examined through combinations of IR, NMR, electronic absorption spectroscopy and cyclic voltammetry. The complexes exhibit extraordinary photophysical properties. Complex (1) in solid state exhibits an emission quantum yield of 4.67% and an excited life time of 1.88 ms (frozen DCM solution up to 6.7 ms). When dissolved in a coordinating solvent (acetonitrile) the charge transfer emission was quenched on a microsecond scale. - Highlights: • Synthesis of copper(I) complexes with 8-hydroxyquinoline carboxylic acid ligands. • Very long lived phosphorescent copper(I) complexes. • [Cu(PPh{sub 3}){sub 2}(L)] where L=8-hydroxy-2-methylquinoline-7-carboxylic acid luminesce in the solid state exhibits extremely long lifetime on millisecond scale (1.9 ms). • In frozen MeOH:EtOH solution lifetime increases to 7 ms. • Quantum efficiency equal to 4.7%.

Design of co-crystals/salts of some Nitrogenous bases and some derivatives of thiophene carboxylic acids through a combination of hydrogen and halogen bonds.

Science.gov (United States)

Jennifer, Samson Jegan; Muthiah, Packianathan Thomas

2014-01-01

The utility of N-heterocyclic bases to obtain molecular complexes with carboxylic acids is well studied. Depending on the solid state interaction between the N-heterocyclic base and a carboxylic acid a variety of neutral or ionic synthons are observed. Meanwhile, pyridines and pyrimidines have been frequently chosen in the area of crystal engineering for their multipurpose functionality. HT (hetero trimers) and LHT (linear heterotetramers) are the well known synthons that are formed in the presence of pyrimidines and carboxylic acids. Fourteen crystals involving various substituted thiophene carboxylic acid derivatives and nitrogenous bases were prepared and characterized by using single crystal X-ray diffraction. The 14 crystals can further be divided into two groups [1a-7a], [8b-14b] based on the nature of the nitrogenous base. Carboxylic acid to pyridine proton transfer has occurred in 3 compounds of each group. In addition to the commonly occurring hydrogen bond based pyridine/carboxylic acid and pyrimidine/carboxylic acid synthons which is the reason for assembly of primary motifs, various other interactions like Cl…Cl, Cl…O, C-H…Cl, C-H…S add additional support in organizing these supermolecules into extended architectures. It is also interesting to note that in all the compounds π-π stacking occurs between the pyrimidine-pyrimidine or pyridine-pyridine or acid-acid moieties rather than acid-pyrimidine/pyridine. In all the compounds (1a-14b) either neutral O-H…Npyridyl/pyrimidine or charge-assisted Npyridinium-H…Ocarboxylate hydrogen bonds are present. The HT (hetero trimers) and LHT (linear heterotetramers) are dominant in the crystal structures of the adducts containing N-heterocyclic bases with two proton acceptors (1a-7a). Similar type supramolecular ladders are observed in 5TPC44BIPY (8b), TPC44BIPY (9b), TPC44TMBP (11b). Among the seven compounds [8b-14b] the extended ligands are linear in all except for the TMBP (10b, 11b, 12b). The

Synthesis, photo-, and electrochemistry of ruthenium bis(bipyridine) complexes comprising a N-heterocyclic carbene ligand.

Science.gov (United States)

Leigh, Vivienne; Ghattas, Wadih; Lalrempuia, Ralte; Müller-Bunz, Helge; Pryce, Mary T; Albrecht, Martin

2013-05-06

Analogues of [Ru(bpy)3](2+) were prepared in which one pyridine ligand site is substituted by a N-heterocyclic carbene (NHC) ligand, that is, either by an imidazolylidene with a variable wingtip group R (R = Me, 3a; R = Et, 3b; R = iPr, 3c), or by a benzimidazolylidene (Me wingtip group, 3d), or by a 1,2,3-triazolylidene (Me wingtip group, 3e). All complexes were characterized spectroscopically, photophysically, and electrochemically. An increase of the size of the wingtip groups from Me to Et or iPr groups distorts the octahedral geometry (NMR spectroscopy) and curtails the reversibility of the ruthenium oxidation. NHC ligands with methyl wingtip groups display reversible ruthenium oxidation at a potential that reflects the donor properties of the NHC ligand (triazolylidene > imidazolylidene > benzimidazolylidene). The most attractive properties were measured for the triazolylidene ruthenium complex 3e, featuring the smallest gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in the series (2.41 eV), a slightly red-shifted absorption profile, and reasonable excited-state lifetime (188 ns) when compared to [Ru(bpy)3](2+). These features demonstrate the potential utility of triazolylidene ruthenium complexes as photosensitizers for solar energy conversion.

Metal-organic coordination architectures of tetrazole heterocycle ligands bearing acetate groups: Synthesis, characterization and magnetic properties

Science.gov (United States)

Hu, Bo-Wen; Zheng, Xiang-Yu; Ding, Cheng

2015-12-01

Two new coordination complexes with tetrazole heterocycle ligands bearing acetate groups, [Co(L)2]n (1) and [Co3(L)4(N3)2·2MeOH]n (2) (L=tetrazole-1-acetate) have been synthesized and structurally characterized. Single crystal structure analysis shows that the cobalt-complex 1 has the 3D 3,6-connected (42.6)2(44.62.88.10)-ant topology. By introducing azide in this system, complex 2 forms the 2D network containing the [Co3] units. And the magnetic properties of 1 and 2 have been studied.

Copper-Catalyzed N-Arylation of Amides Using (S-N-Methylpyrrolidine-2-carboxylate as the Ligand

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Dong-Sheng Ma

2010-03-01

Full Text Available (S-N-methylpyrrolidine-2-carboxylate, a derivative of natural L-proline, was found to be an efficient ligand for the copper-catalyzed Goldberg-type N-arylation of amides with aryl halides under mild conditions. A variety of N-arylamides were synthesized in good to high yields.

Electrochemical synthesis of transition element complexes with carboxyl- and carbonyl-containing ligands

International Nuclear Information System (INIS)

Frolov, V.Yu.; Bolotin, S.N.; Panyushkin, V.T.

2005-01-01

Complexes of d- and f-elements (E = Cu, Ni, Zn, Nd, Tb, Pr, Gd, Er) with carboxyl- and carbonyl-containing ligands were synthesized by the electrochemical method. The products were characterized by elemental analysis, thermal gravimetric analysis and IR spectra. The influence exerted by a number of factors on the process course was studied. The dependence of the electro synthesis parameters on the composition of the forming compounds was established. A new method for anodic synthesis of these compounds was developed [ru

How does the addition of steric hindrance to a typical N-heterocyclic carbene ligand affect catalytic activity in olefin metathesis?

KAUST Repository

Poater, Albert; Falivene, Laura; Urbina-Blanco, Cé sar A.; Manzini, Simone; Nolan, Steven P.; Cavallo, Luigi

2013-01-01

Density functional theory (DFT) calculations were used to predict and rationalize the effect of the modification of the structure of the prototype 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) N-heterocyclic carbene (NHC) ligand. The modification consists in the substitution of the methyl groups of ortho isopropyl substituent with phenyl groups, and here we plan to describe how such significant changes affect the metal environment and therefore the related catalytic behaviour. Bearing in mind that there is a significant structural difference between both ligands in different olefin metathesis reactions, here by means of DFT we characterize where the NHC ligand plays a more active role and where it is a simple spectator, or at least its modification does not significantly change its catalytic role/performance. © 2013 The Royal Society of Chemistry.

Basic deuteroexchange in transition metal complexes with nitrogen-containing aromatic heterocycles

International Nuclear Information System (INIS)

Tupitsyn, I.F.

1986-01-01

Kinetics of deuteroexchange in the methyl group of nitrate complexes of a metal - nickel (2) - with different methyl-substituted aromatic heterocycles and isostructural complexes of a ligand - 2 - methyl quinoline - with different central metal atoms (Mn(2), Ni(2), Cu(2), Zn(2)) is studied. Series for influence of ligand structure on deuteroexchange rate in complexes doesn't correspond qualitatively to series for deuteroexchange rate increase in noncoordinated ligands. Deuteroexchange rate is weakly subjected to influence of exchange in metal-complexing agent. Deuteroexchange mechanism is suggested and discussed. According to this mechanism the structure developed in the course of the exchange process with electron density transfer from the heterocyclic ligand to a metal ion is a transition state of the reaction

Synthesis of new oxovanadium (IV) complexes of potential insulinmimetic activity with coumarin-3-carboxylic acid ligands and substituted derivatives

International Nuclear Information System (INIS)

Salas Fernandez, Paloma; Alvino de la Sota, Nora; Galli Rigo-Righi, Carla

2013-01-01

This work comprises the design and synthesis of four new oxovanadium (IV) complexes, a metal which possesses insulin-mimetic action. Coumarin-3-carboxylic acid and three of its 6 -and 6,8- derivatives were used as ligands. Coumarins are of interest due to their well-known biological properties and pharmacological applications; these include the insulino-sensibilizing effect of certain alcoxy-hydroxy-derivatives which might lead to the eventual existence of a synergetic effect with the active metal center. The synthesis of the vanadyl complexes was preceded by the synthesis of the coumarin-3-carboxylic acid and its 6-bromo- derivative, as well as the syntheses of three derivatives not previously reported: 6-bromo-8-metoxi-, 6-bromo-8-nitro-, and 6-bromo-8-hydroxy-, which were prepared by a Knoevenagel condensation reaction. The complexes, on their part, were prepared by a metathesis reaction between VOSO 4 and the corresponding ligands, on the basis of methods reported for other vanadyl complexes and under strict pH control. The coumarin-3-carboxylic ligands and the derivatives were characterized by 1 H-NMR-, FTIR- and UV-Vis-spectroscopy. In the case of the complexes, their paramagnetic character did not allow for NMR characterization, being thus identified by FT-IR-spectroscopy and by the quantitative determination of their vanadium contents. (author)

Potentiometric studies on mixed-ligand chelates of uranyl ion with carboxylic acid phenolic acids

International Nuclear Information System (INIS)

Bandiwadekar, S.P.; Chavar, A.M.

1988-01-01

Mixed ligand complexes of UO 2 2+ with bidentate carboxylic and phenolic acids have been studied potentiometrically at 30 ± 0.1degC and μ=0.2M (NaClO 4 ). 1:1 and 1:2 complexes of UO 2 2+ with phthalic acid (PTHA), maleic acid (MAE), malonic acid (MAL), quinolinic acid (QA), 5-sulphosalicylic acid (5-SSA), salicylic acid (SA), and only 1:1 complexes in the case of mandelic acid (MAD) have been detected. The formation of 1:1:1 mixed ligand complexes has been inferred from simultaneous equilibria in the present study. The values of ΔlogK, Ksub(DAL), Ksub(2LA) or Ksub(2AL) for the ternary complexes have been calculated. The stabilities of mixed ligand complexes depend on the size of the chelate ring and the stabilities of the binary complexes. (author). 15 refs

Comparisons of the spectroscopic and microbiological activities among coumarin-3-carboxylate, o-phenanthroline and zinc(II) complexes

Science.gov (United States)

Islas, María S.; Martínez Medina, Juan J.; Piro, Oscar E.; Echeverría, Gustavo A.; Ferrer, Evelina G.; Williams, Patricia A. M.

2018-06-01

Coumarins (2H-chromen-2-one) are oxygen-containing heterocyclic compounds that belong to the benzopyranones family. In this work we have synthesized different coordination complexes with coumarin-3-carboxylic acid (HCCA), o-phenanthroline (phen) and zinc(II). In the reported [Zn(CCA)2(H2O)2] complex, coumarin-3-carboxylate (CCA) is acting as a bidentate ligand while in the two prepared complexes, [Zn(phen)3]CCA(NO3) (obtained as a single crystal) and [Zn(CCA)2phen].4H2O, CCA is acting as a counterion of the complex cation [Zn(phen)3]+2 or coordinated to the metal center along with phen, respectively. These compounds were characterized on the basis of elemental analysis and thermogravimetry. NMR, FTIR and Raman spectroscopies of the compounds and the CCA potassium salt (KCCA) allow to determine several similarities and differences among them. Finally, their behavior against alkaline phosphatase enzyme and their antimicrobial activities were also measured.

Crystal structures and luminescence of two cadmium-carboxylate cluster-based compounds with mixed ligands

Energy Technology Data Exchange (ETDEWEB)

Ma, Hui-Fang; Lei, Qian; Wang, Yu-Ling; Yin, Shun-Gao; Liu, Qing-Yan [College of Chemistry and Chemical Engineering and Key Lab. of Functional Small Organic Molecule of Ministry of Education, Jiangxi Normal Univ., Nanchang (China)

2017-04-04

Reactions of Cd(NO{sub 3}){sub 2}.4H{sub 2}O with 2-quinolinecarboxylic acid (H-QLC) in the presence of 1,4-benzenedicarboxylic acid (H{sub 2}-BDC) or 1,3,5-benzenetricarboxylic acid (H-BTC) in DMF/H{sub 2}O solvent afforded two compounds, namely, [Cd(QLC)(BDC){sub 1/2}(H{sub 2}O)]{sub n} (1) and [Cd(QLC)(BTC){sub 1/3}]{sub n} (2). Both compounds are two-dimensional (2D) frameworks but feature different cadmium-carboxylate clusters as a result of the presence of the polycarboxylate ligands with different geometries and coordination preference. The dinuclear Cd{sub 2}(QLC){sub 2} units in 1 are bridged by the pairs of bridging water ligands to give a one-dimensional (1D) chain, which is further linked by the second ligand of BDC{sup 2-} to form a 2D structure. Compound 2 is constructed from unique hexanuclear macrometallacyclic Cd{sub 6}(QLC){sub 6} clusters, which are linked by the surrounding BTC{sup 3-} ligands to generate a 2D structure. Photoluminescence studies showed both compounds exhibit ligand-centered luminescent emissions with emission maxima at 405 and 401 nm, respectively. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Asymmetric Hydrogenation of Seven-Membered C=N-containing Heterocycles and Rationalization of the Enantioselectivity.

Science.gov (United States)

Balakrishna, Bugga; Bauzá, Antonio; Frontera, Antonio; Vidal-Ferran, Anton

2016-07-18

Iridium(I) complexes with phosphine-phosphite ligands efficiently catalyze the enantioselective hydrogenation of diverse seven-membered C=N-containing heterocyclic compounds (eleven examples; up to 97 % ee). The P-OP ligand L3, which incorporates an ortho-diphenyl substituted octahydrobinol phosphite fragment, provided the highest enantioselectivities in the hydrogenation of most of the heterocyclic compounds studied. The observed stereoselection was rationalized by means of DFT calculations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Basic deuteroexchange in complexes of transition metals with nitrogen-containing aromatic heterocycles

International Nuclear Information System (INIS)

Tupitsyn, I.F.

1986-01-01

A study was made of the kinetics of deuteroexchange in the methyl group in complexes of one metal [nickel(II)] with different methyl-substituted aromatic heterocycles and in isostructural complexes of one ligand (2-methylquinoline) with different central metal atoms (Mn 2+ , Ni 2+ , Cu 2+ , Zn 2+ ). The order in which the structures of the ligands influence the rate of deuteroexchange in the complexes does not correspond qualitatively with the order of increase in the rate of deuteroexchange in the noncoordinated ligands. The rate of deuteroexchange is only weakly influenced by change in the identity of the metal complex former. A deuteroexchange mechanism is proposed and discussed. A structure arising in the course of the exchange process with transfer of electron density from the heterocyclic ligand to the metal ion forms the transition state of the reaction

Coordination Architectures of energetic Cd (II) coordination polymers constructed by the bifunctional substituted-tetrazole-carboxylate ligands

Energy Technology Data Exchange (ETDEWEB)

Shen, Lei; Bai, Yu; Min, Yu-Ting; Jia, Tian-Tian; Wu, Qi; Wang, Jing; Geng, Fei; Cheng, Hong-Jian [Department of Chemistry & Materials Engineering, Jiangsu Key Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu 215500 (China); Zhu, Dun-Ru [College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing 210009 (China); Yang, Jie, E-mail: jieyang@cslg.edu.cn [Department of Chemistry & Materials Engineering, Jiangsu Key Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu 215500 (China); Yang, Gao-Wen, E-mail: ygwsx@126.com [Department of Chemistry & Materials Engineering, Jiangsu Key Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu 215500 (China)

2016-12-15

Three different tetrazole-carboxylate ligands, monotetrazole-carboxylate H{sub 2}tza (H{sub 2}tza=1,5-tetrazole-diacetic acid), Hpztza (Hpztza=5-(2-pyrazinyl)tetrazole-2(1-methyl)acetic acid), ditetrazole-carboxylate H{sub 2}tzpha (H{sub 2}tzpha=1,3-di(tetrazole-5-yl)benzene-N2,N2′-diacetic acid) have been chosen to react with CdCl{sub 2}·6H{sub 2}O, resulting in the formation of three new compounds [Cd{sub 2}(tza){sub 2}] (1), [Cd(pztza){sub 2}] (2) and [Cd(tzpha)(CH{sub 3}OH){sub 2}] (3). The coordinate sites of the three ligands are major influenced by the different substituted group of tetrazole ring. These compounds have been characterized by elemental analysis, IR and single crystal X-ray diffraction. Compound 1 displays a complex 3D structure; compound 2 shows a 3D network and compound 3 features a 2D layer network. Furthermore, the luminescence properties investigated at room temperature in the solid state showed excellent ligand-centered luminescence. The obvious enhancement in luminescence makes these compounds potential materials for optical use. The differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses were applied to evaluate the thermal decomposition behavior of such compounds, showing that compounds 2 and 3 can be used as potential energetic materials. The relevant thermodynamic parameters ΔH, ΔS and ΔG were calculated as well. - Graphical abstract: H{sub 2}tza, Hpztza and H{sub 2}tzpha have been prepared. Three novel Cd (II)compounds were synthesized by reactions of CdCl{sub 2}·6H{sub 2}O, namely three dimensional [Cd{sub 2}(tza){sub 2}] (1), three dimensional [Cd(pztza){sub 2}] (2), and two dimensional [Cd(tzpha)(CH{sub 3}O){sub 2}] (3). The luminescences were investigated. Furthermore, the DSC show compounds 1 and 3 can be used as potential explosive materials.

Synthesis and Characterization of Ag(I) and Pd(II) Complexes with a Pyridine Substituted N-Heterocyclic Carbene Ligand

Energy Technology Data Exchange (ETDEWEB)

Kim, Ga Young; Jung, Hyun Jin; Lee, Dong Heon [Chonbuk National Univ., Jeonju (Korea, Republic of); Park, Gyung Se [Kunsan National Univ., Kunsan (Korea, Republic of)

2010-06-15

We have used our new tridentate pyridine substituted N-heterocyclic carbene to generate an interesting trinuclear [((MepyCH{sub 2}){sub 2}-Im){sub 3}Ag{sub 3}]{sup 3+} complex, displaying very short Ag-Ag separations. A Pd(II)-NHC complex was prepared from [((MepyCH{sub 2}){sub 2}-Im){sub 3}Ag{sub 3}]{sup 3+} via a facile transmetallation, leading to a dimeric [(MepyCH{sub 2}){sub 2}-ImPdCl]{sub 2}{sup 2+} complex. Future plans are underway for the survey of the potential applications of these new NHC complexes as luminesent materials or homogeneous catalysts. Since Arduengo's discovery of the first isolable free carbene in 1991, N-heterocyclic carbenes (NHC) have been extensively utilized as ligands for transition metals. NHC are generally more stable than two extreme types of carbenes, the Fischer and the Schrock carbenes. They are good σ donors like most tertiary phosphins, PR{sub 3}, but the π-bonding with the metal is rather weak. The thriving studies of NHC-coordinated metal complexes produced a wide range of applications from homogeneous catalysts to materials science.

Synthesis and pharmacological characterization of novel xanthine carboxylate amides as A2A adenosine receptor ligands exhibiting bronchospasmolytic activity.

Science.gov (United States)

Yadav, Rakesh; Bansal, Ranju; Rohilla, Suman; Kachler, Sonja; Klotz, Karl-Norbert

2016-04-01

The carboxylate amides of 8-phenyl-1,3-dimethylxanthine described herein represent a new series of selective ligands of the adenosine A2A receptors exhibiting bronchospasmolytic activity. The effects of location of 8-phenyl substitutions on the adenosine receptor (AR) binding affinities of the newly synthesized xanthines have also been studied. The compounds displayed moderate to potent binding affinities toward various adenosine receptor subtypes when evaluated through radioligand binding studies. However, most of the compounds showed the maximum affinity for the A2A subtype, some with high selectivity versus all other subtypes. Xanthine carboxylate amide 13b with a diethylaminoethylamino moiety at the para-position of the 8-phenylxanthine scaffold was identified as the most potent A2A adenosine receptor ligand with Ki=0.06μM. Similarly potent and highly A2A-selective are the isovanillin derivatives 16a and 16d. In addition, the newly synthesized xanthine derivatives showed good in vivo bronchospasmolytic activity when tested in guinea pigs. Copyright © 2016 Elsevier Inc. All rights reserved.

Stability constant determinations for technetium (IV) complexation with selected amino carboxylate ligands in high nitrate solutions

Energy Technology Data Exchange (ETDEWEB)

Omoto, Trevor; Wall, Nathalie A. [Washington State Univ., Pullman, WA (United States). Dept. of Chemistry

2017-10-01

The stability constants for Tc(IV) complexation with the ligands IDA, NTA, HEDTA, and DTPA were determined in varied nitrate concentrations using liquid-liquid extraction methods. The determined log β{sub 101} stability constants at 0.5 M NaNO{sub 3} were found to be 9.2±0.3, 10.3±0.3, and 15.3±0.3 for IDA, NTA, and HEDTA, respectively. The log β{sub 111} stability constant for DTPA was determined to be 22.0±0.6. These determined stability constants show a slight decrease in magnitude as a function of increasing NaNO{sub 3} concentration. These stability constants were used to model the total dissolution of Tc(IV) in acidic aqueous solutions in the presence of each ligand. The results of these predictive models indicate that amino carboxylic ligands have a high potential for increasing the aqueous dissolution of Tc(IV); at pH 2.3, 0.01 M ligand yield dissolved Tc(IV) concentrations of 1.42.10{sup -5} M, 1.33.10{sup -5} M, 6.07.10{sup -6} M, 9.65.10{sup -7} M, for DTPA, HEDTA, NTA, and IDA, respectively.

Synthesis, Crystal Structure and Luminescent Property of A Novel Cd(II) Coordination Polymer with Bis-imidazole Ligand

International Nuclear Information System (INIS)

Zhou, Yong Hong

2013-01-01

The key to the successful design of metal-organic coordination polymers is the judicious selection of organic ligand. Recently, polydentate aromatic nitrogen heterocyclic ligands with five-membered rings have been well-studied in the construction of supramolecular structure for their N-coordinated sites apt to coordinating to transition metals. Similar to six-membered N-heterocyclic ligands, the azole-based five-membered N-heterocyclic ligands, such as imidazoles, triazoles and tetrazoles have been extensively employed in the construction of various coordination polymers with diverse topologies and interesting properties. The bis(azole) ligands in which N-donor azole rings (imidazole, triazole, or tetrazole) are separated by alkyl, (CH 2 ) n , spacers are good choices for flexible bridging ligands. The conformational flexibility of the spacers makes the ligands adaptable to various coordination networks with one-, two-, and three dimensional structures

Plastic scintillators with high loading of one or more metal carboxylates

Science.gov (United States)

Cherepy, Nerine; Sanner, Robert Dean

2016-01-12

In one embodiment, a material includes at least one metal compound incorporated into a polymeric matrix, where the metal compound includes a metal and one or more carboxylate ligands, where at least one of the one or more carboxylate ligands includes a tertiary butyl group, and where the material is optically transparent. In another embodiment, a method includes: processing pulse traces corresponding to light pulses from a scintillator material; and outputting a result of the processing, where the scintillator material comprises at least one metal compound incorporated into a polymeric matrix, the at least one metal compound including a metal and one or more carboxylate ligands, where at least one of the one or more carboxylate ligands has a tertiary butyl group, and where the scintillator material is optically transparent and has an energy resolution at 662 keV of less than about 20%.

Copper- and copper–N-heterocyclic carbene-catalyzed C─H activating carboxylation of terminal alkynes with CO2 at ambient conditions

Science.gov (United States)

Yu, Dingyi; Zhang, Yugen

2010-01-01

The use of carbon dioxide as a renewable and environmentally friendly source of carbon in organic synthesis is a highly attractive approach, but its real world applications remain a great challenge. The major obstacles for commercialization of most current protocols are their low catalytic performances, harsh reaction conditions, and limited substrate scope. It is important to develop new reactions and new protocols for CO2 transformations at mild conditions and in cost-efficient ways. Herein, a copper-catalyzed and copper–N-heterocyclic carbene-cocatalyzed transformation of CO2 to carboxylic acids via C─H bond activation of terminal alkynes with or without base additives is reported. Various propiolic acids were synthesized in good to excellent yields under ambient conditions without consumption of any organometallic or organic reagent additives. This system has a wide scope of substrates and functional group tolerances and provides a powerful tool for the synthesis of highly functionalized propiolic acids. This catalytic system is a simple and economically viable protocol with great potential in practical applications. PMID:21059950

New chiral zwitterionic phosphorus heterocycles: synthesis, structure, properties and application as chiral solvating agents.

Science.gov (United States)

Sheshenev, Andrey E; Boltukhina, Ekaterina V; Grishina, Anastasiya A; Cisařova, Ivana; Lyapkalo, Ilya M; Hii, King Kuok Mimi

2013-06-17

A family of new chiral zwitterionic phosphorus-containing heterocycles (zPHC) have been derived from methylene-bridged bis(imidazolines). These structures were unambiguously determined, including single-crystal XRD analysis for two compounds. The stability, acid/base and electronic properties of these dipolar phosphorus heterocycles were subsequently investigated. zPHCs can be successfully employed as a new class of chiral solvating agents for the enantiodifferentiation of chiral carboxylic and sulfonic acids by NMR spectroscopy. The stoichiometry and binding constants for the donor-acceptor complexes formed were established by NMR titration methods. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis, spectroscopic characterization, biological screenings, DNA binding study and POM analyses of transition metal carboxylates

Science.gov (United States)

Uddin, Noor; Sirajuddin, Muhammad; Uddin, Nizam; Tariq, Muhammad; Ullah, Hameed; Ali, Saqib; Tirmizi, Syed Ahmed; Khan, Abdur Rehman

2015-04-01

This article contains the synthesis of a novel carboxylic acid derivative, its transition metal complexes and evaluation of biological applications. Six carboxylate complexes of transition metals, Zn(II) and Hg(II), have been successfully synthesized and characterized by FT-IR and NMR (1H, 13C). The ligand, HL, (4-[(2,6-Diethylphenyl)amino]-4-oxobutanoic acid) was also characterized by single crystal X-ray analysis. The complexation occurs via oxygen atoms of the carboxylate moiety. FT-IR date show the bidentate nature of the carboxylate moiety of the ligand as the Δν value in all complexes is less than that of the free ligand. The ligand and its complexes were screened for antifungal and antileishmanial activities. The results showed that the ligand and its complexes are active with few exceptions. UV-visible spectroscopy and viscometry results reveal that the ligand and its complexes interact with the DNA via intercalative mode of interaction. A new and efficient strategy to identify the pharmacophores and anti-pharmacophores sites in carboxylate derivatives for the antibacterial/antifungal activity using Petra, Osiris and Molinspiration (POM) analyses was also carried out.

Investigation of the structure and properties of heterocyclic compounds and their complexes

International Nuclear Information System (INIS)

Shejnker, V.N.; Troilina, V.S.; Merinova, E.G.; Garnovskij, A.D.; Osipov, O.A.

1988-01-01

Complexing of acetyl derivatives of azoles with iodine and bromine iodide is investigated using UV-spectroscopy and dipole moment methods. In bimolecular complexes σ-acceptor coordination occurs by heterocycle pyridine type nitrogen atom and is not accompanied by the ligand conformation change. The complex stability increases in agreement with azole basicity. For N-acetyltriazole ligand, conformation reversal occurs in its trimolecular complex with IBr

Water-soluble tetrapodal N, O ligands incorporating soft N-heterocycles for the selective complexation of Am(III) over Ln(III)

Energy Technology Data Exchange (ETDEWEB)

Heitzmann, M.; Gateau, Ch.; Delangle, P. [CEA Grenoble, Inac, Service de Chimie Inorganique et Biologique, UMR E 3 CEA UJF, FRE CNRS 3200, F-38054 Grenoble (France); Chareyre, L.; Miguirditchian, M.; Charbonnel, M.Ch. [CEA Marcoule, DEN, DRCP, SCPS, F-30207, Bagnols-sur-Ceze (France)

2010-07-01

A series of four water-soluble N, O-tetrapodal ligands derived from ethylenediamine, bearing hard acetate groups and soft N-heterocycles, either pyridine or pyrazine, was developed to study the impact of the softness of N-donors on the complexation properties with trivalent f ions. Two novel ligands of enhanced soft character, bearing three pyridines (L{sup 3py}) or three pyrazines (L{sup 3pz}), were synthesized and the related lanthanide complexes were studied in solution. The ligand containing three pyridyl-methyl moieties L{sup 3py} gives complexes with a coordination similar to EDTA, i.e. a hexa-dentate coordination mode as indicated by NMR and luminescence decays (q = 3) and stability constants in the range log {beta}{sub 110} = 6.99-9.3 (La-Lu). On the other hand, the softest molecule L{sup 3pz} forms much less stable complexes with log {beta}{sub 110} = 4.0-4.4 (La-Eu). The selective back-extraction of Am(III) from organic solutions containing 4f and 5f elements was tested with the four water-soluble complexing agents. The ligand L{sup 3pz} demonstrates poor stripping ability and selectivity. In contrast, the three ligands L{sup py}, L{sup pz} and L{sup 3py} give interesting back-extraction results with Eu/Am separation factors ranging from 36 to 46, which are significantly higher than with HEDTA. This exemplifies the role of the N-hetero-cycle softness in enhancing the separation between Am(III) and Eu(III). Interestingly, the pyrazine-based ligand, L{sup pz}, demonstrates the best stripping properties, with a distribution factor that approaches that of HEDTA in the same conditions (D{sub Am{approx}}0.3). This molecule is a good compromise between softness and hardness and forms complexes still stable at pH 3 due to its low basicity. (authors)

Elution behavior of N-heterocyclic derivatives of mixed ruthenium(II)-sulfoxide complexes in reversed-phase high-performance liquid chromatography

International Nuclear Information System (INIS)

Toma, H.E.; Silva, D.O.

1991-01-01

The elution behaviour of a series of dichlorobis-(dimethylsulfoxide)bis(N-heterocyclic) ruthenium(II) complexes has been investigated using reversed-phase HPLC. Similar trends as those displayed by the free N-heterocyclic bases have been observed for the complexes, essentially reflecting the hydrophobic properties of the aromatic ligands. (orig.)

Direct Functionalization of Nitrogen Heterocycles via Rh-Catalyzed C-H Bond Activation

Energy Technology Data Exchange (ETDEWEB)

Lewis, Jared; Bergman, Robert; Ellman, Jonathan

2008-02-04

heterocycles, including azoles, azolines, dihydroquinazolines, pyridines, and quinolines, with a wide range of functionalized olefins. They demonstrated the utility of this methodology in the synthesis of natural products, drug candidates, and other biologically active molecules. In addition, they developed conditions to directly arylate these heterocycles with aryl halides. The initial conditions that used PCy{sub 3} as a ligand were successful only for aryl iodides. However, efforts designed to avoid catalyst decomposition led to the development of ligands based on 9-phosphabicyclo[4.2.1]nonane (Phoban) that also facilitated the coupling of aryl bromides. They then replicated the unique coordination environment, stability, and catalytic activity of this complex using the much simpler tetrahydrophosphepine ligands and developed conditions that coupled aryl bromides bearing diverse functional groups without the use of a glovebox or purified reagents. With further mechanistic inquiry, they anticipate that researchers will better understand the details of the aforementioned Rh-catalyzed C-H bond functionalization reactions, resulting in the design of more efficient and robust catalysts, expanded substrate scope, and new transformations.

Aminolysis of resin-bound N-nosylaziridine-2-carboxylic acids

DEFF Research Database (Denmark)

Olsen, Christian A; Christensen, Caspar; Nielsen, Birgitte

2006-01-01

[Structure: see text] Solid-phase synthesis is a rapidly developing area of organic chemistry, of particular importance for medicinal chemistry and chemical biology. Aziridines have previously only rarely been applied in solid-phase synthesis. In the present work, aminolysis of resin-bound, sprin......-loaded N-nitrobenzenesulfonyl-activated aziridine-2-carboxylic acids has been optimized and employed in the synthesis of a number of open-chain and heterocyclic scaffolds, including enantiopure products....

Complexes of Th(IV) perchlorates, nitrates and thiocyanates with some heterocyclic bases

International Nuclear Information System (INIS)

Agarwal, R.K.; Srivastava, A.K.; Srivastava, M.; Bhakru, N.; Srivastava, T.N.

1980-01-01

Some Th(IV) perchlorate complexes of heterocyclic bases have been reported previously. Adducts of Th(IV) nitrates and thiocyanates with some heterocyclic N-oxides have been prepared and physico-chemical properties investigated. Comparatively little is known about the complexes of Th(IV) ion with the ligands containing nitrogen atom acting as electron donating centres. In view of this, the adducts of Th(IV) ion with certain nitrogen heterocyclic bases such as pyridine (Py), α-picoline (Pic), 2-amino pyridine (NH 2 Py), 2:4-lutidine (2,4LN), 2:6-lutidine, (2,6LN), quinoline (Q), isoquinoline (Isoq), 2,2'-bipyridine (Bipy) and 1,10-phenanthroline (Phen) were synthesised and characterised by analysis and IR absorption spectra. The results are presented and discussed. (author)

Highly photoluminescent europium tetraphenylimidodiphosphinate ternary complexes with heteroaromatic co-ligands. Solution and solid state studies

Energy Technology Data Exchange (ETDEWEB)

Pietraszkiewicz, Marek, E-mail: mpietraszkiewicz@ichf.edu.pl [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Pietraszkiewicz, Oksana; Karpiuk, Jerzy; Majka, Alina [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Dutkiewicz, Grzegorz; Borowiak, Teresa [Adam Mickiewicz University, Faculty of Chemistry, Department of Crystallography, Grunwaldzka 6, 60-780 Poznań (Poland); Kaczmarek, Anna M. [L3–Luminescent Lanthanide Lab, f-element coordination chemistry, Ghent University, Department of Inorganic and Physical Chemistry, Krijgslaan 281, Building S3, 9000 Gent (Belgium); Van Deun, Rik, E-mail: rik.vandeun@ugent.be [L3–Luminescent Lanthanide Lab, f-element coordination chemistry, Ghent University, Department of Inorganic and Physical Chemistry, Krijgslaan 281, Building S3, 9000 Gent (Belgium)

2016-02-15

Tetraphenylimidodiphosphinate (tpip) forms neutral 3:1 complexes with lanthanide ions. These complexes can accommodate one ancillary planar heterocyclic ligand to complement their coordination sphere of Eu{sup 3+} to coordination number 8. Several co-ligands were tested to form new complexes: 1,10-phenanthroline, bathophenanthroline, 2,4,6-tris(2-pyridyl)-1,3,5-triazine, dipyrido[3,2-f:2′,3′-h]quinoxaline and 2,2′:6′,2′′-terpyridine. The addition of heterocyclic N,N-bidentate co-ligands to the coordination sphere results in a dramatic (by a factor of 45–50) luminescence enhancement of the parent Eu(tpip){sub 3}. The solid-state measurements confirmed that the ancillary ligands strongly increased the photoluminescence quantum yield (PLQY) of the investigated complexes. - Highlights: • We have disovered highly photoluminescent ternary Eu(III) complexes. • They consist of Eu(III) tetraphenylimidodiphosphinate, and planar heterocyclic ligands. • The increase in photoluminescence quantum yields in solution is enhanced up to 50 times in solution. • The solid-state photoluminescence exceeds 80% at room temperature.

Highly photoluminescent europium tetraphenylimidodiphosphinate ternary complexes with heteroaromatic co-ligands. Solution and solid state studies

International Nuclear Information System (INIS)

Pietraszkiewicz, Marek; Pietraszkiewicz, Oksana; Karpiuk, Jerzy; Majka, Alina; Dutkiewicz, Grzegorz; Borowiak, Teresa; Kaczmarek, Anna M.; Van Deun, Rik

2016-01-01

Tetraphenylimidodiphosphinate (tpip) forms neutral 3:1 complexes with lanthanide ions. These complexes can accommodate one ancillary planar heterocyclic ligand to complement their coordination sphere of Eu 3+ to coordination number 8. Several co-ligands were tested to form new complexes: 1,10-phenanthroline, bathophenanthroline, 2,4,6-tris(2-pyridyl)-1,3,5-triazine, dipyrido[3,2-f:2′,3′-h]quinoxaline and 2,2′:6′,2′′-terpyridine. The addition of heterocyclic N,N-bidentate co-ligands to the coordination sphere results in a dramatic (by a factor of 45–50) luminescence enhancement of the parent Eu(tpip) 3 . The solid-state measurements confirmed that the ancillary ligands strongly increased the photoluminescence quantum yield (PLQY) of the investigated complexes. - Highlights: • We have disovered highly photoluminescent ternary Eu(III) complexes. • They consist of Eu(III) tetraphenylimidodiphosphinate, and planar heterocyclic ligands. • The increase in photoluminescence quantum yields in solution is enhanced up to 50 times in solution. • The solid-state photoluminescence exceeds 80% at room temperature.

Photodecarboxylative Cyclizations of ω-Phthalimido-para-phenoxy Carboxylates

Energy Technology Data Exchange (ETDEWEB)

Kim, Ae Rhan; Lee, Younsik; Yoo, Dong Jin [Chonbuk National Univ., Jeonju (Korea, Republic of); Cho, Hyunseung [Seonam Univ., Namwon (Korea, Republic of)

2012-10-15

The chemistry of electronically-excited phthalimides is dictated by electron and/or hydrogen transfer reactions. The photochemistry of phthalimides has been intensively studied, and numerous synthetically useful transformations with high chemical and quantum yields have been developed. 3 Among the synthetic applications, intra- and intermolecular photodecarboxylation (PDC) of ω-phthalimidoalkyl carboxylates has been developed by Griesbeck and coworkers as a versatile pathway to medium- and large-ring heterocycles. Model reactions were further realized on macro- and micro-scales. We recently described PDC cyclizations of ω-phthalimidoalkynoates to produce macrocyclic alkynes with ring-sizes up to 17. In recent study, we expanded the portfolio of this reaction and investigated the photochemistry of related aryl-linked phthalimides in Scheme 1. Based on these approaches, we demonstrated that ω-phthalimido-ortho/meta-phenoxy carboxylates undergo efficient PDC cyclizations. While the yields of ω-phthalimido-ortho-phenoxy carboxylates steadily decreased with increasing chain-length and the maximum yield of the 6-membered product was obtained in 75%, the yields of meta-phenoxy carboxylates steadily increased with increasing chain-length and the extended 16-membered product was subsequently obtained in 48% yield.

Role of Carboxylate ligands in the Synthesis of AuNPs: Size Control, Molecular Interaction and Catalytic Activity

KAUST Repository

Aljohani, Hind Abdullah

2016-05-22

Nanoparticles (NPs) are the basis of nanotechnology and finding numerous applications in various fields such as health, electronics, environment, personal care products, transportation, and catalysis. To fulfill these functions, the nanoparticles must be synthesized, passivated to control their chemical reactivity, stabilized against aggregation and functionalized to achieve specific performances. The chemistry of metal nanoparticles especially that of noble metals (Gold, Platinum…) is a growing field. The nanoparticles have indeed different properties from those of the corresponding bulk material. These properties are largely influenced by several parameters; the most important are the size, shape, and the local environment of the nanoparticles. One of the most common synthetic methods for the preparation of gold nanoparticles (AuNPs) is based on stabilization by citrate. Since it was reported first by Turkevich et al. in 1951, this synthetic scheme has been widely used, studied and a substantial amount of important information regarding this system has been reported in the literature. The most popular method developed by Frens for controlling the size of the noble gold nanoparticles based on citrate was achieved by varying the concentration of sodium citrate. Despite a large number of investigations focused on utilizing Cit-AuNPs, the structural details of citrate anions adsorbed on the AuNP surface are still unknown. It is known only that citrate anions “coordinate” to the metal surface by inner sphere complexation of the carboxylate groups and there are trace amounts of AuCl4−, Cl−, and OH− on the metal surface. Moreover, it is generally accepted that the ligand shell morphology of Au nanoparticles can be partly responsible for important properties such as oxidation of carbon monoxide. The use of Au-NPs in heterogeneous catalysis started mostly with Haruta who discovered the effect of particle size on the activity for carbon monoxide oxidation at

A spin-crossover complex based on a 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) ligand functionalized with a carboxylate group.

Science.gov (United States)

Abhervé, Alexandre; Clemente-León, Miguel; Coronado, Eugenio; Gómez-García, Carlos J; López-Jordà, Maurici

2014-07-07

Combining Fe(ii) with the carboxylate-functionalized 2,6-bis(pyrazol-1-yl)pyridine (bppCOOH) ligand results in the spin-crossover compound [Fe(bppCOOH)2](ClO4)2 which shows an abrupt spin transition with a T1/2 of ca. 380 K and a TLIESST of 60 K due to the presence of a hydrogen-bonded linear network of complexes.

In Situ Generated Ruthenium-Arene Catalyst for Photoactivated Ring-Opening Metathesis Polymerization through Photolatent N-Heterocyclic Carbene Ligand.

Science.gov (United States)

Pinaud, Julien; Trinh, Thi Kim Hoang; Sauvanier, David; Placet, Emeline; Songsee, Sriprapai; Lacroix-Desmazes, Patrick; Becht, Jean-Michel; Tarablsi, Bassam; Lalevée, Jacques; Pichavant, Loïc; Héroguez, Valérie; Chemtob, Abraham

2018-01-09

1,3-Bis(mesityl)imidazolium tetraphenylborate (IMesH + BPh 4 - ) can be synthesized in one step by anion metathesis between the corresponding imidazolium chloride and sodium tetraphenylborate. In the presence of 2-isopropylthioxanthone (sensitizer), an IMes N-heterocyclic carbene (NHC) ligand can be photogenerated under irradiation at 365 nm through coupled electron/proton transfer reactions. By combining this tandem NHC photogenerator system with metathesis inactive [RuCl 2 (p-cymene)] 2 precatalyst, the highly active RuCl 2 (p-cymene)(IMes) complex can be formed in situ, enabling a complete ring-opening metathesis polymerization (ROMP) of norbornene in the matter of minutes at room temperature. To the best of our knowledge, this is the first example of a photogenerated NHC. Its exploitation in photoROMP has resulted in a simplified process compared to current photocatalysts, because only stable commercial or easily synthesized reagents are required. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A two-dimensional layered Cd(II) coordination polymer with a three-dimensional supramolecular architecture incorporating mixed multidentate N- and O-donor ligands.

Science.gov (United States)

Huang, Qiu-Ying; Su, Ming-Yang; Meng, Xiang-Ru

2015-06-01

The combination of N-heterocyclic and multicarboxylate ligands is a good choice for the construction of metal-organic frameworks. In the title coordination polymer, poly[bis{μ2-1-[(1H-benzimidazol-2-yl)methyl]-1H-tetrazole-κ(2)N(3):N(4)}(μ4-butanedioato-κ(4)O(1):O(1'):O(4):O(4'))(μ2-butanedioato-κ(2)O(1):O(4))dicadmium], [Cd(C4H4O4)(C9H8N6)]n, each Cd(II) ion exhibits an irregular octahedral CdO4N2 coordination geometry and is coordinated by four O atoms from three carboxylate groups of three succinate (butanedioate) ligands and two N atoms from two 1-[(1H-benzimidazol-2-yl)methyl]-1H-tetrazole (bimt) ligands. Cd(II) ions are connected by two kinds of crystallographically independent succinate ligands to generate a two-dimensional layered structure with bimt ligands located on each side of the layer. Adjacent layers are further connected by hydrogen bonding, leading to a three-dimensional supramolecular architecture in the solid state. Thermogravimetric analysis of the title polymer shows that it is stable up to 529 K and then loses weight from 529 to 918 K, corresponding to the decomposition of the bimt ligands and succinate groups. The polymer exhibits a strong fluorescence emission in the solid state at room temperature.

Evaluation of an olefin metathesis pre-catalyst with a bulky and electron-rich N-heterocyclic carbene

KAUST Repository

Manzini, Simone

2015-03-01

The commercially-available metathesis pre-catalyst M23 has been evaluated alongside new complex [RuCl2((3-phenyl)indenylidene)(PPh3)(SIPrOMe)] (1), which bears a para-methoxy-substituted N-heterocyclic carbene ligand. Several model metathesis reactions could be conducted using only parts-per-million levels of ruthenium catalyst. The effects of the different NHC ligands on reactivity have been explored.

Evaluation of an olefin metathesis pre-catalyst with a bulky and electron-rich N-heterocyclic carbene

KAUST Repository

Manzini, Simone; Urbina Blanco, Cé sar A.; Nelson, David J.; Poater, Albert; Lebl, Tomas; Meiries, Sé bastien; Slawin, Alexandra M.Z.; Falivene, Laura; Cavallo, Luigi; Nolan, Steven P.

2015-01-01

The commercially-available metathesis pre-catalyst M23 has been evaluated alongside new complex [RuCl2((3-phenyl)indenylidene)(PPh3)(SIPrOMe)] (1), which bears a para-methoxy-substituted N-heterocyclic carbene ligand. Several model metathesis reactions could be conducted using only parts-per-million levels of ruthenium catalyst. The effects of the different NHC ligands on reactivity have been explored.

Synthesis and antimicrobial activity of new heterocyclic compounds containing thieno[3,2-c] coumarin and pyrazolo[4,3-c] coumarin frameworks.

Science.gov (United States)

El-Dean, Adel M Kamal; Zaki, Remon M; Geies, Ahmed A; Radwan, Shaban M; Tolba, Mahmoud S

2013-01-01

Reaction of 4-chlorocoumarin-3-carbonitrile with ethyl thioglycolate and ethyl glycinate hydrochloride leads to a series of title products. Hydrazinolysis of amino thienocoumarin carboxylate afforded the hydrazine derivative which underwent various reactions to build new heterocyclic rings containing thienocoumarin moiety. Chloro acetylation of aminoester compound afforded the chloro acetyl amino which underwent nucleophilic substitution reactions various amines. The following treatment with formaldehyde under Mannich conditions afforded the corresponding imidazo derivatives. Reaction of Ghloroacetylamino with potassium thiocyanate yielded ethylpyrimidothieno coumarin sulfanylacetate which was used as a versatile precursor for synthesis of other heterocycles. On the other hand, reaction of chloro coumarin carbo nitrile with hydrazine gave the aminopyrazolocoumaine which reacted with bifunctionally compounds to give the substituted pyrimido derivatives. Diazotization and coupling of aminopyrazole with ethylcyanoacetate yielded ethylaminotriazinopyrazolocoumarine carboxylate. Several of the compounds obtained demonstrated considerable antifungal and antibacterial activity in the in vitro test systems.

Far IR spectra of Th(IV) halide complexes of some heterocyclic bases

International Nuclear Information System (INIS)

Srivastava, A.K.; Agarwal, R.K.; Srivastava, M.; Kapoor, V.; Srivastava, T.N.

1981-01-01

The synthesis and IR spectra of Th(IV) perchlorato, nitrato and thiocyanato complexes of some heterocyclic bases have been reported. Halogens are common ligands in coordination chemistry forming coordinate bonds with metals readily. Metal halogen (M-X) stretching bands show a strong absorption in the far-IR region. Very little information is available on Th-X stretching frequencies. In the present communication, adducts of Th(IV) halide with certain nitrogen heterocyclic bases such as pyridine, α-picoline, 2-amino pyridine, 2:4-lutidine, 2:6-lutidine, quinoline, 2,2'-bipyridine and 1,10-phenanthroline were synthesised and characterised. Experimental details are given. Results are presented and discussed. (author)

Multicomponent synthesis of unsymmetrical unsaturated N-heterocyclic carbene precursors and their related transition-metal complexes

KAUST Repository

Queval, Pierre

2013-12-04

A low-cost, modular, and easily scalable multicomponent procedure affording access in good yields and excellent selectivity (up to 93 %) to a wide range of (a)chiral unsymmetrical 1-aryl-3-cycloalkyl-imidazolium salts is disclosed. Electronic and steric properties of the corresponding unsymmetrical unsaturated N-heterocyclic carbene (U2-NHC) ligands were evaluated and evidenced strong electron donor ability, high steric discrimination, and modular steric demand. A low-cost, modular, and easily scalable multicomponent procedure, affording access to a wide range of (a)chiral unsymmetrical 1-aryl-3-cycloalkyl- imidazolium salts in good yields and excellent selectivities, is disclosed. Electronic and steric properties of the corresponding unsymmetrical unsaturated N-heterocyclic carbene (U2-NHC) ligands were evaluated and evidenced strong electron-donor ability, high steric discrimination, and modular steric demand. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cyclometalated N-heterocyclic carbene iridium(iii) complexes with naphthalimide chromophores: a novel class of phosphorescent heteroleptic compounds.

Science.gov (United States)

Lanoë, Pierre-Henri; Chan, Jonny; Groué, Antoine; Gontard, Geoffrey; Jutand, Anny; Rager, Marie-Noelle; Armaroli, Nicola; Monti, Filippo; Barbieri, Andrea; Amouri, Hani

2018-03-06

A series of cyclometalated N-heterocyclic carbene complexes of the general formula [Ir(C^N) 2 (C^C:)] has been prepared. Two sets of compounds were designed, those where (C^C:) represents a bidentate naphthalimide-substituted imidazolylidene ligand and (C^N) = ppy (3a), F2ppy (4a), bzq (5a) and those where (C^C:) represents a naphthalimide-substituted benzimidazolylidene ligand and (C^N) = ppy (3b), F2ppy (4b), bzq (5b). The naphthalimide-imidazole and naphthalimide-benzimidazole ligands 1a,b and the related imidazolium and benzimidazolium salts 2a,b were also prepared and fully characterized. The N-heterocyclic carbene Ir(iii) complexes have been characterized by NMR spectroscopy, cyclic voltammetry and elemental analysis. Moreover, the molecular structures of one imidazolium salt and four Ir(iii) complexes were determined by single-crystal X-ray diffraction. The structures provide us with valuable information, most notably the orientation of the naphthalimide chromophore with respect to the N-heterocyclic carbene moiety. All compounds are luminescent at room temperature and in a frozen solvent at 77 K, exhibiting a broad emission band that extends beyond 700 nm. The presence of the naphthalimide moiety changes the character of the lowest excited state from 3 MLCT to 3 LC, as corroborated by DFT and TD-DFT calculations. Remarkably, replacing imidazole with a benzimidazole unit improves the quantum yields of these compounds by decreasing the k nr values which is an important feature for optimized emission performance. These studies provide valuable insights about a novel class of N-heterocyclic carbene-based luminescent complexes containing organic chromophores and affording metal complexes emitting across the red-NIR range.

Half -sand wish ruthenium complexes of heterocyclic-dithio carboxylato ligands

International Nuclear Information System (INIS)

El-khateeb, M.; Al-Noaimi, M.; Harb, M.; Gorls, H.; Weigand, W.

2008-01-01

The heterocyclic-dithio carboxylato complexes Cp Ru(PPh 3 )(κ 2 S,S-S 2 C-h et) [h et= 2-C 4 H 3 O (1), 2-C 4 H 3 S (2), 1-C 4 H 8 N (3)] are obtained by the reaction of the ruthenium chloride, Cp Ru(PPh 3 ) 2 CI, with the anions, h et-CS 2 . The X-ray structure of Cp Ru(PPh 3 )(κ 2 S, S-S 2 C-1- C 4 H 8 N) (3) is determined by single crystal X-ray diffraction.

Synthesis, characterization, and reactivity of furan- and thiophene-functionalized bis(n-heterocyclic carbene) complexes of iron(II)

KAUST Repository

Rieb, Julia; Raba, Andreas; Haslinger, Stefan; Kaspar, Manuel; Pö thig, Alexander; Cokoja, Mirza; Basset, Jean-Marie; Kü hn, Fritz

2014-01-01

The synthesis of iron(II) complexes bearing new heteroatom-functionalized methylene-bridged bis(N-heterocyclic carbene) ligands is reported. All complexes are characterized by single-crystal X-ray diffraction (SC-XRD), nuclear magnetic resonance

Solvothermal synthesis of uranium(VI) phases with aromatic carboxylate ligands: A dinuclear complex with 4-hydroxybenzoic acid and a 3D framework with terephthalic acid

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yingjie, E-mail: yzx@ansto.gov.au [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Karatchevtseva, Inna [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Bhadbhade, Mohan [Mark Wainwright Analytical Centre, University of New South Wales, Kensington, NSW 2052 (Australia); Tran, Toan Trong; Aharonovich, Igor [School of Physics and Advanced Materials, University of Technology Sydney, Ultimo, NSW 2007 (Australia); Fanna, Daniel J.; Shepherd, Nicholas D. [School of Science and Health, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 (Australia); Lu, Kim [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Li, Feng [School of Science and Health, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 (Australia); Lumpkin, Gregory R. [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia)

2016-02-15

With the coordination of dimethylformamide (DMF), two new uranium(VI) complexes with either 4-hydroxybenzoic acid (H{sub 2}phb) or terephthalic acid (H{sub 2}tph) have been synthesized under solvothermal conditions and structurally characterized. [(UO{sub 2}){sub 2}(Hphb){sub 2}(phb)(DMF)(H{sub 2}O){sub 3}]·4H{sub 2}O (1) has a dinuclear structure constructed with both pentagonal and hexagonal bipyramidal uranium polyhedra linked through a µ{sub 2}-bridging ligand via both chelating carboxylate arm and alcohol oxygen bonding, first observation of such a coordination mode of 4-hydroxybenzoate for 5 f ions. [(UO{sub 2})(tph)(DMF)] (2) has a three-dimensional (3D) framework built with pentagonal bipyramidal uranium polyhedra linked with µ{sub 4}-terephthalate ligands. The 3D channeled structure is facilitated by the unique carboxylate bonding with nearly linear C–O–U angles and the coordination of DMF molecules. The presence of phb ligands in different coordination modes, uranyl ions in diverse environments and DMF in complex 1, and tph ligand, DMF and uranyl ion in complex 2 has been confirmed by Raman spectroscopy. In addition, their thermal stability and photoluminescence properties have been investigated. - Graphical abstract: With the coordination of dimethylformamide, two new uranyl complexes with either 4-hydroxybenzoate or terephthalate have been synthesized under solvothermal conditions and structurally characterized. - Highlights: • Solvent facilitates the synthesis of two new uranium(VI) complexes. • A dinuclear complex with both penta- and hexagonal bipyramidal uranium polyhedral. • A unique µ{sub 2}-bridging mode of 4-hydroxybenzoate via alcohol oxygen for 5 f ions. • A 3D framework with uranium polyhedra and µ{sub 4}-terephthalate ligands. • Vibration modes and photoluminescence properties are reported.

The Ligand Substitution Reactions of Hydrophobic Vitamin B ...

African Journals Online (AJOL)

NJD

Vitamin B. 12. Derivatives. Reaction of Cobyric Acid. Heptapropyl Ester with Heterocyclic N-donor Ligands. Mohamed S.A. .... RESEARCH ARTICLE. M.S.A. Hamza ..... neutralized with NaHCO3 and treated with excess KCN to give. DCCbs-Pr.

Hydrothermal syntheses, characterizations and crystal structures of a new lead(II) carboxylate-phosphonate with a double layer structure and a new nickel(II) carboxylate-phosphonate containing a hydrogen-bonded 2D layer with intercalation of ethylenediamines

International Nuclear Information System (INIS)

Song, J.-L.; Mao, J.-G.; Sun, Y.-Q.; Zeng, H.-Y.; Kremer, R.K.; Clearfield, Abraham

2004-01-01

Hydrothermal reactions of N,N-bis(phosphonomethyl)aminoacetic acid (HO 2 CCH 2 N(CH 2 PO 3 H 2 ) 2 ) with metal(II) salts afforded two new metal carboxylate-phosphonates, namely, Pb 2 [O 2 CCH 2 N(CH 2 PO 3 )(CH 2 PO 3 H)]·H 2 O (1) and {NH 3 CH 2 CH 2 NH 3 }{Ni[O 2 CCH 2 N(CH 2 PO 3 H) 2 ](H 2 O) 2 } 2 (2). Among two unique lead(II) ions in the asymmetric unit of complex 1, one is five coordinated by five phosphonate oxygen atoms from 5 ligands, whereas the other one is five-coordinated by a tridentate chelating ligand (1 N and 2 phosphonate O atoms) and two phosphonate oxygen atoms from two other ligands. The carboxylate group of the ligand remains non-coordinated. The bridging of above two types of lead(II) ions through phosphonate groups resulted in a double layer with the carboxylate group of the ligand as a pendant group. These double layers are further interlinked via hydrogen bonds between the carboxylate groups into a 3D network. The nickel(II) ion in complex 2 is octahedrally coordinated by a tetradentate chelating ligand (two phosphonate oxygen atoms, one nitrogen and one carboxylate oxygen atoms) and two aqua ligands. These {Ni[O 2 CCH 2 N(CH 2 PO 3 H) 2 ][H 2 O] 2 } - anions are further interlinked via hydrogen bonds between non-coordinated phosphonate oxygen atoms to form a hydrogen bonded 2D layer. The 2H-protonated ethylenediamine cations are intercalated between two layers, forming hydrogen bonds with the non-coordinated carboxylate oxygen atoms. Results of magnetic measurements for complex 2 indicate that there is weak Curie-Weiss behavior with θ=-4.4 K indicating predominant antiferromagnetic interaction between the Ni(II) ions. Indication for magnetic low-dimension magnetism could not be detected

Handbook of heterocyclic chemistry

National Research Council Canada - National Science Library

Katritzky, Alan R

2010-01-01

... Heterocyclic Chemistry I (1984) Comprehensive Heterocyclic Chemistry II (1996) Comprehensive Heterocyclic Chemistry III (2008) Comprehensive Organic Functional Group Transformations I (1995) Compreh...

Synthesis and crystal structure of two lead (II) complexes with 1,10-phenanthroline ligand

International Nuclear Information System (INIS)

Olivera, Fiorella L.; Santillan, Guillermo A.

2012-01-01

Two coordination complexes have been synthesized by the reaction of lead nitrate (II) with 1,10-phenanthroline in methanol/water. The crystals of these complexes were obtained by using the diffusion method and structurally characterized by X-ray single crystal diffraction. Both complexes crystallized in the monoclinic space group P2 1 /c. The analysis by crystal X-ray diffraction reveals that in both complexes the coordination around the lead (II) ion is a distorted octahedral structure where the ion is bonded to the heterocyclic nitrogen atoms of chelating ligand 1,10-phenanthroline, three oxygen atoms of three nitrate groups and one oxygen from the water molecule. The difference between the complexes lies in the way of nitrate ion in presence of carboxylic acid aromatics. In addition, the crystal structure of complexes can be regarded as a 3D coordination polymer through Pb-O weak interactions, hydrogen bonds and π-π stacking interactions. (author).

Neutral bidentate N-heterocyclic ligands - phase transfer reagents improving the kinetics of solvent extraction of Am(III) and Eu(III) ions with tetradentate 6,6'-bis-(diethyl-1,2,4-triazin-3-yl)-2,2'-bipyridine

International Nuclear Information System (INIS)

Narbutt, J.; Krejzler, J.

2008-01-01

Poor kinetics of solvent extraction of Am(III) and Eu(III) ions from 1 M HNO 3 with 6,6'-bis-(diethyl-1,2,4-triazin-3-yl)-2,2'-bipyridine (etBTBP) has been improved by adding an auxiliary bidentate N-heterocyclic ligand to the extraction system. Two such ligands were studied, derivatives of bis-triazine and pyridine-triazine, which alone poorly extract the metal ions, but together with etBTBP they act as phase transfer reagents, improving the extraction kinetics to a different degree. The ability to transfer the metal ions from aqueous to organic phase depends on lipophilicity and acid/base properties of these auxiliary ligands, as well as on the mode of shaking the two liquid phases - gentle or vigorous. (orig.)

QSAR studies of multidentate nitrogen ligands used in lanthanide and actinide extraction processes

International Nuclear Information System (INIS)

Drew, Michael G.B.; Hudson, Michael J.; Youngs, Tristan G.A.

2004-01-01

Quantitative structure activity relationships (QSARs) have been developed to optimise the choice of nitrogen heterocyclic molecules that can be used to separate the minor actinides such as americium(III) from europium(III) in the aqueous PUREX raffinate of nuclear waste. Experimental data on distribution coefficients and separation factors (SFs) for 47 such ligands have been obtained and show SF values ranging from 0.61 to 100. The ligands were divided into a training set of 36 molecules to develop the QSAR and a test set of 11 molecules to validate the QSAR. Over 1500 molecular descriptors were calculated for each heterocycle and the Genetic Algorithm was used to select the most appropriate for use in multiple regression equations. Equations were developed fitting the separation factors to 6-8 molecular descriptors which gave r 2 values of >0.8 for the training set and values of >0.7 for the test set, thus showing good predictive quality. The descriptors used in the equations were primarily electronic and steric. These equations can be used to predict the separation factors of nitrogen heterocycles not yet synthesised and/or tested and hence obtain the most efficient ligands for lanthanide and actinide separation

Two new coordination polymers with flexible alicyclic carboxylate and bipyridyl co-ligands bearing trinuclear [Ni3(COO)6] SBUs: Synthesis, crystal structures, and magnetic properties

Science.gov (United States)

Zhu, Xian-Dong; Li, Yong; Gao, Jian-Gang; Wang, Fen-Hua; Li, Qing-Hai; Yang, Hong-Xun; Chen, Lei

2017-02-01

Two new coordination polymers generally formulated as [Ni3(Hchda)2(chda)2(bpy)2(H2O)2]n (1) and [Ni3(Hchda)2(chda)2(bpp)2(H2O)2]n (2) [H2chda = 1,1'-cyclohexanediacetic acid, bpy = 4,4'-bipyridine and bpp = 1,3-bis(4-pyridyl)propane], have been successfully assembled through mixed-ligands synthetic strategy with flexible alicyclic carboxylate and bipyridyl ligands. There structures feature trinuclear nickel secondary building units connected via the bridging bipyridyl spacers to form two-dimensional (4,4) grid layer. The nature of the different N-donor auxiliary ligands leads to the discrepancy in supramolecular structure of the two compounds. Magnetic studies indicate the ferromagnetic intra-complex magnetic interaction in the molecule for 1 and 2.

Effect of alkali metal ions on the pyrrole and pyridine π-electron systems in pyrrole-2-carboxylate and pyridine-2-carboxylate molecules: FT-IR, FT-Raman, NMR and theoretical studies

Science.gov (United States)

Świderski, G.; Wojtulewski, S.; Kalinowska, M.; Świsłocka, R.; Lewandowski, W.

2011-05-01

The FT-IR, FT-Raman and 1H and 13C NMR spectra of pyrrole-2-carboxylic acid (PCA) and lithium, sodium, potassium, rubidium and caesium pyrrole-2-carboxylates were recorded, assigned and compared in the Li → Na → K → Rb → Cs salt series. The effect of alkali metal ions on the electronic system of ligands was discussed. The obtained results were compared with previously reported ones for pyridine-2-carboxylic acid and alkali metal pyridine-2-carboxylates. Calculations for pyrrole-2-carboxylic acid and Li, Na, K pyrrole-2-carboxylates in B3LYP/6-311++G ** level and Møller-Plesset method in MP2/6-311++G ** level were made. Bond lengths, angles and dipole moments as well as aromaticity indices (HOMA, EN, GEO, I 6) for the optimized structures of pyrrole-2-carboxylic acid (PCA) and lithium, sodium, potassium pyrrole-2-carboxylates were also calculated. The degree of perturbation of the aromatic system of ligand under the influence of metals in the Li → Cs series was investigated with the use of statistical methods (linear correlation), calculated aromaticity indices and Mulliken, NBO and ChelpG population analysis method. Additionally, the Bader theory (AIM) was applied to setting the characteristic of the bond critical points what confirmed the influence of alkali metals on the pyrrole ring.

Cationic bis-N-heterocyclic carbene (NHC) ruthenium complex: Structure and application as latent catalyst in olefin metathesis

KAUST Repository

Rouen, Mathieu

2014-09-11

An unexpected cationic bis-N-heterocyclic carbene (NHC) benzylidene ether based ruthenium complex (2 a) was prepared through the double incorporation of an unsymmetrical unsaturated N-heterocyclic carbene (U2-NHC) ligand that bore an N-substituted cyclododecyl side chain. The isolation and full characterization (including X-ray diffraction studies) of key synthetic intermediates along with theoretical calculations allowed us to understand the mechanism of the overall cationization process. Finally, the newly developed complex 2 a displayed interesting latent behavior during ring-closing metathesis, which could be "switched on" under acidic conditions.

Gas adsorption and gas mixture separations using mixed-ligand MOF material

Science.gov (United States)

Hupp, Joseph T [Northfield, IL; Mulfort, Karen L [Chicago, IL; Snurr, Randall Q [Evanston, IL; Bae, Youn-Sang [Evanston, IL

2011-01-04

A method of separating a mixture of carbon dioxiode and hydrocarbon gas using a mixed-ligand, metal-organic framework (MOF) material having metal ions coordinated to carboxylate ligands and pyridyl ligands.

Masked N-Heterocyclic Carbene-Catalyzed Alkylation of Phenols with Organic Carbonates.

Science.gov (United States)

Lui, Matthew Y; Yuen, Alexander K L; Masters, Anthony F; Maschmeyer, Thomas

2016-09-08

An easily prepared masked N-heterocyclic carbene, 1,3-dimethylimidazolium-2-carboxylate (DMI-CO2 ), was investigated as a "green" and inexpensive organocatalyst for the alkylation of phenols. The process made use of various low-toxicity and renewable alkylating agents, such as dimethyl- and diethyl carbonate, in a focused microwave reactor. DMI-CO2 was found to be a very active catalyst and excellent yields of a range of aryl alkyl ethers were obtained under relatively benign conditions. The observed difference in the conversion behavior of phenol methylation, in the presence of either the carbene or 1,8-diazabicycloundec-7-ene (DBU) catalyst, was rationalized on the basis of mechanistic investigations. The primary mode of action for the N-heterocyclic carbene is nucleophilic catalysis. Activation of the dialkyl carbonate electrophile results in concomitant evolution of an organo-soluble alkoxide, which deprotonates the phenolic starting material. In contrast, DBU is initially protonated by the phenol and thus consumed. Subsequent regeneration and participation in nucleophilic catalysis only becomes significant after some phenolate alkylation occurs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterization of new N-heterocyclic carbene ligands: 1,3-Bis(acetamide)imidazol-3-ium bromide and 3-(acetamide)-1-(3-aminopropyl)-1H-imidazol-3-ium bromide

Science.gov (United States)

Turkyilmaz, Murat; Uluçam, Gühergül; Aktaş, Şaban; Okan, S. Erol

2017-05-01

Two new pincer type N-heterocyclic carbene ligands were synthesized. The compounds were characterized by FTIR, NMR (1H, 13C) GC-MS and elemental analyses. They were also both modelled by DFT calculations as the crystal structure of 1,3-bis(acetamide)imidazol-3-ium bromide was determined by XRD which is an orthorhombic system with space group P21212. The structural analyses in gas phase were realized by comparing the experimental NMR and IR spectra with those of the theoretical calculations. In vitro biological activities of the molecules were determined and found that one of them exhibits significant cytotoxic activity.

π-face donation from the aromatic N-substituent of N-heterocyclic carbene ligands to metal and its role in catalysis

KAUST Repository

Credendino, Raffaele

2012-05-16

In this work, we calculate the redox potential in a series of Ir and Ru complexes bearing a N-heterocyclic carbene (NHC) ligand presenting different Y groups in the para position of the aromatic N-substituent. The calculated redox potentials excellently correlate with the experimental ΔE 1/2 potentials, offering a handle to rationalize the experimental findings. Analysis of the HOMO of the complexes before oxidation suggests that electron-donating Y groups destabilize the metal centered HOMO. Energy decomposition of the metal-NHC interaction indicates that electron-donating Y groups reinforce this interaction in the oxidized complexes. Analysis of the electron density in the reduced and oxidized states of representative complexes indicates a clear donation from the C ipso of the N-substituents to an empty d orbital on the metal. In case of the Ru complexes, this mechanism involves the Ru-alkylidene moiety. All of these results suggest that electron-donating Y groups render the aromatic N-substituent able to donate more density to electron-deficient metals through the C ipso atom. This conclusion suggests that electron-donating Y groups could stabilize higher oxidation states during catalysis. To test this hypothesis, we investigated the effect of differently donating Y groups in model reactions of Ru-catalyzed olefin metathesis and Pd-catalyzed C-C cross-coupling. Consistent with the experimental results, calculations indicate an easier reaction pathway if the N-substituent of the NHC ligand presents an electron-donating Y group. © 2012 American Chemical Society.

Tuning and Quantifying Steric and Electronic Effects of N-Heterocyclic Carbenes

KAUST Repository

Falivene, Laura

2014-07-12

This chapter states that the main handles for tuning steric and electronic effects are the substituents on N atoms, the nature of the C4-C5 bridge (either saturated or unsaturated), and the substituents on the C4 and C5 atoms. The initial intuition that steric properties of N-heterocyclic carbenes (NHCs) could be modulated and could impact catalytic behavior stimulated the development of steric descriptors to quantify the steric requirement of different NHCs and, possibly, to compare them with tertiary phosphines. NHCs can be classified as typically strong σ-basic/π-acid ligands, although they have been also shown to exhibit reasonable π-basic properties. This electronic modularity allows NHC ligands to adapt flexibly to different chemical environments represented by a transition metal and the other ligands. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA. All rights reserved.

Secondary ligand-directed assembly of Co(II) coordination polymers based on a pyridine carboxylate ligand

International Nuclear Information System (INIS)

Cao, Ke-Li; Zhang, Yi-Ping; Cai, Yi-Ni; Xu, Xiao-Wei; Feng, Yun-Long

2014-01-01

To investigate the influence of hydrogen bonds and secondary ligands on the structures and properties of the resulting frameworks, five new Co(II) compounds have been synthesized by the reactions of Co(II) salts and 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL) with four rationally selected dicarboxylic acid ligands. Without secondary ligand, we got one compound [CoL 2 (H 2 O) 2 ] n ·2nH 2 O (1), which possesses a 1D chain structure. In the presence of ancillary ligands, namely, 1,3-adamantanedicarboxylic acid (H 2 adbc), terephthalic acid (H 2 tpa), thiophene-2,5-dicarboxylic acid (H 2 tdc) and 1,4-benzenedithioacetic acid (H 2 bdtc), four 3D structures [Co 2 L 2 (adbc)] n ·nH 2 O (2), [Co 2 L 2 (tpa)] n (3), [Co 2 L 2 (tdc)] n (4), [Co 2 L 2 (bdtc)(H 2 O)] n (5) were obtained, respectively. It can be observed from the architectures of 1–5 that hydrogen bonds and secondary ligands both have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. The XRPD, TGA data of title polymers and the magnetic properties for 2 and 5 have also been investigated. - Graphical abstract: The structural differences show that the ancillary ligands have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. - Highlights: • Five new Co(II) coordination polymers have been synthesized by solvothermal reactions based on 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL). • The long-flexible ligand (HL) is a good candidate to produce interpenetrating architectures. • The secondary dicarboxylic acid ligands play important roles in the spatial connective fashions and the formation of various dimensional compounds. • The magnetism studies show that both 2 and 5 exhibit antiferromagnetic interactions

Anaerobic biodegradation of halogenated and nonhalogenated N-, s-, and o-heterocyclic compounds in aquifer slurries

Science.gov (United States)

Adrian, Neal R.; Suflita, Joseph M.

1994-01-01

The fate of several halogenated and nonhalogenated heterocyclic compounds in anoxic aquifer slurries was investigated Substrate depletion and methane formation were monitored in serum bottle incubations by HPLC and GC, respectively Pyridine, pyrimidine, thiophene, and furan were not mineralized following an 11-month incubation, but the corresponding carboxylated or oxygenated compounds were That is, >74% of the theoretically expected amount of methane was recovered from nicotinic acid, uracil, or 2-furoic acid Chlorinated derivatives, like 2 chloro- or 6-chloronicotinic acid, as well as 4 chloro- and 5-chlorouracil resisted mineralization However, 5-bromouracil was reductively dehalogenated to stoichiometric amounts of uracil, whereas 2-chloropyrimidine was metabolized to a more polar unidentified compound that resisted further anaerobic biodegradation Microorganisms acclimated to 5-bromouracil were unable to transform 4 chloro or 5 chlorouracil These findings illustrate how the structure of heterocyclic contaminants influences their susceptibility to anaerobic decay

Sacrificial spacer and non-covalent routes toward the molecular imprinting of 'poorly-functionalized' N-heterocycles

International Nuclear Information System (INIS)

Kirsch, N.; Alexander, C.; Davies, S.; Whitcombe, M.J.

2004-01-01

A comparison of three different methods for the imprinting of small aromatic heterocycles containing only a single nitrogen atom, for the preparation of specific analytical phases, was carried out. A conventional non-covalent approach to the imprinting of pyridine using methacrylic acid as the functional monomer was compared with two sacrificial spacer methods, in which heterocycles were imprinted as covalent template analogues. The results of binding experiments showed that discrimination based on ligand size was possible when polymers were prepared using a silyl ester-based template. The most selective polymer was able to bind pyridine in preference to quinoline or acridine which is opposite to the trend predicted by the pK HB values for the three ligands. Curve fitting of the isotherm for pyridine binding to this polymer to the Langmuir model gave an approximate K d of 1.1±0.1 mM and a binding site concentration of 57±2 mmol g -1 . Acridine binding did not show saturation behaviour and was non-specific and cooperative in nature

Design and synthesis of a tetradentate '3-amine-1-carboxylate' ligand to mimic the metal binding environment at the non-heme iron(II) oxidase active site.

Science.gov (United States)

Dungan, Victoria J; Ortin, Yannick; Mueller-Bunz, Helge; Rutledge, Peter J

2010-04-07

Non-heme iron(II) oxidases (NHIOs) catalyse a diverse array of oxidative chemistry in Nature. As part of ongoing efforts to realize biomimetic, iron-mediated C-H activation, we report the synthesis of a new 'three-amine-one-carboxylate' ligand designed to complex with iron(II) and mimic the NHIO active site. The tetradentate ligand has been prepared as a single enantiomer in nine synthetic steps from N-Cbz-L-alanine, pyridine-2,6-dimethanol and diphenylamine, using Seebach oxazolidinone chemistry to control the stereochemistry. X-Ray crystal structures are reported for two important intermediates, along with variable temperature NMR experiments to probe the hindered interconversion of conformational isomers of several key intermediates, 2,6-disubstituted pyridine derivatives. The target ligand and an N-Cbz-protected precursor were each then complexed with iron(II) and tested for their ability to promote alkene dihydroxylation, using hydrogen peroxide as the oxidant.

Assembly of Four Diverse Heterocyclic Libraries Enabled by Prins Cyclization, Au-Catalyzed Enyne Cycloisomerization, and Automated Amide Synthesis

Science.gov (United States)

Cui, Jiayue; Chai, David I.; Miller, Christopher; Hao, Jason; Thomas, Christopher; Wang, JingQi; Scheidt, Karl A.; Kozmin, Sergey A.

2013-01-01

We describe a unified synthetic strategy for efficient assembly of four new heterocyclic libraries. The synthesis began by creating a range of structurally diverse pyrrolidinones or piperidinones. Such compounds were obtained in a simple one-flask operation starting with readily available amines, ketoesters, and unsaturated anhydrides. The use of tetrahydropyran-containing ketoesters, which were rapidly assembled by our Prins cyclization protocol, enabled efficient fusion of pyran and piperidinone cores. A newly developed Au(I)-catalyzed cycloisomerization of alkyne-containing enamides further expanded heterocyclic diversity by providing rapid entry into a wide range of bicyclic and tricyclic dienamides. The final stage of the process entailed diversification of each of the initially produced carboxylic acids using a fully automated platform for amide synthesis, which delivered 1872 compounds in high diastereomeric and chemical purity. PMID:22860634

NHC-Ag/Pd-Catalyzed Reductive Carboxylation of Terminal Alkynes with CO2 and H2 : A Combined Experimental and Computational Study for Fine-Tuned Selectivity.

Science.gov (United States)

Yu, Dingyi; Zhou, Feng; Lim, Diane S W; Su, Haibin; Zhang, Yugen

2017-03-09

Reductive carboxylation of terminal alkynes utilizing CO 2 and H 2 as reactants is an interesting and challenging transformation. Theoretical calculations indicated it would be kinetically possible to obtain cinnamic acid, the reductive carboxylation product, from phenylacetylene in a CO 2 /H 2 system with an N-heterocyclic carbene (NHC)-supported Ag/Pd bimetallic catalysts through competitive carboxylation/hydrogenation cascade reactions in one step. These calculations were verified experimentally with a poly-NHC-supported Ag/Pd catalyst. By tuning the catalyst composition and reaction temperature, phenylacetylene was selectively converted to cinnamic acid, hydrocinnamic acid, or phenylpropiolic acid in excellent yields. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Silver(I) and copper(II)-imidazolium carboxylates: Efficient catalysts ...

Indian Academy of Sciences (India)

GANESAN PRABUSANKAR

the reaction between corresponding carboxylic acid ligands and metal salts. These new metal .... g), DMF (2 mL) and water (1 mL) was added; then, the sus- pension was ..... ence of five mol% potassium hydroxide as base in 1 and. Scheme 3.

Synthesis, Structure and Catalytic Activity of NHC-AgICarboxylate Complexes

KAUST Repository

Wong, Valerie H. L.; Vummaleti, Sai V. C.; Cavallo, Luigi; White, Andrew J. P.; Nolan, Steven P.; Hii, King Kuok Mimi

2016-01-01

A general synthetic route was used to prepare 15 new N-heterocyclic carbene (NHC)–AgI complexes bearing anionic carboxylate ligands [Ag(NHC)(O2CR)], including a homologous series of complexes of sterically flexible ITent ligands, which permit a systematic spectroscopic and theoretical study of the structural and electronic features of these compounds. The complexes displayed a significant ligand-accelerated effect in the intramolecular cyclisation of propargylic amides to oxazolidines. The substrate scope is highly complementary to that previously achieved by NHC–Au and pyridyl–AgI complexes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Synthesis, Structure and Catalytic Activity of NHC-AgICarboxylate Complexes

KAUST Repository

Wong, Valerie H. L.

2016-08-03

A general synthetic route was used to prepare 15 new N-heterocyclic carbene (NHC)–AgI complexes bearing anionic carboxylate ligands [Ag(NHC)(O2CR)], including a homologous series of complexes of sterically flexible ITent ligands, which permit a systematic spectroscopic and theoretical study of the structural and electronic features of these compounds. The complexes displayed a significant ligand-accelerated effect in the intramolecular cyclisation of propargylic amides to oxazolidines. The substrate scope is highly complementary to that previously achieved by NHC–Au and pyridyl–AgI complexes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Iron(III) complexes of certain tetradentate phenolate ligands as ...

Indian Academy of Sciences (India)

non-heme iron enzymes, which catalyse the oxidative cleavage of catechols to cis, cis-muconic acids with the incorporation of ... nature of heterocyclic rings of the ligands and the methyl substituents on them regulate the electronic spectral features .... and simple substitution reactions.19,21 The complexes of [H2(L5)] and ...

Sacrificial spacer and non-covalent routes toward the molecular imprinting of 'poorly-functionalized' N-heterocycles

Energy Technology Data Exchange (ETDEWEB)

Kirsch, N.; Alexander, C.; Davies, S.; Whitcombe, M.J

2004-02-16

A comparison of three different methods for the imprinting of small aromatic heterocycles containing only a single nitrogen atom, for the preparation of specific analytical phases, was carried out. A conventional non-covalent approach to the imprinting of pyridine using methacrylic acid as the functional monomer was compared with two sacrificial spacer methods, in which heterocycles were imprinted as covalent template analogues. The results of binding experiments showed that discrimination based on ligand size was possible when polymers were prepared using a silyl ester-based template. The most selective polymer was able to bind pyridine in preference to quinoline or acridine which is opposite to the trend predicted by the pK{sub HB} values for the three ligands. Curve fitting of the isotherm for pyridine binding to this polymer to the Langmuir model gave an approximate K{sub d} of 1.1{+-}0.1 mM and a binding site concentration of 57{+-}2 mmol g{sup -1}. Acridine binding did not show saturation behaviour and was non-specific and cooperative in nature.

Synthesis and Properties of Chelating N-Heterocyclic Carbene Rhodium(I) Complexes: Synthetic Experiments in Current Organometallic Chemistry

Science.gov (United States)

Mata, Jose A.; Poyatos, Macarena; Mas-Marza, Elena

2011-01-01

The preparation and characterization of two air-stable Rh(I) complexes bearing a chelating N-heterocyclic carbene (NHC) ligand is described. The synthesis involves the preparation of a Ag(I)-NHC complex and its use as carbene transfer agent to a Rh(I) precursor. The so obtained complex can be further reacted with carbon monoxide to give the…

Steric Maps to Evaluate the Role of Steric Hindrance on the IPr NHC Ligand

KAUST Repository

Poater, Albert; Falivene, Laura; Urbina-Blanco, Cé sar A.; Manzini, Simone; Nolan, Steven P.; Cavallo, Luigi

2013-01-01

Density functional theory (DFT) calculations were used to predict and rationalize the effect of the modification of the structure of the prototype 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) (IPr) N-heterocyclic carbene (NHC) ligand

Water oxidation catalyzed by mononuclear ruthenium complexes with a 2,2'-bipyridine-6,6'-dicarboxylate (bda) ligand: how ligand environment influences the catalytic behavior.

Science.gov (United States)

Staehle, Robert; Tong, Lianpeng; Wang, Lei; Duan, Lele; Fischer, Andreas; Ahlquist, Mårten S G; Sun, Licheng; Rau, Sven

2014-02-03

A new water oxidation catalyst [Ru(III)(bda)(mmi)(OH2)](CF3SO3) (2, H2bda = 2,2'-bipyridine-6,6'-dicarboxylic acid; mmi = 1,3-dimethylimidazolium-2-ylidene) containing an axial N-heterocyclic carbene ligand and one aqua ligand was synthesized and fully characterized. The kinetics of catalytic water oxidation by 2 were measured using stopped-flow technique, and key intermediates in the catalytic cycle were probed by density functional theory calculations. While analogous Ru-bda water oxidation catalysts [Ru(bda)L2] (L = pyridyl ligands) are supposed to catalyze water oxidation through a bimolecular coupling pathway, our study points out that 2, surprisingly, undergoes a single-site water nucleophilic attack (acid-base) pathway. The diversion of catalytic mechanisms is mainly ascribed to the different ligand environments, from nonaqua ligands to an aqua ligand. Findings in this work provide some critical proof for our previous hypothesis about how alternation of ancillary ligands of water oxidation catalysts influences their catalytic efficiency.

Pd(OAc)2/Ph3P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles.

Science.gov (United States)

Kellner, Dominik; Weger, Maximilian; Gini, Andrea; Mancheño, Olga García

2017-01-01

The palladium-catalyzed dimerization of isoprene is a practical approach of synthesizing monoterpenes. Though several highly selective methods have been reported, most of them still required pressure or costly ligands for attaining the active system and desired selectivity. Herein, we present a simple and economical procedure towards the tail-to-tail dimer using readily available Pd(OAc) 2 and inexpensive triphenylphosphine as ligand. Furthermore, simple screw cap vials are employed, allowing carrying out the reaction at low pressure. In addition, the potential of the dimer as a chemical platform for the preparation of heterocyclic terpenes by subsequent (hetero)-Diels-Alder or [4 + 1]-cycloadditions with nitrenes is also depicted.

Spectroscopic study of cadmium (II) complexes with heterocyclic dithiocarbamate ligands

International Nuclear Information System (INIS)

Garcia-Fontan, S.; Rodriguez-Seoane, P.; Casas, J.S.; Sordo, J.; Jones, M.M.

1993-01-01

Cadmium(II) dithiocarbamates [Cd(dtc) 2 ] (dtc=4-carboxamidopiperidine-1-carbodithioate, morpholine-1-carbodithioate or 4-(2-hydroxyethyl)piperazine-1-carbodithioate) and [Cd(dtc) 2 ].H 2 O (dtc=4-hydroxypiperidine-1-carbodithioate} have been prepared and characterized by thermal analysis and IR and NMR ( 13 C, 113 Cd) spectrometry. Two of these ligands have previously been shown capable of removing cadmium from its aged in vivo storage sites. The use of solid state 13 C NMR measurements to establish the coordination mode of the dithiocarbomate ligands is also examined and the difficulties which arise are discussed. (orig.)

Optimized Syntheses of Cyclopentadienyl Nickel Chloride Compounds Containing "N"-Heterocyclic Carbene Ligands for Short Laboratory Periods

Science.gov (United States)

Cooke, Jason; Lightbody, Owen C.

2011-01-01

Experiments are described for the preparation of imidazolium chloride precursors to "N"-heterocyclic carbenes and their cyclopentadienyl nickel chloride derivatives. The syntheses have been optimized for second- and third-year undergraduate laboratories that have a maximum programmed length of three hours per week. The experiments are flexible and…

The tert-Amino Effect in Heterocyclic Chemistry. Synthesis of Spiro Heterocycles

Directory of Open Access Journals (Sweden)

Y. Morzherin

2005-09-01

Full Text Available The tert-amino reaction effect was examined. A new method to synthesize spiro heterocycles is presented. It was shown that the “tert-amino effect” could be applied to the formation of spiro-fused heterocycles. The formation of spiro compounds proceeds in most cases in good yields in a one-pot reaction.

Heterocyclic Scaffolds: Centrality in Anticancer Drug Development.

Science.gov (United States)

Ali, Imran; Lone, Mohammad Nadeem; Al-Othman, Zeid A; Al-Warthan, Abdulrahman; Sanagi, Mohd Marsin

2015-01-01

Cancer has been cursed for human beings for long time. Millions people lost their lives due to cancer. Despite of the several anticancer drugs available, cancer cannot be cured; especially at the late stages without showing any side effect. Heterocyclic compounds exhibit exciting medicinal properties including anticancer. Some market selling heterocyclic anticancer drugs include 5-flourouracil, methortrexate, doxorubicin, daunorubicin, etc. Besides, some natural products such as vinblastine and vincristine are also used as anticancer drugs. Overall, heterocyclic moeities have always been core parts in the expansion of anticancer drugs. This article describes the importance of heterocyclic nuclei in the development of anticancer drugs. Besides, the attempts have been made to discuss both naturally occurring and synthetic heterocyclic compounds as anticancer agents. In addition, some market selling anticancer heterocyclic compounds have been described. Moreover, the efforts have been made to discuss the mechanisms of actions and recent advances in heterocyclic compounds as anticancer agents. The current challenges and future prospectives of heterocyclic compounds have also been discussed. Finally, the suggestions for syntheses of effective, selective, fast and human friendly anticancer agents are discussed into the different sections.

Co(II) and Cd(II) Complexes Derived from Heterocyclic Schiff-Bases: Synthesis, Structural Characterisation, and Biological Activity

Science.gov (United States)

Ahmed, Riyadh M.; Yousif, Enaam I.; Al-Jeboori, Mohamad J.

2013-01-01

New monomeric cobalt and cadmium complexes with Schiff-bases, namely, N′-[(E)-(3-hydroxy-4-methoxyphenyl)methylidene]furan-2-carbohydrazide (L1) and N′-[(E)-(3-hydroxy-4-methoxyphenyl)methylidene]thiophene-2-carbohydrazide (L2) are reported. Schiff-base ligands L1 and L2 were derived from condensation of 3-hydroxy-4-methoxybenzaldehyde (iso-vanillin) with furan-2-carboxylic acid hydrazide and thiophene-2-carboxylic acid hydrazide, respectively. Complexes of the general formula [M(L)2]Cl2 (where M = Co(II) or Cd(II), L = L1 or L2) have been obtained from the reaction of the corresponding metal chloride with the ligands. The ligands and their metal complexes were characterised by spectroscopic methods (FTIR, UV-Vis, 1H, and 13C NMR spectra), elemental analysis, metal content, magnetic measurement, and conductance. These studies revealed the formation of four-coordinate complexes in which the geometry about metal ion is tetrahedral. Biological activity of the ligands and their metal complexes against gram positive bacterial strain Bacillus (G+) and gram negative bacteria Pseudomonas (G−) revealed that the metal complexes become less resistive to the microbial activities as compared to the free ligands. PMID:24027449

Olefin Metathesis with Ru-Based Catalysts Exchanging the Typical N-Heterocyclic Carbenes by a Phosphine–Phosphonium Ylide

Directory of Open Access Journals (Sweden)

Laia Arnedo

2017-03-01

Full Text Available Density functional theory (DFT calculations have been used to describe the first turnover of an olefin metathesis reaction calling for a new in silico family of homogenous Ru-based catalysts bearing a phosphine–phosphonium ylide ligand, with ethylene as a substrate. Equal to conventional Ru-based catalysts bearing an N-heterocyclic carbene (NHC ligand, the activation of these congeners occurs through a dissociative mechanism, with a more exothermic first phosphine dissociation step. In spite of a stronger electron-donating ability of a phosphonium ylide C-ligand with respect to a diaminocarbene analogue, upper energy barriers were calculated to be on average ca. 5 kcal/mol higher than those of Ru–NHC standards. Overall, the study also highlights advantages of bidentate ligands over classical monodentate NHC and phosphine ligands, with a particular preference for the cis attack of the olefin. The new generation of catalysts is constituted by cationic complexes potentially soluble in water, to be compared with the typical neutral Ru–NHC ones.

In-situ carboxylation and synthesis of two novel Sm(III) coordination polymers assembled from 5-hydroxyisophthalate and nitrate, chloride in hydrothermal reaction

International Nuclear Information System (INIS)

Huang Yan; Yan Bing; Shao Min

2008-01-01

By reactions of 5-hydroxyisophthalic acid (H 2 hisp) with Sm(NO 3 ) 3 .6H 2 O or SmCl 3 .6H 2 O in the presence of NaOH, two kinds of samarium coordination polymers, [Sm(H 2 hbtc)(ox) 0.5 (H 2 O) 3 ] n .nH 2 O (1) (H 2 hbtc 2- =6-hydroxy-1,2,4-benzenetricarboxylate) and [Sm(hisp)(Hhisp)(H 2 O) 2 ] n .2nH 2 O (2), have been hydrothermal synthesized and characterized. Single-crystal X-ray analyses reveal that compound 1 features a novel two-dimensional (2D) stair-like structure with oxalate ligands and the new organic ligand (H 2 hbtc 2- ) but without 5-hydroxyisophthalate ligands, while compound 2 gives the expected product and displays a novel layer structure. The oxalate ligands have been formed via the in-situ reductive coupling of CO 2 molecules released from the decomposition of carboxylate ligands with the reduction of NO 3 - and the new organic ligands have been formed via the in-situ carboxylation under the presence of NO 3 - . Reported herein are the syntheses of compounds 1 and 2, crystal structures and possible mechanism information regarding the in-situ carboxylation. - Graphical abstract: Hydrothermal reactions of Sm(NO 3 ) 3 .6H 2 O or SmCl 3 .6H 2 O with 5-hydroxyisophthalic acid (H 2 hisp) have given rise to two different kinds of Sm(III) coordination polymers. Single-crystal X-ray analyses reveal that compound 1 features a novel 2D stair-like structure with oxalate and a new organic ligand, 6-hydroxy-1,2,4-benzenetricarboxylate, while compound 2 gives the normal product and displays a novel 2D layer structure. Oxalate ligands have been formed via the in-situ reductive coupling of CO 2 molecules released from the decomposition of 5-hydroxyisophthalate ligands with the reduction of NO 3 - and the new organic ligands have been formed via the in-situ carboxylation under the presence of NO 3 -

Synthesis of first row transition metal carboxylate complexes by ring ...

Indian Academy of Sciences (India)

tion of pyromellitic dianhydride with methanol and ring opening of pyromellitic dianhydride takes place. The corresponding carboxylate complex formed dur- ing the process can be crystallised by adding biden- tate nitrogen donor ligands such as 1,10-phenanthroline or 2,2 - bipyridine.20 From the reaction with 1,10-.

Pd(OAc2/Ph3P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles

Directory of Open Access Journals (Sweden)

Dominik Kellner

2017-08-01

Full Text Available The palladium-catalyzed dimerization of isoprene is a practical approach of synthesizing monoterpenes. Though several highly selective methods have been reported, most of them still required pressure or costly ligands for attaining the active system and desired selectivity. Herein, we present a simple and economical procedure towards the tail-to-tail dimer using readily available Pd(OAc2 and inexpensive triphenylphosphine as ligand. Furthermore, simple screw cap vials are employed, allowing carrying out the reaction at low pressure. In addition, the potential of the dimer as a chemical platform for the preparation of heterocyclic terpenes by subsequent (hetero-Diels–Alder or [4 + 1]-cycloadditions with nitrenes is also depicted.

In Silico Olefin Metathesis with Ru-Based Catalysts Containing N-Heterocyclic Carbenes Bearing C60Fullerenes

KAUST Repository

Martínez, Juan Pablo

2016-04-10

Density functional theory calculations have been used to explore the potential of Ru-based complexes with 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) ligand backbone (A) being modified in silico by the insertion of a C60 molecule (B and C), as olefin metathesis catalysts. To this end, we investigated the olefin metathesis reaction catalyzed by complexes A, B, and C using ethylene as the substrate, focusing mainly on the thermodynamic stability of all possible reaction intermediates. Our results suggest that complex B bearing an electron-withdrawing N-heterocyclic carbene improves the performance of unannulated complex A. The efficiency of complex B is only surpassed by complex A when the backbone of the N-heterocyclic carbene of complex A is substituted by two amino groups. The particular performance of complexes B and C has to be attributed to electronic factors, that is, the electronic-donating capacity of modified SIMes ligand rather than steric effects, because the latter are predicted to be almost identical for complexes B and C when compared to those of A. Overall, this study indicates that such Ru-based complexes B and C might have the potential to be effective olefin metathesis catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In Silico Olefin Metathesis with Ru-Based Catalysts Containing N-Heterocyclic Carbenes Bearing C60Fullerenes

KAUST Repository

Martí nez, Juan Pablo; Vummaleti, Sai V. C.; Falivene, Laura; Nolan, Steven P.; Cavallo, Luigi; Solà , Miquel; Poater, Albert

2016-01-01

Density functional theory calculations have been used to explore the potential of Ru-based complexes with 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) ligand backbone (A) being modified in silico by the insertion of a C60 molecule (B and C), as olefin metathesis catalysts. To this end, we investigated the olefin metathesis reaction catalyzed by complexes A, B, and C using ethylene as the substrate, focusing mainly on the thermodynamic stability of all possible reaction intermediates. Our results suggest that complex B bearing an electron-withdrawing N-heterocyclic carbene improves the performance of unannulated complex A. The efficiency of complex B is only surpassed by complex A when the backbone of the N-heterocyclic carbene of complex A is substituted by two amino groups. The particular performance of complexes B and C has to be attributed to electronic factors, that is, the electronic-donating capacity of modified SIMes ligand rather than steric effects, because the latter are predicted to be almost identical for complexes B and C when compared to those of A. Overall, this study indicates that such Ru-based complexes B and C might have the potential to be effective olefin metathesis catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterisation of nitrogen poly-heterocyclic molecules using as selective complexing agents of metallic cations

International Nuclear Information System (INIS)

Alphonse, F.A.

2003-12-01

Separation of actinides (III) from lanthanides (III) is a crucial problem in the reprocessing of used nuclear fuels. Experimental results shown that soft donor extractants such as nitrogen polydentate heterocycles containing a NCCNCCN coordination site are potentials ligands for selective extraction of actinides (III). In those cases, two types of liquid-liquid extractions are employed: synergistic combination with lipophilic acid extractants and direct extraction. On the basis of the Hard and Soft Acids and Bases theory and basicity evaluation, new extractants were defined. We have first studied the synthesis of potential 1,3,5-triazine ligands designed for extraction in synergy with α-bromodecanoic acid. Secondly, we have examined the synthesis of bis-triazinyl-pyridine ligands for direct extraction studies. Extraction tests were carried out and perspectives of synthesis were deducted from those extraction results. (author)

Coordination chemistry of gadolinium complexes having pyridine carboxylate units in relation with the medical imagery

International Nuclear Information System (INIS)

Gateau, C.; Chatterton, N.; Nonat, A.; Mazzanti, M.; Pecaut, J.; Borel, A.; Merbach, A.; Heim, L.

2005-01-01

In order to study the influence of the coordination sphere on the properties which govern the relaxivity, ligands containing pyridine carboxylates units have been particularly studied. It has been shown that the tripodal ligand tpaa forms with gadolinium (III) a neutral complex having a relaxivity (r1p=13.3 mM -1 at 298 K and 60 MHz) which is three times superior to the contrast agents currently used in NMR Imaging. To explain this remarkably relaxivity, two new ligands analogous to the tpaa: the tpatcn and the bpeda containing pyridine carboxylate units bound to one or several aliphatic nitrogen have been studied in modulating the number of coordination sites and the symmetry degree. The study of the relaxivity of the corresponding gadolinium (III) complexes gives precious data on the understanding of the results in the case of the complex [Gd(tpaa)]. The synthesis and the properties of these gadolinium (III) complexes will be presented during this conference. (O.M.)

3,6-Bis(2-pyrazinyl)-1,2,4,5-tetrazin: Ein neuer mehrfunktioneller Ligand und sein syn,fac-konfigurierter Bis(tricarbonylchlororhenium)-Komplex

Czech Academy of Sciences Publication Activity Database

Sarkar, B.; Kaim, W.; Schleid, T.; Hartenbach, I.; Fiedler, Jan

2003-01-01

Roč. 629, - (2003), s. 1353-1357 ISSN 0044-2313 R&D Projects: GA MŠk OC D14.20; GA MŠk OC D15.10 Institutional research plan: CEZ:AV0Z4040901 Keywords : carbonyl ligands * heterocyclic ligands * rhenium Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.127, year: 2003

Organic carboxylate anions effect on the structures of a series of Mn(II) complexes based on 2-phenylimidazo[4,5-f]1,10-phenanthroline ligand

International Nuclear Information System (INIS)

Wang Xiuli; Chen Yongqiang; Liu Guocheng; Lin Hongyan; Zhang Jinxia

2009-01-01

In our efforts to tune the structures of Mn(II) complexes by selection of organic carboxylic acid ligands, six new complexes [Mn(PIP) 2 Cl 2 ] (1), [Mn(PIP) 2 (4,4'-bpdc)(H 2 O)].2H 2 O (2), [Mn(PIP) 2 (1,4-bdc)] (3), [Mn(PIP)(1,3-bdc)] (4), [Mn(PIP) 2 (2,6-napdc)].H 2 O (5), and [Mn(PIP)(1,4-napdc)].H 2 O (6) were obtained, where PIP=2-phenylimidazo[4,5-f]1,10-phenanthroline, 4,4'-H 2 bpdc=biphenyl-4,4'-dicarboxylic acid, 1,4-H 2 bdc=benzene-1,4-dicarboxylic acid, 1,3-H 2 bdc=benzene-1,3-dicarboxylic acid, 2,6-H 2 napdc=2,6-naphthalenedicarboxylic acid, 1,4-H 2 napdc=1,4-naphthalenedicarboxylic acid. All complexes have been structurally characterized by IR, elemental analyses, and single crystal X-ray diffraction. Structural analyses show that complexes 1 and 2 possess mononuclear structures, complexes 3, 4, and 5 feature chain structures, and complex 6 exhibits a 2D (4,4) network. The structural difference of 1-6 indicates that organic carboxylate anions play important roles in the formation of such coordination architectures. Furthermore, the thermal properties of complexes 1-6 and the magnetic property of 4 have been investigated. - Graphical Abstract: Through selecting organic carboxylate anions, six Mn(II) complexes have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction.

Carboxylic acid effects on the size and catalytic activity of magnetite nanoparticles.

Science.gov (United States)

Hosseini-Monfared, Hassan; Parchegani, Fatemeh; Alavi, Sohaila

2015-01-01

Magnetite nanoparticles (Fe3O4-NPs) were successfully synthesized in diethylene glycol in the presence of carboxylic acids. They were characterized using XRD, SEM and FTIR. Carboxylic acid plays a critical role in determining the morphology, particle size and size distribution of the resulting particles. The results show that as-prepared magnetite nanoparticles are monodisperse and highly crystalline. The nanoparticles can be easily dispersed in aqueous media and other polar solvents due to coated by a layer of hydrophilic polyol and carboxylic acid ligands in situ. Easily prepared Fe3O4-NPs have been shown to be an active, recyclable, and highly selective catalyst for the epoxidation of cyclic olefins with aqueous 30% H2O2. Copyright © 2014 Elsevier Inc. All rights reserved.

A General Ligand Design for Gold Catalysis allowing Ligand-Directed Anti Nucleophilic Attack of Alkynes

Science.gov (United States)

Wang, Yanzhao; Wang, Zhixun; Li, Yuxue; Wu, Gongde; Cao, Zheng; Zhang, Liming

2014-01-01

Most homogenous gold catalyses demand ≥0.5 mol % catalyst loading. Due to the high cost of gold, these reactions are unlikely to be applicable in medium or large scale applications. Here we disclose a novel ligand design based on the privileged biphenyl-2-phosphine framework that offers a potentially general approach to dramatically lowering catalyst loading. In this design, an amide group at the 3’ position of the ligand framework directs and promotes nucleophilic attack at the ligand gold complex-activated alkyne, which is unprecedented in homogeneous gold catalysis considering the spatial challenge of using ligand to reach antiapproaching nucleophile in a linear P-Au-alkyne centroid structure. With such a ligand, the gold(I) complex becomes highly efficient in catalyzing acid addition to alkynes, with a turnover number up to 99,000. Density functional theory calculations support the role of the amide moiety in directing the attack of carboxylic acid via hydrogen bonding. PMID:24704803

Photo- and thermochromic and adsorption properties of porous coordination polymers based on bipyridinium carboxylate ligands.

Science.gov (United States)

Toma, Oksana; Mercier, Nicolas; Allain, Magali; Kassiba, Abdel Adi; Bellat, Jean-Pierre; Weber, Guy; Bezverkhyy, Igor

2015-09-21

The zwitterionic bipyridinium carboxylate ligand 1-(4-carboxyphenyl)-4,4'-bipyridinium (hpc1) in the presence of 1,4-benzenedicarboxylate anions (BDC(2-)) and Zn(2+) ions affords three porous coordination polymers (PCPs): [Zn5(hpc1)2(BDC)4(HCO2)2]·2DMF·EtOH·H2O (1), [Zn3(hpc1)(BDC)2(HCO2)(OH)(H2O)]·DMF·EtOH·H2O (2), and [Zn10(hpc1)4(BDC)7(HCO2)2(OH)4(EtOH)2]·3DMF·3H2O (3), with the formate anions resulting from the in situ decomposition of dimethylformamide (DMF) solvent molecules. 1 and 3 are photo- and thermochromic, turning dark green as a result of the formation of bipyridinium radicals, as shown by electron paramagnetic resonance measurements. Particularly, crystals of 3 are very photosensitive, giving an eye-detectable color change upon exposure to the light of the microscope in air within 1-2 min. A very nice and interesting feature is the regular discoloration of crystals from the "edge" to the "core" upon exposition to O2 (reoxidation of organic radicals) due to the diffusion of O2 inside the pores, with this discoloration being slower in an oxygen-poor atmosphere. The formation of organic radicals is explained by an electron transfer from the oxygen atoms of the carboxylate groups to pyridinium cycles. In the structure of 3', [Zn10(hpc1)4(BDC)7(OH)6(H2O)2], resulting from the heating of sample 3 (desolvation and loss of CO molecules due to the decomposition of formate anions), no suitable donor-acceptor interaction is present, and as a consequence, this compound does not exhibit any chromic properties. The presence of permanent porosity in desolvated 1, 2, and 3' is confirmed by methanol adsorption at 25 °C with the adsorbed amount reaching 5 wt % for 1, 10 wt % for 3', and 13 wt % for 2. The incomplete desorption of methanol at 25 °C under vacuum points to strong host-guest interactions.

Radical C-H functionalization to construct heterocyclic compounds.

Science.gov (United States)

Yu, Jin-Tao; Pan, Changduo

2016-02-07

Heterocyclic compounds are widely present in natural products, pharmaceuticals and bioactive molecules. Thus, organic and pharmaceutical chemists have been making extensive efforts to construct those heterocyclic frameworks through developing versatile and efficient synthetic strategies. The direct C-H functionalization via the radical pathway has emerged as a promising and dramatic approach towards heterocycles with high atom- and step-economy. Heterocyclic compounds such as coumarins, furans, benzofurans, xanthones, benzothiazoles, indoles, indolines, oxindoles, quinolines, isoquinolines, quinoxaline, and phenanthridines have been successfully synthesized by C-H functionalization through the radical pathway. In this review, recent advances on radical C-H functionalization to construct heterocyclic compounds are highlighted with discussions.

Crystal and molecular structure of three molybdenum (6) dioxocomplexes with heterocyclic hydrazones

International Nuclear Information System (INIS)

Ilyukhin, A.B.; Sergienko, V.S.

1994-01-01

The X-ray diffraction investigation into three Mo(6) dioxocomplexes with heterocyclic hydrazones has been made. In all compounds the Mo atom has a deformed octahedral coordination by two O atoms of cis-dioxogroups, N atoms (azomethane), N (heterocyclie), O (phenol) of tridentate organic ligand. Sixth position in Mo coordination octahedron is due to O atom of methanol solvated molecule in the 1,3 structures or N atom of γ-picoline molecule in the 2 structure. The packing of structural units in the crystals of the 1-3 compounds is under consideration. 12 refs., 5 figs., 3 tabs

Diaqua­bis­(pyridine-2-carboxyl­ato-κ2 N,O)manganese(II) dimethyl­formamide hemisolvate

Science.gov (United States)

Golenya, Irina A.; Boyko, Alexander N.; Kalibabchuk, Valentina A.; Haukka, Matti; Tomyn, Stefania V.

2011-01-01

There are two crystallographically independent complex mol­ecules with very similar geometries in the unit cell of the title compound, [Mn(C6H4NO2)2(H2O)2]·0.5C3H7NO. The central ion is situated in a distorted octa­hedral environment of two N- and four O-donor atoms from two pyridine-2-carboxyl­ate ligands and two cis-disposed water mol­ecules. The carboxyl­ate ligands are coordinated in a chelate fashion with the formation of two five-membered rings. In the crystal, the complex mol­ecules are connected by O—H⋯O hydrogen bonds between the coordinated water mol­ecules and the uncoordinated carboxyl­ate O atoms, thus forming hydrogen-bonded walls disposed perpendicularly to the bc plane. PMID:22219799

Synthesis of New Functionalized Indoles Based on Ethyl Indol-2-carboxylate

Directory of Open Access Journals (Sweden)

Ahmed T. A. Boraei

2016-03-01

Full Text Available Successful alkylations of the nitrogen of ethyl indol-2-carboxylate were carried out using aq. KOH in acetone. The respective N-alkylated acids could be obtained without separating the N-alkylated esters by increasing the amount of KOH and water. The use of NaOMe in methanol led to transesterification instead of the alkylation, while the use of NaOEt led to low yields of the N-alkylated acids. Hydrazinolysis of the ester gave indol-2-carbohydrazide which then was allowed to react with different aromatic aldehydes and ketones in ethanol catalyzed by acetic acid. Indol-2-thiosemicarbazide was used in a heterocyclization reaction to form thiazoles. The new structures were confirmed using NMR, mass spectrometry and X-ray single crystal analysis.

Two- and three-dimensional lanthanide-organic frameworks constructed using 1-hydro-6-oxopyridine-3-carboxylate and oxalate ligands.

Science.gov (United States)

Liu, Cai-Ming; Xiong, Ming; Zhang, De-Qing; Du, Miao; Zhu, Dao-Ben

2009-08-07

6-Hydroxypyridine-3-carboxylic acid (6-HOPy-3-CO(2)H) reacts with Ln(2)O(3) (Ln = Nd, Sm, Eu, Gd) and oxalic acid (H(2)OX) under hydrothermal conditions to generate four novel lanthanide-organic coordination polymeric networks [Ln(2)(1H-6-Opy-3-CO(2))(2)(OX)(2)(H(2)O)(3)] x 2.5 H(2)O (Ln = Nd, 1; Sm, 2; 1H-6-Opy-3-CO(2)(-) = 1-hydro-6-oxopyridine-3-carboxylate) and [Ln(1H-6-Opy-3-CO(2))(OX)(H(2)O)(2)] x H(2)O (Ln = Eu, 3; Gd, 4). The new co-ligand 1H-6-Opy-3-CO(2)(-) anion was generated by the autoisomerization of the single deprotonated 6-HOPy-3-CO(2)(-) anion (from the enol form into the ketone one). 1 and 2 are isomorphous, they possess a three-dimensional architecture constructed from Ln(3+) ions bridged by oxalate anions and two types of 1H-6-Opy-3-CO(2)(-) bridges, showing a three-nodal (4,5)-connected topology (3.4(2).5(2).6(3).7.8)(2)(3.5(3).6(2))(2)(3(2).6.7(2).8) or a simplified uninodal 6-connected topology (3(3).4(6).5(5).6), both topologies are completely new; while only one type of 1H-6-Opy-3-CO(2)(-) bridge is used to construct the two-dimensional layer networks of 3 and 4 besides oxalate bridges, both complexes 3 and 4 are isostructural, exhibiting the honeycomb topology 6(3). The lanthanide contraction effect is believed to play a key role in directing the formation of a particular structure. A magnetic study of 1-3 indicated that the coupling interaction between Ln(3+) ions is weak.

Synthesis and complexation properties towards uranyl cation of carboxylic acid derivatives of p-tert-butyl-calix[6]arene

International Nuclear Information System (INIS)

Souane, R.

2005-03-01

In the fuel reprocessing plants radioactive metals, and more particularly, uranium in UO 2 2+ form in the various installations, have many varied physico-chemical forms and there is a risk of exposure and internal contamination in the nuclear industry. It is necessary to exert a medical control to ensure the protection of the health of the workers. This medical control is done by dosing uranyl cation in the urine of the exposed people. This work forms part of this context. Indeed, we prepared a ligand able to complex the ion uranyl and which is also to be grafted on a solid support. In the family of calixarenes, the calix[6]arenes functionalized by three or four carboxylic functions were selected like chelating molecules of the ion uranyl. The properties of complexation of these calixarenes were studied by potentiometry in methanol, under these conditions balances of protonation and complexation were determined and the constant partners were obtained using the Hyperquad program. We synthesized tri-carboxylic calix[6]arenes comprising of the groupings nitro (NO 2 ) in para position of phenol in order to see the influence of a substitution in para position on the complexation. We also synthesized calix[6]arenes tetra-carboxylic in order to show the role of an additional carboxylic acid grouping. The potentiometric study determined thermodynamic parameters of protonation and complexation of carboxylic calix[6]arenes. The results of the complexation highlighted which complex UO 2 L corresponding to the ligand para-tert-butyl-calix[6]arene tetra-acid is more stable than that corresponding to the ligand mono-nitro calix[6]arene tri-acid (ΔlogΒ110 = 4.3), and than the effect of the groupings nitro in para position has low influence on the complexation of UO 2 2+ . This makes it possible to consider as possible the grafting of the calix[6]arenes which one knows the behaviour of trapping. To this end we synthesized the ligand 23. (author)

Anions mediate ligand binding in Adineta vaga glutamate receptor ion channels.

Science.gov (United States)

Lomash, Suvendu; Chittori, Sagar; Brown, Patrick; Mayer, Mark L

2013-03-05

AvGluR1, a glutamate receptor ion channel from the primitive eukaryote Adineta vaga, is activated by alanine, cysteine, methionine, and phenylalanine, which produce lectin-sensitive desensitizing responses like those to glutamate, aspartate, and serine. AvGluR1 LBD crystal structures reveal an unusual scheme for binding dissimilar ligands that may be utilized by distantly related odorant/chemosensory receptors. Arginine residues in domain 2 coordinate the γ-carboxyl group of glutamate, whereas in the alanine, methionine, and serine complexes a chloride ion acts as a surrogate ligand, replacing the γ-carboxyl group. Removal of Cl(-) lowers affinity for these ligands but not for glutamate or aspartate nor for phenylalanine, which occludes the anion binding site and binds with low affinity. AvGluR1 LBD crystal structures and sedimentation analysis also provide insights into the evolutionary link between prokaryotic and eukaryotic iGluRs and reveal features unique to both classes, emphasizing the need for additional structure-based studies on iGluR-ligand interactions. Copyright © 2013 Elsevier Ltd. All rights reserved.

Comparisons Between Tridentate Bis(benzazoles-pyridine and Bis(benzazolestriazine Ligands: a Theoretical Study

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Mihaiela Andoni

2015-12-01

Full Text Available Twelve bis(benzazole structures with potential ligand character were investigated by means of computational chemistry. Global and local reactivity descriptors within DFT (Density Functional Theory theory (Fukui functions, chemical potential, hardness, electrophilicity index have been computed at B3LYP/6-31G(d,p level of theory. NICS(0 (Nucleus Independent Chemical Shift index computations were employed for the evaluation of the local aromatic character of each heterocyclic moiety. Best results have been reported for the bis(benzimidazole derivatives. Copper and zinc complexes of the investigated tridentate ligands have been proposed.

Ternary complexes of Zn(II) and Cu(II) with 1-((2-hydroxynaphthalen-1-yl)methylene)-4-phenylthiosemicarbazide in the presence of heterocyclic bases as auxiliary ligands: Synthesis, spectroscopic and structural characterization and antibacterial activity

Science.gov (United States)

Azarkish, Mohammad; Akbari, Alireza; Sedaghat, Tahereh; Simpson, Jim

2018-03-01

The new ternary complexes, ZnLL‧ [L = 1-((2-hydroxynaphthalen-1-yl)methylene)-4-phenylthiosemicarbazide and L‧ = imidazole (1), 2, 2‧-bipyridine (2) and 2-methyimidazole (3)], Zn2L2L‧ [L‧ = 4, 4‧-bipy (4)] and CuLL‧ [L‧ = 2, 2‧-bipy (5)] have been synthesized by the reaction of a metal(II) acetate salt with the thiosemicarbazone and in presence of heterocyclic bases as auxiliary ligands. The synthesized compounds were investigated by elemental analysis and IR, 1H NMR, and 13C NMR spectroscopy and complex 5 was structurally characterized by X-ray crystallography. The results indicate the thiosemicarbazone doubly deprotonated and coordinates to metal through the thiolate sulfur, imine nitrogen and phenolic oxygen atoms. The nitrogen atom(s) of the auxiliary ligand complete the coordination sphere. Complex 4 is binuclear with 4, 4‧-bipy acting as a bridging ligand. The structure of 5 is a distorted square pyramid with one of the bipyridine nitrogen atoms in the apical position. This compound creates an inversion dimer in solid state by intermolecular hydrogen bonds of Nsbnd H⋯S type. The in vitro antibacterial activity of the synthesized compounds were evaluated against Gram-positive (B. subtilis and S. aureus) and Gram-negative (P. aeruginosa) bacteria and is compared to that of standard antibacterial drugs. All complexes exhibit good inhibitory effects and are significantly more effective than the parent ligand.

Structure and spectroscopic properties of the dimeric copper(I) N-heterocyclic carbene complex [Cu₂(CNC(t-Bu))₂](PF₆)₂.

Science.gov (United States)

Riener, Korbinian; Pöthig, Alexander; Cokoja, Mirza; Herrmann, Wolfgang A; Kühn, Fritz E

2015-08-01

In recent years, the use of copper N-heterocyclic carbene (NHC) complexes has expanded to fields besides catalysis, namely medicinal chemistry and luminescence applications. In the latter case, multinuclear copper NHC compounds have attracted interest, however, the number of these complexes in the literature is still quite limited. Bis[μ-1,3-bis(3-tert-butylimidazolin-2-yliden-1-yl)pyridine]-1κ(4)C(2),N:N,C(2');2κ(4)C(2),N:N,C(2')-dicopper(I) bis(hexafluoridophosphate), [Cu2(C19H25N5)2](PF6)2, is a dimeric copper(I) complex bridged by two CNC, i.e. bis(N-heterocyclic carbene)pyridine, ligands. Each Cu(I) atom is almost linearly coordinated by two NHC ligands and interactions are observed between the pyridine N atoms and the metal centres, while no cuprophilic interactions were observed. Very strong absorption bands are evident in the UV-Vis spectrum at 236 and 274 nm, and an emission band is observed at 450 nm. The reported complex is a new example of a multinuclear copper NHC complex and a member of a compound class which has only rarely been reported.

Carboxylated dithiafulvenes and tetrathiafulvalene vinylogues: synthesis, electronic properties, and complexation with zinc ions

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Yunfei Wang

2015-06-01

Full Text Available A class of carboxyl and carboxylate ester-substituted dithiafulvene (DTF derivatives and tetrathiafulvalene vinylogues (TTFVs has been synthesized and their electronic and electrochemical redox properties were characterized by UV–vis spectroscopic and cyclic voltammetric analyses. The carboxyl-TTFV was applied as a redox-active ligand to complex with Zn(II ions, forming a stable Zn-TTFV coordination polymer. The structural, electrochemical, and thermal properties of the coordination polymer were investigated by infrared spectroscopy, cyclic voltammetry, powder X-ray diffraction, and differential scanning calorimetric analyses. Furthermore, the microscopic porosity and surface area of the Zn-TTFV coordination polymer were measured by nitrogen gas adsorption analysis, showing a BET surface of 148.2 m2 g−1 and an average pore diameter of 10.2 nm.

Preparation and reactivity of carboxylic acid-terminated boron-doped diamond electrodes

International Nuclear Information System (INIS)

Niedziolka-Joensson, Joanna; Boland, Susan; Leech, Donal; Boukherroub, Rabah; Szunerits, Sabine

2010-01-01

The paper reports on the formation of carboxy-terminated boron-doped diamond (BDD) electrodes. The carboxylic acid termination was prepared in a controlled way by reacting photochemically oxidized BDD with succinic anhydride. The resulting interface was readily employed for the linking of an amine-terminated ligand such as an osmium complex bearing an amine terminal group. The interfaces were characterized using X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). Contact angle measurements were used to follow the changes in surface wetting properties due to surface functionalization. The chemical reactivity of the carboxyl-terminated BDD was investigated by covalent coupling of the acid groups to an amine-terminated osmium complex.

Synthesis, crystal structures, and luminescent properties of two series' of new lanthanide (III) amino-carboxylate-phosphonates.

Science.gov (United States)

Zhou, Tian-Hua; Yi, Fei-Yan; Li, Pei-Xin; Mao, Jiang-Gao

2010-02-01

Hydrothermal reactions of lanthanide(III) chlorides with 4-HOOC-C(6)H(4)-CH(2)NHCH(2)PO(3)H(2) (H(3)L) at different ligand-to-metal (L/M) ratios afforded nine new lanthanide(III) carboxylate-phosphonates with two types of 3D network structures, namely, LnCl(HL)(H(2)O)(2) (Ln = Sm, 1; Eu, 2; Gd, 3; Tb, 4; Dy, 5; Er, 6) and [Ln(2)(HL)(H(2)L)(L)(H(2)O)(2)].4H(2)O (Ln = Nd, 7; Sm, 8; Eu, 9). Compounds 1-6 are isostructural and feature a 3D network in which the LnO(7)Cl polyhedra are interconnected by bridging CPO(3) tetrahedra into 2D inorganic layers parallel to the bc plane. These layers are further cross-linked by organic groups of the carboxylate-phosphonate ligands via the coordination of the carboxylate groups into a pillared-layered architecture. Compounds 7-9 are also isostructural and feature a 3D open-framework composed of 1D lanthanide(III) phosphonate inorganic slabs which are further bridged by organic groups of the carboxylate-phosphonate liagnds via the coordination of the carboxylate groups, forming large 1D tunnels along the b-axis which are filled by lattice water molecules. Luminescent measurements indicate that compounds 2, 4, and 5 show strong emission bands in red, green, and yellow light region, respectively. Magnetic properties of 2, 3, 5, and 7 have also been studied.

Construction of a monoanionic S,N,S-pincer ligand with a pyrrole core by sequential [1,2] phospho-Fries rearrangement. Characterization of palladium and silver coordination complexes

NARCIS (Netherlands)

Fraix, A.; Lutz, M.; Spek, A.L.; Klein Gebbink, R.J.M.; van Koten, G.; Salaun, J. -Y; Jaffrès, P. -A

2010-01-01

The synthesis of an S,NH,S-pincer ligand possessing a pyrrole core and two O,O-diethylthiophosphonyl groups to design PS lateral coordination sites is reported. The synthetic procedure to produce this ligand makes use of the nitrogen atom of the pyrrole heterocycle to successively functionalize the

Reactivity of N-heterocyclic carbene-pyridine palladacyclopentadiene complexes toward halogen addition. The unpredictable course of the reaction.

Science.gov (United States)

Visentin, Fabiano; Santo, Claudio; Scattolin, Thomas; Demitri, Nicola; Canovese, Luciano

2017-08-08

As an extension of a previously published work we have reacted some palladacyclopentadiene complexes stabilized by bidentate N-heterocyclic carbene-pyridine or monodentate N-heterocyclic carbene-pyridine and isocyanide ligands with the halogens I 2 and Br 2 . All the bidentate and monodentate complexes react with halogens to give at first the expected σ-coordinated butadienyl fragment. However, two of the less hindered NHC carbene-pyridine bidentate butadienyl iodo derivatives undergo a further rearrangement and novel Pd(ii) complexes characterized by a ten term coordinative ring were isolated and characterized. In the most favorable case we were able to carry out the kinetics of rearrangement and measure its reaction rate. Moreover, we have surmised a plausible mechanism on the basis of a dedicated computational approach and in one case the surprising structure characterized by the ten term coordinative ring was resolved by X-ray diffraction.

Synthesis of novel '4+1' Tc(III)/Re(III) mixed-ligand complexes with dendritically modified ligands

International Nuclear Information System (INIS)

Gniazdowska, E.; Kuenstler, J.U.; Stephan, H.; Pietzsch, H.J.

2006-01-01

Coordination chemistry of technetium and rhenium attracts a considerable interest due to the nuclear medicine applications of their radionuclides. Inert, so-called '3+1' or '4+1' technetium/rhenium mixed-ligand complexes open a new way to application of 99 mTc/ 188 Re labeled compounds in tumor diagnosis and therapy. In the presented paper, authors describe the synthesis and study of novel 99 mTc/ 188 Re complexes with dendritically functionalized tetradentate (tripodal chelator 2,2',2''-nitrilotris(ethanethiol), NS 3 and carboxyl group-bearing ligand, NS 3 (COOH) 3 ) and monodentate (dendritically modified isocyanide, CN-R(COOMe) 3 and isocyanide-modified peptide, CN-GGY) ligands. To verify the identity of the prepared n.c.a. complexes, non-radioactive analogous '4+1' Re compounds were synthesized. The experimental data show that a dendritic modification of the tetradentate/monodentate ligands changes the complex lipophilicity and does not influence its stability

Alkyne hydroarylation with Au N-heterocyclic carbene catalysts

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Cristina Tubaro

2013-02-01

Full Text Available Mono- and dinuclear gold complexes with N-heterocyclic carbene (NHC ligands have been employed as catalysts in the intermolecular hydroarylation of alkynes with simple unfunctionalised arenes. Both mono- and dinuclear gold(III complexes were able to catalyze the reaction; however, the best results were obtained with the mononuclear gold(I complex IPrAuCl. This complex, activated with one equivalent of silver tetrafluoroborate, exhibited under acidic conditions at room temperature much higher catalytic activity and selectivity compared to more commonly employed palladium(II catalysts. Moreover, the complex was active, albeit to a minor extent, even under neutral conditions, and exhibited lower activity but higher selectivity compared to the previously published complex AuCl(PPh3. Preliminary results on intramolecular hydroarylations using this catalytic system indicate, however, that alkyne hydration by traces of water may become a serious competing reaction.

N-heterocyclic carbene metal complexes as bio-organometallic antimicrobial and anticancer drugs.

Science.gov (United States)

Patil, Siddappa A; Patil, Shivaputra A; Patil, Renukadevi; Keri, Rangappa S; Budagumpi, Srinivasa; Balakrishna, Geetha R; Tacke, Matthias

2015-01-01

Late transition metal complexes that bear N-heterocyclic carbene (NHC) ligands have seen a speedy growth in their use as both, metal-based drug candidates and potentially active homogeneous catalysts in a plethora of C-C and C-N bond forming reactions. This review article focuses on the recent developments and advances in preparation and characterization of NHC-metal complexes (metal: silver, gold, copper, palladium, nickel and ruthenium) and their biomedical applications. Their design, syntheses and characterization have been reviewed and correlated to their antimicrobial and anticancer efficacies. All these initial discoveries help validate the great potential of NHC-metal derivatives as a class of effective antimicrobial and anticancer agents.

Kappa-receptor selective binding of opioid ligands with a heterocyclic bicyclo[3.3.1]nonan-9-one structure.

Science.gov (United States)

Benyhe, S; Márki, A; Nachtsheim, Corina; Holzgrabe, Ulrike; Borsodi, Anna

2003-01-01

Previous pharmacological results have suggested that members of the heterocyclic bicyclo[3.3.1]nonan-9-one-like compounds are potent kappa-opioid receptor specific agonists. One lead molecule of this series. called compound 1 (dimethyl 7-methyl-2,4-di-2-pyridyl-3.7-diazabicyclo[3.3.1]nonan-9-one-1,5-dicarboxylate) exhibited high affinity for [3H]ethylketocyclazocine and [3H]U-69.593 binding sites in guinea pig cerebellar membranes which known to be a good source for kappa1 receptors. It was shown by molecular modelling that heterocyclic bicyclo[3.3.1]nonan-9-ones fit very well with the structure of ketazocine, a prototypic kappa-selective benzomorphan compound; when compared to the arylacetamide structure of U-69.593, a specific kappa1-receptor agonist, a similar geometry was found with a slightly different distribution of the charges. It is postulated, that the essential structural skeleton involved in the opioid activity is an aryl-propyl-amine element distributed along the N7-C6-C5-C4-aryl bonds.

Insight into eukaryotic topoisomerase II-inhibiting fused heterocyclic compounds in human cancer cell lines by molecular docking.

Science.gov (United States)

Taskin, T; Yilmaz, S; Yildiz, I; Yalcin, I; Aki, E

2012-01-01

Etoposide is effective as an anti-tumour drug by inhibiting eukaryotic DNA topoisomerase II via establishing a covalent complex with DNA. Unfortunately, its wide therapeutic application is often hindered by multidrug resistance (MDR), low water solubility and toxicity. In our previous study, new derivatives of benzoxazoles, benzimidazoles and related fused heterocyclic compounds, which exhibited significant eukaryotic DNA topoisomerase II inhibitory activity, were synthesized and exhibited better inhibitory activity compared with the drug etoposide itself. To expose the binding interactions between the eukaryotic topoisomerase II and the active heterocyclic compounds, docking studies were performed, using the software Discovery Studio 2.1, based on the crystal structure of the Topo IIA-bound G-segment DNA (PDB ID: 2RGR). The research was conducted on a selected set of 31 fused heterocyclic compounds with variation in structure and activity. The structural analyses indicate coordinate and hydrogen bonding interactions, van der Waals interactions and hydrophobic interactions between ligands and the protein, as Topo IIA-bound G-segment DNA are responsible for the preference of inhibition and potency. Collectively, the results demonstrate that the compounds 1a, 1c, 3b, 3c, 3e and 4a are significant anti-tumour drug candidates that should be further studied.

fac-Tris(pyridine-2-carboxyl­ato-κ2 N,O)cobalt(III)

Science.gov (United States)

Golenia, Irina A.; Boyko, Alexander N.; Kotova, Natalia V.; Haukka, Matti; Kalibabchuk, Valentina A.

2011-01-01

In the title compound, [Co(C6H4NO2)3], the CoIII ion lies on a threefold rotation axis and is in a distorted octa­hedral environment defined by three N and three O donor atoms from three fac-disposed pyridine-2-carboxyl­ate ligands. The ligands are coordinated in a chelate fashion, forming three five-membered rings. In the crystal, translationally related complex molecules are organized into columns along [001] via C—H⋯O hydrogen bonds. PMID:22219826

Combinatorial Libraries of Bis-Heterocyclic Compounds with Skeletal Diversity

OpenAIRE

Soural, Miroslav; Bouillon, Isabelle; Krchňák, Viktor

2008-01-01

Combinatorial solid-phase synthesis of bis-heterocyclic compounds, characterized by the presence of two heterocyclic cores connected by a spacer of variable length/structure, provided structurally heterogeneous libraries with skeletal diversity. Both heterocyclic rings were assembled on resin in a combinatorial fashion.

Supramolecular Coordination Assemblies Constructed From Multifunctional Azole-Containing Carboxylic Acids

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Yuheng Deng

2010-05-01

Full Text Available This paper provides a brief review of recent progress in the field of metal coordination polymers assembled from azole-containing carboxylic acids and gives a diagrammatic summary of the diversity of topological structures in the resulting infinite metal-organic coordination networks (MOCNs. Azole-containing carboxylic acids are a favorable kind of multifunctional ligand to construct various metal complexes with isolated complexes and one, two and three dimensional structures, whose isolated complexes are not the focus of this review. An insight into the topology patterns of the infinite coordination polymers is provided. Analyzed topologies are compared with documented topologies and catalogued by the nature of nodes and connectivity pattern. New topologies which are not available from current topology databases are described and demonstrated graphically.

Photoacidic and Photobasic Behavior of Transition Metal Compounds with Carboxylic Acid Group(s)

Energy Technology Data Exchange (ETDEWEB)

O’Donnell, Ryan M. [Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States; Sampaio, Renato N. [Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States; Li, Guocan [Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States; Johansson, Patrik G. [Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States; Ward, Cassandra L. [Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States; Meyer, Gerald J. [Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States

2016-03-10

Excited state proton transfer studies of six Ru polypyridyl compounds with carboxylic acid/carboxylate group(s) revealed that some were photoacids and some were photobases. The compounds [Ru^II(btfmb)₂(LL)]²⁺, [Ru^II(dtb)2(LL)]2+, and [RuII(bpy)2(LL)]2+, where bpy is 2,2'-bipyridine, btfmb is 4,4'-(CF₃)₂-bpy, and dtb is 4,4'-((CH₃)₃C)₂-bpy, and LL is either dcb = 4,4'-(CO₂H)₂-bpy or mcb = 4-(CO₂H),4'-(CO2Et)-2,2'-bpy, were synthesized and characterized. The compounds exhibited intense metal-to-ligand charge-transfer (MLCT) absorption bands in the visible region and room temperature photoluminescence (PL) with long τ > 100 ns excited state lifetimes. The mcb compounds had very similar ground state pKa’s of 2.31 ± 0.07, and their characterization enabled accurate determination of the two pK_a values for the commonly utilized dcb ligand, pK_a1 = 2.1 ± 0.1 and pKa2 = 3.0 ± 0.2. Compounds with the btfmb ligand were photoacidic, and the other compounds were photobasic. Transient absorption spectra indicated that btfmb compounds displayed a [Ru^III(btfmb–)L₂]^2+* localized excited state and a [Ru^III(dcb–)L₂]^2+* formulation for all the other excited states. Time dependent PL spectral shifts provided the first kinetic data for excited state proton transfer in a transition metal compound. PL titrations, thermochemical cycles, and kinetic analysis (for the mcb compounds) provided self-consistent pK_a* values. The ability to make a single ionizable group photobasic or photoacidic through ligand design was unprecedented and was understood based on the orientation of the lowest-lying MLCT excited state dipole relative to the ligand that contained the carboxylic acid group(s).

Combinatorial Libraries of Bis-Heterocyclic Compounds with Skeletal Diversity

Science.gov (United States)

Soural, Miroslav; Bouillon, Isabelle; Krchňák, Viktor

2009-01-01

Combinatorial solid-phase synthesis of bis-heterocyclic compounds, characterized by the presence of two heterocyclic cores connected by a spacer of variable length/structure, provided structurally heterogeneous libraries with skeletal diversity. Both heterocyclic rings were assembled on resin in a combinatorial fashion. PMID:18811208

Aspects and prospects of the chemistry of organic heterocycles (review)

International Nuclear Information System (INIS)

Schroth, W.

1986-01-01

The systematics of heterocycles, their place in organic chemistry, and their significance for theory and practice are discussed. Problems of the chemistry of heterocycles are discussed on the examples of systems with various types of conjugation and ring sizes. The focus is on the principles of synthesis of heterocycles, in particular, those based on acetylene, various C 3 fragments, carbon disulfide, and maleic anhydride. Individual sections of the survey are devoted to the role of heterocycles in biosynthesis, as well as certain problems common to the chemistry of heterocycles, biochemistry, and macromolecular chemistry

Antioxidant evaluation of heterocyclic compounds by cytokinesis-block micronucleus assay.

Science.gov (United States)

Godevac, Dejan; Tesević, Vele; Vajs, Vlatka; Milosavljević, Slobodan; Stanković, Miroslava

2013-03-01

This article summarizes the results of using cytokinesis-block micronucleus (CBMN) assay to evaluate the antioxidant potential of heterocyclic compounds. Most studies were carried out with naturally occurring heterocyclic compounds such as plant polyphenols: flavonoids, xanthones, coumarins, and ellagitannins, or plant derived products (juices, extracts, supplements) rich in bioactive heterocyclic compounds. There are also some studies dealing with synthetic heterocyclic antioxidants. CBMN assay is an in vitro study that has been used to evaluate antioxidant and protective effects of heterocyclic compounds on induced chromosome aberration in human lymphocytes.

Synthesis and characterization of silver nanoparticles from (bis)alkylamine silver carboxylate precursors

Energy Technology Data Exchange (ETDEWEB)

Uznanski, Pawel, E-mail: puznansk@cbmm.lodz.pl; Zakrzewska, Joanna [Centre of Molecular and Macromolecular Studies, PAS (Poland); Favier, Frederic, E-mail: fredf@univ-montp2.fr [Université Montpellier II, ICGM - UMR5253- Equipe AIME (France); Kazmierski, Slawomir; Bryszewska, Ewa [Centre of Molecular and Macromolecular Studies, PAS (Poland)

2017-03-15

A comparative study of amine and silver carboxylate adducts [R{sub 1}COOAg-2(R{sub 2}NH{sub 2})] (R{sub 1} = 1, 7, 11; R{sub 2} = 8, 12) as a key intermediate in NPs synthesis is carried out via differential scanning calorimetry, solid-state FT-infrared spectroscopy, {sup 13}C CP MAS NMR, powder X-ray diffraction and X-ray photoelectron spectroscopy, and various solution NMR spectroscopies ({sup 1}H and {sup 13}C NMR, pulsed field gradient spin-echo NMR, and ROESY). It is proposed that carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination as opposed to bridging bidentate coordination of pure silver carboxylates resulting from the formation of dimeric units. All complexes are packed as lamellar bilayer structures. Silver carboxylate/amine complexes show one first-order melting transition. The evidence presented in this study shows that phase behavior of monovalent metal carboxylates are controlled, mainly, by head group bonding. In solution, insoluble silver salt is stabilized by amine molecules which exist in dynamic equilibrium. Using (bis)amine-silver carboxylate complex as precursor, silver nanoparticles were fabricated. During high-temperature thermolysis, the (bis)amine-carboxylate adduct decomposes to produce silver nanoparticles of small size. NPs are stabilized by strongly interacting carboxylate and trace amounts of amine derived from the silver precursor interacting with carboxylic acid. A corresponding aliphatic amide obtained from silver precursor at high-temperature reaction conditions is not taking part in the stabilization. Combining NMR techniques with FTIR, it was possible to follow an original stabilization mechanism.

Giant regular polyhedra from calixarene carboxylates and uranyl

Science.gov (United States)

Pasquale, Sara; Sattin, Sara; Escudero-Adán, Eduardo C.; Martínez-Belmonte, Marta; de Mendoza, Javier

2012-01-01

Self-assembly of large multi-component systems is a common strategy for the bottom-up construction of discrete, well-defined, nanoscopic-sized cages. Icosahedral or pseudospherical viral capsids, built up from hundreds of identical proteins, constitute typical examples of the complexity attained by biological self-assembly. Chemical versions of the so-called 5 Platonic regular or 13 Archimedean semi-regular polyhedra are usually assembled combining molecular platforms with metals with commensurate coordination spheres. Here we report novel, self-assembled cages, using the conical-shaped carboxylic acid derivatives of calix[4]arene and calix[5]arene as ligands, and the uranyl cation UO22+ as a metallic counterpart, which coordinates with three carboxylates at the equatorial plane, giving rise to hexagonal bipyramidal architectures. As a result, octahedral and icosahedral anionic metallocages of nanoscopic dimensions are formed with an unusually small number of components. PMID:22510690

Synthesis and characterization of ligands and bifunctional chelating agents by modification of cysteine for complexation studies with 99mTc

International Nuclear Information System (INIS)

Pillai, M.R.A.; Kothari, K.; Banerjee, S.; Samuel, G.; Suresh, M.; Sarma, H.D.

1998-01-01

The synthesis of four novel ligands using the amino-acid cysteine and its ethyl carboxylate derivative is described. The synthetic method involves a two-step procedure, wherein the intermediate Schiff base formed by the condensation of the amino group of the cysteine substrate and salicylaldehyde is reduced to give the target ligands. The intermediates and the final products are characterised by high resolution NMR spectroscopy. Complexation studies of the ligands with 99m Tc are standardised using stannous tartrate as the reducing agent at varying reaction conditions. The complexes are characterised using standard quality control techniques such as TLC, paper electrophoresis and PC. Lipophilicities of the complexes are estimated by solvent extraction into chloroform. Substantial changes in net charge and lipophilicity in the 99m Tc complexes are observed on substituting the carboxylic acid residue in ligand I and II with the ethyl carboxylate groups (ligands III and IV). All the ligands formed complexes in high yield. While the complexes of ligand I and II are observed to be hydrophilic in nature and are not extractable into CHCl 3 , ligands III and IV gave neutral and lipophilic complexes. Though the distribution ratios of the complexes of ligands III and IV in CHCl 3 /saline system are observed to be very high, considerable differences in lipophilicities are also observed as evidenced by the difference in their respective extractabilities in chloroform. On storage, the complex of ligand III exhibit a tendency to get converted to a hydrophilic and non-extractable species. The bio-distribution of the complexes of ligands I and II showed that they have predominantly renal clearances whereas the complexes of ligands III and IV exhibited a significant hepatobiliary uptake and did not show much uptake in brain in spite of its favourable properties such as neutrality, lipophilicity and conversion into a hydrophilic species. (author)

Cycloalkyl-based unsymmetrical unsaturated (U2)-NHC ligands: Flexibility and dissymmetry in ruthenium-catalysed olefin metathesis

KAUST Repository

Rouen, Mathieu

2014-01-01

Air-stable Ru-indenylidene and Hoveyda-type complexes bearing new unsymmetrical unsaturated N-heterocyclic carbene (U2-NHC) ligands combining a mesityl unit and a flexible cycloalkyl moiety as N-substituents were synthesised. Structural features, chemical stabilities and catalytic profiles in olefin metathesis of this new library of cycloalkyl-based U2-NHC Ru complexes were studied and compared with their unsymmetrical saturated NHC-Ru homologues as well as a set of commercially available Ru-catalysts bearing either symmetrical SIMes or IMes NHC ligands. © 2014 the Partner Organisations.

Spectrochemical study on different ligand neodymium complexes

International Nuclear Information System (INIS)

Khomenko, V.S.; Lozinskij, M.O.; Fialkov, Yu.A.; Krasovskaya, L.I.; Rasshinina, T.A.; AN Ukrainskoj SSR, Kiev. Inst. Organicheskoj Khimii)

1986-01-01

A series of new adducts of neodymium complexes with 1, 1, 1, 5, 5, 5-hexafluoropentadione - 2, 4 and 2-heptafluoropropoxy-1, 1, 1, 2-tetrafluoro-5-phenylpentadione-3, 5: Nd(HFPTFPhPD) 3 x2H 2 O, Nd(HFPTFPhPD) 3 xDipy, Nd(HFPTFPhPD) 3 xPhen, Nd(HFPTFPhPD) 3 xDphen, Nd(HFA) 3 x2H 2 O, Nd(HFA) 3 xDipy, Nd(HFA) 3 xPhen, Nd(HFA) 3 xDphen, have been synthesized. Ways of their fragmentation under electron impact are established. Bond strength of additional ligands with central atom in the complexes studied is evaluated. Data on decomposition mechanisms of bicharged ions have been obtained for the first time. Addition of bis-heterocycles to neodymium three-ligand complexes changes the properties of the complexes - their thermal stability and photochemical stability increase, in certain cases their volatility increases

Enantioselective [3+3] atroposelective annulation catalyzed by N-heterocyclic carbenes

KAUST Repository

Zhao, Changgui

2018-02-05

Axially chiral molecules are among the most valuable substrates in organic synthesis. They are typically used as chiral ligands or catalysts in asymmetric reactions. Recent progress for the construction of these chiral molecules is mainly focused on the transition-metal-catalyzed transformations. Here, we report the enantioselective NHC-catalyzed (NHC: N-heterocyclic carbenes) atroposelective annulation of cyclic 1,3-diones with ynals. In the presence of NHC precatalyst, base, Lewis acid and oxidant, a catalytic C–C bond formation occurs, providing axially chiral α-pyrone−aryls in moderate to good yields and with high enantioselectivities. Control experiments indicated that alkynyl acyl azoliums, acting as active intermediates, are employed to atroposelectively assemble chiral biaryls and such a methodology may be creatively applied to other useful NHC-catalyzed asymmetric transformations.

Quantum mechanics and molecular dynamics simulations of complexation of alkaline-earth and lanthanide cations by poly-amino-carboxylate ligands

International Nuclear Information System (INIS)

Durand, S.

1999-01-01

Molecular dynamics (MD) simulations on lanthanide(III) and alkaline-earth(II) complexes with poly-amino-carboxylates (ethylene-diamino-tetra-acetate EDTA 4- , ethylene-diamino-tri-acetate-acetic acid EDTA(H) 3- , tetra-aza-cyclo-dodecane-tetra-acetate DOTA 4- , methylene-imidine-acetate MIDA 2- ) are reported. First, a consistent set of Lennard-Jones parameters for La 3+ , Eu 3+ and Lu 3+ cations has been derived from free energy calculations in aqueous solution. Observed differences in hydration free energies, coordination distances and hydration numbers are reproduced. Then, the solution structures of 1:1 complexes of alkaline-earth and/or lanthanide cations with EDTA 4- , EDTA(H) 3- , DOTA 4- and 1:2 complexes of lanthanide cations with MIDA 2- were studied by MD in water. In addition, free energy calculations were performed to study, for each ligand, the relative thermodynamic stabilities of complexes with Ca 2+ vs Sr 2+ and vs Ba 2+ on the one hand, and with La 3+ vs Eu 3+ and vs Lu 3+ on the other hand. Model does not take into account explicitly polarization and charge transfer. However, the results qualitatively agree with experimental complexation data (structure and selectivities). (author)

Preparation and characterizations of new U(IV) and U(VI) complexes with carboxylate ligands

Energy Technology Data Exchange (ETDEWEB)

Sbrignadello, G; Tomat, G; Battiston, G; Vigato, P A [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi

1978-01-01

The synthesis and characterization of some uranyl(VI) complexes containing glycolate (gly = CH/sub 2/OHCOO/sup -/) and methoxyacetate (MeOAc = CH/sub 3/OCH/sub 2/COO/sup -/) ligands with metal:ligand ratios of 1:1 and 1:2 are reported. In addition, new stable uranium(IV) complexes containing the same ligands, or the oxydiacetate (oda = /sup -/OOCCH/sub 2/OCH/sub 2/COO/sup -/) anion, have been prepared by photolysing aqueous solutions of uranyl(VI) nitrate in the presence of an excess of ligand. The possible structures of these complexes are discussed on the basis of IR results. The photoproduction mechanism of U(IV) complexes is proposed from electronic and spectrofluorimetric spectra and quantum yield data.

Recent advances in the electrochemical construction of heterocycles

Directory of Open Access Journals (Sweden)

Robert Francke

2014-12-01

Full Text Available Due to the fact that the major portion of pharmaceuticals and agrochemicals contains heterocyclic units and since the overall number of commercially used heterocyclic compounds is steadily growing, heterocyclic chemistry remains in the focus of the synthetic community. Enormous efforts have been made in the last decades in order to render the production of such compounds more selective and efficient. However, most of the conventional methods for the construction of heterocyclic cores still involve the use of strong acids or bases, the operation at elevated temperatures and/or the use of expensive catalysts and reagents. In this regard, electrosynthesis can provide a milder and more environmentally benign alternative. In fact, numerous examples for the electrochemical construction of heterocycles have been reported in recent years. These cases demonstrate that ring formation can be achieved efficiently under ambient conditions without the use of additional reagents. In order to account for the recent developments in this field, a selection of representative reactions is presented and discussed in this review.

Synthesis, characterization, and reactivity of furan- and thiophene-functionalized bis(n-heterocyclic carbene) complexes of iron(II)

KAUST Repository

Rieb, Julia

2014-09-15

The synthesis of iron(II) complexes bearing new heteroatom-functionalized methylene-bridged bis(N-heterocyclic carbene) ligands is reported. All complexes are characterized by single-crystal X-ray diffraction (SC-XRD), nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis. Tetrakis(acetonitrile)-cis-[bis(o-imidazol-2-ylidenefuran)methane]iron(II) hexafluorophosphate (2a) and tetrakis(acetonitrile)-cis-[bis(o-imidazol-2-ylidenethiophene)methane]iron(II) hexafluorophosphate (2b) were obtained by aminolysis of [Fe{N(SiMe3)2}2(THF)] with furan- and thiophene-functionalized bis(imidazolium) salts 1a and 1b in acetonitrile. The SC-XRD structures of 2a and 2b show coordination of the bis(carbene) ligand in a bidentate fashion instead of a possible tetradentate coordination. The four other coordination sites of these distorted octahedral complexes are occupied by acetonitrile ligands. Crystallization of 2a in an acetone solution by the slow diffusion of Et2O led to the formation of cisdiacetonitriledi[ bis(o-imidazol-2-ylidenefuran)methane]iron(II) hexafluorophosphate (3a) with two bis(carbene) ligands coordinated in a bidentate manner and two cis-positioned acetonitrile molecules. Compounds 2a and 2b are the first reported iron(II) carbene complexes with four coordination sites occupied by solvent molecules, and it was demonstrated that those solvent ligands can undergo ligand-exchange reactions.

Synthesis and anticancer activity of silver(I)-N-heterocyclic carbene complexes derived from the natural xanthine products caffeine, theophylline and theobromine.

Science.gov (United States)

Mohamed, Heba A; Lake, Benjamin R M; Laing, Thomas; Phillips, Roger M; Willans, Charlotte E

2015-04-28

A new library of silver(I)-N-heterocyclic carbene complexes prepared from the natural products caffeine, theophylline and theobromine is reported. The complexes have been fully characterised using a combination of NMR spectroscopy, mass spectrometry, elemental analysis and X-ray diffraction analysis. Furthermore, the hydrophobicity of the complexes has been measured. The silver(I)-N-heterocyclic carbenes have been evaluated for their antiproliferative properties against a range of cancer cell lines of different histological types, and compared to cisplatin. The data shows different profiles of response when compared to cisplatin in the same panel of cells, indicating a different mechanism of action. Furthermore, it appears that the steric effect of the ligand and the hydrophobicity of the complex both play a role in the chemosensitivity of these compounds, with greater steric bulk and greater hydrophilicity delivering higher cytotoxicity.

Synthesis of Well-Defined Copper "N"-Heterocyclic Carbene Complexes and Their Use as Catalysts for a "Click Reaction": A Multistep Experiment that Emphasizes the Role of Catalysis in Green Chemistry

Science.gov (United States)

Ison, Elon A.; Ison, Ana

2012-01-01

A multistep experiment for an advanced synthesis lab course that incorporates topics in organic-inorganic synthesis and catalysis and highlights green chemistry principles was developed. Students synthesized two "N"-heterocyclic carbene ligands, used them to prepare two well-defined copper(I) complexes and subsequently utilized the complexes as…

Activation of trans geometry in bifunctional mononuclear platinum complexes by a non-bulky methylamine ligand

Czech Academy of Sciences Publication Activity Database

Frýbortová, M.; Nováková, Olga; Štěpánková, Jana; Novohradský, Vojtěch; Gibson, D.; Kašpárková, Jana; Brabec, Viktor

2013-01-01

Roč. 126, SEP2013 (2013), s. 46-54 ISSN 0162-0134 R&D Projects: GA ČR(CZ) GAP301/10/0598; GA ČR(CZ) GA13-08273S Institutional research plan: CEZ:AV0Z50040702 Institutional support: RVO:68081707 Keywords : HETEROCYCLIC AMINE LIGAND * INTERSTRAND CROSS-LINKS * DNA-BINDING MODE Subject RIV: BO - Biophysics Impact factor: 3.274, year: 2013

The affinity plutonium(IV) for nitrogen donor ligands

International Nuclear Information System (INIS)

Jarvis, N.V.; Hancock, R.D.

1994-01-01

Established ligand design principles are used to predict the solution chemistry of Pu(IV) with nitrogen donor ligands which do not contain carboxylate donors. pK a 's of the nitrogen donors are lowered by addition of hydroxyalkyl groups causing Pu(IV) to have a greater affinity for these ligands than for hydroxide. Potentiometric studies using the ligands N,N,N'N',N''-pentakis(2-hydroxypropyl)-1,4,7-triazaheptane; N,N,N',N',N''-pentakis(2-hydroxyethyl)-1,4,7-triazaheptane; N,N,N',N',N'-tetrakis(2-hydroxyethyl)-1,2-diaminoethane; N,N,N',N'-tetrakis(2-hydroxyethyl)-trans-1,2-diaminocyclohexane; 1,4,8,11-tetrakis(2-hydroxyethyl)-1,4,8,11-tetraazacyclotetradecane and N,N-bis(2-hydroxyethyl)glycine with Pu(IV) showed that Pu(IV) has a considerable aqueous solution chemistry with these ligands. Data were processed by the ESTA library of programs and stability constants for all the systems are reported. Implications for selective ligand design for Pu(IV) are discussed. (orig.)

Structural, spectral and magnetic studies of two Co(II)-N-heterocyclic diphosphonates based on multinuclear units

Science.gov (United States)

Zhao, Chen; Ma, Kui-Rong; Zhang, Yu; Kan, Yu-He; Li, Rong-Qing; Hu, Hua-You

2016-01-01

Two examples of Co(II)-N-heterocyclic coordination polymers based on 1-hydroxyethylidenediphosphonic acid (H5L = CH3C(OH)(PO3H2)2), namely 0.5(H3NCH2CH2NH3)·[Co6(Cl2)(H3L)2(H2L)(HL)(2,2‧-bipy)6] 1 and 2(NH4)·[Co3(HL)2(H2O)2(phen)2]·2(H2O) 2, have been solvothermally obtained by introducing the second ligands 2,2‧-bipyridine/1,10-phenanthroline (2,2‧-bipy/phen) and characterized by powder X-ray diffraction (PXRD), elemental analysis, IR, TG-DSC. The single-crystal X-ray diffractions show that compound 1 possesses a 0-D structure with hexa-nuclear cluster [Co6(O-P-O)8] built through single/double O-P-O bridges and compound 2 displays a 1-D ladder-like chain structure with magnetic topology building blocks [Co4(O-P-O)4]n. Then H-bonding and π-π stacking interactions further expand the two low-dimensional structures into three-dimensional supramolecular frameworks. Fluorescent measurements reveal that both the maximum emission peaks of 1-2 are centered at 423 nm, mainly deriving from intraligand π*-π transition state of N-heterocyclic ligand 2,2‧-bipy/phen, respectively. Magnetism data indicate that 1 exhibits antiferromagnetic behavior within hexa-nuclear Co(II) clusters, while 2 shows weak ferromagnetic interactions in 1-D topology Co(II)-chain, showing promising potential as magnetic materials.

Silver(I) complexes of mono- and bidentate N-heterocyclic carbene ligands: synthesis, crystal structures, and in vitro antibacterial and anticancer studies.

Science.gov (United States)

Haque, Rosenani A; Choo, Sze Yii; Budagumpi, Srinivasa; Iqbal, Muhammad Adnan; Al-Ashraf Abdullah, Amirul

2015-01-27

A series of benzimidazole-based N-heterocyclic carbene (NHC) proligands {1-benzyl-3-(2-methylbenzyl)-benzimidazolium bromide/hexafluorophosphate (1/4), 1,3-bis(2-methylbenzyl)-benzimidazolium bromide/hexafluorophosphate (2/5) and 1,3-bis(3-(2-methylbenzyl)-benzimidazolium-1-ylmethylbenzene dibromide/dihexafluorophosphate (3/6)} has been synthesized by the successive N-alkylation method. Ag complexes {1-benzyl-3-(2-methylbenzyl)-benzimidazol-2-ylidenesilver(I) hexafluorophosphate (7), 1,3-bis(2-methylbenzyl)-benzimidazol-2-ylidenesilver(I) hexafluorophosphate (8) and 1,3-bis(3-(2-methylbenzyl)-benzimidazol-2-ylidene)-1-ylmethylbenzene disilver(I) dihexafluorophosphate (9)} of NHC ligands have been synthesized by the treatment of benzimidazolium salts with Ag2O at mild reaction conditions. Both, NHC proligands and Ag-NHC complexes have been characterized by (1)H and (13)C{(1)H} NMR and FTIR spectroscopy and elemental analysis technique. Additionally, the structure of the NHC proligand 5 and the mononuclear Ag complexes 7 and 8 has been elucidated by the single crystal X-ray diffraction analysis. Both the complexes exhibit the same general structural motif with linear coordination geometry around the Ag centre having two NHC ligands. Preliminary in vitro antibacterial potentials of reported compounds against a Gram negative (Escherichia coli) and a Gram positive (Bacillus subtilis) bacteria evidenced the higher activity of mononuclear silver(I) complexes. The anticancer studies against the human derived colorectal cancer (HCT 116) and colorectal adenocarcinoma (HT29) cell lines using the MTT assay method, revealed the higher activity of Ag-NHC complexes. The benzimidazolium salts 4-6 and Ag-NHC complexes 7-9 displayed the following IC50 values against the HCT 116 and HT29 cell lines, respectively, 31.8 ± 1.9, 15.2 ± 1.5, 4.8 ± 0.6, 10.5 ± 1.0, 18.7 ± 1.6, 1.20 ± 0.3 and 245.0 ± 4.6, 8.7 ± 0.8, 146.1 ± 3.1, 7.6 ± 0.7, 5.5 ± 0.8, 103.0 ± 2.3 μM. Copyright �

Ligand-Controlled Synthesis of Azoles via Ir-Catalyzed Reactions of Sulfoxonium Ylides with 2-Amino Heterocycles.

Science.gov (United States)

Phelps, Alicia M; Chan, Vincent S; Napolitano, José G; Krabbe, Scott W; Schomaker, Jennifer M; Shekhar, Shashank

2016-05-20

An iridium-catalyzed method was developed for the synthesis of imidazo-fused pyrrolopyrazines. The presence or absence of a nitrogenated ligand controlled the outcome of the reaction, leading to simple β-keto amine products in the absence of added ligand and the cyclized 7- and 8-substituted-imidazo[1,2-a]pyrrolo[2,3-e]pyrazine products in the presence of ligand. This catalyst control was conserved across a variety of ylide and amine coupling partners. The substrate was shown to act as a ligand for the iridium catalyst in the absence of other ligands via NMR spectroscopy. Kinetic studies indicated that formation of the Ir-carbene was reversible and the slow step of the reaction. These mechanistic investigations suggest that the β-keto amine products form via an intramolecular carbene N-H insertion, and the imidazopyrrolopyrazines form via an intermolecular carbene N-H insertion.

Conformational diversity of flexible ligand in metal-organic frameworks controlled by size-matching mixed ligands

International Nuclear Information System (INIS)

Hua, Xiu-Ni; Qin, Lan; Yan, Xiao-Zhi; Yu, Lei; Xie, Yi-Xin; Han, Lei

2015-01-01

Hydrothermal reactions of N-auxiliary flexible exo-bidentate ligand 1,3-bis(4-pyridyl)propane (bpp) and carboxylates ligands naphthalene-2,6-dicarboxylic acid (2,6-H_2ndc) or 4,4′-(hydroxymethylene)dibenzoic acid (H_2hmdb), in the presence of cadmium(II) salts have given rise to two novel metal-organic frameworks based on flexible ligands (FL-MOFs), namely, [Cd_2(2,6-ndc)_2(bpp)(DMF)]·2DMF (1) and [Cd_3(hmdb)_3(bpp)]·2DMF·2EtOH (2) (DMF=N,N-Dimethylformamide). Single-crystal X-ray diffraction analyses revealed that compound 1 exhibits a three-dimensional self-penetrating 6-connected framework based on dinuclear cluster second building unit. Compound 2 displays an infinite three-dimensional ‘Lucky Clover’ shape (2,10)-connected network based on the trinuclear cluster and V-shaped organic linkers. The flexible bpp ligand displays different conformations in 1 and 2, which are successfully controlled by size-matching mixed ligands during the self-assembly process. - Graphical abstract: Compound 1 exhibits a 3D self-penetrating 6-connected framework based on dinuclear cluster, and 2 displays an infinite 3D ‘Lucky Clover’ shape (2,10)-connected network based on the trinuclear cluster. The flexible 1,3-bis(4-pyridyl)propane ligand displays different conformations in 1 and 2, which successfully controlled by size-matching mixed ligands during the self-assembly process.

Conformational diversity of flexible ligand in metal-organic frameworks controlled by size-matching mixed ligands

Energy Technology Data Exchange (ETDEWEB)

Hua, Xiu-Ni; Qin, Lan; Yan, Xiao-Zhi; Yu, Lei; Xie, Yi-Xin; Han, Lei, E-mail: hanlei@nbu.edu.cn

2015-12-15

Hydrothermal reactions of N-auxiliary flexible exo-bidentate ligand 1,3-bis(4-pyridyl)propane (bpp) and carboxylates ligands naphthalene-2,6-dicarboxylic acid (2,6-H{sub 2}ndc) or 4,4′-(hydroxymethylene)dibenzoic acid (H{sub 2}hmdb), in the presence of cadmium(II) salts have given rise to two novel metal-organic frameworks based on flexible ligands (FL-MOFs), namely, [Cd{sub 2}(2,6-ndc){sub 2}(bpp)(DMF)]·2DMF (1) and [Cd{sub 3}(hmdb){sub 3}(bpp)]·2DMF·2EtOH (2) (DMF=N,N-Dimethylformamide). Single-crystal X-ray diffraction analyses revealed that compound 1 exhibits a three-dimensional self-penetrating 6-connected framework based on dinuclear cluster second building unit. Compound 2 displays an infinite three-dimensional ‘Lucky Clover’ shape (2,10)-connected network based on the trinuclear cluster and V-shaped organic linkers. The flexible bpp ligand displays different conformations in 1 and 2, which are successfully controlled by size-matching mixed ligands during the self-assembly process. - Graphical abstract: Compound 1 exhibits a 3D self-penetrating 6-connected framework based on dinuclear cluster, and 2 displays an infinite 3D ‘Lucky Clover’ shape (2,10)-connected network based on the trinuclear cluster. The flexible 1,3-bis(4-pyridyl)propane ligand displays different conformations in 1 and 2, which successfully controlled by size-matching mixed ligands during the self-assembly process.

The affinity of the uranyl ion for nitrogen donor ligands

International Nuclear Information System (INIS)

Jarvis, N.V.; De Sousa, A.S.; Hancock, R.D.

1992-01-01

Established ligand design principles are used to predict the solution chemistry of UO 2 2+ with nitrogen donor ligands which do not contain carboxylate donors. pK a 's of the nitrogen donors are lowered by addition of hydroxylalkyl groups causing UO 2 2+ to have a greater affinity for these ligands than for hydroxide. Potentiometric studies using the ligands N,N,N',N',N''-pentakis(2-hydroxypropyl)-1,4,7-triazaheptane; N,N,N',N',N''-pentakis(2-hydroxyethyl)-1,4,7-triazaheptane; N,N,N',N'-tetrakis(2-hydroxypropyl)1,2-diaminoethane, N,N,N',N'-tetrakis(2-hydroxyethyl)-trans-1,2-diaminocyclohexane; 1,4,8,11-tetrakis(2-hydroxyethyl)-1,4,8,11-tetraazacyclotetradecane and N,N-bis(2-hydroxyethyl)glycine with UO 2 2+ showed that UO 2 2+ has a considerable aqueous solution chemistry with these ligands. (orig.)

Dehydrogenative Synthesis of Imines from Alcohols and Amines Catalyzed by a Ruthenium N-Heterocyclic Carbene Complex

DEFF Research Database (Denmark)

Maggi, Agnese; Madsen, Robert

2012-01-01

A new method for the direct synthesis of imines from alcohols and amines is described where hydrogen gas is liberated. The reaction is catalyzed by the ruthenium N-heterocyclic carbene complex [RuCl2(IiPr)(p-cymene)] in the presence of the ligand DABCO and molecular sieves. The imination can...... be applied to a variety of primary alcohols and amines and can be combined with a subsequent addition reaction. A deuterium labeling experiment indicates that the catalytically active species is a ruthenium dihydride. The reaction is believed to proceed by initial dehydrogenation of the alcohol...

Alkynylation of heterocyclic compounds using hypervalent iodine reagent.

Science.gov (United States)

Kamlar, M; Císařová, I; Veselý, J

2015-03-14

The alkynylation of various nitrogen- and/or sulphur-containing heterocyclic compounds using hypervalent iodine TMS-EBX by utilization of tertiary amines under mild conditions is described. The developed metal-free methodology furnishes the corresponding alkynylated heterocycles bearing quaternary carbon in high yields.

Crystal structure of a mixed-ligand terbium(III coordination polymer containing oxalate and formate ligands, having a three-dimensional fcu topology

Directory of Open Access Journals (Sweden)

Chainok Kittipong

2016-01-01

Full Text Available The title compound, poly[(μ3-formato(μ4-oxalatoterbium(III], [Tb(CHO2(C2O4]n, is a three-dimensional coordination polymer, and is isotypic with the LaIII, CeIII and SmIII analogues. The asymmetric unit contains one TbIII ion, one formate anion (CHO2− and half of an oxalate anion (C2O42−, the latter being completed by application of inversion symmetry. The TbIII ion is nine-coordinated in a distorted tricapped trigonal–prismatic manner by two chelating carboxylate groups from two C2O42− ligands, two carboxylate oxygen atoms from another two C2O42− ligands and three oxygen atoms from three CHO2− ligands, with the Tb—O bond lengths and the O—Tb—O bond angles ranging from 2.4165 (19 to 2.478 (3 Å and 64.53 (6 to 144.49 (4°, respectively. The CHO2− and C2O42− anions adopt μ3-bridging and μ4-chelating-bridging coordination modes, respectively, linking adjacent TbIII ions into a three-dimensional 12-connected fcu topology with point symbol (324.436.56. The title compound exhibits thermal stability up to 623 K, and also displays strong green photoluminescence in the solid state at room temperature.

2-(2′-Pyridyl)-4,6-diphenylphosphinine versus 2-(2′-Pyridyl)-4,6-diphenylpyridine: Synthesis, Characterization, and Reactivity of Cationic RhIII and IrIII Complexes Based on Aromatic Phosphorus Heterocycles

NARCIS (Netherlands)

de Krom, I.; Broeckx, L.E.E.; Lutz, M.; Müller, Christian

2013-01-01

The bidentate P,N hybrid ligand 1 allows access for the first time to novel cationic phosphinine-based RhIII and IrIII complexes, broadening significantly the scope of low-coordinate aromatic phosphorus heterocycles for potential applications. The coordination chemistry of 1 towards RhIII and IrIII

Luminescent hybrid lanthanide sulfates and lanthanide sulfonate-carboxylates with 1,10-phenanthroline involving in-situ oxidation of 2-mercaptonbenzoic acid

International Nuclear Information System (INIS)

Zhong, Jie-Cen; Wan, Fang; Sun, Yan-Qiong; Chen, Yi-Ping

2015-01-01

A series of lanthanide sulfates and lanthanide sulfonate-carboxylates, [Ln 2 (phen) 2 (SO 4 ) 3 (H 2 O) 2 ] n (I:Ln=Nd(1a), Sm(1b), Eu(1c), phen=1,10-phenanthroline) and [Ln(phen)(2-SBA)(BZA)] n (II: Ln=Sm(2a), Eu(2b), Dy(2c), 2-SBA=2-sulfobenzoate, BZA=benzoate) have been hydrothermally synthesized from lanthanide oxide, 2-mercaptonbenzoic acid with phen as auxiliary ligand and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, TG analyses and luminescence spectroscopy. Interestingly, SO 4 2− anions in I came from the in situ deep oxidation of thiol groups of 2-mercaptonbenzoic acid while 2-sulfobenzoate and benzoate ligands in II from the middle oxidation and desulfuration reactions of 2-mercaptonbenzoic acid. Compounds I are organic–inorganic hybrid lanthanide sulfates, which have rare one-dimensional column-like structures. Complexes II are binuclear lanthanide sulfonate-carboxylates with 2-sulfobenzoate and benzoate as bridges and 1,10-phenanthroline as terminal. Photoluminescence studies reveal that complexes I and II exhibit strong lanthanide characteristic emission bands in the solid state at room temperature. - Graphical abstract: Lanthanide sulfates and lanthanide sulfonate-carboxylates have been hydrothermally synthesized. Interestingly, sulfate anions, 2-sulfobenzoate and benzoate ligands came from the in situ oxidation and desulfuration reactions of 2-mercaptonbenzoic acid. - Highlights: • In situ oxidation and desulfuration reactions of 2-mercaptonbenzoic acid. • The organic–inorganic hybrid lanthanide sulfates with one-dimensional column-like structure. • The dinuclear lanthanide sulfonate-carboxylates. • The emission spectra exhibit the characteristic transition of 5 D 0 → 7 F J (J=0–4) of the Eu(III)

Poly-N-Heterocyclic Carbene Ligands with Polyaromatic Linkers. Self-Assembly and Host-Guest Chemistry

OpenAIRE

Mejuto Nieblas, Carmen

2017-01-01

In summary, a series of polytopic ligands based on NHC and MIC ligands have been synthesized in this Doctoral Thesis by means of different synthetic routes that gave rise to systems with very sophisticated architectures. A large variety of metal complexes have been formed based on these salt precursors that allowed the preparation of homo and heteroleptic mono-, di- and tri-metal complexes with different geometries. The luminescence properties of various imidazolium salts, the catalytic activ...

Ligand-Promoted C(sp(3) )-H Olefination en Route to Multi-functionalized Pyrazoles.

Science.gov (United States)

Yang, Weibo; Ye, Shengqing; Schmidt, Yvonne; Stamos, Dean; Yu, Jin-Quan

2016-05-17

A Pd-catalyzed/N-heterocycle-directed C(sp(3) )-H olefination has been developed. The monoprotected amino acid ligand (MPAA) is found to significantly promote Pd-catalyzed C(sp(3) )-H olefination for the first time. Cu(OAc)2 instead of Ag(+) salts are used as the terminal oxidant. This reaction provides a useful method for the synthesis of alkylated pyrazoles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Palladium-catalyzed allylation of tautomerizable heterocycles with alkynes.

Science.gov (United States)

Lu, Chuan-Jun; Chen, Dong-Kai; Chen, Hong; Wang, Hong; Jin, Hongwei; Huang, Xifu; Gao, Jianrong

2017-07-21

A method for the allylic amidation of tautomerizable heterocycles was developed by a palladium catalyzed allylation reaction with 100% atom economy. A series of structurally diverse N-allylic substituted heterocycles can be synthesized in good yields with high chemo-, regio-, and stereoselectivities under mild conditions.

In vitro disposition profiling of heterocyclic compounds.

Science.gov (United States)

Keemink, Janneke; Wuyts, Benjamin; Nicolaï, Johan; Jonghe, Steven De; Stella, Alessandro; Herdewijn, Piet; Augustijns, Patrick; Annaert, Pieter

2015-08-01

Compound libraries that are screened for biological activity commonly contain heterocycles. Besides potency, drug-like properties need to be evaluated to ensure in vivo efficacy of test compounds. In this context, we determined hepatic and intestinal disposition profiles for 17 heterocyclic compounds. All studied compounds showed rapid uptake in suspended rat hepatocytes, whereas metabolism was poor and the rate-limiting step in hepatic elimination. In vitro assays demonstrated a relatively low solubility and high intestinal permeability. Based on these in vitro data, heterocycles were categorized in the biopharmaceutics classification system (BCS) and the biopharmaceutics drug disposition classification system (BDDCS) to predict disposition characteristics before clinical data are available. Our findings emphasized the importance to use hepatocytes in addition to microsomes to study metabolism, since the latter lack non-microsomal enzymes and cellular context. Moreover, intracellular exposure should be considered to gain insight in the relevant fraction of the compound available at the enzymatic site. Finally, the study reveals discrepancies associated with the classification of heterocycles in BCS versus BDDCS. These probably originate from the binary character of both systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Sulfur-Kβ /sub emission studies on sulfur-bearing heterocycles

International Nuclear Information System (INIS)

Phillips, D.R.; Andermann, G.G.; Fujiwara, F.

1986-01-01

Sulfur-K/β /sub x-ray fluorescence spectroscopy (XFS) has been used to study the electronic structure and bonding in sulfur-bearing heterocycles. XFS not only has the capability of experimentally measuring valence electron energies in molecular species, but can also provide intensity data which can help define the nature of the molecular orbitals defined by the electrons. This report discusses the feasibility of using XFS as an analytical tool for the determination of total and specific sulfur heterocycle content in samples. A variety of compounds were studied. These include thiophene, thiophene derivatives, tetranydrothiophene, several more complex saturated and unsaturated sulfur heterocycles, and heterocycles containing both sulfur and nitrogen. The sulfur-K/β /sub spectra were obtained using a double crystal spectrometer which provided an instrumental resolution of about 0.7 eV

Serotonergic 5-HT6 Receptor Antagonists: Heterocyclic Chemistry and Potential Therapeutic Significance.

Science.gov (United States)

Bali, Alka; Singh, Shalu

2015-01-01

The serotonin 5-HT(6) receptor (5- HT(6)R) is amongst the recently discovered serotonergic receptors with almost exclusive localization in the brain. Hence, this receptor is fast emerging as a promising target for cognition enhancement in central nervous system (CNS) diseases such as Alzheimer's disease (cognitive function), obesity, schizophrenia and anxiety. The last decade has seen a surge of literature reports on the functional role of this receptor in learning and memory processes and investigations related to the chemistry and pharmacology of 5-HT(6) receptor ligands, especially 5- HT(6) receptor antagonists. Studies show the involvement of multiple neurotransmitter systems in cognitive enhancement by 5-HT(6)R antagonists including cholinergic, glutamatergic, and GABAergic systems. Several of the 5-HT(6)R ligands are indole based agents bearing structural similarity to the endogenous neurotransmitter serotonin. Based on the pharmacophoric models proposed for these agents, drug designing has been carried out incorporating various heterocyclic replacements for the indole nucleus. In this review, we have broadly summarized the medicinal chemistry and current status of this fairly recent class of drugs along with their potential therapeutic applications.

Adsorptive stripping voltammetric behaviour of copper complexes of some heterocyclic azo compounds.

Science.gov (United States)

Farias, P A; Ferreira, S L; Ohara, A K; Bastos, M B; Goulart, M S

1992-10-01

Controlled adsorptive accumulation of copper complexed with TAN, TAC, TAR and TAM (heterocyclic azo-compounds) on a static mercury drop electrode provides the basis for the direct stripping measurement of this element in the nanomolar concentration level. The ligand TAN exhibited great sensitivity and better separation of the peak current of the ligand in relation to the complex. The reduction current of adsorbed complex ions of copper is measured by linear scan cathodic stripping voltammetry, preceded by a period of accumulation of a few minutes. The peak potential is at approximately -0.37 V vs. Ag/AgCl. Optimal experimental parameters were found to be a TAN concentration of 1 x 10(-5)M, an accumulation potential of -0.22 V, and a solution pH of 3.7 (acetate buffer). The detection limit is 0.8nM after a 5-min accumulation with a stirred solution, and the response is linear up to 50 mug/l. Many common cations and anions do not interfere in the determination of copper. The interference of titanium is eliminated by addition of fluoride ion. Results are reported for a fresh water sample.

Biological Screening of Newly Synthesized BIAN N-Heterocyclic Gold Carbene Complexes in Zebrafish Embryos

Science.gov (United States)

Farooq, Muhammad; Abu Taha, Nael; Butorac, Rachel R.; Evans, Daniel Anthony; Elzatahry, Ahmed A.; Elsayed, Elsayed Ahmed; Wadaan, Mohammad A. M.; Al-Deyab, Salem S.; Cowley, Alan H.

2015-01-01

N-Heterocyclic carbene (NHC) metal complexes possess diverse biological activities but have yet to be extensively explored as potential chemotherapeutic agents. We have previously reported the synthesis of a new class of NHC metal complexes N-heterocyclic with acetate [IPr(BIAN)AuOAc] and chloride [IPr(BIAN)AuCl] ligands. In the experiments reported herein, the zebrafish embryos were exposed to serial dilutions of each of these complexes for 10–12 h. One hundred percent mortality was observed at concentrations ≥50 µM. At sub-lethal concentrations (10–30 µM), both compounds influenced zebrafish embryonic development. However, quite diverse categories of abnormalities were found in exposed embryos with each compound. Severe brain deformation and notochord degeneration were evident in the case of [IPr(BIAN)AuOAc]. The zebrafish embryos treated with [IPr(BIAN)AuCl] exhibited stunted growth and consequently had smaller body sizes. A depletion of 30%–40% glutathione was detected in the treated embryos, which could account for one of the possible mechanism of neurotoxicity. The fact that these compounds are capable of both affecting the growth and also compromising antioxidant systems by elevating intracellular ROS production implies that they could play an important role as a new breed of therapeutic molecules. PMID:26501273

Structural studies on the actinide carboxylates. 4. The crystal and molecular structure of succinate dioxouranium(VI) monohydrate

Energy Technology Data Exchange (ETDEWEB)

Bombieri, G; Benetollo, F [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi; Del Pra, A; Rojas, R

1979-01-01

The structure of the title compound, UO/sub 2/(CH/sub 2/COO)/sub 2/.H/sub 2/O, has been determined from three-dimensional X-ray data. The crystals are orthorhombic, space group Pbcn with four formula units in a cell. The coordination geometry about the uranium atom is pentagonal bipyramidal. The uranyl ions are equatorially surrounded by one water oxygen and by four carboxylate oxygen atoms of different succinic ligands. Each ligand is shared by four uranyl units giving rise to a polymeric-like structure.

Photometabolism of Heterocyclic Aromatic Compounds by Rhodopseudomonas palustris OU 11

Science.gov (United States)

Sasikala, C.; Ramana, C. V.; Rao, P. Raghuveer

1994-01-01

Rhodopseudomonas palustris OU 11 (ATCC 51186; DSM 7375) isolated from a pond of chemical industry effluent could anaerobically photometabolize heterocyclic aromatic compounds belonging to the pyridine and pyrazine groups only after a period of adaptation on pyrazinoic acid of 5 to 6 weeks. Growth on heterocyclic compounds was light dependent. The effects of various concentrations of heterocyclic compounds on growth suggest that higher concentrations of these compounds inhibit growth and are toxic. PMID:16349307

An insight into the biological activities of heterocyclic-fatty acid hybrid molecules.

Science.gov (United States)

Venepally, Vijayendar; Reddy Jala, Ram Chandra

2017-12-01

Heterocyclic compounds are the interesting core structures for the development of new bioactive compounds. Fatty acids are derived from renewable raw materials and exhibit various biological activities. Several researchers are amalgamating these two bioactive components to yield bioactive hybrid molecules with some desirable features. Heterocyclic-fatty acid hybrid derivatives are a new class of heterocyclic compounds with a broad range of biological activities and significance in the field of medicinal chemistry. Over the last few years, many research articles emphasized the significance of heterocyclic-fatty acid hybrid derivatives. The present review article focuses the developments in designing and biological evaluation of heterocyclic-fatty acid hybrid molecules. Copyright © 2017. Published by Elsevier Masson SAS.

METHODS OF SYNTHESIS EIGHT-TELLURIUM-CONTAINING HETEROCYCLES WITH MORE HETEROATOMS

Directory of Open Access Journals (Sweden)

G. M. Abakarov

2013-01-01

Full Text Available In this article systematized and summarized data on the synthesis of neweight-embered tellurium-containing heterocycles and new preparative methods described above produce heterocyclic tellurium.

The affinity of the uranyl ion for nitrogen donor ligands

Energy Technology Data Exchange (ETDEWEB)

Jarvis, N.V. (Atomic Energy Corp. of South Africa Ltd., Pretoria (South Africa). Dept. of Process Technology); De Sousa, A.S.; Hancock, R.D. (Univ. of the Witwatersrand, Johannesburg (South Africa). Centre for Molecular Design)

1992-01-01

Established ligand design principles are used to predict the solution chemistry of UO[sub 2][sup 2+] with nitrogen donor ligands which do not contain carboxylate donors. pK[sub a]'s of the nitrogen donors are lowered by addition of hydroxylalkyl groups causing UO[sub 2][sup 2+] to have a greater affinity for these ligands than for hydroxide. Potentiometric studies using the ligands N,N,N',N',N''-pentakis(2-hydroxypropyl)-1,4,7-triazaheptane; N,N,N',N',N''-pentakis(2-hydroxyethyl)-1,4,7-triazaheptane; N,N,N',N'-tetrakis(2-hydroxypropyl)1,2-diaminoethane, N,N,N',N'-tetrakis(2-hydroxyethyl)-trans-1,2-diaminocyclohexane; 1,4,8,11-tetrakis(2-hydroxyethyl)-1,4,8,11-tetraazacyclotetradecane and N,N-bis(2-hydroxyethyl)glycine with UO[sub 2][sup 2+] showed that UO[sub 2][sup 2+] has a considerable aqueous solution chemistry with these ligands. (orig.).

Structural mechanisms of photoeffect in polyimide structures containing heterocyclic fragments

International Nuclear Information System (INIS)

Aleksandrova, E. L.

2006-01-01

Trends in the variation in the quantum yields of charge-carrier photogeneration in polyimide structures containing heterocyclic fragments are studied. It is shown that the efficiency of sensitization of polyimides depends on the donor and acceptor properties of the fragments of monomeric units of the polyimide. It is established that the range of spectral sensitivity for heterocyclic fragments representing intramolecular complexes with charge transport is wider than that for heterocycles that do not represent such complexes

Engineering Copper Carboxylate Functionalities on Water Stable Metal–Organic Frameworks for Enhancement of Ammonia Removal Capacities

Energy Technology Data Exchange (ETDEWEB)

Joshi, Jayraj N.; Garcia-Gutierrez, Erika Y.; Moran, Colton M.; Deneff, Jacob I.; Walton, Krista S.

2017-02-02

Functionalization of copper carboxylate groups on a series of UiO-66 metal organic framework (MOF) analogues and their corresponding impact on humid and dry ammonia adsorption behavior were studied. Relative locations of possible carboxylic acid binding sites for copper on the MOF analogues were varied on ligand and missing linker defect sites. Materials after copper incorporation exhibited increased water vapor and ammonia affinity during isothermal adsorption and breakthrough experiments, respectively. The introduction of copper markedly increased ammonia adsorption capacities for all adsorbents possessing carboxyl binding sites. In particular, the new MOF UiO-66-(COOCu)2 displayed the highest ammonia breakthrough capacities of 6.38 and 6.84 mmol g–1 under dry and humid conditions, respectively, while retaining crystallinity and porosity. Relative carboxylic acid site locations were also found to impact sorbent stability, as missing linker defect functionalized materials degraded under humid conditions after copper incorporation. Postsynthetic metal insertion provides a method for adding sites that are analogous to open metal sites while maintaining good structural stability.

Blue Chitin columns for the extraction of heterocyclic amines from urine samples

DEFF Research Database (Denmark)

Bang, J.; Frandsen, Henrik Lauritz; Skog, K.

2004-01-01

During normal cooking of meat, a class of mutagenic/carcinogenic compounds called heterocyclic amines is formed. Heterocyclic amines are rapidly absorbed and metabolised in the human body, and for estimation of the intake of heterocyclic amines, it is useful to determinate their levels in the uri...

Binuclear complexes of technetium. Evidence for bis(terdentate)bidentate coordination by the bridging ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine to technetium(V)

International Nuclear Information System (INIS)

Du Preez, J.G.H.; Gerber, T.I.A.; Gibson, M.L.; Geyser, R.

1990-01-01

The authors have used the potentially bis(terdentate) nitrogen aromatic heterocyclic ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) to prepare mono- and bimetallic technetium(V) complexes bound to tppz. The stimulus for the development of the coordination chemistry of the man-made element technetium is provided by the use of complexes of this element as anatomical imaging agents in nuclear medicine. Although the chemistry of technetium(V) with nitrogen donor ligands is well understood, no complexes have been prepared using potentially terdentate neutral nitrogen donor ligands of this metal in the +5 oxidation state

Surface-Bound Ligands Modulate Chemoselectivity and Activity of a Bimetallic Nanoparticle Catalyst

KAUST Repository

Vu, Khanh B.

2015-04-03

"Naked" metal nanoparticles (NPs) are thermodynamically and kinetically unstable in solution. Ligands, surfactants, or polymers, which adsorb at a particle\\'s surface, can be used to stabilize NPs; however, such a mode of stabilization is undesirable for catalytic applications because the adsorbates block the surface active sites. The catalytic activity and the stability of NPs are usually inversely correlated. Here, we describe an example of a bimetallic (PtFe) NP catalyst stabilized by carboxylate surface ligands that bind preferentially to one of the metals (Fe). NPs stabilized by fluorous ligands were found to be remarkably competent in catalyzing the hydrogenation of cinnamaldehyde; NPs stabilized by hydrocarbon ligands were significantly less active. The chain length of the fluorous ligands played a key role in determining the chemoselectivity of the FePt NP catalysts. (Chemical Presented). © 2015 American Chemical Society.

Transformation of saturated nitrogen-containing heterocyclic compounds by microorganisms.

Science.gov (United States)

Parshikov, Igor A; Silva, Eliane O; Furtado, Niege A J C

2014-02-01

The saturated nitrogen-containing heterocyclic compounds include many drugs and compounds that may be used as synthons for the synthesis of other pharmacologically active substances. The need for new derivatives of saturated nitrogen-containing heterocycles for organic synthesis, biotechnology and the pharmaceutical industry, including optically active derivatives, has increased interest in microbial synthesis. This review provides an overview of microbial technologies that can be valuable to produce new derivatives of saturated nitrogen-containing heterocycles, including hydroxylated derivatives. The chemo-, regio- and enantioselectivity of microbial processes can be indispensable for the synthesis of new compounds. Microbial processes carried out with fungi, including Beauveria bassiana, Cunninghamella verticillata, Penicillium simplicissimum, Aspergillus niger and Saccharomyces cerevisiae, and bacteria, including Pseudomonas sp., Sphingomonas sp. and Rhodococcus erythropolis, biotransform many substrates efficiently. Among the biological activities of saturated nitrogen-containing heterocyclic compounds are antimicrobial, antitumor, antihypertensive and anti-HIV activities; some derivatives are effective for the treatment and prevention of malaria and trypanosomiasis, and others are potent glycosidase inhibitors.

Nickel(0)-catalyzed enantioselective annulations of alkynes and arylenoates enabled by a chiral NHC ligand: efficient access to cyclopentenones.

Science.gov (United States)

Ahlin, Joachim S E; Donets, Pavel A; Cramer, Nicolai

2014-11-24

Cyclopentenones are versatile structural motifs of natural products as well as reactive synthetic intermediates. The nickel-catalyzed reductive [3+2] cycloaddition of α,β-unsaturated aromatic esters and alkynes constitutes an efficient method for their synthesis. Here, nickel(0) catalysts comprising a chiral bulky C1-symmetric N-heterocyclic carbene ligand were shown to enable an efficient asymmetric synthesis of cyclopentenones from mesityl enoates and internal alkynes under mild conditions. The bulky NHC ligand provided the cyclopentenone products in very high enantioselectivity and led to a regioselective incorporation of unsymmetrically substituted alkynes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fe(II) and Co (II) complexes of (4-(4-bromophenyl)-[2,2'-bipyridine]-6-carboxylic acid) synthesis, characterization and electrochromic studies

International Nuclear Information System (INIS)

Saba, A.; Maqsood, Z.T.; Wasim, A.A.; Basha, F.Z.

2017-01-01

In this study novel complexes of substituted bipyridine (4-(4-bromophenyl)-[2,2'-bipyridine]-6-carboxylic acid) with Fe/sup +2/ and Co/sup +2/ were synthesized and characterized by different physical, analytical and spectral techniques which includes /sup 1/ H-NMR, MALDI-MS, FTIR, UV-VIS Spectrophotometry, CHN analysis and conductometry. Mole ratio method revealed that both complexes satisfied ML2 stoichiometry. Other characterization studies showed that substituted bipyridine acted as a tridentate ligand, with two pyridine N and one carboxylic O atom as binding sites per ligand molecule. The complexes were found octahedral, neutral and possessed fairly high molar absorptivities in visible region. Electrochromic studies revealed that Fe (II) complex had relatively good electrochromic properties with a reversible color change from blue to pale yellow. Co (II) complex, however, did not show significant electrochromic properties in the visible region. (author)

Mitsunobu mischief: Neighbor-directed histidine N(π)–alkylation provides access to peptides containing selectively functionalized imidazolium heterocycles

Science.gov (United States)

Qian, Wen-Jian

2015-01-01

There are few methodologies that yield peptides containing His residues with selective N(π), N(π)-bis-alkylated imidazole rings. We have found that, under certain conditions, on-resin Mitsunobu coupling of alcohols with peptides having a N(π)-alkylated His residue results in selective and high-yield alkylation of the imidazole N(π) nitrogen. The reaction requires the presence of a proximal phosphoric, carboxylic or sulfonic acid, and proceeds through an apparent intramolecular mechanism involving Mitsunobu intermediates. These transformations have particular application to phosphopeptides, where “charge masking” of one phosphoryl anionic charge by the cationic histidine imidazolium ion is now possible. This chemistry opens selective access to peptides containing differentially functionalized imidazolium heterocycles, which provide access to new classes of peptides and peptide mimetics. PMID:25739367

A chemical-biological evaluation of rhodium(I) N-heterocyclic carbene complexes as prospective anticancer drugs.

Science.gov (United States)

Oehninger, Luciano; Küster, Laura Nadine; Schmidt, Claudia; Muñoz-Castro, Alvaro; Prokop, Aram; Ott, Ingo

2013-12-23

Rhodium(I) complexes bearing N-heterocyclic carbene (NHC) ligands have been widely used in catalytic chemistry, but there are very few reports of biological properties of these organometallics. A series of Rh(I)-NHC derivatives with 1,5-cyclooctadiene and CO as secondary ligands were synthesized, characterized, and biologically investigated as prospective antitumor drug candidates. Pronounced antiproliferative effects were noted for all complexes, along with moderate inhibitory activity of thioredoxin reductase (TrxR) and efficient binding to biomolecules (DNA, albumin). Biodistribution studies showed that the presence of albumin lowered the cellular uptake and confirmed the transport of rhodium into the nuclei. Changes in the mitochondrial membrane potential (MMP) were observed as well as DNA fragmentation in wild-type and daunorubicin- or vincristine-resistant Nalm-6 leukemia cells. Overall, these studies indicated that Rh(I)-NHC fragments could be used as partial structures of new antitumor agents, in particular in those drugs designed to address resistant malignant tissues. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

synthesis and characterization of some poly functionalized heterocyclic derivatives of expected biological activity

International Nuclear Information System (INIS)

El-sayed, M.S.

2001-01-01

The present work was aimed and designed to fulfil The following objectives : 1- Continuation of the effort done by our research group in the field of chemistry of pyridinethione derivatives and their biological activities. 2- Synthesis of several new heterocyclic derivatives containing N and/or S using the laboratory available reagents. 3- Establishment of the structures of the newly synthesized heterocyclic compounds by the data of IR, 1 H-NMR, mass spectra in addition to the elemental analysis. 4- Synthesis of some of these heterocyclic derivatives via alternative routs and this used as a tool to confirm the structures of the newly synthesized heterocyclic derivatives. 5- study of the most probable mechanisms leading to the formation of the new heterocyclic derivatives. 6- The antimicrobial activity of some of the newly synthesized heterocyclic derivatives was tested against several types of organisms

Structure and photoluminescence property of complexes of aromatic carboxylic acid-functionalized polysulfone with Eu(Ⅲ) and Tb(Ⅲ)

International Nuclear Information System (INIS)

Gao, Baojiao; Qiao, Zongwen; Chen, Tao

2014-01-01

With chloromethylated polysulfone as starting substance, naphthoic acid (NA) and benzoic acid (BA) were bonded onto the side chains of polysulfone (PSF) via polymer reactions, obtaining two kinds of aromatic carboxyl acid-functionalized polysulfone, PSFNA and PSFBA. Subsequently, the luminescent binary and ternary polymer-rare earth complexes of Eu(Ⅲ) and Tb(Ⅲ) were prepared through coordination reactions, respectively, with PSFNA and PSFBA as macromolecule ligands and with 1,10-phenanthroline (Phen) and 4,4′-bipyridine (Bipy) as small-molecule co-ligands. This work focuses on investigating the relationship between structure and photoluminescence property of these complexes. The experimental results indicate that the macromolecule ligands PSFNA and PSFBA can strongly sensitize the fluorescence emissions of Eu 3+ ion or Tb 3+ ion, and the sensitization effect is strongly dependent on the structure of the ligands and the property of the central ions. The fluorescence emission of the binary complex PSF–(NA) 3 –Eu(Ⅲ) is stronger than that PSF–(BA) 3 –Eu(Ⅲ), suggesting the bonded ligand NA has stronger sensitization action for Eu 3+ ion than ligand BA; The binary complex PSF–(BA) 3 –Tb(Ⅲ) emit very strong characteristic fluorescence of Tb 3+ ion, displaying that ligand BA can strongly sensitize Tb 3+ ion, whereas PSF–(NA) 3 –Tb(Ⅲ) does not emit the characteristic fluorescence of Tb 3+ ion, showing that the bonded ligand NA does not sensitize Tb 3+ ion. The fluorescence intensity of the ternary complexes is stronger than that of the binary complexes in the same series. The solid films of these complexes also emit the strong characteristic fluorescence of Eu 3+ ion or Tb 3+ ion. - Highlights: • We prepared two kinds of aromatic carboxyl acid-functionalized polysulfone, PSFNA and PSFBA via polymer reaction. • Various binary and ternary luminescent polymer-rare earth complexes of Eu(Ⅲ) and Tb (Ⅲ) were obtained. • The relationship

Microwave-assisted synthesis of bio-active heterocycles in aqueous media

KAUST Repository

Polshettiwar, Vivek; Varma, Rajender S.

2010-01-01

Synthesis of bio-active heterocycles and fine chemicals in aqueous media are one of the best solutions for the development of green and sustainable protocols. To illustrate the advantages of aqueous MW chemistry in heterocycle synthesis

Heterocycles [h]-Fused Onto 4-Oxoquinoline-3-Carboxylic Acid, Part VIII [1]. Convenient Synthesis and Antimicrobial Properties of Substituted Hexahydro[1,4]diazepino[2,3-h]quinoline-9-carboxylic acid and Its Tetrahydroquino[7,8-b]benzodiazepine Analog

Directory of Open Access Journals (Sweden)

Yusuf M. Al-Hiari

2008-11-01

Full Text Available [1,4]Diazepino[2,3-h]quinolone carboxylic acid 3 and its benzo-homolog tetrahydroquino[7,8-b]benzodiazepine-3-carboxylic acid 5 were prepared via PPAcatalyzed thermal lactamization of the respective 8-amino-7-substituted-1,4-dihydroquinoline-3-carboxylic acid derivatives 8, 10. The latter compounds were obtained by reduction of their 8-nitro-7-substituted-1,4-dihydroquinoline-3-carboxylic acid precursors 7, 9 which, in turn, were prepared by reaction of 7-chloro-1-cyclopropyl-6-fluoro-8-nitro-1,4-dihydroquinoline-3-carboxylic acid (6 with each of β-alanine and anthranilic acid. All intermediates and target compounds were characterized using elemental analysis, NMR, IR and MS spectral data. The prepared targets and the intermediates have shown interesting antibacterial activity mainly against Gram positive strains. In particular, compound 8 showed good activity against S. aureus (MIC = 0.39 μg/mL and B. subtilis (MIC = 0.78 μg/mL. Compounds 5a and 9 have also displayed good antifungal activity against C. albicans (MIC = 1.56 μg/mL and 0.78 μg/mL, respectively. None of the compounds tested showed any anticancer activity against solid breast cancer cell line MCF-7 cells or a human breast adenocarcinoma cell line.

Effect of ligand self-assembly on nanostructure and carrier transport behaviour in CdSe quantum dots

Energy Technology Data Exchange (ETDEWEB)

Li, Kuiying, E-mail: kuiyingli@ysu.edu.cn; Xue, Zhenjie

2014-11-14

Adjustment of the nanostructure and carrier behaviour of CdSe quantum dots (QDs) by varying the ligands used during QD synthesis enables the design of specific quantum devices via a self-assembly process of the QD core–shell structure without additional technologies. Surface photovoltaic (SPV) technology supplemented by X-ray diffractometry and infrared absorption spectroscopy were used to probe the characteristics of these QDs. Our study reveals that while CdSe QDs synthesized in the presence of and capped by thioglycolic acid, 3-mercaptopropionic acid, mercaptoethanol or α-thioglycerol ligands display zinc blende nanocrystalline structures, CdSe QDs modified by L-cysteine possess wurtzite nanocrystalline structures, because different end groups in these ligands induce distinctive nucleation and growth mechanisms. Carboxyl end groups in the ligand served to increase the SPV response of the QDs, when illuminated by hν ≥ E{sub g,nano-CdSe}. Increased length of the alkyl chains and side-chain radicals in the ligands partially inhibit photo-generated free charge carrier (FCC) transfer transitions of CdSe QDs illuminated by photon energy of 4.13 to 2.14 eV. The terminal hydroxyl group might better accommodate energy released in the non-radiative de-excitation process of photo-generated FCCs in the ligand's lowest unoccupied molecular orbital in the 300–580 nm wavelength region, when compared with other ligand end groups. - Highlights: • CdSe QDs modified by L-cysteine possess wurtzite nanocrystalline structures. • Carboxyl end groups in the ligand serve to increase the SPV response of CdSe QDs. • Terminal hydroxyl group in the ligand might accommodate non-radiative de-excitation process in CdSe QDs. • Increased length of the alkyl chains and side-chain radicals in the ligands partially inhibit carriers transport of CdSe QDs.

Steric Maps to Evaluate the Role of Steric Hindrance on the IPr NHC Ligand

KAUST Repository

Poater, Albert

2013-06-01

Density functional theory (DFT) calculations were used to predict and rationalize the effect of the modification of the structure of the prototype 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) (IPr) N-heterocyclic carbene (NHC) ligand. The modification consists in the substitution of the methyl groups of ortho isopropyl substituent with phenyl groups, and here we plan to describe how such significant changes effect the metal environment and therefore the related catalytic behaviour by simple steric maps. Bearing in mind that there is a significant structural difference between IPr and IPr* ligands, that translated in different reactivity for several olefin metathesis reactions, here by means of DFT we characterize where the NHC ligand plays a more active role and where it is a simple spectator, or at least its modification does not significantly change its catalytic role/performance. Furthermore, this communication endeavours to modify further the skeleton of the IPr NHC ligand. The optimization of these bulky new systems go to the limits of the DFT computational method.

The use of phosphite-type ligands in the Ir-catalyzed asymmetric hydrogenation of heterocyclic compounds.

Science.gov (United States)

Lyubimov, Sergey E; Ozolin, Dmitry V; Ivanov, Pavel Yu; Melman, Artem; Velezheva, Valeriya S; Davankov, Vadim A

2014-01-01

A series of chiral phosphite-type ligands was tested in asymmetric Ir-catalyzed hydrogenation of quinolines and 2,4,5,6-tetrahydro-1H-pyrazino(3,2,1-j,k)carbazole. Hydrogenation of quinaldine hydrochloride provided superior enantioselectivity up to 65% ee compared to quinaldine free base. The ligands were tested for the first time in the asymmetric Ir-Ircatalyzed hydrogenation of 2,4,5,6-tetrahydro-1H-pyrazino(3,2,1-j,k)carbazole yielding the antidepressant drug, pirlindole. © 2013 Wiley Periodicals, Inc.

Radiosynthesis of a novel potential adenosine A{sub 3} receptor ligand, 5-ethyl 2,4-diethyl-3-((2-[{sup 18}F]fluoroethyl)sulfanylcarbonyl)-6-phenylpyridine-5-carboxylate ([{sup 18}F]FE rate at SUPPY:2)

Energy Technology Data Exchange (ETDEWEB)

Haeusler, D. [Dept. of Nuclear Medicine, Medical Univ. of Vienna (Austria); Dept. of Pharmaceutical Tech. and Biopharmaceutics, Univ. of Vienna (Austria); Mitterhauser, M. [Dept. of Nuclear Medicine, Medical Univ. of Vienna (Austria); Dept. of Pharmaceutical Tech. and Biopharmaceutics, Univ. of Vienna (Austria); Hospital Pharmacy of the General Hospital of Vienna (Austria); Mien, L.K. [Dept. of Nuclear Medicine, Medical Univ. of Vienna (Austria); Dept. of Pharmaceutical Tech. and Biopharmaceutics, Univ. of Vienna (Austria); Dept. of Psychiatry and Psychotherapy, Medical Univ. of Vienna (Austria); Shanab, K.; Spreitzer, H. [Dept. of Drug and Natural Product Synthesis, Univ. of Vienna (Austria); Lanzenberger, R.R [Dept. of Psychiatry and Psychotherapy, Medical Univ. of Vienna (Austria); Schirmer, E. [Dept. of Nuclear Medicine, Medical Univ. of Vienna (Austria); Dept. of Drug and Natural Product Synthesis, Univ. of Vienna (Austria); Ungersboeck, J.; Wadsak, W. [Dept. of Nuclear Medicine, Medical Univ. of Vienna (Austria); Dept. of Inorganic Chemistry, Univ. of Vienna (Austria); Nics, L. [Dept. of Nuclear Medicine, Medical Univ. of Vienna (Austria); Dept. of Nutritional Sciences, Univ. of Vienna (Austria); Viernstein, H. [Dept. of Pharmaceutical Tech. and Biopharmaceutics, Univ. of Vienna (Austria); Dudezak, R.; Kletter, K. [Dept. of Nuclear Medicine, Medical Univ. of Vienna (Austria)

2009-07-01

Since, to date very limited information on the distribution and function of the adenosine A{sub 3} receptor is available, the development of suitable radioligands is needed. Recently, we introduced [{sup 18}F]FE rate at SUPPY (5-(2-[{sup 18}F]fluoroethyl) 2,4-diethyl-3-(ethylsulfanylcarbonyl)-6-phenylpyridine-5-carboxylate) as the first PET-ligand for the A3R. Regarding the metabolic profile - this class of dialkylpyridines comprises two ester functions within one molecule, one carboxylic and one thiocarboxylic - one could expect carboxylesterases significantly contributing to cleavage and degradation. Therefore, our aim was the development of [{sup 18}F]FE rate at SUPPY:2 (5-ethyl 2,4-diethyl-3-((2-[{sup 18}F]fluoroethyl)sulfanylcarbonyl)-6-phenylpyridine-5-carboxylate), the functional isomer containing the label at the thiocarboxylic moiety. For satisfactory yields in high scale radiosyntheses, a reaction temperature of 75 C has to be applied for at least 20 min using 20 mg/mL of precursor. So far, 6 complete high-scale radiosyntheses were performed. Starting from an average of 51.2 {+-} 21.8 GBq (mean{+-}SD) [{sup 18}F]fluoride, 5.8 {+-} 4.1 GBq of formulated [{sup 18}F]FE rate at SUPPY:2 (12.0{+-}5.4%, based on [{sup 18}F]fluoride, not corrected for decay) were prepared in 75 {+-} 8 min. (orig.)

Kinetics of molybdenum(6) complexation with o,o'-dihydroxyazo compounds or heterocyclic azo compounds in the presence of hydroxylamine

International Nuclear Information System (INIS)

Kochelaeva, G.A.; Degtyarev, M.Yu.; Ivanov, V.M.; Prokhorova, G.V.; Figurovskaya, V.N.

1999-01-01

The kinetics of complexation in the system molybdenum(6)-azo compound-hydroxylamine was studied. Azo compounds of the types o,o'-dihydroxyazo compounds, such as Lyumogallion IREA and Magneson IREA, and heterocyclic azo compounds, such as 4-(2-pyridylazo)resorcinol and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol, were studied. The formation of mixed-ligand complexes with the ratio of component 1 : 1 : 1 was detected. Rate constants, activation energies, and stability constants of the forming compounds were evaluated. It was concluded that the reagents under study are promising for the analytical chemistry of molybdenum [ru

Nitric Acid Dehydration Using Perfluoro Carboxylate and Mixed Sulfonate/Carboxylate Membranes

Energy Technology Data Exchange (ETDEWEB)

Ames, Richard L. [Colorado School of Mines, Golden, CO (United States)

2004-09-01

Perfluoro ionomer membranes are tetrafluoro ethylene-based materials with microheterogeneous structures consisting of a hydrophobic polymer backbone and a hydrophilic side-chain cluster region. Due to the ionomer cluster morphology, these films exhibit unique transport properties. Recent investigations with perfluoro sulfonate and perfluoro sulfonate/carboxylate composite polymers have demonstrated their value in the dehydration of nitric acid and they show potential as an alternative to conventional, energy intensive unit operations in the concentration of acid feeds. As a result, investigations were conducted to determine the feasibility of using pure perfluoro carboxylate and mixed perfluoro sulfonate/carboxylate films for the dehydration of nitric acid because of the speculation of improved water selectivity of the carboxylate pendant chain. During the first phase of these investigations the effort was focused on generating a thin, solution cast perfluoro carboxylate ionomer film, to evaluate the general, chemical and physical characteristics of the polymer, and to assess the material's aqueous transport performance (flux and nitrate separation efficiencies) in pervaporation and high-pressure environments. Results demonstrated that generating robust solution-cast films was difficult yet a number of membranes survived high trans-membrane pressures up to 700 psig. General characterization of the solution cast product showed reduced ion exchange capacities when compared with thicker, ''as received'' perfluoro carboxylate and similar sulfonate films. Small angle x-ray scattering analysis results suggested that the solution cast carboxylate films contained a small fraction of sulfonate terminated side-chains. Aqueous transport experimentation showed that permeate fluxes for both pure water and nitric acid were approximately two orders of magnitude smaller for the carboxylate solution cast membranes when compared to their sulfonate

Mass spectrometric behaviour of carboxylated polyethylene glycols and carboxylated octylphenol ethoxylates.

Science.gov (United States)

Frańska, Magdalena; Zgoła, Agnieszka; Rychłowska, Joanna; Szymański, Andrzej; Łukaszewski, Zenon; Frański, Rafał

2003-01-01

Mass spectrometric behaviour of mono- and di-carboxylated polyethylene glycols (PEGCs and CPEGCs) and carboxylated octylphenol ethoxylates (OPECs) are discussed. The tendency for ionisation (deprotonation, protonation and cationisation by alkali metal cations) of carboxylated PEGs was compared with that of non-carboxylated correspondents by using both secondary ion mass spectrometry (SIMS) and electrospray ionisation (ESI). The fragmentation of the PEGCs and CPEGCs is discussed and also compared with their neutral correspondents, PEGs. The B/E mass spectra were recorded, using secondary ion mass spectrometry as a method for generation, for deprotonated and protonated molecules and molecules cationised by alkali metal cations. The fragmentation behaviour of PEGs is found to be different from that of CPEGCs, The presence of carboxylic groups may be confirmed not only by the determination of molecular weights of the ethoxylates studied, but also on the basis of the fragment ions formed. The metastable decomposition of the [OPEC-H](-) ions proceed through the cleavage of the bond between the octylphenol moiety and the ethoxylene chain leading to the octylphenoxy anions. It permits determination of the mass of the hydrophobic moiety of the studied carboxylated alkylphenol ethoxylate. ESI mass spectra recorded in the negative ion mode were found to be more suitable for the determination of the average molecular weight of carboxylated ethoxylates than SI mass spectra.

3-Carboxyquinolin-1-ium-2-carboxylate monohydrate

Directory of Open Access Journals (Sweden)

Qing Zhang

2012-03-01

Full Text Available The title compound, C11H7NO4·H2O, contains a 3-carboxyquinolin-1-ium-2-carboxylate (qda zwitterion and one water molecule. In the crystal, pairs of N—H...O hydrogen bonds link the molecules into inversion dimers, and these dimers are further connected by O—H...O hydrogen bonds into a three-dimensional supramolecular architecture. In addition, π–π interactions occur between pyridine and benzene rings from different qda ligands [centroid–centroid distance = 3.749 (1 Å] and the dihedral angles of the –CO2H and –CO2 groups to the quinoline system are 8.47 (3 and 88.16 (6°, respectively.

Enthalpies of ligand substitution for [Mo(η5C5H5)(CO)2(NO)] – The role of π-bonding effects in metal–ligand bond strengths

International Nuclear Information System (INIS)

Majumdar, Subhojit; Captain, Burjor; Cazin, Catherine S.J.; Nolan, Steven P.; Hoff, Carl D.

2014-01-01

Graphical abstract: - Highlights: • Enthalpies of ligand substitution are measured for Mo(C 5 H 5 )(CO) 2 (NO). • Phosphines and N-heterocyclic carbenes are stronger ligands and displace CO. • Backbonding to π ∗ orbitals is an important part of complex stability. • FTIR studies show shifts to lower wavenumbers of ν-CO and ν-NO. • Structural studies show lengthening of the C-O and N-O bonds. - Abstract: Enthalpies of ligand substitution for [Mo(η 5 -C 5 H 5 )(CO) 2 (NO)] producing [Mo(η 5 -C 5 H 5 )Mo(CO)(L)(NO)] have been measured by solution calorimetry at 30 °C in THF for L = P(OMe) 3 2 2 Ph 3 (SIPr = 1,3-bis(2,6-bis(diisopropylphenyl)imidazolinylidene; IPr = 1,3-bis(2,6-bis(diisopropylphenyl)-imidazol-2-ylidene)). The accepting metal fragment [Mo(η 5 -C 5 H 5 )(CO)(NO)] has a vacant site containing strongly π-accepting carbonyl and nitrosyl ligands and this is shown to influence the stability of the product complex. Infrared studies of both ν CO and ν NO show that metal-to-ligand backbonding increases in the order P(OMe) 3 3 5 -C 5 H 5 )(CO)(IPr)(NO)] and [Mo(η 5 -C 5 H 5 )(CO)(SIPr)(NO)] are reported

Utilization of mixed ligands to construct diverse Ni(II)-coordination polymers based on terphenyl-2,2′,4,4′-tetracarboxylic acid and varied N-donor co-ligands

International Nuclear Information System (INIS)

Wang, Chao; Zhao, Jun; Xia, Liang; Wu, Xue-Qian; Wang, Jian-Fang; Dong, Wen-Wen; Wu, Ya-Pan

2016-01-01

Three new coordination polymers, namely, {[Ni(H 2 L)(bix)(H 2 O) 2 ]·2h 2 O} n (1), {[Ni(HL)(Hdpa)(H 2 O) 2 ]·H 2 O} n (2), {[Ni(L) 0.5 (bpp)(H 2 O)]·H 2 O} n (3) (H 4 L=terphenyl-2,2′,4,4′-tetracarboxylic acid; bix=1,4-bis(imidazol-1-ylmethyl)benzene; dpa =4,4′-dipyridylamine; bpp=1,3-bis(4-pyridyl)propane), based on rigid H 4 L ligand and different N-donor co-ligands, have been synthesized under hydrothermal conditions. Compound 1 features a 3D 4-connected 6 6 -dia-type framework with H 4 L ligand adopts a μ 2 -bridging mode with two symmetry-related carboxylate groups in μ 1 -η 1 :η 0 monodentate mode. Compound 2 displays a 1D [Ni(HL)(Hdpa)] n ribbon chains motif, in which the H 4 L ligand adopts a μ 2 -bridging mode with two carboxylate groups in μ 1 -η 1 :η 1 and μ 1 -η 1 :η 0 monodentate modes, while 3 possesses a (4,4)-connected 3D frameworks with bbf topology, with H 4 L ligand displays a μ 4 -bridging coordination mode. The H 4 L ligand displays not only different deprotonated forms but also diverse coordination modes and conformations. The structural diversities among 1–3 have been carefully discussed, and the roles of N-donor co-ligands in the self-assembly of coordination polymers have been well documented. - Graphical abstract: Three nickel coordination polymers with different architectures based on mixed ligand system were synthesized and structurally characterized. Topology analyses indicate that 1 shows the 4-connected 6 6 -dia net, 1D ribbon chains for 2 and 3D (4,4)-connected bbf network for 3. Display Omitted - Highlights: • Three Ni-based coordination polymers with distinct features have been prepared. • Compound 1 features a 3D 4-connected 66-dia-type framework, 2 displays a 1D [Ni(HL)(Hdpa)] n ribbon chains motif, while 3 possesses a (4,4)-connected 3D frameworks with bbf topology. • The “mixed ligand assembled” strategy is significant potential for network design.

Heterocyclic Dications as a New Class of Telomeric G-Quadruplex Targeting Agents

Science.gov (United States)

Nanjunda, Rupesh; Musetti, Caterina; Kumar, Arvind; Ismail, Mohamed A.; Farahat, Abdelbasset A.; Wang, Siming; Sissi, Claudia; Palumbo, Manlio; Boykin, David W.; Wilson, W. David

2013-01-01

Small molecules that can induce and stabilize G-quadruplex DNA structures represent a novel approach for anti-cancer and anti-parasitic therapy and extensive efforts have been directed towards discovering lead compounds that are capable of stabilizing quadruplexes. The purpose of this study is to explore conformational modifications in a series of heterocyclic dications to discover structural motifs that can selectively bind and stabilize specific G-quadruplexes, such as those present in the human telomere. The G-quadruplex has various potential recognition sites for small molecules; however, the primary interaction site of most of these ligands is the terminal tetrads. Similar to duplex-DNA groove recognition, quadruplex groove recognition by small molecules offers the potential for enhanced selectivity that can be developed into a viable therapeutic strategy. The compounds investigated were selected based on preliminary studies with DB832, a bifuryl-phenyl diamidine with a unique telomere interaction. This compound provides a paradigm that can help in understanding the optimum compound-DNA interactions that lead to quadruplex groove recognition. DNA recognition by the DB832 derivatives was investigated by biophysical experiments such as thermal melting, circular dichroism, mass spectrometry and NMR. Biological studies were also performed to complement the biophysical data. The results suggest a complex binding mechanism which involves the recognition of grooves for some ligands as well as stacking at the terminal tetrads of the human telomeric G-quadruplex for most of the ligands. These molecules represent an excellent starting point for further SAR analysis for diverse modes of quadruplex recognition and subsequent structure optimization for drug development. PMID:22380518

A series of novel metal–organic coordination polymers constructed from the new 5-(4-imidazol-1-yl-phenyl)-2H-tetrazole spacer and aromatic carboxylates: Synthesis, crystal structures, and luminescence properties

International Nuclear Information System (INIS)

Sun, Jiayin; Zhang, Daojun; Wang, Li; Zhang, Renchun; Wang, Junjie; Zeng, Ying; Zhan, Jinling; Xu, Jianing; Fan, Yong

2013-01-01

Using bifunctional organic ligand 5-(4-imidazol-1-yl-phenyl)-2H-tetrazole (HL) and different aromatic carboxylates as secondary ligands, four novel metal-organic coordination polymers, [Zn(L)(1,4-bdc) 0.5 ] (1), [Zn 1.5 (L)(2,5-pydc)] (2), [Zn(HL)(1,2,4,5-btec) 0.5 ] (3), and [Cd(HL)(1,2,4,5-btec) 0.5 ] (4) (1,4-bdc, 1,4-benzenedicarboxylate; 2,5-pydc, 2,5-pyridinedicarboxylate; 1,2,4,5-btec, 1,2,4,5-benzenetetracarboxylate) have been successfully synthesized and analyzed. Compound 1 features the 2D [Zn(L)] n layers built by μ 3 -L bridging ligands and Zn(II) ions, which are further linked by pillared 1,4-bdc 2− ligands to form a 2-fold interpenetrating dmc framework. The 3D network of compound 2 can be simplified as a rare 2-nodal (3,6)-connected rtl (rutile) topology. Compound 3 possesses a 2D layer structure which is accomplished by connecting ladder-chains to L ligands. Compound 4 exhibits 2D [Cd(1,2,4,5-btec)] layers with infinite Cd–O–Cd rods and the adjacent 2D networks are further pillared by L with terminal bidentate coordination mode to generate the final 3D structure. The solid-state luminescent studies show that compounds 1–4 display intense fluorescent emissions. - Graphical abstract: Using bifunctional organic ligand 5-(4-imidazol-1-yl-phenyl)-2H-tetrazole (HL) and different aromatic carboxylates as secondary ligands, four novel metal-organic coordination polymers have been obtained. All compounds show good luminescence properties at room temperature. Display Omitted - Highlights: • Four Zn(II)/Cd(II)-MOCPs have been successfully prepared with the rigid bifunctional ligand 5-(4-imidazol -1-yl-phenyl) -2H-tetrazole and different aromatic carboxylates mixed ligands. • Compound 2 is a 2-nodal rtl (rutile) net and compound 4 is a binodal (5, 6)-connected net with yav topology. • Compounds 1-4 display intense fluorescent emissions at room temperature

Heterocyclic aramid nanoparticle-assisted graphene exfoliation for fabrication of pristine graphene-based composite paper

Energy Technology Data Exchange (ETDEWEB)

Mo, Yao; Liu, Qi; Fan, Jinchen, E-mail: Jinchen.fan@shiep.edu.cn; Shi, Penghui; Min, Yulin, E-mail: ahaqmylin@126.com; Xu, Qunjie [Shanghai University of Electric Power, Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power, College of Environmental and Chemical Engineering (China)

2015-07-15

Mechanically strong, electrically conductive, and flexible pristine graphene-based composite paper was prepared based on heterocyclic aramid nanoparticle-assisted liquid-phase exfoliation of graphite. The macroscopic heterocyclic aramid yarns were split and assembled into heterocyclic aramid nanoparticles with the size of ∼30 nm by deprotonation in dimethylsulfoxide in the presence of potassium hydroxide. The obtained heterocyclic aramid nanoparticles dimethylsulfoxide dispersion was used as good medium solvent for highly efficiency liquid-phase exfoliation of graphite. The results demonstrated that the concentration of exfoliated graphene can facile reaches ∼2.72 mg/mL after direct sonication of 7 h with assist of heterocyclic aramid nanoparticles. After exfoliation, the self-assembled pristine graphene-based composite paper was fabricated by vacuum-assisted filtration. Due to the introduction of heterocyclic aramid nanoparticles, the self-assembled pristine graphene/heterocyclic aramid nanoparticles composite paper exhibited good mechanical property with tensile strength of ∼129.7 MPa, meantime, has a high electrical conductivity of ∼1.42 × 10{sup 4} S/m.

Heterocyclic aramid nanoparticle-assisted graphene exfoliation for fabrication of pristine graphene-based composite paper

International Nuclear Information System (INIS)

Mo, Yao; Liu, Qi; Fan, Jinchen; Shi, Penghui; Min, Yulin; Xu, Qunjie

2015-01-01

Mechanically strong, electrically conductive, and flexible pristine graphene-based composite paper was prepared based on heterocyclic aramid nanoparticle-assisted liquid-phase exfoliation of graphite. The macroscopic heterocyclic aramid yarns were split and assembled into heterocyclic aramid nanoparticles with the size of ∼30 nm by deprotonation in dimethylsulfoxide in the presence of potassium hydroxide. The obtained heterocyclic aramid nanoparticles dimethylsulfoxide dispersion was used as good medium solvent for highly efficiency liquid-phase exfoliation of graphite. The results demonstrated that the concentration of exfoliated graphene can facile reaches ∼2.72 mg/mL after direct sonication of 7 h with assist of heterocyclic aramid nanoparticles. After exfoliation, the self-assembled pristine graphene-based composite paper was fabricated by vacuum-assisted filtration. Due to the introduction of heterocyclic aramid nanoparticles, the self-assembled pristine graphene/heterocyclic aramid nanoparticles composite paper exhibited good mechanical property with tensile strength of ∼129.7 MPa, meantime, has a high electrical conductivity of ∼1.42 × 10 4  S/m.

A 3D porous zinc MOF constructed from a flexible tripodal ligand: Synthesis, structure, and photoluminescence property

International Nuclear Information System (INIS)

Wen Lili; Wang Dong'e; Wang Chenggang; Wang Feng; Li Dongfeng; Deng Kejian

2009-01-01

A new metal-organic framework, [Zn 5 (trencba) 2 (OH) 2 Cl 2 .4H 2 O] (1) [H 3 trencba=N,N,N',N',N'',N''-tris[(4-carboxylate-2-yl)methyl]-tris (2-aminoethyl)amine], constructed from a flexible tripodal ligand based on C 3 symmetric tris(2-aminoethyl)amine, has been synthesized hydrothermally and characterized by elemental analysis, IR, TG, XRD and single-crystal X-ray diffraction analysis. Compound 1 contains an unprecedented linear penta-nuclear zinc cluster fragment. Each ligand links four penta-nuclear fragments, and every fragment links eight ligands to generate a three-dimensional non-interpenetrated porous framework. The uncoordinated water molecules were observed trapped in the void pores. Compound 1 represents the first example of (6,8)-connected 3D bi-nodal framework based on a single kind of organic ligand. The photoluminescence measurements showed that complex 1 exhibits relatively stronger blue emissions at room temperature than that of the ligand. - Graphical abstract: The MOF [Zn 5 (trencba) 2 (OH) 2 Cl 2 .4H 2 O] (H 3 trencba=N,N,N',N',N',N'-tris[(4-carboxylate-2-yl)methyl]-tris (2-aminoethyl)amine) reveals a (6,8)-connected bi-nodal three-dimensional porous framework with unprecedented penta-nuclear fragment, which appears to be a good candidate of hybrid inorganic-organic photoactive materials

Gold-catalyzed heterocyclizations in alkynyl- and allenyl-β-lactams

Directory of Open Access Journals (Sweden)

Pedro Almendros

2011-05-01

Full Text Available New gold-catalyzed methods using the β-lactam scaffold have been recently developed for the synthesis of different sized heterocycles. This overview focuses on heterocyclization reactions of allenic and alkynic β-lactams which rely on the activation of the allene and alkyne component. The mechanism as well as the regio- and stereoselectivity of the cyclizations are also discussed.

Amide Synthesis from Alcohols and Amines Catalyzed by Ruthenium N-Heterocyclic Carbene Complexes

DEFF Research Database (Denmark)

Dam, Johan Hygum; Osztrovszky, Gyorgyi; Nordstrøm, Lars Ulrik Rubæk

2010-01-01

The direct synthesis of amides from alcohols and amines is described with the simultaneous liberation of dihydrogen. The reaction does not require any stoichiometric additives or hydrogen acceptors and is catalyzed by ruthenium N-heterocyclic carbene complexes. Three different catalyst systems...... are presented that all employ 1,3-diisopropylimidazol-2-ylidene (IiPr) as the carbene ligand. In addition, potassium tert-butoxide and a tricycloalkylphosphine are required for the amidation to proceed. In the first system, the active catalyst is generated in situ from [RuCl2(cod)] (cod = 1,5-cyclooctadiene), 1...... chloride and base. A range of different primary alcohols and amines have been coupled in the presence of the three catalyst systems to afford the corresponding amides in moderate to excellent yields. The best results are obtained with sterically unhindered alcohols and amines. The three catalyst systems do...

A multi-target caffeine derived rhodium(i) N-heterocyclic carbene complex: evaluation of the mechanism of action.

Science.gov (United States)

Zhang, Jing-Jing; Muenzner, Julienne K; Abu El Maaty, Mohamed A; Karge, Bianka; Schobert, Rainer; Wölfl, Stefan; Ott, Ingo

2016-08-16

A rhodium(i) and a ruthenium(ii) complex with a caffeine derived N-heterocyclic carbene (NHC) ligand were biologically investigated as organometallic conjugates consisting of a metal center and a naturally occurring moiety. While the ruthenium(ii) complex was largely inactive, the rhodium(i) NHC complex displayed selective cytotoxicity and significant anti-metastatic and in vivo anti-vascular activities and acted as both a mammalian and an E. coli thioredoxin reductase inhibitor. In HCT-116 cells it increased the reactive oxygen species level, leading to DNA damage, and it induced cell cycle arrest, decreased the mitochondrial membrane potential, and triggered apoptosis. This rhodium(i) NHC derivative thus represents a multi-target compound with promising anti-cancer potential.

Thiosemicarbazides in the synthesis of five- and six-membered heterocyclic compounds

International Nuclear Information System (INIS)

Gazieva, Galina A; Kravchenko, Angelina N

2012-01-01

Data on key chemical transformations of thiosemicarbazides resulting in heterocyclic compounds are generalized and described systematically. Methods for the synthesis of five- and six-membered heterocycles with two and three heteroatoms are considered. The bibliography includes 190 references.

Ruthenium(II) Complexes Containing Lutidine-Derived Pincer CNC Ligands: Synthesis, Structure, and Catalytic Hydrogenation of C-N bonds.

Science.gov (United States)

Hernández-Juárez, Martín; López-Serrano, Joaquín; Lara, Patricia; Morales-Cerón, Judith P; Vaquero, Mónica; Álvarez, Eleuterio; Salazar, Verónica; Suárez, Andrés

2015-05-11

A series of Ru complexes containing lutidine-derived pincer CNC ligands have been prepared by transmetalation with the corresponding silver-carbene derivatives. Characterization of these derivatives shows both mer and fac coordination of the CNC ligands depending on the wingtips of the N-heterocyclic carbene fragments. In the presence of tBuOK, the Ru-CNC complexes are active in the hydrogenation of a series of imines. In addition, these complexes catalyze the reversible hydrogenation of phenantridine. Detailed NMR spectroscopic studies have shown the capability of the CNC ligand to be deprotonated and get involved in ligand-assisted activation of dihydrogen. More interestingly, upon deprotonation, the Ru-CNC complex 5 e(BF4 ) is able to add aldimines to the metal-ligand framework to yield an amido complex. Finally, investigation of the mechanism of the hydrogenation of imines has been carried out by means of DFT calculations. The calculated mechanism involves outer-sphere stepwise hydrogen transfer to the C-N bond assisted either by the pincer ligand or a second coordinated H2 molecule. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of novel binuclear palladium-thallium carboxylates of the type PdTl(O2CR)5 and their structural characterization based on observation of J(203,205T1-1H) and J(203,205T1-13C)

NARCIS (Netherlands)

Koten, G. van; Ploeg, A.F.M.J. van der; Vrieze, K.

1980-01-01

Reactions of palladium(II) carboxylates with thallium(III) carboxylates in toluene yield complexes of the type PdTl(O{2}CR){5} (I), R = Me, Et, i-Pr, or PdTl(O{2}CR){2}(O{2}CR'){3}(II), R = Me, Et, i-Pr, Ph; R' = Me, Et, i-Pr. Substitution of the ligands in PdTl(O{2}CMe){5} by free carboxylic acid

Carbon-14 labelled nitrogen heterocycles; the syntheses of three phosphodiesterase inhibitors

International Nuclear Information System (INIS)

Lawrie, K.W.M.; Novelli, C.E.A.; Saunders, David

1995-01-01

The syntheses of three heterocyclic phosphodiesterase inhibitors are described from a common radiolabelled precursor, namely 2-propoxybenzo[cyano- 14 C] nitrile. Conversion of the nitrile to the corresponding methyl ketone or amidine allows elaboration of the heterocycles radiolabelled within the ring systems. (Author)

Microwave-assisted synthesis of bio-active heterocycles in aqueous media

KAUST Repository

Polshettiwar, Vivek

2010-01-01

Synthesis of bio-active heterocycles and fine chemicals in aqueous media are one of the best solutions for the development of green and sustainable protocols. To illustrate the advantages of aqueous MW chemistry in heterocycle synthesis, in this chapter, various synthetic pathways developed in recent years in aqueous reaction media using microwave irradiation are described.

Synthesis of heterocyclic compounds through palladium-catalyzed C-H cyclization processes.

Science.gov (United States)

Inamoto, Kiyofumi

2013-01-01

Herein, we describe our development of synthetic methods for heterocyclic compounds based on the palladium-catalyzed carbon-hydrogen bond (C-H) functionalization/intramolecular carbon-heteroatom (nitrogen or sulfur) bond formation process. By this C-H cyclization method, we efficiently prepared various N-heterocycles, including indazoles, indoles, and 2-quinolinones, as well as S-heterocycles such as benzothiazoles and benzo[b]thiophenes. Yields are typically good to high and good functional-group tolerance is observed for each process, thereby indicating that the method provides a novel, highly applicable synthetic route to the abovementioned biologically important heterocyclic frameworks. As an application of this approach, an auto-tandem-type, one-pot process involving the oxidative Heck reaction and subsequent C-H cyclization using cinnamamides and arylboronic acids as starting materials in the presence of a palladium catalyst was also developed for the rapid construction of the 2-quinolinone nucleus.

Heterocyclic N-Oxides – An Emerging Class of Therapeutic Agents

Science.gov (United States)

Mfuh, Adelphe M.; Larionov, Oleg V.

2016-01-01

Heterocyclic N-oxides have emerged as potent compounds with anticancer, antibacterial, antihypertensive, antiparasitic, anti-HIV, anti-inflammatory, herbicidal, neuroprotective, and procognitive activities. The N-oxide motif has been successfully employed in a number of recent drug development projects. This review surveys the emergence of this scaffold in the mainstream medicinal chemistry with a focus on the discovery of the heterocyclic N-oxide drugs, N-oxide-specific mechanisms of action, drug-receptor interactions and synthetic avenues to these compounds. As the first review on this subject that covers the developments since 1950s to date, it is expected that it will inspire wider implementation of the heterocyclic N-oxide motif in the rational design of new medicinal agents. PMID:26087764

C-C coupling of N-heterocycles at the fac-Re(CO)(3) fragment: synthesis of pyridylimidazole and bipyridine ligands.

Science.gov (United States)

Viguri, Maialen Espinal; Pérez, Julio; Riera, Lucía

2014-05-05

A new family of cationic rhenium tricarbonyl complexes with either two N-alkylimidazole (N-RIm) and one pyridine (Py) ligand, or two pyridine and one N-RIm ligand, [Re(CO)3 (N-RIm)(3-x) (Py)x ](+) , has been prepared. The reaction of these complexes with a strong base, followed by an oxidant, selectively afforded 2,2'-pyridylimidazole complexes as the result of intramolecular dehydrogenative CC coupling reactions. For tris(pyridine) complexes [Re(CO)3 (Py)3 ](+) the reaction pattern upon a deprotonation/oxidation sequence is maintained, which allows the generation of complexes with 2,2'-bipyridine ligands. In the particular combination of two different types of pyridine ligand in the cationic fac-Re(CO)3 complexes only the cross-coupling products with asymmetric 2,2'-bipyridine ligands were obtained; the homocoupling products were not observed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of a novel poly-thiolated magnetic nano-platform for heavy metal adsorption. Role of thiol and carboxyl functions

International Nuclear Information System (INIS)

Odio, Oscar F.; Lartundo-Rojas, Luis; Palacios, Elia Guadalupe; Martínez, Ricardo; Reguera, Edilso

2016-01-01

Graphical abstract: Poly-thiols capping of magnetite nanoparticles for Pb(2+) and Cd(2+) adsorption. Display Omitted - Highlights: • A novel magnetic nano-platform containing free thiol and carboxyl groups is reported. • Thiols are protected by disulfide bridges during magnetite functionalization. • Adsorption of Pb"2"+ and Cd"2"+ onto the nano-platform was studied by XPS measurements. • Metal-sulfur interactions dominate if free thiol groups are present. • Metal-carboxyl interactions dominate if thiol groups are depleted by oxidation. - Abstract: We report a novel strategy for the synthesis of magnetic nano-platforms containing free thiol groups. It first involves the synthesis of a poly(acrylic acid) copolymer containing disulfide bridges between the linear chains through di-ester linkages, followed by the anchoring of this new ligand to magnetite nanoparticles using a ligand exchange reaction. Finally, free −SH groups are obtained by treating the resulting disulfide-functionalized magnetic nano-system with tributyl phosphine as reducing agent. The characterization of the resulting 17 nm nanoparticles (Fe_3O_4@PAA-HEDred) by FTIR and TGA confirms the attachment of the copolymer through iron carboxylates. XRD, TEM and magnetic measurements indicate an increase in the inorganic core diameter and the occurrence of strong magnetic inter-particle interactions during the exchange reaction, although coercitivity and remanence drop to near zero at room temperature. Afterwards, Fe_3O_4@PAA-HEDred nanoparticles were tested as sorbent for Pb"2"+ and Cd"2"+ cations in aqueous media. XPS measurements were performed in order to unravel the role of both carboxyl and thiol functions in the adsorption process. For the sake of comparison, the same study was performed using bare Fe_3O_4 nanoparticles and a nanosystem with disulfide groups (Fe_3O_4@DMSA). The joint analysis of the Pb 4f, Cd 3d, Fe 2p and S 2p high resolution spectra for the nanostructured materials

Synthesis of a novel poly-thiolated magnetic nano-platform for heavy metal adsorption. Role of thiol and carboxyl functions

Energy Technology Data Exchange (ETDEWEB)

Odio, Oscar F. [Instituto de Ciencia y Tecnología de Materiales, Universidad de La Habana, La Habana 10400 (Cuba); Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada-Unidad Legaria, IPN, 11500 México City (Mexico); Lartundo-Rojas, Luis [Centro de Nanociencias y Micro-Nanotecnologías, IPN, 07738 México City (Mexico); Palacios, Elia Guadalupe [Instituto Politécnico Nacional, ESIQIE, UPALM Zacatenco, 07738 México City (Mexico); Martínez, Ricardo [Instituto de Ciencia y Tecnología de Materiales, Universidad de La Habana, La Habana 10400 (Cuba); Reguera, Edilso, E-mail: edilso.reguera@gmail.com [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada-Unidad Legaria, IPN, 11500 México City (Mexico)

2016-11-15

Graphical abstract: Poly-thiols capping of magnetite nanoparticles for Pb(2+) and Cd(2+) adsorption. Display Omitted - Highlights: • A novel magnetic nano-platform containing free thiol and carboxyl groups is reported. • Thiols are protected by disulfide bridges during magnetite functionalization. • Adsorption of Pb{sup 2+} and Cd{sup 2+} onto the nano-platform was studied by XPS measurements. • Metal-sulfur interactions dominate if free thiol groups are present. • Metal-carboxyl interactions dominate if thiol groups are depleted by oxidation. - Abstract: We report a novel strategy for the synthesis of magnetic nano-platforms containing free thiol groups. It first involves the synthesis of a poly(acrylic acid) copolymer containing disulfide bridges between the linear chains through di-ester linkages, followed by the anchoring of this new ligand to magnetite nanoparticles using a ligand exchange reaction. Finally, free −SH groups are obtained by treating the resulting disulfide-functionalized magnetic nano-system with tributyl phosphine as reducing agent. The characterization of the resulting 17 nm nanoparticles (Fe{sub 3}O{sub 4}@PAA-HEDred) by FTIR and TGA confirms the attachment of the copolymer through iron carboxylates. XRD, TEM and magnetic measurements indicate an increase in the inorganic core diameter and the occurrence of strong magnetic inter-particle interactions during the exchange reaction, although coercitivity and remanence drop to near zero at room temperature. Afterwards, Fe{sub 3}O{sub 4}@PAA-HEDred nanoparticles were tested as sorbent for Pb{sup 2+} and Cd{sup 2+} cations in aqueous media. XPS measurements were performed in order to unravel the role of both carboxyl and thiol functions in the adsorption process. For the sake of comparison, the same study was performed using bare Fe{sub 3}O{sub 4} nanoparticles and a nanosystem with disulfide groups (Fe{sub 3}O{sub 4}@DMSA). The joint analysis of the Pb 4f, Cd 3d, Fe 2p and S 2p high

Carbon-14 labelled nitrogen heterocycles; the syntheses of three phosphodiesterase inhibitors

Energy Technology Data Exchange (ETDEWEB)

Lawrie, K.W.M.; Novelli, C.E.A.; Saunders, David [SmithKline Beecham Pharmaceuticals Research and Development, Harlow (United Kingdom). Synthetic Isotope Chemistry Dept.; Coates, W.J. [SmithKline Beecham Pharmaceuticals Research and Development, Welwyn (United Kingdom)

1995-09-01

The syntheses of three heterocyclic phosphodiesterase inhibitors are described from a common radiolabelled precursor, namely 2-propoxybenzo[cyano-{sup 14}C] nitrile. Conversion of the nitrile to the corresponding methyl ketone or amidine allows elaboration of the heterocycles radiolabelled within the ring systems. (Author).

XAFS Study of the Ferro- and Antiferromagnetic Binuclear Copper(II) Complexes of Azomethine Based Tridentate Ligands

International Nuclear Information System (INIS)

Vlasenko, Valery G.; Vasilchenko, Igor S.; Shestakova, Tatiana E.; Uraev, Ali I.; Burlov, Anatolii S.; Garnovskii, Alexander D.; Pirog, Irina V.

2007-01-01

Binuclear copper complexes are known to be models for metalloenzymes containing copper active sites, and some of them are of considerable interest due to their magnetic and charge transfer properties. The reactions of the complex formation of bibasic tridentate heterocyclic imines with copper acetate leads to two types of chelates with mono deprotonated ligands and with totally deprotonated ligands. Cu K-edge EXAFS has been applied to determine the local structure around the metal center in copper(II) azomethine complexes with five tridentate ligands: 1-(salycilideneimino)- or 1-(2-tosylaminobenzilideneimino)-2-amino(oxo, thio)benzimidazoles. It has been found that some of the chelates studied are bridged binuclear copper complexes, and others are mononuclear complexes. The copper-copper interatomic distances in the bridged binuclear copper complexes were found to be 2.85-3.01 A. Variable temperature magnetic susceptibility data indicate the presence of both ferromagnetic and antiferromagnetic interactions within the dimer, the former is dominating at low temperatures and the latter at high temperatures

Utilization of mixed ligands to construct diverse Ni(II)-coordination polymers based on terphenyl-2,2′,4,4′-tetracarboxylic acid and varied N-donor co-ligands

Energy Technology Data Exchange (ETDEWEB)

Wang, Chao [College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, China Three Gorges University, Yichang 443002 (China); Zhao, Jun, E-mail: junzhao08@126.com [College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, China Three Gorges University, Yichang 443002 (China); State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 35002 (China); Xia, Liang [College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, China Three Gorges University, Yichang 443002 (China); State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 35002 (China); Wu, Xue-Qian; Wang, Jian-Fang; Dong, Wen-Wen; Wu, Ya-Pan [College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, China Three Gorges University, Yichang 443002 (China)

2016-06-15

Three new coordination polymers, namely, {[Ni(H_2L)(bix)(H_2O)_2]·2h_2O}{sub n} (1), {[Ni(HL)(Hdpa)(H_2O)_2]·H_2O}{sub n} (2), {[Ni(L)_0_._5(bpp)(H_2O)]·H_2O}{sub n} (3) (H{sub 4}L=terphenyl-2,2′,4,4′-tetracarboxylic acid; bix=1,4-bis(imidazol-1-ylmethyl)benzene; dpa =4,4′-dipyridylamine; bpp=1,3-bis(4-pyridyl)propane), based on rigid H{sub 4}L ligand and different N-donor co-ligands, have been synthesized under hydrothermal conditions. Compound 1 features a 3D 4-connected 6{sup 6}-dia-type framework with H{sub 4}L ligand adopts a μ{sub 2}-bridging mode with two symmetry-related carboxylate groups in μ{sub 1}-η{sup 1}:η{sup 0} monodentate mode. Compound 2 displays a 1D [Ni(HL)(Hdpa)]{sub n} ribbon chains motif, in which the H{sub 4}L ligand adopts a μ{sub 2}-bridging mode with two carboxylate groups in μ{sub 1}-η{sup 1}:η{sup 1} and μ{sub 1}-η{sup 1}:η{sup 0} monodentate modes, while 3 possesses a (4,4)-connected 3D frameworks with bbf topology, with H{sub 4}L ligand displays a μ{sub 4}-bridging coordination mode. The H{sub 4}L ligand displays not only different deprotonated forms but also diverse coordination modes and conformations. The structural diversities among 1–3 have been carefully discussed, and the roles of N-donor co-ligands in the self-assembly of coordination polymers have been well documented. - Graphical abstract: Three nickel coordination polymers with different architectures based on mixed ligand system were synthesized and structurally characterized. Topology analyses indicate that 1 shows the 4-connected 6{sup 6}-dia net, 1D ribbon chains for 2 and 3D (4,4)-connected bbf network for 3. Display Omitted - Highlights: • Three Ni-based coordination polymers with distinct features have been prepared. • Compound 1 features a 3D 4-connected 66-dia-type framework, 2 displays a 1D [Ni(HL)(Hdpa)]{sub n} ribbon chains motif, while 3 possesses a (4,4)-connected 3D frameworks with bbf topology. • The “mixed ligand assembled�

Quantum mechanics/molecular mechanics simulation of the ligand vibrations of the water-oxidizing Mn4CaO5 cluster in photosystem II.

Science.gov (United States)

Nakamura, Shin; Noguchi, Takumi

2016-10-11

During photosynthesis, the light-driven oxidation of water performed by photosystem II (PSII) provides electrons necessary to fix CO 2 , in turn supporting life on Earth by liberating molecular oxygen. Recent high-resolution X-ray images of PSII show that the water-oxidizing center (WOC) is composed of an Mn 4 CaO 5 cluster with six carboxylate, one imidazole, and four water ligands. FTIR difference spectroscopy has shown significant structural changes of the WOC during the S-state cycle of water oxidation, especially within carboxylate groups. However, the roles that these carboxylate groups play in water oxidation as well as how they should be properly assigned in spectra are unresolved. In this study, we performed a normal mode analysis of the WOC using the quantum mechanics/molecular mechanics (QM/MM) method to simulate FTIR difference spectra on the S 1 to S 2 transition in the carboxylate stretching region. By evaluating WOC models with different oxidation and protonation states, we determined that models of high-oxidation states, Mn(III) 2 Mn(IV) 2 , satisfactorily reproduced experimental spectra from intact and Ca-depleted PSII compared with low-oxidation models. It is further suggested that the carboxylate groups bridging Ca and Mn ions within this center tune the reactivity of water ligands bound to Ca by shifting charge via their π conjugation.

Azomesogens with a heterocyclic moiety

Indian Academy of Sciences (India)

Unknown

Azomesogens with a heterocyclic moiety. †. JAYRANG S DAVE and MEERA MENON*. Department of Applied Chemistry, Faculty of Technology and Engineering, MS University of Baroda,. Baroda 390 001, India. Abstract. Azobenzene derivatives were among the first ten liquid crystalline compounds. But there have been.

Anticancer Gold N-Heterocyclic Carbene Complexes: A Comparative in vitro and ex vivo Study.

Science.gov (United States)

Estrada-Ortiz, Natalia; Guarra, Federica; de Graaf, Inge A M; Marchetti, Lorella; de Jager, Marina H; Groothuis, Geny M M; Gabbiani, Chiara; Casini, Angela

2017-09-07

A series of organometallic Au I N-heterocyclic carbene (NHC) complexes was synthesized and characterized for anticancer activity in four human cancer cell lines. The compounds' toxicity in healthy tissue was determined using precision-cut kidney slices (PCKS) as a tool to determine the potential selectivity of the gold complexes ex vivo. All evaluated compounds presented cytotoxic activity toward the cancer cells in the nano- or low micromolar range. The mixed Au I NHC complex, (tert-butylethynyl)-1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene gold(I), bearing an alkynyl moiety as ancillary ligand, showed high cytotoxicity in cancer cells in vitro, while being barely toxic in healthy rat kidney tissues. The obtained results open new perspectives toward the design of mixed NHC-alkynyl gold complexes for cancer therapy. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Combinatorial synthesis of oxazol-thiazole bis-heterocyclic compounds.

Science.gov (United States)

Murru, Siva; Nefzi, Adel

2014-01-13

A combinatorial library of novel oxazol-thiazole bis-heterocycles was synthesized in good to excellent overall yields with high purity using a solution and solid-phase parallel synthesis approach. Oxazole amino acids, prepared from serine methyl ester and amino acids via coupling and cyclodehydration, were treated with Fmoc-NCS and α-haloketones for the parallel synthesis of diverse bis-heterocycles. Fmoc-isothiocyanate is used as a traceless reagent for thiazole formation. Oxazole diversity can be achieved by using variety of amino acids, whereas thiazole diversity is produced with various haloketones.

Cationic mononuclear ruthenium carboxylates as catalyst prototypes for self-induced hydrogenation of carboxylic acids.

Science.gov (United States)

Naruto, Masayuki; Saito, Susumu

2015-08-28

Carboxylic acids are ubiquitous in bio-renewable and petrochemical sources of carbon. Hydrogenation of carboxylic acids to yield alcohols produces water as the only byproduct, and thus represents a possible next generation, sustainable method for the production of these alternative energy carriers/platform chemicals on a large scale. Reported herein are molecular insights into cationic mononuclear ruthenium carboxylates ([Ru(OCOR)](+)) as prototypical catalysts for the hydrogenation of carboxylic acids. The substrate-derived coordinated carboxylate was found to function initially as a proton acceptor for the heterolytic cleavage of dihydrogen, and subsequently also as an acceptor for the hydride from [Ru-H](+), which was generated in the first step (self-induced catalysis). The hydrogenation proceeded selectively and at high levels of functional group tolerance, a feature that is challenging to achieve with existing heterogeneous/homogeneous catalyst systems. These fundamental insights are expected to significantly benefit the future development of metal carboxylate-catalysed hydrogenation processes of bio-renewable resources.

Synthesis and antiacetylcholinesterase activity of new D-glyceraldehyde heterocyclic derivatives

Energy Technology Data Exchange (ETDEWEB)

Scorzo, Cecilia M.; Fascio, Mirta L.; D' Accorso, Norma B. [Universidad de Buenos Aires, Buenos Aires (Argentina). Facultad de Ciencias Exactas y Naturales. Dept. de Quimica Organica; Cabrera, Margarita Gutierrez; Saavedra, Luis Astudillo [Universidad de Talca (Chile). Inst. de Quimica de Productos Naturales. Lab. de Sintesis Organica

2010-07-01

We report herein the convenient procedures for the syntheses of different heterocyclic compounds from 2,3-O-isopropylidene-D-glyceraldehyde using intramolecular cyclization, 1,3-dipolar cycloaddition or bimolecular coupling reactions. The products were characterized by {sup 1}H and {sup 13}C NMR spectroscopy and elemental analysis. The new heterocycles and their derivatives were evaluated as inhibitors of acetylcholinesterase enzyme. (author)

Synthesis and antiacetylcholinesterase activity of new D-glyceraldehyde heterocyclic derivatives

International Nuclear Information System (INIS)

Scorzo, Cecilia M.; Fascio, Mirta L.; D'Accorso, Norma B.; Cabrera, Margarita Gutierrez; Saavedra, Luis Astudillo

2010-01-01

We report herein the convenient procedures for the syntheses of different heterocyclic compounds from 2,3-O-isopropylidene-D-glyceraldehyde using intramolecular cyclization, 1,3-dipolar cycloaddition or bimolecular coupling reactions. The products were characterized by 1 H and 13 C NMR spectroscopy and elemental analysis. The new heterocycles and their derivatives were evaluated as inhibitors of acetylcholinesterase enzyme. (author)

Variable Denticity in Carboxylate Binding to the Uranyl Coordination Complexes

International Nuclear Information System (INIS)

Groenewold, G.S.; De Jong, Wibe A.; Oomens, Jos; Van Stipdonk, Michael J.

2010-01-01

Tris-carboxylate complexes of the uranyl (UO2)2+ cation with acetate and benzoate were generated using electrospray ionization mass spectrometry, and then isolated in a Fourier transformion cyclotron resonance mass spectrometer. Wavelength-selective infrared multiple photon dissociation (IRMPD) of the tris-acetatouranyl anion resulted in a redox elimination of an acetate radical, which was used to generate an IR spectrum that consisted of six prominent absorption bands. These were interpreted with the aid of density functional theory calculations in terms of symmetric and antisymmetric -CO2 stretches of both the monodentate and bidentate acetate, CH3 bending and umbrella vibrations, and a uranyl O-U-O asymmetric stretch. The comparison of the calculated and measured IR spectra indicated that the tris-acetate complex contained two acetate ligands bound in a bidentate fashion, while the third acetate was monodentate. In similar fashion, the tris-benzoate uranyl anion was formed and photodissociated by loss of a benzoate radical, enabling measurement of the infrared spectrum that was in close agreement with that calculated for a structure containing one monodentate, and two bidentate benzoate ligands.

Cooperative Metal–Ligand Catalyzed Intramolecular Hydroamination and Hydroalkoxylation of Allenes Using a Stable Iron Catalyst

KAUST Repository

El-Sepelgy, Osama

2018-01-18

A new iron-catalyzed chemoselective intramolecular hydroamination and hydroalkoxylation of the readily available α-allenic amines and alcohols to valuable unsaturated 5-membered heterocycles, 2,3-dihydropyrrole and 2,3-dihydrofuran, is reported. Effective selectivity control is achieved by a metal–ligand cooperative activation of the substrates. The mild reaction conditions and the use of low amounts of an air and moisture stable iron catalyst allow for the hydrofunctionalization of a wide range of allenes bearing different functional groups in good yields in the absence of base or any sensitive additives.

Cooperative Metal–Ligand Catalyzed Intramolecular Hydroamination and Hydroalkoxylation of Allenes Using a Stable Iron Catalyst

KAUST Repository

El-Sepelgy, Osama; Brzozowska, Aleksandra; Sklyaruk, Jan; Jang, Yoon Kyung; Zubar, Viktoriia; Rueping, Magnus

2018-01-01

A new iron-catalyzed chemoselective intramolecular hydroamination and hydroalkoxylation of the readily available α-allenic amines and alcohols to valuable unsaturated 5-membered heterocycles, 2,3-dihydropyrrole and 2,3-dihydrofuran, is reported. Effective selectivity control is achieved by a metal–ligand cooperative activation of the substrates. The mild reaction conditions and the use of low amounts of an air and moisture stable iron catalyst allow for the hydrofunctionalization of a wide range of allenes bearing different functional groups in good yields in the absence of base or any sensitive additives.

Acid-base-controlled stereoselective metalation of overhanging carboxylic acid porphyrins: consequences for the formation of heterobimetallic complexes.

Science.gov (United States)

Le Gac, Stéphane; Najjari, Btissam; Dorcet, Vincent; Roisnel, Thierry; Fusaro, Luca; Luhmer, Michel; Furet, Eric; Halet, Jean-François; Boitrel, Bernard

2013-08-12

Overhanging carboxylic acid porphyrins have revealed promising ditopic ligands offering a new entry in the field of supramolecular coordination chemistry of porphyrinoids. Notably, the adjunction of a so-called hanging-atop (HAT) Pb(II) cation to regular Pb(II) porphyrin complexes allowed a stereoselective incorporation of the N-core bound cation, and an allosterically controlled Newton's cradle-like motion of the two Pb(II) ions also emerged from such bimetallic complexes. In this contribution, we have extended this work to other ligands and metal ions, aiming at understanding the parameters that control the HAT Pb(II) coordination. The nature of the N-core bound metal ion (Zn(II), Cd(II)), the influence of the deprotonation state of the overhanging COOH group and the presence of a neutral ligand on the opposite side (exogenous or intramolecular), have been examined through (1)H NMR spectroscopic experiments with the help of radiocrystallographic structures and DFT calculations. Single and bis-strap ligands have been considered. They all incorporate a COOH group hung over the N-core on one side. For the bis-strap ligands, either an ester or an amide group has been introduced on the other side. In the presence of a base, the mononuclear Zn(II) or Cd(II) complexes incorporate the carbonyl of the overhanging carboxylate as apical ligand, decreasing its availability for the binding of a HAT Pb(II). An allosteric effector (e.g., 4-dimethylaminopyridine (DMAP), in the case of a single-strap ligand) or an intramolecular ligand (e.g., an amide group), strong enough to compete with the carbonyl of the hung COO(-), is required to switch the N-core bound cation to the opposite side with concomitant release of the COO(-), thereby allowing HAT Pb(II) complexation. In the absence of a base, Zn(II) or Cd(II) binds preferentially the carbonyl of the intramolecular ester or amide groups in apical position rather than that of the COOH. This better preorganization, with the

Synthesis and characterisation of nitrogen poly-heterocyclic molecules using as selective complexing agents of metallic cations; Synthese et caracterisation de molecules polyheterocycliques azotees utilisables en tant que complexants selectifs de cations metalliques

Energy Technology Data Exchange (ETDEWEB)

Alphonse, F.A

2003-12-15

Separation of actinides (III) from lanthanides (III) is a crucial problem in the reprocessing of used nuclear fuels. Experimental results shown that soft donor extractants such as nitrogen polydentate heterocycles containing a NCCNCCN coordination site are potentials ligands for selective extraction of actinides (III). In those cases, two types of liquid-liquid extractions are employed: synergistic combination with lipophilic acid extractants and direct extraction. On the basis of the Hard and Soft Acids and Bases theory and basicity evaluation, new extractants were defined. We have first studied the synthesis of potential 1,3,5-triazine ligands designed for extraction in synergy with {alpha}-bromodecanoic acid. Secondly, we have examined the synthesis of bis-triazinyl-pyridine ligands for direct extraction studies. Extraction tests were carried out and perspectives of synthesis were deducted from those extraction results. (author)

Biological roles and therapeutic potential of hydroxy-carboxylic acid receptors

Directory of Open Access Journals (Sweden)

Kashan eAhmed

2011-10-01

Full Text Available In the recent past, deorphanization studies have described intermediates of energy metabolism to activate G protein-coupled receptors (GPCRs and to thereby regulate metabolic functions. GPR81, GPR109A and GPR109B, formerly known as the nicotinic acid receptor family, are encoded by clustered genes and share a high degree of sequence homology. Recently, hydroxy-carboxylic acids were identified as endogenous ligands of GPR81, GPR109A and GPR109B, and therefore these receptors have been placed into a novel receptor family of hydroxy-carboxylic acid (HCA receptors. The HCA1 receptor (GPR81 is activated by the glycolytic metabolite 2-hydroxy-propionic acid (lactate, the HCA2 receptor is activated by the ketone body 3-hydroxy-butyric acid and the HCA3 receptor (GPR109B is a receptor for the β-oxidation intermediate 3-hydroxy-octanoic acid. While HCA1 and HCA2 receptors are present in most mammalian species, the HCA3 receptor is exclusively found in humans and higher primates. HCA receptors are expressed in adipose tissue and mediate anti-lipolytic effects in adipocytes through Gi-type G-protein-dependent inhibition of adenylyl cyclase. HCA2 and HCA3 inhibit lipolysis during conditions of increased β-oxidation such as prolonged fasting, whereas HCA1 mediates the anti-lipolytic effects of insulin in the fed state. As HCA2 is a receptor for the established anti-dyslipidemic drug nicotinic acid, HCA1 and HCA3 also represent promising drug targets and several synthetic ligands for HCA receptors have been developed. In this article, we will summarize the deorphanization and pharmacological characterization of HCA receptors. Moreover, we will discuss recent progress in elucidating the physiological and pathophysiological role to further evaluate the therapeutic potential of the HCA receptor family for the treatment of metabolic disease.

Trinuclear rhenium(III) halide clusters with carboxylate ligands

Science.gov (United States)

Dougan, Jeffrey Steven

Four mono(carboxylato)trirhenium complexes and three bis(carboxylato)trirhenium complexes have been synthesized and characterized, principally by mass spectrometry, with supporting evidence from X-ray diffraction. These compounds represent the first trinuclear rhenium carboxylate complexes. The reactions generally proceed readily under comparatively mild conditions. Mass spectrometry has again proved its usefulness as a technique in the field of metal cluster chemistry, having provided the initial identification of the products of the reactions studied. These compounds provide a further base to which future mass spectra of metal cluster compounds can be compared. Re-examination of a reaction reported by Taha and Wilkinson has also cast considerable doubt onto the validity of a conversion widely reported in the literature that transforms (Re3Cl9) x into [Re2(O2CCH3)4Cl 2]. We believe that the literature result is a consequence of the purity of the metal precursor, and suggest that the starting material in the earlier work may have contained ReCl4 or ReCl5. The importance of mass spectrometry in the characterization of the new compounds synthesized in this project has led to a thorough study of calculated isotopic distributions. The information gathered suggests that for isotopically simple molecules, the choice of algorithm for computing an isotopic distribution is unimportant. However, it is important to compute the mass spectrum of an isotopically complex molecule using an algorithm that can, if desired, show the underlying isotopic fine structure of a peak of interest. In the last chapter of this thesis, the results of a project in chemistry education research are presented. Predicting the success of students in general chemistry has long been of interest to the chemistry education community, and several factors have been identified as contributing factors. An off-hand comment by a student inspired an examination of whether continuity with the same instructor for

The reactions of anthronylidene carbene with some heterocyclic compounds

International Nuclear Information System (INIS)

Divisia, Bernadette

1970-01-01

The action of the anthronylidene carbene, generated by photochemical decomposition of 9-diazo 10-anthron, on four heterocyclic compounds (furan, thiophene, 1-methyl-pyrrole and 2,5-dihydrofuran) has been examined. Two classical carbene reactions have been observed: the addition on double bond (furan, thiophene, 1-methylpyrrole) and hydrogen atom abstraction of the heterocyclic compound (2,5-dihydrofuran). In the case of furan and thiophene, the cyclo-propanic compound resulting from the addition is spontaneously transformed into an ethylenic derivative by valence isomerization. The furan derivative undergoes a cis-trans isomerization, while the thiophene one undergoes an extra carbene attack. In the case of 1-methylpyrrole, the corresponding cyclo-propanic compound undergoes a ring cleavage, followed by a hydrogen atom migration leading to the formation of a substituted anthron. Only an allylic hydrogen atom selective abstraction of heterocyclic compound takes place in the reaction of anthronylidene carbene with 2,5-dihydrofuran. The asymmetrical coupling of radicals so obtained yields the corresponding substituted anthron. (author) [fr

Investigations on organogermanium compounds; III. N-tributylgermyl-substituted aliphatic and heterocyclic amines

NARCIS (Netherlands)

Rijkens, F.; Janssen, M.J.; Kerk, G.J.M. van der

1965-01-01

A series of new organogermanium compounds containing a germanium‐nitrogen bond, in many of which the nitrogen atom forms part of an heterocyclic ring, are prepared, in some cases by new methods: transamination reactions and reactions of germoxanes with heterocyclic amines. Striking differences in

Microwave-Assisted Multicomponent Synthesis of Heterocycles

NARCIS (Netherlands)

Kruithof, A.; Ruijter, E.; Orru, R.V.A.

2011-01-01

Multicomponent reactions are valuable tools for the generation of diverse heterocycles. As in many fields or organic chemistry, microwave irradiation is rapidly replacing conventional heating methods in multicomponent chemistry. In this review, we present an overview of recent applications of the

Peculiarities of structure of rare earth β-diketonates and carboxylates with mostly ionic type of bond

International Nuclear Information System (INIS)

Kuz'mina, N.P.; Martynenko, L.I.

1996-01-01

X-ray diffraction data on β-diketonates and carboxylates of rare earths (3) have been analyzed. Essential features of the compounds structure have been formulated. It is shown that in the compounds mentioned irregular distortions of chelate cycles over the length and angles of bonds are observed, there is no regularity in the ratios of metal-ligand bridge and chelate bond lengths both in the series of compounds of different composition and inside one compound. 2 refs

Crystal structure of mixed ligand compound [HgPhen{(C2H5)2NCS2}2] and character of intermolecular interaction in the structures of [MPhen{(C2H5)2NCS2}2] (M = Zn, Cd, Hg) complexes

International Nuclear Information System (INIS)

Klevtsova, R.F.; Glinskaya, L.A.; Zemskova, S.M.; Larionov, S.V.

2002-01-01

Monocrystals of mixed ligand complex [HgPhen(Et 2 NCS 2 ) 2 ] (Phen = 1, 10-phenanthroline) have been prepared and by the method of X-ray diffraction its crystal structure has been determined. The structure of mercury complex has been compared with structures of previously studied cadmium and zinc complexes similar in composition. The character of interaction between molecules of cadmium, zinc, mercury mixed ligand complexes and ways of their packing have been considered. It is shown that the structure of the complexes presents a molecular group assembled from two monomeric compounds at the expense of interaction between heterocyclic ligands contained in the mixed ligand complexes [ru

Spectroscopic properties and antimicrobial activity of dioxomolybdenum(VI complexes with heterocyclic S,S’-ligands

Directory of Open Access Journals (Sweden)

Sovilj Sofija P.

2012-01-01

Full Text Available Five new dioxomolybdenum(VI complexes of the general formula[MoO2(Rdtc2], 1-5, where Rdtc-refer to piperidine- (Pipdtc, 4-morpholine-(Morphdtc, 4-thiomorpholine-(Timdtc, piperazine- (Pzdtc or Nmethylpiperazine- (N-Mepzdtc dithiocarbamates, respectively, have been prepared. Elemental analysis, conductometric measurements, electronic, IR and NMR spectroscopy have been employed to characterize them. Complexes 1-5 contain a cis-MoO2 group and are of an octahedral geometry. Two dithiocarbamato ions join as bidentates with both the sulphur atoms to the molybdenum atom. The presence of different heteroatom in the piperidinо moiety influences the v(C----N and v(C----S vibrations, which decrease in the order of the complexes with: Pipdtc > N-Mepipdtc > Morphdtc > Pzdtc > Timdtc ligands. On the basis of spectral data, molecular structures of complexes 1-5 were optimized on semiempirical molecular-orbital level, and the geometries, as obtained from calculations, described. Antimicrobial activity was tested against nine different laboratory control strains of bacteria and two strains of yeast Candida albicans. All tested strains were sensitive. Complexes bearing heteroatom in position 4 of piperidine moiety are significantly more potent against bacteria tested comparing to corresponding ligands.

Dietary exposure to heterocyclic amines in high-temperature cooked meat and fish in Malaysia.

Science.gov (United States)

Jahurul, M H A; Jinap, S; Ang, S J; Abdul-Hamid, A; Hajeb, P; Lioe, H N; Zaidul, I S M

2010-08-01

The intake of heterocyclic amines is influenced by the amount and type of meat and fish ingested, frequency of consumption, cooking methods, cooking temperature, and duration of cooking. In this study, the dietary intake of heterocyclic amines in Malaysia and their main sources were investigated. Forty-two samples of meat and fish were analysed by high-performance liquid chromatography with photodiode array detector to determine the concentration of the six predominant heterocyclic amines, namely: 2-amino-3-methylimidazo[4,5-f] quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f] quinoline(MeIQ), 2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f] quinoxaline (4,8-DiMeIQx), 2-amino-3,7,8-trimethylimidazo[4,5-f] quinoxaline (7,8-DiMeIQx), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Dietary intake data were obtained using a food-frequency questionnaire when interviewing 600 Malaysian respondents. The level of total heterocyclic amines in food samples studies ranged from not detected to 38.7 ng g(-1). The average daily intake level of heterocyclic amine was 553.7 ng per capita day(-1). The intake of PhIP was the highest, followed by MeIQx and MeIQ. The results reveal that fried and grilled chicken were the major dietary source of heterocyclic amines in Malaysia. However, the heterocyclic amine intake by the Malaysian population was lower than those reported from other regions.

Synthesis, Characterization and catalytic activity of triorganotin(IV) carboxylates for the production of biodiesel from rocket seed oil

International Nuclear Information System (INIS)

Tariq, M.; Ali, S.

2013-01-01

Organotin(IV) carboxylates have a wide range of industrial applications such as antifouling paints, PVC stabilization, ion carries in electrochemical membranes and homogeneous catalysts. The catalytic application of organotin carboxylates are in the field of silicone curing, polyurethane formation and esterification. Only a limited literature is available regarding the use of organotin carboxylates in the transesterification of vegetable oil to produce biodiesel . The present study deals with the synthesis of some new triorganotin(IV) carboxylates for their subsequent use as catalyst for transesterification of rocket seed oil to produce biodiesel. The three new triorganotin(IV) i.e. (Me/sub 3/SnL) (1),(Bu/sub 3/Snl) (2) and (Ph/sub 3/SnL) (3), were synthesized by refluxing sodium salt of ligand (NaL), where L=O/sub 2/C(CH/sub 3/)C=CHC/sub 6/H/sub 4/F with trimethyl, tributyl and triphenyl tin(IV) chlorides, respectively for 10 hrs. The synthesized compounds were characterized by instrumental techniques like FT-IR and NMR (1H, 13C). The catalytic activity of these compounds was assessed for transesterification of triglycerides in rocket seed oil to produce biodiesel. All the tested compounds showed good catalytic activity in the order 1> 2 > 3. (author)

Fusing porphyrins with polycyclic aromatic hydrocarbons and heterocycles for optoelectronic applications

Science.gov (United States)

Thompson, Mark E.; Diev, Viacheslav; Hanson, Kenneth; Forrest, Stephen R.

2015-08-18

A compound that can be used as a donor material in organic photovoltaic devices comprising a non-activated porphyrin fused with one or more non-activated polycyclic aromatic rings or one or more non-activated heterocyclic rings can be obtained by a thermal fusion process. The compounds can include structures of Formula I: ##STR00001## By heating the reaction mixture of non-activated porphyrins with non-activated polycyclic aromatic rings or heterocyclic rings to a fusion temperature and holding for a predetermined time, fusion of one or more polycyclic rings or heterocyclic rings to the non-activated porphyrin core in meso,.beta. fashion is achieved resulting in hybrid structures containing a distorted porphyrin ring with annulated aromatic rings. The porphyrin core can be olygoporphyrins.

Synthesis of heterocycles through transition-metal-catalyzed isomerization reactions

DEFF Research Database (Denmark)

Ishøy, Mette; Nielsen, Thomas Eiland

2014-01-01

of structurally complex and diverse heterocycles. In this Concept article, we attempt to cover this area of research through a selection of recent versatile examples. A sea of opportunities! Transition-metal-catalyzed isomerization of N- and O-allylic compounds provides a mild, selective and synthetically...... versatile method to form iminium and oxocarbenium ions. Given the number of reactions involving these highly electrophilic intermediates, this concept provides a sea of opportunities for heterocycle synthesis, (see scheme; Nu=nucleophile). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim....

Inorganic heterocycles with two manganes or rhenium carbonyl units

International Nuclear Information System (INIS)

Kuellmer, V.; Vahrenkamp, H.

1977-01-01

From the reactive complexes [(CO) 4 M-E-Sn(CH 3 ) 3 ] 2 (M = Mn,Re; E = S,Se) with (CH 3 ) 2 PCl via the non-isolable four-membered ring intermediates [(CO) 4 M-E-P(CH 3 ) 2 ] 2 the six-membered heterocycles[-(CO) 4 M-P(CH 3 ) 2 -E-] 2 are formed. By use of (CH 3 ) 2 AsCl both the four-membered ring intermediates and the six-membered ring products can be isolated. The six-membered heterocycles can be opened by trimethylphosphine. (orig./HK) [de

Synthesis and Characterization of a New Heterocyclic Azo Pigment

International Nuclear Information System (INIS)

Asniza, M.; Issam, A.M.; Khalil, H.P.S.A.

2011-01-01

A new heterocyclic coupling agent has been produced from the reaction of maleic anhydride and p-aminophenol, namely N-(4-hexahydrophenol)maleimide. The coupling agent underwent azo coupling reaction with aromatic amine, which is p-aminophenol to produce a new heterocyclic azo pigment. The pigment was then subjected to solubility, hiding power and light fastness test. Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet/ Visible (UV/Vis) Spectroscopy, and Nuclear Magnetic Resonance Spectroscopy ( 1 H-NMR, 13 C-NMR) were used to obtain the characteristics and structural features of the pigment. (author)

Synthesis of heterocyclic chalcone derivatives and their radical scavenging ability toward 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals

International Nuclear Information System (INIS)

Hwang, Kijun; Kim, Hoseok; Kim, Beomtae; Han, Incheol

2012-01-01

A series of heterocyclic chalcone derivatives bearing heterocycles such as thiophene or furan ring as an isostere of benzene ring were carefully prepared, and the influence of heterocycles on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities was systematically investigated. Structure-activity relationships (SAR) analysis showed that the activities of thiophene ring-containing chalcones were higher than those of furan ring containing chalcones, and the presence of methyl substituent of heterocyclic ring distinctly affected the activities compared with non-substituted heterocycles in an opposite manner, with the 4'-methyl group of thiophene ring increasing activity and the 3'-methyl group of the furan ring decreasing activity. The distinct isosteric effect of heterocycles (i.e., thiophene or furan ring) on radical scavenging activities of heterocyclic chalcones was distinctly demonstrated in our work

Highly Luminescent Dinuclear Platinum(II) Complexes Incorporating Bis-Cyclometallating Pyrazine-Based Ligands: A Versatile Approach to Efficient Red Phosphors

OpenAIRE

Culham, Stacey; Lanoe, Pierre-Henri; Whittle, Victoria; Durrant, Marcus; Williams, Gareth; Kozhevnikov, Valery

2013-01-01

A series of luminescent dinuclear platinum(II) complexes incorporating diphenylpyrazine-based bridging ligands ((LH2)-H-n) has been prepared. Both 2,5-diphenylpyrazine ((LH2)-H-2) and 2,3-diphenylpyrazine ((LH2)-H-3) are able to undergo cyclometalation of the two phenyl rings, with each metal ion binding to the two nitrogen atoms of the central heterocycle, giving, after treatment with the anion of dipivaloyl methane (dpm), complexes of formula \\{Pt(dpm)\\}(2)L-n. These compounds are isomers o...

Synthesis, characterization and antimicrobial activities of novel silver(I) complexes with coumarin substituted N-heterocyclic carbene ligands.

Science.gov (United States)

Karataş, Mert Olgun; Olgundeniz, Begüm; Günal, Selami; Özdemir, İlknur; Alıcı, Bülent; Çetinkaya, Engin

2016-02-15

Eight new coumarin substituted silver(I) N-heterocyclic carbene (NHC) complexes were synthesized by the interaction of the corresponding imidazolium or benzimidazolium chlorides and Ag2O in dichloromethane at room temperature. Structures of these complexes were established on the basis of elemental analysis, (1)H NMR, (13)C NMR, IR and mass spectroscopic techniques. The antimicrobial activities of carbene precursors and silver NHC complexes were tested against standard strains: Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and the fungi Candida albicans and Candida tropicalis. Results showed that all the compounds inhibited the growth of the all bacteria and fungi strains and some complexes performed good activities against different microorganisms. Among all the compounds, the most lipophilic complex bis[1-(4-methylene-6,8-dimethyl-2H-chromen-2-one)-3-(naphthalene-2-ylmethyl)benzimidazol-2-ylidene]silver(I) dichloro argentate (5e) was found out as the most active one. Copyright © 2015 Elsevier Ltd. All rights reserved.

Aromatic carboxylate effect on dimensionality of three bis(benzimidazole)-based cobalt(II) coordination polymers: Syntheses, structures and properties

International Nuclear Information System (INIS)

Zhang, Ju-Wen; Gong, Chun-Hua; Hou, Li-Li; Tian, Ai-Xiang; Wang, Xiu-Li

2013-01-01

Three new metal-organic coordination polymers [Co(4-bbc) 2 (bbbm)] (1), [Co(3,5-pdc)(bbbm)]·2H 2 O (2) and [Co(1,4-ndc)(bbbm)] (3) (4-Hbbc=4-bromobenzoic acid, 3,5-H 2 pdc=3,5-pyridinedicarboxylic acid, 1,4-H 2 ndc=1,4-naphthalenedicarboxylic acid and bbbm=1,1-(1,4-butanediyl)bis-1H-benzimidazole) were hydrothermally synthesized and structurally characterized. Polymer 1 is a 1D chain formed by the bbbm ligands and Co II ions. Polymer 2 exhibits a 2D network with a (3·4·5)(3 2 ·4·5·6 2 ·7 4 ) topology. Polymer 3 possesses a 3D three-fold interpenetrating framework. The versatile structures of title polymers indicate that the aromatic carboxylates have an important influence on the dimensionality of 1–3. Moreover, the thermal stability, electrochemical and luminescent properties of 1–3 were investigated. - graphical abstract: Three bis(benzimidazole)-based cobalt(II) coordination polymers tuned by aromatic carboxylates were hydrothermally synthesized and structurally characterized. The aromatic carboxylates play a key role in the dimensionality of three polymers. The electrochemical and luminescent properties of three polymers were investigated. Display Omitted - Highlights: • Three bis(benzimidazole)-based cobalt(II) coordination polymers tuned by aromatic carboxylates were obtained. • The aromatic carboxylates have an important influence on the dimensionality of three polymers. • The electrochemical and luminescent properties of three polymers were investigated

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

Science.gov (United States)

2016-01-01

Summary Multicomponent reactions (MCRs) are one of the most important processes for the preparation of highly functionalized organic compounds in modern synthetic chemistry. As shown in this review, they play an important role in organophosphorus chemistry where phosphorus reagents are used as substrates for the synthesis of a wide range of phosphorylated heterocycles. In this article, an overview about multicomponent reactions used for the synthesis of heterocyclic compounds bearing a phosphonate group on the ring is given. PMID:27559377

Luminescent hybrid lanthanide sulfates and lanthanide sulfonate-carboxylates with 1,10-phenanthroline involving in-situ oxidation of 2-mercaptonbenzoic acid

Science.gov (United States)

Zhong, Jie-Cen; Wan, Fang; Sun, Yan-Qiong; Chen, Yi-Ping

2015-01-01

A series of lanthanide sulfates and lanthanide sulfonate-carboxylates, [Ln2(phen)2(SO4)3(H2O)2]n (I:Ln=Nd(1a), Sm(1b), Eu(1c), phen=1,10-phenanthroline) and [Ln(phen)(2-SBA)(BZA)]n (II: Ln=Sm(2a), Eu(2b), Dy(2c), 2-SBA=2-sulfobenzoate, BZA=benzoate) have been hydrothermally synthesized from lanthanide oxide, 2-mercaptonbenzoic acid with phen as auxiliary ligand and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, TG analyses and luminescence spectroscopy. Interestingly, SO4 2 - anions in I came from the in situ deep oxidation of thiol groups of 2-mercaptonbenzoic acid while 2-sulfobenzoate and benzoate ligands in II from the middle oxidation and desulfuration reactions of 2-mercaptonbenzoic acid. Compounds I are organic-inorganic hybrid lanthanide sulfates, which have rare one-dimensional column-like structures. Complexes II are binuclear lanthanide sulfonate-carboxylates with 2-sulfobenzoate and benzoate as bridges and 1,10-phenanthroline as terminal. Photoluminescence studies reveal that complexes I and II exhibit strong lanthanide characteristic emission bands in the solid state at room temperature.

Ruthenium(III) Complexes of Heterocyclic Tridentate (ONN) Schiff Base: Synthesis, Characterization and its Biological Properties as an Antiradical and Antiproliferative Agent

Science.gov (United States)

Ejidike, Ikechukwu P.; Ajibade, Peter A.

2016-01-01

The current work reports the synthesis, spectroscopic studies, antiradical and antiproliferative properties of four ruthenium(III) complexes of heterocyclic tridentate Schiff base bearing a simple 2′,4′-dihydroxyacetophenone functionality and ethylenediamine as the bridging ligand with RCHO moiety. The reaction of the tridentate ligands with RuCl3·3H2O lead to the formation of neutral complexes of the type [Ru(L)Cl2(H2O)] (where L = tridentate NNO ligands). The compounds were characterized by elemental analysis, UV-vis, conductivity measurements, FTIR spectroscopy and confirmed the proposed octahedral geometry around the Ru ion. The Ru(III) compounds showed antiradical potentials against 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, with DPPH scavenging capability in the order: [(PAEBOD)RuCl2] > [(BZEBOD)RuCl2] > [(MOABOD)RuCl2] > [Vit. C] > [rutin] > [(METBOD)RuCl2], and ABTS radical in the order: [(PAEBOD)RuCl2] < [(MOABOD)RuCl2] < [(BZEBOD)RuCl2] < [(METBOD)RuCl2]. Furthermore, in vitro anti-proliferative activity was investigated against three human cancer cell lines: renal cancer cell (TK-10), melanoma cancer cell (UACC-62) and breast cancer cell (MCF-7) by SRB assay. PMID:26742030

Ruthenium(III Complexes of Heterocyclic Tridentate (ONN Schiff Base: Synthesis, Characterization and its Biological Properties as an Antiradical and Antiproliferative Agent

Directory of Open Access Journals (Sweden)

Ikechukwu P. Ejidike

2016-01-01

Full Text Available The current work reports the synthesis, spectroscopic studies, antiradical and antiproliferative properties of four ruthenium(III complexes of heterocyclic tridentate Schiff base bearing a simple 2′,4′-dihydroxyacetophenone functionality and ethylenediamine as the bridging ligand with RCHO moiety. The reaction of the tridentate ligands with RuCl3·3H2O lead to the formation of neutral complexes of the type [Ru(LCl2(H2O] (where L = tridentate NNO ligands. The compounds were characterized by elemental analysis, UV-vis, conductivity measurements, FTIR spectroscopy and confirmed the proposed octahedral geometry around the Ru ion. The Ru(III compounds showed antiradical potentials against 2,2-Diphenyl-1-Picrylhydrazyl (DPPH and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS radicals, with DPPH scavenging capability in the order: [(PAEBODRuCl2] > [(BZEBODRuCl2] > [(MOABODRuCl2] > [Vit. C] > [rutin] > [(METBODRuCl2], and ABTS radical in the order: [(PAEBODRuCl2] < [(MOABODRuCl2] < [(BZEBODRuCl2] < [(METBODRuCl2]. Furthermore, in vitro anti-proliferative activity was investigated against three human cancer cell lines: renal cancer cell (TK-10, melanoma cancer cell (UACC-62 and breast cancer cell (MCF-7 by SRB assay.

Highly efficient bioinspired molecular Ru water oxidation catalysts with negatively charged backbone ligands.

Science.gov (United States)

Duan, Lele; Wang, Lei; Li, Fusheng; Li, Fei; Sun, Licheng

2015-07-21

The oxygen evolving complex (OEC) of the natural photosynthesis system II (PSII) oxidizes water to produce oxygen and reducing equivalents (protons and electrons). The oxygen released from PSII provides the oxygen source of our atmosphere; the reducing equivalents are used to reduce carbon dioxide to organic products, which support almost all organisms on the Earth planet. The first photosynthetic organisms able to split water were proposed to be cyanobacteria-like ones appearing ca. 2.5 billion years ago. Since then, nature has chosen a sustainable way by using solar energy to develop itself. Inspired by nature, human beings started to mimic the functions of the natural photosynthesis system and proposed the concept of artificial photosynthesis (AP) with the view to creating energy-sustainable societies and reducing the impact on the Earth environments. Water oxidation is a highly energy demanding reaction and essential to produce reducing equivalents for fuel production, and thereby effective water oxidation catalysts (WOCs) are required to catalyze water oxidation and reduce the energy loss. X-ray crystallographic studies on PSII have revealed that the OEC consists of a Mn4CaO5 cluster surrounded by oxygen rich ligands, such as oxyl, oxo, and carboxylate ligands. These negatively charged, oxygen rich ligands strongly stabilize the high valent states of the Mn cluster and play vital roles in effective water oxidation catalysis with low overpotential. This Account describes our endeavors to design effective Ru WOCs with low overpotential, large turnover number, and high turnover frequency by introducing negatively charged ligands, such as carboxylate. Negatively charged ligands stabilized the high valent states of Ru catalysts, as evidenced by the low oxidation potentials. Meanwhile, the oxygen production rates of our Ru catalysts were improved dramatically as well. Thanks to the strong electron donation ability of carboxylate containing ligands, a seven

C-N Bond Activation and Ring Opening of a Saturated N-Heterocyclic Carbene by Lateral Alkali-Metal-Mediated Metalation.

Science.gov (United States)

Hernán-Gómez, Alberto; Kennedy, Alan R; Hevia, Eva

2017-06-01

Combining alkali-metal-mediated metalation (AMMM) and N-heterocyclic carbene (NHC) chemistry, a novel C-N bond activation and ring-opening process is described for these increasingly important NHC molecules, which are generally considered robust ancillary ligands. Here, mechanistic investigations on reactions of saturated NHC SIMes (SIMes=[:C{N(2,4,6-Me 3 C 6 H 2 )CH 2 } 2 ]) with Group 1 alkyl bases suggest this destructive process is triggered by lateral metalation of the carbene. Exploiting co-complexation and trans-metal-trapping strategies with lower polarity organometallic reagents (Mg(CH 2 SiMe 3 ) 2 and Al(TMP)iBu 2 ), key intermediates in this process have been isolated and structurally defined. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Complexation of vanadium with amidoxime and carboxyl groups. Uncovering the competitive role of vanadium in uranium extraction from seawater

Energy Technology Data Exchange (ETDEWEB)

Wang, Cong-Zhi; Wu, Qun-Yan; Lan, Jian-Hui; Shi, Wei-Qun [Chinese Academy of Sciences, Beijing (China). Inst. of High Energy Physics; Chai, Zhi-Fang [Chinese Academy of Sciences, Beijing (China). Inst. of High Energy Physics; Soochow Univ., Suzhou (China). School of Radiological and Interdisciplinary Sciences (RAD-X); Wu, Guo-Zhong [Chinese Academy of Sciences, Shanghai (China). Shanghai Inst. of Applied Physics

2017-09-01

At present, amidoxime-based adsorbents are considered to be the most promising materials for extraction of uranium from seawater. However, the high concentrations of transition metals especially vanadium strongly compete with uranium in the sequestration process, which is extremely limited the commercial use of amidoxime-based adsorbents. In this work, the coordination modes, bonding nature, and stabilities of possible vanadium(IV) (VO{sup 2+}) and (V) (VO{sub 2}{sup +}, VO{sup 3+}, V{sup 5+}) complexes with amidoximate (AO{sup -}), carboxyl (Ac{sup -}), glutarimidedioximate (HA{sup -}) and deprotonated glutarimidedioximate (A{sup 2-}) on single and double alkyl chains (R=C{sub 13}H{sub 26}) are systematically explored by quantum chemical calculations. Different from the uranyl (UO{sub 2}{sup 2+}) complexes, the AO{sup -} groups of the vanadium(IV) and (V) complexes prefer to coordinate as monodentate and chelate ligands, while few species with AO{sup -} groups in η{sup 2}-binding mode have been observed in the vanadium complexes. Besides, the vanadium complexes are predicted to have obvious covalent metal-ligand bonds. According to thermodynamic stability analysis, all the vanadium complexes with AO{sup -}, Ac{sup -}, HA{sup -} and A{sup 2-} ligands on double alkyl chains are found to be more stable than corresponding complexes with ligands on a single chain. The synergistic effect of the amidoxime and carboxyl groups can be observed in most of VO{sub 2}{sup +} and VO{sup 3+} complexes with mixed ligands (AO{sup -}/Ac{sup -}). The vanadium(IV) and (V) complexes are more stable than the corresponding uranyl complexes, and the adsorption capability of the amidoxime-based adsorbents toward vanadium(V) ions decrease in the order of VO{sub 2}{sup +}>VO{sup 3+}> V{sup 5+}. The dioxovanadium cation VO{sub 2}{sup +} is predicted to form multinuclear vanadium complex in the sequestration process, possibly resulting in higher stable VO{sub 2}{sup +} complexes. Therefore

γ-Sultam-cored N,N-ligands in the ruthenium(ii)-catalyzed asymmetric transfer hydrogenation of aryl ketones.

Science.gov (United States)

Rast, Slavko; Modec, Barbara; Stephan, Michel; Mohar, Barbara

2016-02-14

The synthesis of new enantiopure syn- and anti-3-(α-aminobenzyl)-benzo-γ-sultam ligands 6 and their application in the ruthenium(ii)-catalyzed asymmetric transfer hydrogenation (ATH) of ketones using formic acid/triethylamine is described. In particular, benzo-fused cyclic ketones afforded excellent enantioselectivities in reasonable time employing a low loading of the syn ligand-containing catalyst. A never-before-seen dynamic kinetic resolution (DKR) during reduction of a γ-keto carboxylic ester (S7) derivative of 1-indanone is realized leading as well to excellent induction.

Remediation of lead-contaminated soil with non-toxic biodegradable natural ligands extracted from soybean.

Science.gov (United States)

Lee, Yong-Woo; Kim, Chulsung

2012-01-01

Bench-scale soil washing studies were performed to evaluate the potential application of non-toxic, biodegradable extracted soybean-complexing ligands for the remediation of lead-contaminated soils. Results showed that, with extracted soybean-complexing ligands, lead solubility extensively increased when pH of the solution was higher than 6, and approximately 10% (500 mg/kg) of lead was removed from a rifle range soil. Two potential primary factors controlling the effectiveness of lead extraction from lead-contaminated soils with natural ligands are adsorption of extracted aqueous lead ions onto the ground soybean and the pH of the extraction solution. More complexing ligands were extracted from the ground soybean as the reaction pH increased. As a result, significantly higher lead extraction efficiency was observed under basic environments. In addition, less adsorption onto soybean was observed when the pH of the solution was higher than 7. Among two available Lewis base functional groups in the extracted soybean-complexing ligands such as carboxylate and the alpha-amino functional groups, the non-protonated alpha-amino functional groups may play an important role for the dissolution of lead from lead-contaminated soil through the formation of soluble lead--ligand complexes.

Nucleobases in Space: Laboratory Studies of Polycyclic Aromatic Nitrogen Heterocycles

Science.gov (United States)

Elsila, Jamie; Mattioda, Andy; Bernstein, Max; Sandford, Scott; Hudgins, Doug

2005-01-01

Polycyclic Aromatic Nitrogen Heterocycles (PANHs) are heterocyclic aromatics Le., PAHs with carbon atoms replaced by a nitrogen atom. These molecules have been detected in meteorite extracts, and in general these nitrogen heterocycles are of astrobiological interest since this class of molecules include nucleobases, basic components of our nucleic acids. These compounds are predicted to be present in the interstellar medium and in Titan tholin, but have received relatively little attention. We will present spectra and reactions of PANHs, frozen in solid H2O at 12 K, conditions germane to astronomical observations. In contrast to simple PAHs, that do not interact strongly with solid H2O, the nitrogen atoms in PANHs are potentially capable of hydrogen bonding with H20 changing their spectra, complicating their remote detection on the surfaces of icy bodies. Moreover, we have studied the photo-chemistry of these interesting compounds under astrophysical conditions and will use our lab studies to assess a potential interstellar heritage of these compounds in carbonaceous chondrites.

Ligand recognition by RAR and RXR receptors: binding and selectivity.

Science.gov (United States)

Sussman, Fredy; de Lera, Angel R

2005-10-06

Fundamental biological functions, most notably embriogenesis, cell growth, cell differentiation, and cell apoptosis, are in part regulated by a complex genomic network that starts with the binding (and activation) of retinoids to their cognate receptors, members of the superfamily of nuclear receptors. We have studied ligand recognition of retinoic receptors (RXRalpha and RARgamma) using a molecular-mechanics-based docking method. The protocol used in this work is able to rank the affinity of pairs of ligands for a single retinoid receptor, the highest values corresponding to those that adapt better to the shape of the binding site and generate the optimal set of electrostatic and apolar interactions with the receptor. Moreover, our studies shed light onto some of the energetic contributions to retinoid receptor ligand selectivity. In this regard we show that there is a difference in polarity between the binding site regions that anchor the carboxylate in RAR and RXR, which translates itself into large differences in the energy of interaction of both receptors with the same ligand. We observe that the latter energy change is canceled off by the solvation energy penalty upon binding. This energy compensation is borne out as well by experiments that address the effect of site-directed mutagenesis on ligand binding to RARgamma. The hypothesis that the difference in binding site polarity might be exploited to build RXR-selective ligands is tested with some compounds having a thiazolidinedione anchoring group.

Synthesis and complexation properties towards uranyl cation of carboxylic acid derivatives of p-tert-butyl-calix[6]arene; Synthese et proprietes complexantes vis-a-vis de l'ion uranyle de derives carboxyliques du p-tert-butyl-calix[6]arene

Energy Technology Data Exchange (ETDEWEB)

Souane, R

2005-03-15

In the fuel reprocessing plants radioactive metals, and more particularly, uranium in UO{sub 2}{sup 2+} form in the various installations, have many varied physico-chemical forms and there is a risk of exposure and internal contamination in the nuclear industry. It is necessary to exert a medical control to ensure the protection of the health of the workers. This medical control is done by dosing uranyl cation in the urine of the exposed people. This work forms part of this context. Indeed, we prepared a ligand able to complex the ion uranyl and which is also to be grafted on a solid support. In the family of calixarenes, the calix[6]arenes functionalized by three or four carboxylic functions were selected like chelating molecules of the ion uranyl. The properties of complexation of these calixarenes were studied by potentiometry in methanol, under these conditions balances of protonation and complexation were determined and the constant partners were obtained using the Hyperquad program. We synthesized tri-carboxylic calix[6]arenes comprising of the groupings nitro (NO{sub 2}) in para position of phenol in order to see the influence of a substitution in para position on the complexation. We also synthesized calix[6]arenes tetra-carboxylic in order to show the role of an additional carboxylic acid grouping. The potentiometric study determined thermodynamic parameters of protonation and complexation of carboxylic calix[6]arenes. The results of the complexation highlighted which complex UO{sub 2}L corresponding to the ligand para-tert-butyl-calix[6]arene tetra-acid is more stable than that corresponding to the ligand mono-nitro calix[6]arene tri-acid ({delta}log{beta}110 = 4.3), and than the effect of the groupings nitro in para position has low influence on the complexation of UO{sub 2}{sup 2+}. This makes it possible to consider as possible the grafting of the calix[6]arenes which one knows the behaviour of trapping. To this end we synthesized the ligand 23

Short Carboxylic Acid–Carboxylate Hydrogen Bonds Can Have Fully Localized Protons

Energy Technology Data Exchange (ETDEWEB)

Lin, Jiusheng; Pozharski, Edwin; Wilson, Mark A.

2017-01-17

Short hydrogen bonds (H-bonds) have been proposed to play key functional roles in several proteins. The location of the proton in short H-bonds is of central importance, as proton delocalization is a defining feature of low-barrier hydrogen bonds (LBHBs). Experimentally determining proton location in H-bonds is challenging. Here, bond length analysis of atomic (1.15–0.98 Å) resolution X-ray crystal structures of the human protein DJ-1 and its bacterial homologue, YajL, was used to determine the protonation states of H-bonded carboxylic acids. DJ-1 contains a buried, dimer-spanning 2.49 Å H-bond between Glu15 and Asp24 that satisfies standard donor–acceptor distance criteria for a LBHB. Bond length analysis indicates that the proton is localized on Asp24, excluding a LBHB at this location. However, similar analysis of the Escherichia coli homologue YajL shows both residues may be protonated at the H-bonded oxygen atoms, potentially consistent with a LBHB. A Protein Data Bank-wide screen identifies candidate carboxylic acid H-bonds in approximately 14% of proteins, which are typically short [O–O> = 2.542(2) Å]. Chemically similar H-bonds between hydroxylated residues (Ser/Thr/Tyr) and carboxylates show a trend of lengthening O–O distance with increasing H-bond donor pK_a. This trend suggests that conventional electronic effects provide an adequate explanation for short, charge-assisted carboxylic acid–carboxylate H-bonds in proteins, without the need to invoke LBHBs in general. This study demonstrates that bond length analysis of atomic resolution X-ray crystal structures provides a useful experimental test of certain candidate LBHBs.

Antiradiation compounds XV: condensations of carbon disulfide with amino, chloro, cyanomethyl, and sulfonamido heterocycles

International Nuclear Information System (INIS)

Foye, W.O.; Kauffman, J.M.; Lanzillo, J.J.; LaSala, E.F.

1975-01-01

Condensations of carbon disulfide were carried out with amino, chloro, and diamino heterocycles to give condensed ring thiazoline-2-thiones and imidazoline-2-thiones, with cyanomethyl heterocycles to give dithio acid derivatives, and with heterocyclic sulfonamides to give sulfonyldithiocarbamates. Of several examples tested, pyrido[3,2-d]thiazoline-2-thione, disodium 2-(5-chloro-2-thienyl)-3,3-dimercaptoacrylonitrile, triethylammonium 4-sulfamoylphenyldithiocarbamate, ammonium β-phenethyldithiocarbamate, and methyl N-(thiophene-2-sulfonyl)dithiocarbamate, only the last-named compound showed any radiation protection for mice. Several compounds gave negative tests for antimalarial activity

New heterocyclic compounds from Ranunculus ternatus Thunb.

Science.gov (United States)

Feng, Zi-Ming; Zhan, Zhi-Lai; Yang, Ya-Nan; Jiang, Jian-Shuang; Zhang, Pei-Cheng

2017-10-01

Five new heterocyclic compounds, 5-α-d-fructofuranosylmethyl-furfural (1), 5-β-d-fructofuranosylmethyl-furfural (2), 5-β-d-fructopyranosylmethyl-furfural (3), 4-(2-((2S-2,3-dihydroxypropoxy)methyl)-5-formyl-1H-pyrrol-1-yl)butanoic acid (4), and 3S,4S-4,5,8-trihydroxy-3-(prop-1-en-2-yl)isochroman-1-one (5), were obtained from the root of Ranunculus ternatus Thunb., which is a traditional Chinese anti-tuberculosis medicine. Their structures were elucidated by UV, IR, HRESIMS, NMR data, and the comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Notably, compounds 1-3 are rarely occurring furfural fructosides in natural sources. These heterocyclic compounds could be further studied for the synthetic chemists and pharmacologists due to the source and structural properties. Copyright © 2017 Elsevier Inc. All rights reserved.

Phosphorylated Derivatives of Alkaloids and Nitrogen-containing Heterocycles — Cholinesterase Inhibitors

Science.gov (United States)

Sadykov, Abid S.; Dalimov, D. N.; Godovikov, Nikolai N.

1983-10-01

The review deals with the synthesis and anticholinesterase activities of phosphorylated derivatives of certain alkaloids and nitrogen-containing heterocycles. It is shown that the conformational properties of the alkaloid and nitrogen-containing heterocycle residues in the composition of the organophosphorus inhibitor (OPI) molecule play an important role in the inhibition of the catalytic activity of cholinesterases. The type of inhibition of cholinesterases also varies as a function of chemical structure. The bibliography includes 45 references.

Protein-ligand interfaces are polarized: discovery of a strong trend for intermolecular hydrogen bonds to favor donors on the protein side with implications for predicting and designing ligand complexes.

Science.gov (United States)

Raschka, Sebastian; Wolf, Alex J; Bemister-Buffington, Joseph; Kuhn, Leslie A

2018-04-01

Understanding how proteins encode ligand specificity is fascinating and similar in importance to deciphering the genetic code. For protein-ligand recognition, the combination of an almost infinite variety of interfacial shapes and patterns of chemical groups makes the problem especially challenging. Here we analyze data across non-homologous proteins in complex with small biological ligands to address observations made in our inhibitor discovery projects: that proteins favor donating H-bonds to ligands and avoid using groups with both H-bond donor and acceptor capacity. The resulting clear and significant chemical group matching preferences elucidate the code for protein-native ligand binding, similar to the dominant patterns found in nucleic acid base-pairing. On average, 90% of the keto and carboxylate oxygens occurring in the biological ligands formed direct H-bonds to the protein. A two-fold preference was found for protein atoms to act as H-bond donors and ligand atoms to act as acceptors, and 76% of all intermolecular H-bonds involved an amine donor. Together, the tight chemical and geometric constraints associated with satisfying donor groups generate a hydrogen-bonding lock that can be matched only by ligands bearing the right acceptor-rich key. Measuring an index of H-bond preference based on the observed chemical trends proved sufficient to predict other protein-ligand complexes and can be used to guide molecular design. The resulting Hbind and Protein Recognition Index software packages are being made available for rigorously defining intermolecular H-bonds and measuring the extent to which H-bonding patterns in a given complex match the preference key.

Protein-ligand interfaces are polarized: discovery of a strong trend for intermolecular hydrogen bonds to favor donors on the protein side with implications for predicting and designing ligand complexes

Science.gov (United States)

Raschka, Sebastian; Wolf, Alex J.; Bemister-Buffington, Joseph; Kuhn, Leslie A.

2018-02-01

Understanding how proteins encode ligand specificity is fascinating and similar in importance to deciphering the genetic code. For protein-ligand recognition, the combination of an almost infinite variety of interfacial shapes and patterns of chemical groups makes the problem especially challenging. Here we analyze data across non-homologous proteins in complex with small biological ligands to address observations made in our inhibitor discovery projects: that proteins favor donating H-bonds to ligands and avoid using groups with both H-bond donor and acceptor capacity. The resulting clear and significant chemical group matching preferences elucidate the code for protein-native ligand binding, similar to the dominant patterns found in nucleic acid base-pairing. On average, 90% of the keto and carboxylate oxygens occurring in the biological ligands formed direct H-bonds to the protein. A two-fold preference was found for protein atoms to act as H-bond donors and ligand atoms to act as acceptors, and 76% of all intermolecular H-bonds involved an amine donor. Together, the tight chemical and geometric constraints associated with satisfying donor groups generate a hydrogen-bonding lock that can be matched only by ligands bearing the right acceptor-rich key. Measuring an index of H-bond preference based on the observed chemical trends proved sufficient to predict other protein-ligand complexes and can be used to guide molecular design. The resulting Hbind and Protein Recognition Index software packages are being made available for rigorously defining intermolecular H-bonds and measuring the extent to which H-bonding patterns in a given complex match the preference key.

Complexation of trivalent cationic lanthanides by N.O donor ligands: physico-chemical studies of the association and selectivity in solution

International Nuclear Information System (INIS)

Bravard, F.

2004-01-01

The aim of this work is to study the complexation of f-elements in solution by ligands incorporating N-heterocyclic donors. These ligands display interesting properties for the selective separation of An(III)/Ln(III) have been studied to obtain a better understanding of the coordination properties with f-elements and to develop more selective extractants. The hepta-dentate ligand tpaam shows an affinity for Ln(III) similar to the tetradentate ligand tpa in water even when the three additional amide groups are bonded to the metal. Even though the complexation with tpa is exothermic, that with tpaam is endothermic with a more positive entropy. The dehydration of the cation disfavours the formation of Ln(III) complexes with ligands containing weak donors. The analysis of the solution paramagnetic relaxation times of the tpaam complexes is in agreement with data in the solid-state. There is little difference between the formation constants of the Ln 3+ complexes with different ligands (tpaam, tpzen, tpa and tpza) as determined by UV-vis spectrophotometry in anhydrous acetonitrile. The limitations encountered during this study are intrinsic to the ligands studied. The preliminary study of two tetrapodal ligands containing acid and pyridine groups (L py )or pyrazine (L pz ) show the formation of 1:1 complexes in water. Analysis of the formation constants of the corresponding Gd(III) complexes shows that replacement of a pyridine group by pyrazine result in a loss of stability of 1.6 logarithmic units. (author) [fr

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

Directory of Open Access Journals (Sweden)

Michael Nonnenmacher

2016-08-01

Full Text Available Rh(CO2Cl(NHC complexes of dipyrido-annelated N-heterocyclic carbenes were prepared. From the C–H coupling constant of the respective imidazolium salts and the N–C–N angle of the N-heterocyclic carbene (NHC, a weaker σ-donor character than that of typical unsaturated NHCs is expected. However, the IR stretching frequencies of their Rh(CO2Cl complexes suggest an electron-donor character even stronger than that of saturated NHCs. We ascribe this to the extremely weak π-acceptor character of the dipyrido-annelated NHCs caused by the conjugated 14 πe− system that thus allows for an enhanced Rh–CO backbonding. This extremely low π-acceptor ability is also corroborated by the 77Se NMR chemical shift of −55.8 ppm for the respective selenourea, the lowest value ever measured for imidazole derived selenoureas. DFT-calculations of the free carbene confirm the low σ-donor character by the fact that the σ-orbital of the carbene is the HOMO−1 that lies 0.58 eV below the HOMO which is located at the π-system. Natural population analysis reveals the lowest occupation of the pπ-orbital for the saturated carbene carbon atom and the highest for the pyrido-annelated carbene. Going from the free carbene to the Rh(CO2Cl(NHC complexes, the increase in occupancy of the complete π-system of the carbene ligand upon coordination is lowest for the pyrido-annelated carbene and highest for the saturated carbene.

Oxygen Atom Transfer Using an Iron(IV)-Oxo Embedded in a Tetracyclic N-Heterocyclic Carbene System: How Does the Reactivity Compare to Cytochrome P450 Compound I?

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Cantú Reinhard, Fabián G; de Visser, Sam P

2017-02-24

N-Heterocyclic carbenes (NHC) are commonly featured as ligands in transition metal catalysis. Recently, a cyclic system containing four NHC groups with a central iron atom was synthesized and its iron(IV)-oxo species, [Fe IV (O)(cNHC 4 )] 2+ , was characterized. This tetracyclic NHC ligand system may give the iron(IV)-oxo species unique catalytic properties as compared to traditional non-heme and heme iron ligand systems. Therefore, we performed a computational study on the structure and reactivity of the [Fe IV (O)(cNHC 4 )] 2+ complex in substrate hydroxylation and epoxidation reactions. The reactivity patterns are compared with cytochrome P450 Compound I and non-heme iron(IV)-oxo models and it is shown that the [Fe IV (O)(cNHC 4 )] 2+ system is an effective oxidant with oxidative power analogous to P450 Compound I. Unfortunately, in polar solvents, a solvent molecule will bind to the sixth ligand position and decrease the catalytic activity of the oxidant. A molecular orbital and valence bond analysis provides insight into the origin of the reactivity differences and makes predictions of how to further exploit these systems in chemical catalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Room-temperature hydrohydrazination of terminal alkynes catalyzed by saturated abnormal N-heterocyclic carbene-gold(I) complexes.

Science.gov (United States)

Manzano, Rubén; Wurm, Thomas; Rominger, Frank; Hashmi, A Stephen K

2014-06-02

A number of saturated abnormal N-heterocyclic carbene (NHC) complexes of gold, in combination with KBAr(F) 4 as activator, were successfully applied in the chemoselective addition of hydrazine to alkynes. The reaction proceeds even at room temperature, which was not possible to date with gold catalysts. The reaction can be applied to a number of substituted arylalkynes. With alkylalkynes the yields are low. The saturated abnormal NHC ligands are resistant to isomerization to the saturated normal NHC coordination mode under basic reaction conditions. Under acidic conditions, a simple protonation at the nitrogen atom not neighboring the carbene center was observed and unambiguously characterized by an X-ray crystal-structure analysis. Computational studies confirm that such an isomerization would be highly exothermic, the observed kinetic stability probably results from the need to shift two protons in such a process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Depolymerization of Poly(Ethylene Terephthalate) (PET) Using N-Heterocyclic Carbenes from Ionic Liquids

Science.gov (United States)

Kamber, Nahrain E.; Tsujii, Yasuhito; Keets, Kate; Waymouth, Robert M.; Pratt, Russell C.; Nyce, Gregory W.; Hedrick, James L.

2010-01-01

The depolymerization of the plastic polyethylene terephthalate (PET or PETE) is described in this laboratory procedure. The transesterification reaction used to depolymerize PET employs a highly efficient N-heterocyclic carbene catalyst derived from a commercially available imidazolium ionic liquid. N-heterocyclic carbenes are potent nucleophilic…

[Distribution and sources of oxygen and sulfur heterocyclic aromatic compounds in surface soil of Beijing, China].

Science.gov (United States)

He, Guang-Xiu; Zhang, Zhi-Huan; Peng, Xu-Yang; Zhu, Lei; Lu, Ling

2011-11-01

62 surface soil samples were collected from different environmental function zones in Beijing. Sulfur and oxygen heterocyclic aromatic compounds were detected by GC/MS. The objectives of this study were to identify the composition and distribution of these compounds, and discuss their sources. The results showed that the oxygen and sulfur heterocyclic aromatic compounds in the surface soils mainly contained dibenzofuran, methyl- and C2-dibenzofuran series, dibenzothiophene, methyl-, C2- and C3-dibenzothiophene series and benzonaphthothiophene series. The composition and distribution of the oxygen and sulfur heterocyclic aromatic compounds in the surface soil samples varied in the different environmental function zones, of which some factories and the urban area received oxygen and sulfur heterocyclic aromatic compounds most seriously. In Beijing, the degree of contamination by oxygen and sulfur heterocyclic aromatic compounds in the north surface soil was higher than that in the south. There were preferable linear correlations between the concentration of dibenzofuran series and fluorene series, as well as the concentration of dibenzothiophene series and dibenzofuran series. The oxygen and sulfur heterocyclic aromatic compounds in the surface soil were mainly derived from combustion products of oil and coal and direct input of mineral oil, etc. There were some variations in pollution sources of different environmental function zones.

Regio- and Enantioselective N-Allylations of Imidazole, Benzimidazole, and Purine Heterocycles Catalyzed by Single-Component Metallacyclic Iridium Complexes

Science.gov (United States)

Stanley, Levi M.

2010-01-01

Highly regio- and enantioselective iridium-catalyzed N-allylations of benzimidazoles, imidazoles, and purines have been developed. N-Allylated benzimidazoles and imidazoles were isolated in high yields (up to 97%) with high branched-to-linear selectivity (up to 99:1) and enantioselectivity (up to 98% ee) from the reactions of benzimidazole and imidazole nucleophiles with unsymmetrical allylic carbonates in the presence of single component, ethylene-bound, metallacyclic iridium catalysts. N-Allylated purines were also obtained in high yields (up to 91%) with high N9:N7 selectivity (up to 96:4), high branched-to-linear selectivity (98:2), and high enantioselectivity (up to 98% ee) under similar conditions. The reactions encompass a range of benzimidazole, imidazole, and purine nucleophiles, as well as a variety of unsymmetrical aryl, heteroaryl, and aliphatic allylic carbonates. Competition experiments between common amine nucleophiles and the heterocyclic nitrogen nucleophiles studied in this work illustrate the effect of nucleophile pKa on the rate of iridium-catalyzed N-allylation reactions. Kinetic studies on the allylation of benzimidazole catalyzed by metallacyclic iridium-phosphoramidite complexes, in combination with studies on the deactivation of these catalysts in the presence of heterocyclic nucleophiles, provide insight into the effects of the structure of the phosphoramidite ligands on the stability of the metallacyclic catalysts. The data obtained from these studies has led to the development of N-allylations of benzimidazoles and imidazoles in the absence of an exogenous base. PMID:19480431

Synthesis, crystal structures, and thermal and spectroscopic properties of two Cd(II) metal-organic frameworks with a versatile ligand

Energy Technology Data Exchange (ETDEWEB)

Li, Jia-Ming; He, Kun-Huan; Shi, Zhong-Feng [Qinzhou Univ. (China). Guangxi Colleges and Univs. Key Lab. of Beibu Gulf Oil and Natural Gas Resource Effective Utilization; Gao, Hui-Yuan; Jiang, Yi-Min [Guangxi Normal Univ., Guilin (China). Key Lab. for the Chemistry and Molecular Engineering of Medicinal Resources

2016-11-01

Two new metal-organic frameworks, namely, [Cd(L)(H{sub 2}O)]{sub n} (1) and {[Cd_0_._5(L)(4,4"'-bipy)_0_._5][Cd_0_._5(H_2O)(4,4"'-bipy)_0_._5].H_2O}{sub n} (2), where H{sub 2}L = N-pyrazinesulfonyl-glycine and 4,4{sup '}-bipy = 4,4{sup '}-bipyridine, have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental, thermogravimetric, and photoluminescent analysis. X-ray diffraction crystallographic analyses indicate that 1 displays a distorted octahedral metal coordination in a 3-connected (4, 8{sup 2}) topology, while the molecular structure of 2 has a 4-connected (4, 4) topology with two perfectly octahedrally coordinated Cd centers. The L{sup 2-} ligand serves as a N,N,O-tridentate, μ{sub 2}-pyrazine-bridging, and μ{sub 2}-carboxylate-bridging ligand in 1, and as a N,O-bidentate and μ{sub 2}-carboxylate-bridging ligand in 2. In the crystal, a 3D supramolecular architecture is formed by O-H..O hydrogen bond interactions in 1, but through O-H..O as well as π..π stacking in 2. The two compounds show intense fluorescence in the solid state at room temperature.

Heterocycles by Transition Metals Catalyzed Intramolecular Cyclization of Acetylene Compounds

International Nuclear Information System (INIS)

Vizer, S.A.; Yerzhanov, K.B.; Dedeshko, E.C.

2003-01-01

Review shows the new strategies in the synthesis of heterocycles, having nitrogen, oxygen and sulfur atoms, via transition metals catalyzed intramolecular cyclization of acetylenic compounds on the data published at the last 30 years, Unsaturated heterocyclic compounds (pyrroles and pyrroline, furans, dihydro furans and benzofurans, indoles and iso-indoles, isoquinolines and isoquinolinones, aurones, iso coumarins and oxazolinone, lactams and lactones with various substitutes in heterocycles) are formed by transition metals, those salts [PdCl 2 , Pd(OAc) 2 , HgCl 2 , Hg(OAc) 2 , Hg(OCOCF 3 ) 2 , AuCl 3 ·2H 2 O, NaAuCl 4 ·2H 2 O, CuI, CuCl], oxides (HgO) and complexes [Pd(OAc) 2 (PPh 3 )2, Pd(PPh 3 ) 4 , PdCl 2 (MeCN) 2 , Pd(OAc ) 2 /TPPTS] catalyzed intramolecular cyclization of acetylenic amines, amides, ethers, alcohols, acids, ketones and βdiketones. More complex hetero polycyclic systems typical for natural alkaloids can to obtain similar. Proposed mechanisms of pyrroles, isoquinolines, iso indoles and indoles, benzofurans and iso coumarins, thiazolopyrimidinones formation are considered. (author)

Polymer complexes.. XXXX. Supramolecular assembly on coordination models of mixed-valence-ligand poly[1-acrylamido-2-(2-pyridyl)ethane] complexes

Science.gov (United States)

El-Sonbati, A. Z.; El-Bindary, A. A.; Diab, M. A.

2003-02-01

The build-up of polymer metallic supramolecules based on homopolymer (1-acrylamido-2-(2-pyridyl)ethane (AEPH)) and ruthenium, rhodium, palladium as well as platinum complexes has been pursued with great interest. The homopolymer shows three types of coordination behaviour. In the mixed valence paramagnetic trinuclear polymer complexes [( 11)+( 12)] in the paper and in mononuclear polymer complexes ( 1)-( 5) it acts as a neutral bidentate ligand coordinating through the N-pyridine and NH-imino atoms, while in the mixed ligand diamagnetic poly-chelates, which are obtained from the reaction of AEPH with PdX 2 and KPtCl 4 in the presence of N-heterocyclic base consisting of polymer complexes ( 9)+( 10), and in monouclear compounds ( 6)-( 8), it behaves as a monobasic bidentate ligand coordinating through the same donor atoms. In mononuclear compounds ( 13)+( 14) it acts as a monobasic and neutral bidentate ligand coordinating only through the same donor atoms. Monomeric distorted octahedral or trimeric chlorine-bridged, approximately octahedral structures are proposed for these polymer complexes. The poly-chelates are of 1:1, 1:2 and 3:2 (metal-homopolymer) stoichiometry and exhibit six coordination. The values of ligand field parameters were calculated. The homopolymer and their polymer complexes have been characterized physicochemically.

Sulfamides in the synthesis of heterocyclic compounds

International Nuclear Information System (INIS)

Gazieva, Galina A; Kravchenko, Angelina N; Lebedev, Oleg V

2000-01-01

A comparative analysis of the structures and physicochemical properties of sulfamides and ureas has been performed. New procedures for the synthesis of heterocyclic compounds containing the sulfamide fragment are surveyed and the properties of the resulting compounds are described. The bibliography includes 112 references.

Ligand exchange chromatography of free amino acids and proteins on porous microparticulate zirconium oxide

International Nuclear Information System (INIS)

Blackwell, J.A.; Carr, P.W.

1992-01-01

The Lewis acid sites present on the underlying zirconium oxide particles are responsible for the unusual elution sequence for amino acids on copper loaded, phosphated zirconium oxide supports reported in an earlier study. To more thoroughly examine the effect of these strong Lewis acid sites in this paper. The authors have studied ligand exchange chromatography on copper loaded zirconium oxide particles. It is shown here that carboxylate functional groups on amino acid solutes strongly interact with surface Lewis acid sites. Addition of competing hard Lewis bases to the eluent attenuates these specific interactions. The result is a chromatographic system with high selectivity which is also suitable for ligand exchange chromatography of proteins

Bifunctional Zn(II)Ln(III) dinuclear complexes combining field induced SMM behavior and luminescence: enhanced NIR lanthanide emission by 9-anthracene carboxylate bridging ligands.

Science.gov (United States)

Palacios, María A; Titos-Padilla, Silvia; Ruiz, José; Herrera, Juan Manuel; Pope, Simon J A; Brechin, Euan K; Colacio, Enrique

2014-02-03

There were new dinuclear Zn(II)-Ln(III) complexes of general formulas [Zn(μ-L)(μ-OAc)Ln(NO3)2] (Ln(III) = Tb (1), Dy (2), Er (3), and Yb (4)), [Zn(μ-L)(μ-NO3)Er(NO3)2] (5), [Zn(H2O)(μ-L)Nd(NO3)3]·2CH3OH (6), [Zn(μ-L)(μ-9-An)Ln(NO3)2]·2CH3CN (Ln(III) = Tb (7), Dy (8), Er (9), Yb(10)), [Zn(μ-L)(μ-9-An)Yb(9-An)(NO3)3]·3CH3CN (11), [Zn(μ-L)(μ-9-An)Nd(9-An)(NO3)3]·2CH3CN·3H2O (12), and [Zn(μ-L)(μ-9-An)Nd(CH3OH)2(NO3)]ClO4·2CH3OH (13) prepared from the reaction of the compartmental ligand N,N',N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L), with ZnX2·nH2O (X = NO3(-) or OAc(-)) salts, Ln(NO3)3·nH2O, and, in some instances, 9-anthracenecarboxylate anion (9-An). In all these complexes, the Zn(II) ions invariably occupy the internal N3O2 site whereas the Ln(III) ions show preference for the O4 external site, giving rise to a Zn(μ-diphenoxo)Ln bridging fragment. Depending on the Zn(II) salt and solvent used in the reaction, a third bridge can connect the Zn(II) and Ln(III) metal ions, giving rise to triple-bridged diphenoxoacetate in complexes 1-4, diphenoxonitrate in complex 5, and diphenoxo(9-anthracenecarboxylate) in complexes 8-13. Dy(III) and Er(III) complexes 2, 8 and 3, 5, respectively, exhibit field induced single molecule magnet (SMM) behavior, with Ueff values ranging from 11.7 (3) to 41(2) K. Additionally, the solid-state photophysical properties of these complexes are presented showing that ligand L(2-) is able to sensitize Tb(III)- and Dy(III)-based luminescence in the visible region through an energy transfer process (antenna effect). The efficiency of this process is much lower when NIR emitters such as Er(III), Nd(III), and Yb(III) are considered. When the luminophore 9-anthracene carboxylate is incorporated into these complexes, the NIR luminescence is enhanced which proves the efficiency of this bridging ligand to act as antenna group. Complexes 2, 3, 5, and 8 can be considered as dual materials

-Heterocyclic Carbene Complexes of Mineral Acids

KAUST Repository

Brill, Marcel; Nahra, Fady; Gó mez-Herrera, Alberto; Zinser, Caroline; Cordes, David B.; Slawin, Alexandra M. Z.; Nolan, Steven P.

2016-01-01

We have synthesized and characterized new gold-N-heterocyclic carbene (NHC) complexes derived from the deprotonation of mineral acids. The use of sulfuric acid was a particularly interesting case. These complexes were tested in known gold-catalyzed reactions, such as the hydration of alkynes and the Meyer–Schuster rearrangement. They proved to be highly efficient in both reactions.

-Heterocyclic Carbene Complexes of Mineral Acids

KAUST Repository

Brill, Marcel

2016-11-08

We have synthesized and characterized new gold-N-heterocyclic carbene (NHC) complexes derived from the deprotonation of mineral acids. The use of sulfuric acid was a particularly interesting case. These complexes were tested in known gold-catalyzed reactions, such as the hydration of alkynes and the Meyer–Schuster rearrangement. They proved to be highly efficient in both reactions.

Exploring the novel heterocyclic derivatives as lead molecules for design and development of potent anticancer agents.

Science.gov (United States)

Azad, Iqbal; Nasibullah, Malik; Khan, Tahmeena; Hassan, Firoj; Akhter, Yusuf

2018-05-01

This paper deals with in silico evaluation of newly proposed heterocyclic derivatives in search of potential anticancer activity. Best possible drug candidates have been proposed using a rational approach employing a pipeline of computational techniques namely MetaPrint2D prediction, molinspiration, cheminformatics, Osiris Data warrior, AutoDock and iGEMDOCK. Lazar toxicity prediction, AdmetSAR predictions, and targeted docking studies were also performed. 27 heterocyclic derivatives were selected for bioactivity prediction and drug likeness score on the basis of Lipinski's rule, Viber rule, Ghose filter, leadlikeness and Pan Assay Interference Compounds (PAINS) rule. Bufuralol, Sunitinib, and Doxorubicin were selected as reference standard drug for the comparison of molecular descriptors and docking. Bufuralol is a known non-selective adreno-receptor blocking agent. Studies showed that beta blockers are also used against different types of cancers. Sunitinib is well known Food and Drug administration (FDA) approved pyrrole containing tyrosine kinase inhibitor and our proposed molecules possess similarities with both drug and doxorubicin is another moiety having anticancer activity. All heterocyclic derivatives were found to obey the drug filters except standard drug Doxorubicin. Bioactivity score of the compounds was predicted for drug targets including enzymes, nuclear receptors, kinase inhibitors, G protein-coupled receptor (GPCR) ligands and ion channel modulators. Absorption, distribution, metabolism and toxicity (ADMET) prediction of all proposed compound showed good Blood-brain barrier (BBB) penetration, Human intestinal absorption (HIA), Caco-2 cell permeability except compound-11 and was found to have no AdmetSAR toxicity as well as carcinogenic effect. Compounds 1-9 were slightly mutagenic while compound 2, 11, 20 and 21 showed carcinogenic effect according to Lazar toxicity prediction. Rests of the compounds were predicted to have no side effect

Lanthanide coordination polymers based on multi-donor ligand containing pyridine and phthalate moieties: Structures, luminescence and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Feng, Xun [College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); Liu, Lang [College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450002 (China); College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); Wang, Li-Ya, E-mail: wlya@lynu.edu.cn [College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); College of Chemistry and Pharmacy Engineering, Nanyang Normal University, Nanyang 473601 (China); Song, Hong-Liang; Qiang Shi, Zhi; Wu, Xu-Hong [College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); Ng, Seik-Weng [Department of Chemistry, University of Malaya, Kuala Lumpur 50603 (Malaysia); Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 80203 (Saudi Arabia)

2013-10-15

A new family of five lanthanide-organic coordination polymers incorporating multi-functional N-hetrocyclic dicarboxylate ligand, namely, [Ln{sub 2}(Hdpp){sub 2}(dpp){sub 2}]{sub n}Ln=Pr(1), Eu(2), Gd(3), Dy(4), Er(5) (H{sub 2}dpp=1-(3, 4-dicarboxyphenyl) pyridin-4-ol) have been fabricated successfully through solvothermal reaction of 1-(3,4-dicarboxyphenyl)-4-hydroxypyridin-1-ium chloride with trivalent lanthanide salts, and have been characterized systematically. The complexes 1–5 are isomorphous and isostructural. They all feature three dimensional (3D) frameworks based on the interconnection of 1D double chains composed of the binuclear moiety [Ln{sub 2}(Hdpp){sub 2}]{sup 4+} basic carboxylate as secondary building unit (SBU). The results of magnetic analysis shows the same bridging fashion of carboxylic group in this case results in the different magnetic properties occurring within lanthanide polymers. Moreover, the Eu(III) and Dy(III) complexes display characteristic luminescence emission in the visible regions. - Graphical abstract: A new family of lanthanide-organic frameworks incorporating multi-donor twisted ligand has been fabricated successfully, and has been characterized systematically. The complexes 1–5 are isostructural, and all feather three dimensional (3D) frameworks based on the interconnection of 1D double stride chains composed of the binuclear moiety [Ln{sub 2}(Hdpp){sub 2}]{sup 2+} basic carboxylate as secondary building unit (SBU). Display Omitted - Highlights: • New family of lanthanide–organic coordination polymers incorporating multifunctional N-hetrocyclic dicarboxylate ligand has been fabricated. • They have been characterized systematically. • They all feather three dimensional frameworks based on the binuclear moiety of [Ln{sub 2}(Hdpp){sub 2}]{sup 2+}. • The Eu(III) and Dy(III) analogues exhibit intense photoluminescence.

Heterocyclic Anticancer Compounds: Recent Advances and the Paradigm Shift towards the Use of Nanomedicine's Tool Box.

Science.gov (United States)

Martins, Pedro; Jesus, João; Santos, Sofia; Raposo, Luis R; Roma-Rodrigues, Catarina; Baptista, Pedro Viana; Fernandes, Alexandra R

2015-09-16

The majority of heterocycle compounds and typically common heterocycle fragments present in most pharmaceuticals currently marketed, alongside with their intrinsic versatility and unique physicochemical properties, have poised them as true cornerstones of medicinal chemistry. Apart from the already marketed drugs, there are many other being investigated for their promising activity against several malignancies. In particular, anticancer research has been capitalizing on the intrinsic versatility and dynamic core scaffold of these compounds. Nevertheless, as for any other promising anticancer drugs, heterocyclic compounds do not come without shortcomings. In this review, we provide for a concise overview of heterocyclic active compounds and families and their main applications in medicine. We shall focus on those suitable for cancer therapy while simultaneously addressing main biochemical modes of action, biological targets, structure-activity relationships as well as intrinsic limitation issues in the use of these compounds. Finally, considering the advent of nanotechnology for effective selective targeting of drugs, we shall discuss fundamental aspects and considerations on nanovectorization of such compounds that may improve pharmacokinetic/pharmacodynamic properties of heterocycles.

Organic ligand-induced dissolution kinetics of antimony trioxide

Institute of Scientific and Technical Information of China (English)

Xingyun Hu; Mengchang He

2017-01-01

The influence of low-molecular-weight dissolved organic matter (LMWDOM) on the dissolution rate of Sb2O3 was investigated.Some representative LMWDOMs with carboxyl,hydroxyl,hydrosulfuryl and amidogen groups occurring naturally in the solution were chosen,namely oxalic acid,citric acid,tartaric acid,EDTA,salicylic acid,phthalandione,glycine,thiolactic acid,xylitol,glucose and catechol.These LMWDOMs were dissolved in inert buffers at pH =3.7,6.6 and 8.6 and added to powdered Sb2O3 in a stirred,thermostatted reactor (25℃).The addition of EDTA,tartaric acid,thiolactic acid,citric acid and oxalic acid solutions at pH 3.7 and catechol at pH 8.6 increased the rate of release of antimony.In the 10 mmol/L thiolactic acid solution,up to 97％ by mass of the antimony was released after 120 min reaction.There was no effect on the dissolution of Sb2O3 for the other ligands.A weak correlation between dissolution rate with the dissociation constant of ligands and the stability of the dissolved complex was also found.All the results showed that the extent of the promoting effect of ligands on the dissolution of Sb2O3 was not determined by the stability of the dissolved complex,but by the dissociation constant of ligands and detachment rate of surface chelates from the mineral surface.This study can not only help in further understanding the effect of individual low-molecular-weight organic ligands,but also provides a reference to deduce the effect of natural organic matters with oxygen-bearing functional groups on the dissolution of antimony oxide minerals.

Water purification by reverse osmosis using heterocyclic polymer membranes

Science.gov (United States)

Scott, H.

1972-01-01

Pyrrone (polyimidazopyrrolone) polymers are a new class of thermally stable, radiation and chemical resistant aromatic-heterocyclic polymers featuring a greater chemical and mechanical durability than cellulose acetate.

Cytotoxic effects of chemotherapeutic drugs and heterocyclic compounds at application on the cells of primary culture of neuroepithelium tumors.

Science.gov (United States)

Kulchitsky, Vladimir A; Potkin, Vladimir I; Zubenko, Yuri S; Chernov, Alexander N; Talabaev, Michael V; Demidchik, Yuri E; Petkevich, Sergei K; Kazbanov, Vladimir V; Gurinovich, Tatiana A; Roeva, Margarita O; Grigoriev, Dmitry G; Kletskov, Alexei V; Kalunov, Vladimir N

2012-01-01

Neuroepithelial tumor cells were cultured in vitro. The biopsy material was taken from 93 children at removal of the brain tumors during neurosurgical operations. The individual features of the cells sensitivity of primary cultures in respect to protocol-approved chemotherapy drugs and changes in the Interleukin-6 (Il-6) level in the culture medium after the application of chemotherapy were established. The initial level of Il-6 exceeded 600.0 pg/ml in the cultural medium with histologically verified pilomyxoid astrocytoma cells, and ranged from 100.0 to 200.0 pg/ml in the medium at cultivation of ganglioneuroblastoma and pilocytic astrocytoma. A decrease in the Il-6 level in the medium culture of primary tumors cells was observed after the application of chemotherapeutic agents on the cells of pilomyxoid astrocytoma, astrocytomas, and pilocytic desmoplastic/nodular medulloblastoma. The production of Il-6 increased after application of cytostatic drugs on the cells of oligoastrocytomas. A decrease in Il-6 level after application of Cisplatin and Methotrexate and a 5-10 fold increase in the level of Il-6 after application of Etoposide, Carboplatin, Cytarabine, and Gemcitabine were registered in the medium with ganglioneuroblastoma. To improve the cytotoxic action of chemotherapeutic agents, the combined application of cytostatics with heterocyclic compounds was carried out. A computer modeling of ligand-protein complexes of carbamide using the Dock 6.4 and USF Chimera program packages was performed with molecular mechanics method. Special attention was drawn to the ability of several isoxazole heterocycles and isothiazolyl to inhibit the tyrosine kinase. It was proved in vitro that the joint application of chemotherapeutic agents and heterocyclic compounds could reduce the concentration of the cytostatic factor by 10 or more times, having maintained the maximum cytotoxic effect. It was assumed that the target amplification of cytotoxic action of chemotherapeutic

Heterocyclic N-oxides - A Promising Class of Agents Against Tuberculosis, Malaria and Neglected Tropical Diseases.

Science.gov (United States)

Dos Santos Fernandes, Guilherme Felipe; Pavan, Aline Renata; Dos Santos, Jean Leandro

2018-04-17

Heterocyclic N-oxides have emerged as promising agents against a number of diseases and disorders, especially infectious diseases. This review analyzes the emergence and development of this scaffold in the medicinal chemistry, focusing mainly on the discovery of new heterocyclic N-oxide compounds with potent activity against tuberculosis, malaria and neglected tropical diseases (i.e. leishmaniasis and Chagas disease). A number of heterocyclic N-oxide are described herein, nevertheless, the following chemical classes deserve to be highlighted due to the large number of reports in the literature about their promising pharmacological effects: furoxan, benzofuroxan, quinoxaline 1,4-di-N-oxide, indolone N-oxide and benzimidazole N-oxide. In order to describe those most promising compounds, we included in this review only those most biologically active heterocyclic N-oxide published since 2000. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Synthesis and Characterization of New Silver (I N-Heterocyclic Ccarbene Ccomplex Dderived from Imidazol-2-ylidene salt

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Mohammedl Mujbe Hasson

2018-04-01

Full Text Available A new N, N'-imidazolium salt 1-(2,6-diisopropylphenyl-3- (4,6-dimorpholino -1,3,5-traizine-2-yl-1H-imidazol-3-ium chloride as a precursor of N - heterocyclic carbene ligand was prepared via the reaction of 1 - (2, 6 - diisopropyl phenyl - 1H - imidazole with 1, 3, 5 - triazine derivative bearing morpholine substituent (2, 6 -dimorpholine - 6- chloro-1, 3, 5-triaziazine. Linear coordi-nated Ag (І NHC complex was synthesised via deprotonation of the imidazolium salt and reac-tion with Ag2O in darkness at room temperature by in situ method. The complex was synthesised for using as transfer agent to prepare another transition metals complexes by transmetallation method in the future. The imidazolium salt and their silver complex have been characterized by 1 H and 13C NMR spectroscopy as well as mass spectrometry.

The GR-value deviation from the additivity rule for irradiated systems containing heterocyclic compounds

International Nuclear Information System (INIS)

Nanobashvili, H.M.; Shanidze, G.V.; Khidesheli, G.I.; Panchvidze, M.V.

1988-01-01

The investigation of the low temperature radiolysis of binary systems containing heterocyclic compounds has been carried out. In the systems under study the G R -value deviation from the additivity rule is observed due to the energy transfer processes from matrix molecules. It is shown that heterocyclic compounds are good radioprotectors. (author)

Geometric and electronic structures of boron(III)-cored dyes tailored by incorporation of heteroatoms into ligands.

Science.gov (United States)

Sun, Lin; Zhang, Fan; Wang, Xinyang; Qiu, Feng; Xue, Minzhao; Tregnago, Giulia; Cacialli, Franco; Osella, Silvio; Beljonne, David; Feng, Xinliang

2015-03-01

Complexation of a boron atom with a series of bidentate heterocyclic ligands successfully gives rise to corresponding BF2-chelated heteroarenes, which could be considered as novel boron(III)-cored dyes. These dye molecules exhibit planar structures and expanded π-conjugated backbones due to the locked conformation with a boron center. The geometric and electronic structures of these BF2 complexes can be tailored by embedding heteroatoms in the unique modes to form positional isomer and isoelectronic structures. The structure-property relationship is further elucidated by studying the photophysical properties, electrochemical behavior and quantum-chemical calculations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Copper(II) and zinc(II) as metal-carboxylate coordination complexes based on (1-methyl-1H-benzo[d]imidazol-2-yl) methanol derivative: Synthesis, crystal structure, spectroscopy, DFT calculations and antioxidant activity

Science.gov (United States)

Benhassine, Anfel; Boulebd, Houssem; Anak, Barkahem; Bouraiou, Abdelmalek; Bouacida, Sofiane; Bencharif, Mustapha; Belfaitah, Ali

2018-05-01

This work presents a combined experimental and theoretical study of two new metal-carboxylate coordination compounds. These complexes were prepared from (1-methyl-1H-benzimidazol-2-yl)methanol under mild conditions. The structures of the prepared compounds were characterized by single-crystal X-ray analysis, FTIR and UV-Vis spectroscopy. In the Cupper complex, the Cu(II) ion is coordinated by two ligands, which act as bidentate chelator through the non-substituted N and O atoms, and two carboxylicg oxygen atoms, displaying a hexa-coordinated compound in a distorted octahedral geometry, while in the Zinc complex the ligand is ligated to the Zn(II) ion in monodentate fashion through the N atom, and the metal ion is also bonded to carboxylic oxygen atoms. The tetra-coordinated compound displays a distorted tetrahedral shape. The density functional theory calculations are carried out for the determination of the optimized structures. The electronic transitions and fundamental vibrational wave numbers are calculated and are in good agreement with experimental. In addition, the ligand and its Cu(II) and Zn(II) complexes were screened and evaluated for their potential as DPPH radical scavenger.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications.

Science.gov (United States)

Stępień, Marcin; Gońka, Elżbieta; Żyła, Marika; Sprutta, Natasza

2017-02-22

Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

Metal coordination by sterically hindered heterocyclic ligands, including 2-vinylpyridine, assessed by investigation of cobaloximes.

Science.gov (United States)

Siega, Patrizia; Randaccio, Lucio; Marzilli, Patricia A; Marzilli, Luigi G

2006-04-17

Structural and 1H NMR data have been obtained for cobaloximes with the bulkiest substituted pyridines reported so far. We have isolated in noncoordinating solvents the complexes CH3Co(DH)2L (methylcobaloxime, where DH = the monoanion of dimethylglyoxime) with L = sterically hindered N-donor ligands: quinoline, 4-CH3quinoline, 2,4-(CH3)2pyridine, and 2-R-pyridine (R = CH3, OCH3, CH2CH3, CH=CH2). We have found that the Co-N(ax) bond is very long in the structurally characterized complexes. In particular, CH3Co(DH)2(4-CH3quinoline) has a longer Co-N(ax) bond (2.193(3) A) than any reported for methylcobaloximes. The main cause of the long bonds is unambiguously identified as the steric bulk of L by the fairly linear relationship found for Co-N(ax) distance vs CCA (calculated cone angle, CCA, a computed measure of bulk) over an extensive series of methylcobaloximes. The linear relationship improves if L basicity (quantified by pKa) is taken into account. In anhydrous CDCl3 at 25 degrees C, all complexes except the 2-aminopyridine adduct exhibit 1H NMR spectra consistent with partial dissociation of L to form the methylcobaloxime dimer. 1H NMR experiments at -20 degrees C allowed us to assess qualitatively the relative binding ability of L as follows: 2,4-(CH3)2pyridine > 4-CH3quinoline approximately = quinoline approximately = 2-CH3pyridine > 2-CH3Opyridine > 2-CH3CH2pyridine > 2-CH2=CHpyridine. The broadness of the 1H NMR signals at 25 degrees C suggests a similar order for the ligand exchange rate. The lack of dissociation by 2-aminopyridine is attributed to an intramolecular hydrogen bond between the NH2 group and an oxime O atom. The weaker than expected binding of 2-vinylpyridine relative to the Co-N(ax) bond length is attributed to rotation of the 2-vinyl group required for this bulky ligand to bind to the metal center, a conclusion supported by pronounced changes in 2-vinylpyridine signals upon coordination.

Water oxidation catalyzed by molecular di- and nonanuclear Fe complexes: importance of a proper ligand framework.

Science.gov (United States)

Das, Biswanath; Lee, Bao-Lin; Karlsson, Erik A; Åkermark, Torbjörn; Shatskiy, Andrey; Demeshko, Serhiy; Liao, Rong-Zhen; Laine, Tanja M; Haukka, Matti; Zeglio, Erica; Abdel-Magied, Ahmed F; Siegbahn, Per E M; Meyer, Franc; Kärkäs, Markus D; Johnston, Eric V; Nordlander, Ebbe; Åkermark, Björn

2016-09-14

The synthesis of two molecular iron complexes, a dinuclear iron(iii,iii) complex and a nonanuclear iron complex, based on the dinucleating ligand 2,2'-(2-hydroxy-5-methyl-1,3-phenylene)bis(1H-benzo[d]imidazole-4-carboxylic acid) is described. The two iron complexes were found to drive the oxidation of water by the one-electron oxidant [Ru(bpy)3](3+).

Synthesis and research of benzylamides of some isocyclic and heterocyclic acids as potential anticonvulsants.

Science.gov (United States)

Strupińska, Marzanna; Rostafińska-Suchar, Grazyna; Pirianowicz-Chaber, Elzbieta; Stables, James P; Jiang, Jeff; Paruszewski, Ryszard

2013-01-01

A series of benzylamides of isocyclic and heterocyclic acids was synthesized and tested in Anticonvulsant Screening Project (ASP) of Antiepileptic Drug Development Program (ADDP) of NIH. Near all synthesized derivatives of heterocyclic acids showed activity. All obtained derivatives of mono- and bicyclic isocyclic acids were inactive. The power of action of heterocyclic acids derivatives seems does not depend upon kind of heteroatom (N, O or S). One of the compounds (2-furoic acid benzylamide (4)) appeared most promising. It showed in minimal clonic seizure (6Hz) test (ASP) in rats after i. p. administration: MES ED50 = 36.5 mg/kg, TOX TD50 = 269.75 mg/kg, and PI = 7.39.

Quantum mechanics and molecular dynamics simulations of complexation of alkaline-earth and lanthanide cations by poly-amino-carboxylate ligands; Simulations par mecanique quantique et dynamique moleculaire de la complexation de cations alcalino-terreux et lanthanides par des ligands polyaminocarboxylates

Energy Technology Data Exchange (ETDEWEB)

Durand, S

1999-07-01

Molecular dynamics (MD) simulations on lanthanide(III) and alkaline-earth(II) complexes with poly-amino-carboxylates (ethylene-diamino-tetra-acetate EDTA{sup 4-}, ethylene-diamino-tri-acetate-acetic acid EDTA(H){sup 3-}, tetra-aza-cyclo-dodecane-tetra-acetate DOTA{sup 4-}, methylene-imidine-acetate MIDA{sup 2-}) are reported. First, a consistent set of Lennard-Jones parameters for La{sup 3+}, Eu{sup 3+} and Lu{sup 3+} cations has been derived from free energy calculations in aqueous solution. Observed differences in hydration free energies, coordination distances and hydration numbers are reproduced. Then, the solution structures of 1:1 complexes of alkaline-earth and/or lanthanide cations with EDTA{sup 4-}, EDTA(H){sup 3-}, DOTA{sup 4-} and 1:2 complexes of lanthanide cations with MIDA{sup 2-} were studied by MD in water. In addition, free energy calculations were performed to study, for each ligand, the relative thermodynamic stabilities of complexes with Ca{sup 2+} vs Sr{sup 2+} and vs Ba{sup 2+} on the one hand, and with La{sup 3+} vs Eu{sup 3+} and vs Lu{sup 3+} on the other hand. Model does not take into account explicitly polarization and charge transfer. However, the results qualitatively agree with experimental complexation data (structure and selectivities). (author)

Nuclear magnetic resonance titration studies of simple host-guest amine-carboxylic acid systems

International Nuclear Information System (INIS)

Mahinay, Myrna S.; Lindoy, Leonard F.

1999-01-01

Adduct formation for the open-chain 1,2-diaminoethane and its N-methyl derivatives [N,N-dimethyl-ethylenediamine (N,N-DMEN),N,N'-dimethylethylenediamine (N,N'-DMEN);N,N,N',N'-tetramethyl-ethylenediamine (N,N,N',N'-TMEN)]; 1,4-diaminobutane; diethylenetriamine (DIEN); triethylenetramine (TRIEN); and the carboxylic acid systems in polar CD 3 OH and nonpolar CDCl 3 solvents were elucidated by nmr titration. The stoichiometries of the adducts were found to correspond to the number of nitrogen present in the amine species with the exception of ligand incorporating N-donors of low basicity; that is, whose log K values for the protonated species in water were less than approximately 6 to 7.(Author)

Electron and ligand transfer reactions between cyclometallated platinum(II) compounds and thallium(III) carboxylates

NARCIS (Netherlands)

Koten, G. van; Ploeg, A.F.M.J. van der; Vrieze, K.

1982-01-01

Reaction of trans-[(2-Me{2}NCH{2}C{6}H{4}{2}Pt}I{}I{] with Tl}I{}I{}I{(O{2}CR){3} (R = Me, i-Pr) gave direct elimination of Tl}I{(O{2}CR) and formation of the oxidative addition product [(2-Me{2}NCH{2}C{6}H{4}){2}Pt}I{}V{ (O{2}CR){2}], in two isomeric forms. A structure with the carbon ligands in

1-Azaniumylcyclobutane-1-carboxylate monohydrate

Directory of Open Access Journals (Sweden)

Ray J. Butcher

2014-02-01

Full Text Available In the title compound, C5H9NO2·H2O, the amino acid is in the usual zwitterionic form involving the α-carboxylate group. The cyclobutane backbone of the amino acid is disordered over two conformations, with occupancies of 0.882 (7 and 0.118 (7. In the crystal, N—H...O and O—H...O hydrogen bonds link the zwitterions [with the water molecule involved as both acceptor (with the NH3+ and donor (through a single carboxylate O from two different aminocyclobutane carboxylate moities], resulting in a two-dimensional layered structure lying parallel to (100.

Design, synthesis and antibreast cancer MCF-7 cells biological evaluation of heterocyclic analogs of resveratrol.

Science.gov (United States)

Du, Cheng; Dong, Ming-Hui; Ren, Yu-Jie; Jin, Lu; Xu, Cheng

2017-09-01

A new series of resveratrol heterocyclic analogs (4a-m) were designed and synthesized, and their inhibitiory effects on MCF-7 cells were evaluated to investigate structure-activity relationship. The effects of these analogs on human breast cancer MCF-7 cells were also determined. Results showed that MCF-7 cells could be inhibited more potently by these analogs than by resveratrol (IC 50  = 80.0 μM). Among the analogs, compounds 4c, 4e, and 4k showed a significantly higher activity (IC 50  = 42.7, 48.1, and 43.4 μM) than resveratrol. Furthermore, the derivatives without additional heterocyclic structure in the 4'-OH position exhibited a more potent activity than that with addition heterocyclic structure. In addition, docking simulation was performed to adequately position compound 4c in a human F 1 -ATPase active site to determine a probable binding model. These heterocyclic analogs could be effective candidates for the chemoprevention of human breast cancer.

Syntheses, structures, photoluminescence and photocatalysis of 2D layered lanthanide-carboxylates with 2, 2′-dithiodibenzoic acid

Energy Technology Data Exchange (ETDEWEB)

Ding, Ling; Zhong, Jie-Cen; Qiu, Xing-Tai; Sun, Yan-Qiong, E-mail: sunyq@fzu.edu.cn; Chen, Yi-Ping

2017-02-15

Two series of lanthanide-carboxylates, [Ln(2,2′-dtba)(2,2′-Hdtba)(EtOH)]{sub n} (I:Ln=Eu(1a), Dy(1b)) and [Ln(2,2′-dtba)(2,2′-Hdtba)(4,4′-bpy){sub 0.5}]{sub n} (II:Ln=Eu(2a), Dy(2b), Tb(2c) 2,2′-H{sub 2}dtba=2,2′-dithiodibenzoic acid, 4,4′-bpy=4,4′-bipyridine) have been synthesized under hydrothermal conditions. Interestingly, the H{sub 2}dtba organic ligand was generated by in situ S–S reaction of 2-mercaptobenzoic acid. Compounds I and II possess different 2D layered structures based on similar 1D [Ln(2,2′-dtba)]{sup +} chains. Photoluminescence studies reveal that compounds I and II exhibit strong lanthanide characteristic emission bands. Remarkably, Compounds 1b and 2a both exhibit good photocatalytic activity for degradation of Rhodamine-B (Rh-B) under the simulated sunlight irradiation. - Graphical abstract: Two series of lanthanide-carboxylates have been in situ synthesized under hydrothermal conditions. The lanthanide-carboxylates exhibit strong lanthanide characteristic emission bands and good photocatalytic activity for degradation of Rhodamine-B. - Highlights: • 2D layered lanthanide-carboxylates with 2,2′-dithiodibenzoic acid. • In situ S–S reaction of 2-mercaptobenzoic acid under hydrothermal condition. • The Emission spectra of I and II exhibit the characteristic transition of lanthanide ions. • Compounds 1b and 2a exhibit good photocatalytic activity for degradation of Rhodamine-B.

GREENER SYNTHESIS OF HETEROCYCLIC COMPOUNDS USING MICROWAVE IRRADIATION

Science.gov (United States)

An introduction of our interest in the microwave-assisted greener synthesis of a variety of heterocyclic compounds will be presented. It involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports, such as alumina, sili...

MICROBIAL DEGRADATION OF NITROGEN, OXYGEN AND SULFUR HETEROCYCLIC COMPOUNDS UNDER ANAEROBIC CONDITIONS: STUDIES WITH AQUIFER SAMPLES

Science.gov (United States)

The potential for anaerobic biodegradation of 12 heterocyclic model compounds was studied. Nine of the model compounds were biotransformed in aquifer slurries under sulfate-reducing or methanogenic conditions. The nitrogen and oxygen heterocyclic compounds were more susceptible t...

Correction: Synthesis of pyrrolidine-3-carboxylic acid derivatives via asymmetric Michael addition reactions of carboxylate-substituted enones.

Science.gov (United States)

Yin, Feng; Garifullina, Ainash; Tanaka, Fujie

2018-04-25

Correction for 'Synthesis of pyrrolidine-3-carboxylic acid derivatives via asymmetric Michael addition reactions of carboxylate-substituted enones' by Feng Yin et al., Org. Biomol. Chem., 2017, 15, 6089-6092.

Complexation studies of actinides (U, Pu, Am) with linear polyamino-carboxylate ligands and sidero-chelates

International Nuclear Information System (INIS)

Nguyen, L.V.

2010-01-01

As part of our research endeavour aimed at developing and improving decontamination processes of wastewater containing alpha emitters, physico-chemical complexation studies of actinides (U, Pu, Am) with organic open-chain ligands such as poly-aminocarboxylic acids (H 4 EDTA) and sidero-chelates (di-hydroxamic acids and desferrioxamine B) have been carried out. Gaining a clear understanding of the coordination properties of the targeted actinides is an essential step towards the selection of the most appropriate chelating agents that will exhibit high uptake efficiencies. EXAFS (Extended X-ray Absorption Fine Structure) measurements at the ESRF synchrotron enabled to elucidate the coordination scheme of uranium and plutonium complexes. Solution thermodynamic investigations were intended to provide valuable information about the nature and the stability of the uranium(VI) and americium(III) complexes prevailing at a given pH in solution. The set of stability constants determined from potentiometric and UV-visible spectrophotometric titrations, allowed to predict the speciation of the selected actinides in presence of the aforementioned ligands and to determine the pH range required for achieving 'ultimate' decontamination. (author) [fr

Heterocyclic Anticancer Compounds: Recent Advances and the Paradigm Shift towards the Use of Nanomedicine’s Tool Box

Directory of Open Access Journals (Sweden)

Pedro Martins

2015-09-01

Full Text Available The majority of heterocycle compounds and typically common heterocycle fragments present in most pharmaceuticals currently marketed, alongside with their intrinsic versatility and unique physicochemical properties, have poised them as true cornerstones of medicinal chemistry. Apart from the already marketed drugs, there are many other being investigated for their promising activity against several malignancies. In particular, anticancer research has been capitalizing on the intrinsic versatility and dynamic core scaffold of these compounds. Nevertheless, as for any other promising anticancer drugs, heterocyclic compounds do not come without shortcomings. In this review, we provide for a concise overview of heterocyclic active compounds and families and their main applications in medicine. We shall focus on those suitable for cancer therapy while simultaneously addressing main biochemical modes of action, biological targets, structure-activity relationships as well as intrinsic limitation issues in the use of these compounds. Finally, considering the advent of nanotechnology for effective selective targeting of drugs, we shall discuss fundamental aspects and considerations on nanovectorization of such compounds that may improve pharmacokinetic/pharmacodynamic properties of heterocycles.

Structure-Activity Relationship Study of Ionotropic Glutamate Receptor Antagonist (2S,3R)-3-(3-Carboxyphenyl)pyrrolidine-2-carboxylic Acid

DEFF Research Database (Denmark)

Krogsgaard-Larsen, Niels; Storgaard, Morten; Møller, Charlotte

2015-01-01

Herein we describe the first structure-activity relationship study of the broad-range iGluR antagonist (2S,3R)-3-(3-carboxyphenyl)pyrrolidine-2-carboxylic acid (1) by exploring the pharmacological effect of substituents in the 4, 4', or 5' positions and the bioisosteric substitution of the distal...... carboxylic acid for a phosphonic acid moiety. Of particular interest is a hydroxyl group in the 4' position 2a which induced a preference in binding affinity for homomeric GluK3 over GluK1 (Ki = 0.87 and 4.8 μM, respectively). Two X-ray structures of ligand binding domains were obtained: 2e in GluA2-LBD...... and 2f in GluK1-LBD, both at 1.9 Å resolution. Compound 2e induces a D1-D2 domain opening in GluA2-LBD of 17.3-18.8° and 2f a domain opening in GluK1-LBD of 17.0-17.5° relative to the structures with glutamate. The pyrrolidine-2-carboxylate moiety of 2e and 2f shows a similar binding mode as kainate...

Greener Synthetic Alternatives to Heterocycles, Nanomaterials and Nanocomposites

Science.gov (United States)

Microwave (MW) expedited reaction of neat reactants or catalyzed by mineral support surfaces, such as alumina, silica, clay, or their ‘doped’ versions, for the rapid one-pot assembly of heterocyclic compounds from in situ generated reactive intermediates via enamines or using hyp...

Synthesis and properties of heterocyclic type I photoinitiators

International Nuclear Information System (INIS)

Liska, R.; Knaus, S.; Wendrinsky, J.

1999-01-01

The synthesis and properties of a series of new heterocyclic hydroxyalkylphenone-analogous photoinitiators (PIs) is described. The PIs are obtained by reaction of aromatic organolithium compounds with nitriles or by Friedel-Craft's-acylation. Preliminary photocalorimetric tests and UV absorption data are included

Formation of the Imidazolinone Ring Under Mild Conditions in the Presence of Sodium Hydride

Directory of Open Access Journals (Sweden)

Anibal J. Mocchi

2004-06-01

Full Text Available Substituted imidazolinones containing heterocyclic carboxylic acids as substituents and possessing herbicidal properties were synthesized by cyclization of 2-amino-2,3-dimethylbutyramide with heterocyclic ethyl dicarboxylates under mild conditions. The use of NaH as base leads to a significant increase in the reaction rate and allows the preparation of the target compounds in high yields.

Synthesis of 123I-labelled analogues of imidazobenzodiazepine receptor ligands

International Nuclear Information System (INIS)

Katsifis, A.G.; Mattner, F.; McPhee, M.E.; Ridley, D.D.

1999-01-01

Reaction of bromo- or iodo-substituted isatoic anhydrides with N-methylglycine, L-proline or D-proline afforded bromo- or iodo-substituted 1,4-benzodiazepinediones which on condensation with ethyl or t-butyl isocyanoacetates gave ethyl or t-butyl bromo- or iodo-imidazobenzodiazepine carboxylates. These aryl halides were converted into the corresponding tributylstannanes with bis(tributyltin) in the presence of (triphenylphosphine)palladium(0), and the stannanes were treated with sodium ( 123 I)iodide in the presence of chloramine-T to give the required 123 I-labelled analogues of the imidazobenzodiazepine receptor ligands flumazenil and bretazenil. Copyright (1999) CSIRO Australia

Organic ligand-induced dissolution kinetics of antimony trioxide.

Science.gov (United States)

Hu, Xingyun; He, Mengchang

2017-06-01

The influence of low-molecular-weight dissolved organic matter (LMWDOM) on the dissolution rate of Sb 2 O 3 was investigated. Some representative LMWDOMs with carboxyl, hydroxyl, hydrosulfuryl and amidogen groups occurring naturally in the solution were chosen, namely oxalic acid, citric acid, tartaric acid, EDTA, salicylic acid, phthalandione, glycine, thiolactic acid, xylitol, glucose and catechol. These LMWDOMs were dissolved in inert buffers at pH=3.7, 6.6 and 8.6 and added to powdered Sb 2 O 3 in a stirred, thermostatted reactor (25°C). The addition of EDTA, tartaric acid, thiolactic acid, citric acid and oxalic acid solutions at pH3.7 and catechol at pH8.6 increased the rate of release of antimony. In the 10mmol/L thiolactic acid solution, up to 97% by mass of the antimony was released after 120min reaction. There was no effect on the dissolution of Sb 2 O 3 for the other ligands. A weak correlation between dissolution rate with the dissociation constant of ligands and the stability of the dissolved complex was also found. All the results showed that the extent of the promoting effect of ligands on the dissolution of Sb 2 O 3 was not determined by the stability of the dissolved complex, but by the dissociation constant of ligands and detachment rate of surface chelates from the mineral surface. This study can not only help in further understanding the effect of individual low-molecular-weight organic ligands, but also provides a reference to deduce the effect of natural organic matters with oxygen-bearing functional groups on the dissolution of antimony oxide minerals. Copyright © 2016. Published by Elsevier B.V.

Effects of Ligands on a Ternary Hydroxo Complex Formation with Eu(III) in a Aqueous Solution: Comparison of a Pyridine-2,6-dicarboxylate with a Phthalate

International Nuclear Information System (INIS)

Park, K. K.; Cho, H. R.; Kim, W. H.; Jung, E. C.

2008-01-01

The interaction of a radionuclide with ligands in a groundwater influences its migration through a hydrogeological system due to a change in the characteristics of a dissolution and a sorption. Actinide ions are classified as a hard acid and strongly interact with ligands having an oxygen donor atom of a hard base such as a hydroxide, carbonate and carboxylate. These ligands reveal a large ionic bonding character. A number of experimental results on a binary complex formation of actinides have been reported. However, actinides may easily form a ternary complex by interacting simultaneously with two different ligands, since an ionic bonding does not restrict the spatial orientation of a ligand. In previous studies, a ternary hydroxo complex formation was investigated by using pyridine-2,6-dicarboxylate (PDA) or phthalate as an organic ligand and Eu(III) as an analogue of an actinide(III) ion. Although these organic ligands equally contain two carboxylate groups that interact with an Eu(III) ion, their stabilities reveal big differences. PDA is a tridentate ligand forming two 5-membered chelates, while phthalate is a bidentate ligand forming a 7-membered chelate. The latter reveals a lower stability than the former due to an angle strain. This is one of the reasons for the lower stability of the Eu(III)-phthalate than that of the Eu(III)- PDA. The difference in the stabilities of binary complexes, EuL + (L=organic ligand), influences the stabilities of the ternary hydroxo complexes, Eu(OH)L. The coordination of a phenylic or pyridine ligand can greatly enhance the fluorescence of an Eu(III) ion due to the high absorbance of a ligand by a π → π * transition and the transfer of this energy to an Eu(III) ion. These fluorescence characteristics in a binary complex system could be changed in a ternary complex. In this study, the effect of a ligand on the stability of a ternary hydroxo complex is reported by comparing the stabilities of Eu-PDA with Eu-phthalate systems

Structural and spectral comparisons between isomeric benzisothiazole and benzothiazole based aromatic heterocyclic dyes

Science.gov (United States)

Wang, Yin-Ge; Wang, Yue-Hua; Tao, Tao; Qian, Hui-Fen; Huang, Wei

2015-09-01

A pair of isomeric heterocyclic compounds, namely 3-amino-5-nitro-[2,1]-benzisothiazole and 2-amino-6-nitrobenzothiazole, are used as the diazonium components to couple with two N-substituted 4-aminobenzene derivatives. As a result, two pairs of isomeric aromatic heterocyclic azo dyes have been produced and they are structurally and spectrally characterized and compared including single-crystal structures, electronic spectra, solvatochromism and reversible acid-base discoloration, thermal stability and theoretically calculations. It is concluded that both benzisothiazole and benzothiazole based dyes show planar molecular structures and offset π-π stacking interactions, solvatochromism and reversible acid-base discoloration. Furthermore, benzisothiazole based aromatic heterocyclic dyes exhibit higher thermal stability, larger solvatochromic effects and maximum absorption wavelengths than corresponding benzothiazole based ones, which can be explained successfully by the differences of their calculated isomerization energy, dipole moment and molecular band gaps.

Versatile lanthanide-azide complexes with azide/carboxylate/hydroxy mixed bridged chain exhibiting magnetic and luminescent properties

International Nuclear Information System (INIS)

Wang Haichao; Xue Min; Guo Qian; Zhao Jiongpeng; Liu Fuchen; Ribas, Joan

2012-01-01

Two new lanthanide-azide complexes, [Ln 2 (N 3 )(isonic) 2 (OH) 3 (Hisonic)(H 2 O)] n (Ln=Yb for 1 and Tb for 2, isonic=isonicotinate), were obtained in hydrothermal condition. X-ray diffraction analysis indicated the two complexes are isomorphic chain structure in which the Ln III ions are mixed bridged by the azide anions, hydroxyl anions and carboxylate groups of the isonicotinate ligands. Further studies indicated weak antiferromagnetic interactions between the Ln III ions in 1 and 2, and complex 2 exhibit green sensitized Luminescent character of Tb III ion. - Graphical abstract: Two new 1D lanthanide-azide complexes, [Ln 2 (N 3 )(isonic) 2 (OH) 3 (Hisonic)(H 2 O)] n (Ln=Yb III for 1 and Tb III for 2, isonic=isonicotinate), were synthesized by hydrothermal reaction and exhibit interesting magnetism and fluorescence properties. Highlights: ► The research provided a new method for synthesizing lanthanide-azide complexes. ► The complexes have an interesting azide/hydroxyl/carboxylate mixed bridged1D chain structure. ► The antiferromagnetic coupling between the complexes and 2 displays green luminescence.

Structure and luminescent property of complexes of aryl carboxylic acid-functionalized polystyrene with Eu(III) and Tb(III) ions.

Science.gov (United States)

Gao, Baojiao; Shi, Nan; Qiao, Zongwen

2015-11-05

Via polymer reactions, naphthoic acid (NA) and benzoic acid (BA) were bonded onto the side chains of polystyrene (PS), respectively, and two aryl carboxylic acid-functionalized polystyrenes, PSNA and PSBA, were obtained. Using PSNA and PSBA as macromolecule ligands and Eu(3+) and Tb(3+) ions as central ions, various luminescent binary polymer-rare earth complexes were prepared. At the same time, with 1,10-phenanthroline (Phen) and 4,4'-bipyridine (Bipy) as small-molecule co-ligands, various ternary polymer-rare earth complexes were also prepared. On the basis of characterizing PSNA, PSBA and complexes, the relationship between structure and luminescent property for these prepared complexes were mainly investigated. The study results show that the macromolecule ligands PSNA and PSBA, or the bonded NA and BA ligands, can strongly sensitize the fluorescence emissions of Eu(3+) ion or Tb(3+) ion, but the sensitization effect is strongly dependent on the structure of the ligands and the property of the central ions, namely it is strongly dependent on the matching degree of energy levels. The fluorescence emission of the binary complex PS-(NA)3-Eu(III) is stronger than that PS-(BA)3-Eu(III), indicating ligand NA has stronger sensitization action for Eu(3+) ion than ligand BA; the binary complex PS-(BA)3-Tb(III) emit strong characteristic fluorescence of Tb(3+) ion, displaying that ligand BA can strongly sensitize Tb(3+) ion, whereas the binary complex PS-(NA)3-Tb(III) nearly does not emit the characteristic fluorescence of Tb(3+) ion, showing that ligand NA does not sensitize Tb(3+) ion. The fluorescence intensity of the ternary complexes is much stronger than that of the binary complexes in the same series. Copyright © 2015 Elsevier B.V. All rights reserved.

Self-association and infrared spectres of some heterocyclic compounds based on pyrrol in solid state

International Nuclear Information System (INIS)

Mulloev, N.; Nurulloev, M.; Narziev, B.N.

1993-01-01

Present article is devoted to self-association and infrared spectres of some heterocyclic compounds based on pyrrol in solid state. The study results of self-association specified by molecular hydrogen bonds of some heterocyclic compounds based on pyrrol on spectres of infrared absorption of stretching vibrations of N-H group were considered.

CARBOXYLIC ACIDS ELECTROOXIDATION ON SHUNGITE ELECTRODE

Directory of Open Access Journals (Sweden)

Oleksandr Davydenko

2017-03-01

Full Text Available Purpose: This article discusses the electrochemical method of directional conversion of carboxylic acids, which are the most aggressive hydrocarbons oxidation products back into the corresponding hydrocarbons. Existing methods for the regeneration of waste petroleum oils have significant drawbacks, which include the formation of new hard-reclaimed waste and loss of a significant part of the oil during regeneration. Methods: Electrooxidation processes of carboxylic acid on various electrode materials: platinum, graphite and shungite anodes were studied. Results: Potentiostatic polarization curves with simultaneous measurement of near-electrode solution pH showed differences in the process on these anode materials: dimer yield for Kolbe is decreased under the transition from platinum to shungite. At potentials higher than 2.0 v, carboxylic acid has a higher adsorbability compared to water. Therefore Faraday’s side-process of water oxidation doesn’t almost occur, which contributes to high yield of expected product according to current. Electrolysis of carboxylic acids solutions under controlled potential (2.0 and 2.4 V and chromatographic analysis of the formed products showed that along with the dimeric structures formation for Kolbe reaction, the occurrence of a hydrocarbons mixture takes place, which may be the result of disproportionation of hydrocarbon radicals (alkane and alkene and hydrocarbons of isomeric structure, by further oxidation of the hydrocarbon radical to carbocation and its subsequent transformation into the corresponding saturated and unsaturated isomers. Such statement is not supported by conception of the process of one- and two-electron carboxylic acid oxidation. Discussion: General carboxylic acid oxidation scheme according to one-electron mechanism (dimerization and disproportionation of the radical and two-electron mechanism (formation and carbocation rearrangement is proposed. The formation of hydrocarbons under

Comprehensive database of Manufactured Gas Plant tars. Part C. Heterocyclic and hydroxylated polycyclic aromatic hydrocarbons.

Science.gov (United States)

Gallacher, Christopher; Thomas, Russell; Lord, Richard; Kalin, Robert M; Taylor, Chris

2017-08-15

Coal tars are a mixture of organic and inorganic compounds that were by-products from the manufactured gas and coke making industries. The tar compositions varied depending on many factors such as the temperature of production and the type of retort used. For this reason a comprehensive database of the compounds found in different tar types is of value to understand both how their compositions differ and what potential chemical hazards are present. This study focuses on the heterocyclic and hydroxylated compounds present in a database produced from 16 different tars from five different production processes. Samples of coal tar were extracted using accelerated solvent extraction (ASE) and derivatized post-extraction using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane (TMCS). The derivatized samples were analysed using two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GCxGC/TOFMS). A total of 865 heterocyclic compounds and 359 hydroxylated polycyclic aromatic hydrocarbons (PAHs) were detected in 16 tar samples produced by five different processes. The contents of both heterocyclic and hydroxylated PAHs varied greatly with the production process used, with the heterocyclic compounds giving information about the feedstock used. Of the 359 hydroxylated PAHs detected the majority would not have been be detected without the use of derivatization. Coal tars produced using different production processes and feedstocks yielded tars with significantly different heterocyclic and hydroxylated contents. The concentrations of the individual heterocyclic compounds varied greatly even within the different production processes and provided information about the feedstock used to produce the tars. The hydroxylated PAH content of the samples provided important analytical information that would otherwise not have been obtained without the use of derivatization and GCxGC/TOFMS. Copyright © 2017 John Wiley & Sons, Ltd.

Synthesis, structure and stability of a chiral imine-based Schiff-based ligand derived from L-glutamic acid and its [Cu4] complex

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Muche, Simon; Levacheva, Irina; Samsonova, Olga; Biernasiuk, Anna; Malm, Anna; Lonsdale, Richard; Popiołek, Łukasz; Bakowsky, Udo; Hołyńska, Małgorzata

2017-01-01

Studies of the stability of a ligand derived from L-glutamic acid and ortho-vanillin and its new [Cu4] complex are presented. The [Cu4] complex contains a heterocubane [CuII4O4] core and pendant carboxylic groups increasing its solubility in water, also under basic conditions. The stability of the complex in different solvents is confirmed with ESI-MS studies and such experiments as successful recrystallization. The complex is stable also under physiological conditions whereas the ligand is partly decomposed to L-glutamic acid and ortho-vanillin.

Synthesis and bioactivities of Phenazine-1-carboxylic acid derivatives based on the modification of PCA carboxyl group.

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Xiong, Zhipeng; Niu, Junfan; Liu, Hao; Xu, Zhihong; Li, Junkai; Wu, Qinglai

2017-05-01

Phenazine-1-carboxylic acid (PCA) as a natural product widely exists in microbial metabolites of Pseudomonads and Streptomycetes and has been registered for the fungicide against rice sheath blight in China. To find higher fungicidal activities compounds and study the effects on fungicidal activities after changing the carboxyl group of PCA, we synthesized a series of PCA derivatives by modifying the carboxyl group of PCA and their structures were confirmed by 1 H NMR and HRMS. Most compounds exhibited significant fungicidal activities in vitro. In particular, compound 6 exhibited inhibition effect against Rhizoctonia solani with EC 50 values of 4.35mg/L and compound 3b exhibited effect against Fusarium graminearum with EC 50 values of 8.30mg/L, compared to the positive control PCA with its EC 50 values of 7.88mg/L (Rhizoctonia solani) and 127.28mg/L (Fusarium graminearum), respectively. The results indicated that the carboxyl group of PCA could be modified to be amide group, acylhydrazine group, ester group, methyl, hydroxymethyl, chloromethyl and ether group etc. And appropriate modifications on carboxyl group of PCA were useful to extend the fungicidal scope. Copyright © 2017 Elsevier Ltd. All rights reserved.

Carboxyl group reactivity in actin

Energy Technology Data Exchange (ETDEWEB)

Elzinga, M.

1986-01-01

While earlier work showed that the carboxyl groups of proteins could be quantitatively coupled to amino groups at pH 4.75 in the presence of EDC and a denaturing agent, the work presented here indicates that under milder conditions the modification of sidechain carboxyls is limited and somewhat specific. Most of the incorporated glycine ethyl ester (GEE) is apparently bound to five carboxyls. The total GEE incorporated was 3 to 4 moles/mole of protein as measured by an increase in Gly upon acid hydrolysis and amino acid analysis, as well as total radioactivity. 3.55 residues were found in peptides, 2.75 bound to residues 1 to 4, and 0.8 bound to Gly-100. 9 refs., 2 figs., 2 tabs.

Carboxyl group reactivity in actin

International Nuclear Information System (INIS)

Elzinga, M.

1986-01-01

While earlier work showed that the carboxyl groups of proteins could be quantitatively coupled to amino groups at pH 4.75 in the presence of EDC and a denaturing agent, the work presented here indicates that under milder conditions the modification of sidechain carboxyls is limited and somewhat specific. Most of the incorporated glycine ethyl ester (GEE) is apparently bound to five carboxyls. The total GEE incorporated was 3 to 4 moles/mole of protein as measured by an increase in Gly upon acid hydrolysis and amino acid analysis, as well as total radioactivity. 3.55 residues were found in peptides, 2.75 bound to residues 1 to 4, and 0.8 bound to Gly-100. 9 refs., 2 figs., 2 tabs

Improve the biodegradability of post-hydrothermal liquefaction wastewater with ozone: conversion of phenols and N-heterocyclic compounds.

Science.gov (United States)

Yang, Libin; Si, Buchun; Martins, Marcio Arêdes; Watson, Jamison; Chu, Huaqiang; Zhang, Yuanhui; Tan, Xiaobo; Zhou, Xuefei; Zhang, Yalei

2017-04-01

Hydrothermal liquefaction is a promising technology to convert wet biomass into bio-oil. However, post-hydrothermal liquefaction wastewater (PHWW) is also produced during the process. This wastewater contains a high concentration of organic compounds, including phenols and N-heterocyclic compounds which are two main inhibitors for biological treatment. Thus, proper treatment is required. In this work, ozone was used to convert phenols and N-heterocyclic compounds with a dosage range of 0-4.64 mg O 3 /mL PHWW. After ozone treatment, the phenols were fully converted, and acids were produced. However, N-heterocyclic compounds were found to have a low conversion rate (21.7%). The kinetic analysis for the degradation of phenols and N-heterocyclic compounds showed that the substitute played an important role in determining the priority of ozone reactions. The OH moiety in the ring compounds (phenols and pyridinol) may form hydroxyl radical, which lead to an efficient reaction. A substantial improved biodegradability of PHWW was observed after ozone treatment. The ratio of BOD 5 /COD was increased by about 32.36%, and reached a maximum of 0.41. The improved biodegradability of PHWW was justified by the conversion of phenols and N-heterocyclic compounds.

Extended mechanistic aspects on photoinitiated polymerization of 1,6-hexanediol diacrylate by hexaarylbisimidazoles and heterocyclic mercapto compounds.

Science.gov (United States)

Berdzinski, Stefan; Strehmel, Nadine; Lindauer, Heike; Strehmel, Veronika; Strehmel, Bernd

2014-05-01

Chlorine substituted hexaarylbisimidazole (o-Cl-HABI) efficiently initiates radical polymerization of multifunctional acrylic esters in the presence of a heterocyclic mercapto compound if the latter can form its tautomeric thione. Exposure of o-Cl-HABI results in lophyl radicals, which efficiently add to the thione in the first step while the second step releases a highly reactive thiyl radical from this intermediate. LC-MS and CID-MS measurements support this reaction scheme. Furthermore, photo-DSC experiments applying UV light between 320 and 380 nm showed that mercaptotriazole and phenylmercaptotriazole exhibited the best reactivity in the monomer 1,6-hexanediol diacrylate (HDDA) while alkyl substituted mercaptotriazoles showed less reactivity. Change of the triazole heterocycle by mercaptoimidazole resulted in a significant decrease of photoinitiation efficiency. This heterocycle does not form the corresponding thione in HDDA as shown by NMR measurements. Replacement of mercaptotriazole by an alkylthiol leads to a system showing the lowest photoinitiation efficiency in this series. Formation of thione structure in the case of heterocyclic mercapto compounds may cause higher reactivity of the heterocyclic mercapto compounds with the lophyl radical in the monomer chosen.

An endogenous aryl hydrocarbon receptor ligand inhibits proliferation and migration of human ovarian cancer cells.

Science.gov (United States)

Wang, Kai; Li, Yan; Jiang, Yi-Zhou; Dai, Cai-Feng; Patankar, Manish S; Song, Jia-Sheng; Zheng, Jing

2013-10-28

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor mediates many biological processes. Herein, we investigated if 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE, an endogenous AhR ligand) regulated proliferation and migration of human ovarian cancer cells via AhR. We found that AhR was widely present in many histotypes of ovarian cancer tissues. ITE suppressed OVCAR-3 cell proliferation and SKOV-3 cell migration in vitro, which were blocked by AhR knockdown. ITE also suppressed OVCAR-3 cell growth in mice. These data suggest that the ITE might potentially be used for therapeutic intervention for at least a subset of human ovarian cancer. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

One-Pot Two-Step Multicomponent Process of Indole and Other Nitrogenous Heterocycles or Amines toward α-Oxo-acetamidines.

Science.gov (United States)

Martinez-Ariza, Guillermo; McConnell, Nicholas; Hulme, Christopher

2016-04-15

A cesium carbonate promoted three-component reaction of N-H containing heterocycles, primary or secondary amines, arylglyoxaldehydes, and anilines is reported. The key step involves a tandem sequence of N-1 addition of a heterocycle or an amine to preformed α-iminoketones, followed by an air- or oxygen-mediated oxidation to form α-oxo-acetamidines. The scope of the reaction is enticingly broad, and this novel methodology is applied toward the synthesis of various polycyclic heterocycles.

Mn(III)-initiated facile oxygenation of heterocyclic 1,3-dicarbonyl compounds.

Science.gov (United States)

Rahman, Md Taifur; Haque, Md Aminul; Igarashi, Hikaru; Nishino, Hiroshi

2011-11-16

The Mn(III)-initiated aerobic oxidation of heterocyclic 1,3-dicarbonyl compounds, such as 4-alkyl-1,2-diphenylpyrazolidine-3,5-diones, 1,3-dialkylpyrrolidine-2,4-diones, 3-alkyl-1,5-dimethylbarbituric acids, and 3-butyl-4-hydroxy-2-quinolinone gave excellent to good yields of the corresponding hydroperoxides, which were gradually degraded by exposure to the metal initiator after the reaction to afford the corresponding alcohols. The synthesis of 30 heterocyclic 1,3-dicarbonyl compounds, the corresponding hydroperoxides and the 10 alcohols, their characterization, and the limitations of the procedure are described. In addition, the mechanism of the hydroperoxidation and the redox decomposition of the hydroperoxides are discussed.

Production of carboxylic acid and salt co-products

Science.gov (United States)

Hanchar, Robert J.; Kleff, Susanne; Guettler, Michael V.

2014-09-09

This invention provide processes for producing carboxylic acid product, along with useful salts. The carboxylic acid product that is produced according to this invention is preferably a C.sub.2-C.sub.12 carboxylic acid. Among the salts produced in the process of the invention are ammonium salts.

Synthesis and antibacterial activity of some heterocyclic derivatives of sulfanilamide

Directory of Open Access Journals (Sweden)

B.B. Subudhi

2012-12-01

Full Text Available Considering the promising antimicrobial potential of carbonic anhydrase inhibitors and heterocyclic compounds some heterocyclic derivatives of sulfanilamide (2a-e were synthesized. The diazotisation of sulfanilamide followed by substitution with ethylacetoacetate and further condensation yielded compounds 2a-c. Schiff base of sulfanilamide with salicylaldehyde on reaction with thioglycollic acid and chloroacetyl chloride resulted in compound 2d-e. The susceptibility of Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa to the title compounds (300 μg/disc was investigated and compared to that of nitrofurantoin (300 μg/disc and ciprofloxacin (25 μg/disc. The title compounds showed good antimicrobial activity.DOI: http://dx.doi.org/10.4314/bcse.v26i3.15

A relativistic density functional study of uranyl hydrolysis and complexation by carboxylic acids in aqueous solution

International Nuclear Information System (INIS)

Ray, Rupashree Shyama

2009-01-01

In this work, the complexation of uranium in its most stable oxidation state VI in aqueous solution was studied computationally, within the framework of density functional (DF) theory. The thesis is divided into the following parts: Chapter 2 briefly summarizes the relevant general aspects of actinide chemistry and then focuses on actinide environmental chemistry. Experimental results on hydrolysis, actinide complexation by carboxylic acids, and humic substances are presented to establish a background for the subsequent discussion. Chapter 3 describes the computational method used in this work and the relevant features of the parallel quantum chemistry code PARAGAUSS employed. First, the most relevant basics of the applied density functional approach are presented focusing on relativistic effects. Then, the treatment of solvent effects, essential for an adequate modeling of actinide species in aqueous solution, will be introduced. At the end of this chapter, computational parameters and procedures will be summarized. Chapter 4 presents the computational results including a comparison to available experimental data. In the beginning, the mononuclear hydrolysis product of UO_2"2"+, [UO_2OH]"+, will be discussed. The second part deals with actinide complexation by carboxylate ligands. First of all the coordination number for uranylacetate will be discussed with respect to implications for the complexation of actinides by humic substances followed by the uranyl complexation of aromatic carboxylic acids in comparison to earlier results for aliphatic ones. In the end, the ternary uranyl-hydroxo-acetate are discussed, as models of uranyl humate complexation at ambient condition.

Photoactivation of heterocyclic change-transfer complexes-electrolytes

International Nuclear Information System (INIS)

Studzinskij, O.P.; Ponomareva, R.P.; Proskuryakova, T.V.

1999-01-01

Effect of light on the systems containing of five- or six-number nitrogen-containing heterocycles, molecular iodine and different-nature organic solvents, has been studied by the methods of absorption spectroscopy and electric conductivity measurement. It has been ascertained that in proton-donor solvents the complexes of 1:1 composition are formed with charge transfer, their electric conductivity increasing essentially with photoactivation [ru

Synthesis and antimicrobial activity of some novel fused heterocyclic 1,2,4-triazolo [3,4-b][1,3,4] thiadiazine derivatives

Science.gov (United States)

Sahu, Jagdish K.; Ganguly, Swastika; Kaushik, Atul

2014-01-01

In the present investigation, the synthesis and antimicrobial evaluation of 1,2,4-triazolo [3,4-b][1,3,4] thiadiazine including different pharmacophores are aimed at. In this study, a series of 6-aryl-3- (3,4 -dialkoxyphenyl)-7H -[1,2,4]triazolo [3,4-b][1,3,4] thiadiazine (7a-7k) was synthesized by condensing 4-amino-5-(3,4-dialkoxyphenyl)-4H-[1,2,4]- triazole-3-thiol (6) with various aromatic carboxylic acids in the presence of phenacyl bromides through one-pot reaction. Eleven fused heterocyclic derivatives were successfully synthesized. The structures of these newly synthesized compounds were characterized by IR, 1H NMR and mass spectroscopic studies. All the synthesized compounds were screened for their antimicrobial evaluation. Some of the compounds exhibited promising antimicrobial activity. From the present study it may be concluded that synthesized compounds are fruitful in terms of their structural novelty and marked biological activities. These compounds could be further modified to develop potential and safer antifungal agents. PMID:24959418

Sulfur ylides in the synthesis of heterocyclic and carbocyclic compounds

International Nuclear Information System (INIS)

Lakeev, Sergei N; Maydanova, Irina O; Galin, Fanur Z; Tolstikov, Genrikh A

2001-01-01

Data on the use of sulfonium ylides in the synthesis of carbocyclic and heterocyclic compounds published over the last 15 years are analysed, systematised and generalised. The bibliography includes 139 references.

N,S,O-Heterocycles in Aged Champagne Reserve Wines and Correlation with Free Amino Acid Concentrations.

Science.gov (United States)

Le Menn, Nicolas; Marchand, Stephanie; de Revel, Gilles; Demarville, Dominique; Laborde, Delphine; Marchal, Richard

2017-03-22

Champagne regulations allow winegrowers to stock still wines to compensate for quality shifts in vintages, mainly due to climate variations. According to their technical requirements and house style, Champagne producers use these stored wines in their blends to enhance complexity. The presence of lees and aging at low pH (2.95-3.15), as in Champagne wines, lead to several modifications in wine composition. These conditions, combined with extended aging, result in the required environment for the Maillard chemical reaction, involving aromatic molecules, including sulfur, oxygen, and nitrogen heterocycles (such as thiazole, furan, and pyrazine derivatives), which may have a sensory impact on wine. Some aromatic heterocycles in 50 monovarietal wines aged from 1 to 27 years provided by Veuve Clicquot Ponsardin Champagne house were determined by the SPME-GC-MS method. The most interesting result highlighted a strong correlation between certain heterocycle concentrations and wine age. The second revealed a correlation between heterocyclic compound and free amino acid concentrations measured in the wines, suggesting that these compounds are potential aromatic precursors when wine is aged on lees and, thus, potential key compounds in the bouquet of aged Champagnes. The principal outcome of these assays was to reveal, for the first time, that aromatic heterocycle concentrations in Champagne base wines are correlated with wine age.

40 CFR 721.10003 - Manganese heterocyclic tetraamine complex (generic).

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Manganese heterocyclic tetraamine complex (generic). 721.10003 Section 721.10003 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... section. (2) The significant new uses are: (i) Industrial, commercial, and consumer activities...

A two-dimensional zinc(II) coordination polymer based on mixed dimethyl succinate and bipyridine ligands: synthesis, structure, thermostability and luminescence properties.

Science.gov (United States)

Liu, Yang; Feng, Yong Lan; Fu, Wei Wei

2016-04-01

From the viewpoint of crystal engineering, the construction of crystalline polymeric materials requires a rational choice of organic bridging ligands for the self-assembly process. Multicarboxylate ligands are of particular interest due to their strong coordination activity towards metal ions, as well as their various coordination modes and versatile conformations. The structural chemistry of dicarboxylate-based coordination polymers of transition metals has been developed through the grafting of N-containing organic linkers into carboxylate-bridged transition metal networks. A new luminescent two-dimensional zinc(II) coordination polymer containing bridging 2,2-dimethylsuccinate and 4,4'-bipyridine ligands, namely poly[[aqua(μ2-4,4'-bipyridine-κ(2)N:N')bis(μ3-2,2-dimethylbutanedioato)-κ(4)O(1),O(1'):O(4):O(4');κ(5)O(1):O(1),O(4):O(4),O(4')-dizinc(II)] dihydrate], {[Zn2(C6H8O4)2(C10H8N2)(H2O)]·2H2O}n, has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction and elemental, IR and thermogravimetric analyses. In the structure, the 2,2-dimethylsuccinate ligands link linear tetranuclear Zn(II) subunits into one-dimensional chains along the c axis. 4,4'-Bipyridine acts as a tethering ligand expanding these one-dimensional chains into a two-dimensional layered structure. Hydrogen-bonding interactions between the water molecules (both coordinated and free) and carboxylate O atoms strengthen the packing of the layers. Furthermore, the luminescence properties of the complex were investigated. The compound exhibits a blue photoluminescence in the solid state at room temperature and may be a good candidate for potential hybrid inorganic-organic photoactive materials.

A theoretical investigation on the neutral Cu(I) phosphorescent complexes with azole-based and phosphine mixed ligand

Science.gov (United States)

Ding, Xiao-Li; Shen, Lu; Zou, Lu-Yi; Ma, Ming-Shuo; Ren, Ai-Min

2018-04-01

A theoretical study on a series of neutral heteroleptic Cu(I) complexes with different azole-pyridine-based N^N ligands has been presented to get insight into the effect of various nitrogen atoms in the azole ring on photophysical properties. The results reveal that the highest occupied molecular orbital (HOMO) levels and the emission wavelengths of these complexes are mainly governed by the nitrogen atom number in azole ring. With the increasing number of nitrogen atom , the electron density distribution of HOMO gradually extend from the N^N ligand to the whole molecule, meanwhile, the improved contribution from Cu(d) orbits in HOMO results in an effective mixing of various charge transfermodes, and hence, the fast radiative decay(kr) and the slow non-radiative decay rate(knr) are achieved. The photoluminescence quantum yield (PLQY) show an apparent dependence on the nitrogen atom number in the five-membered nitrogen heterocycles. However, the increasing number of nitrogen atoms is not necessary for increasing PLQY. The complex 3 with 1,2,4-triazole-pyridine-based N^N ligands is considered to be a potential emitter with high phosphorescence efficiency. Finally, we hope that our investigations will contribute to systematical understanding and guiding for material molecular engineering.

Theoretical study of ionization and one-electron oxidation potentials of N-heterocyclic compounds.

Science.gov (United States)

Sviatenko, Liudmyla K; Gorb, Leonid; Hill, Frances C; Leszczynski, Jerzy

2013-05-15

A number of density functionals was utilized to predict gas-phase adiabatic ionization potentials (IPs) for nitrogen-rich heterocyclic compounds. Various solvation models were applied to the calculation of difference in free energies of solvation of oxidized and reduced forms of heterocyclic compounds in acetonitrile (AN) for correct reproduction of their standard oxidation potentials. We developed generally applicable protocols that could successfully predict the gas-phase adiabatic ionization potentials of nitrogen-rich heterocyclic compounds and their standard oxidation potentials in AN. This approach is supported by a MPW1K/6-31+G(d) level of theory which uses SMD(UA0) approximation for estimation of solvation energy of neutral molecules and PCM(UA0) model for ionized ones. The mean absolute derivation (MAD) and root mean square error (RMSE) of the current theoretical models for IP are equal to 0.22 V and 0.26, respectively, and for oxidation potentials MAD = 0.13 V and RMSE = 0.17. Copyright © 2013 Wiley Periodicals, Inc.

Derisking the Cu-Mediated 18F-Fluorination of Heterocyclic Positron Emission Tomography Radioligands.

Science.gov (United States)

Taylor, Nicholas J; Emer, Enrico; Preshlock, Sean; Schedler, Michael; Tredwell, Matthew; Verhoog, Stefan; Mercier, Joel; Genicot, Christophe; Gouverneur, Véronique

2017-06-21

Molecules labeled with fluorine-18 ( 18 F) are used in positron emission tomography to visualize, characterize and measure biological processes in the body. Despite recent advances in the incorporation of 18 F onto arenes, the development of general and efficient approaches to label radioligands necessary for drug discovery programs remains a significant task. This full account describes a derisking approach toward the radiosynthesis of heterocyclic positron emission tomography (PET) radioligands using the copper-mediated 18 F-fluorination of aryl boron reagents with 18 F-fluoride as a model reaction. This approach is based on a study examining how the presence of heterocycles commonly used in drug development affects the efficiency of 18 F-fluorination for a representative aryl boron reagent, and on the labeling of more than 50 (hetero)aryl boronic esters. This set of data allows for the application of this derisking strategy to the successful radiosynthesis of seven structurally complex pharmaceutically relevant heterocycle-containing molecules.

Alkoxy(alkyl)silylalkyl derivatives of nitrogen-containing heterocycles

International Nuclear Information System (INIS)

Trofimova, Ol'ga M; Voronkov, Mikhail G; Chernov, Nikolai F

1999-01-01

The published data on the synthesis, properties and transformations of alkoxy(alkyl)silylalkyl derivatives of nitrogen-containing heterocycles of the general formula Het(CH 2 ) n SiX 3 are surveyed and systematised. Data on the biological activities and applications of these compounds are presented. The bibliography includes 255 references.

Connecting small ligands to generate large tubular metal-organic architectures

International Nuclear Information System (INIS)

Goforth, Andrea M.; Su, Cheng-Yong; Hipp, Rachael; Macquart, Rene B.; Smith, Mark D.; Loye, Hans-Conrad zur

2005-01-01

The new metal-organic framework materials, ZnF(Am 2 TAZ).solvents and ZnF(TAZ).solvents (Am 2 TAZ=3,5-diamino-1,2,4-triazole, TAZ=1,2,4-triazole), have been synthesized solvothermally and structurally characterized by either Rietveld refinement from powder XRD data or by single crystal X-ray diffraction. The three-dimensional structures of the compounds display open-ended, tubular channels, which are constituted of covalently bonded hexanuclear metallamacrocycles (Zn 6 F 6 (ligand) 6 ). The tubular channels are subsequently covalently joined into a honeycomb-like hexagonal array to generate the three-dimensional porous framework. In the case of ZnF(Am 2 TAZ).solvents, hydrophilic -NH 2 groups point into the channels, effectively reducing their inner diameter relative to ZnF(TAZ).solvents. The present compounds are isostructural to one another and to the previously reported ZnF(AmTAZ).solvents (AmTAZ=3-amino-1,2,4-triazole), illustrative of the fact that the internal size and chemical properties of the framework may be altered by modification of the small, heterocyclic ligand. In addition to demonstrating the ability to modify the basic framework, ZnF(TAZ).solvents and ZnF(Am 2 TAZ).solvents are two of the most thermally stable coordination frameworks known to date. - Graphical abstract: Top view of the open-ended, honeycomb tubular architecture of ZnF(Am 2 TAZ)

Advances in heterocycle synthesis via [3+m]-cycloaddition reactions involving an azaoxyallyl cation as the key intermediate.

Science.gov (United States)

Xuan, Jun; Cao, Xia; Cheng, Xiao

2018-05-17

Heterocyclic compounds are widely found in many natural isolates and medicinally relevant compounds, as well as some fine chemicals. The development of general and efficient methods for the construction of heterocyclic compounds is one of the most important tasks in synthetic organic chemistry. Along these lines, [3+m]-cycloaddition reactions involving in situ generated azaoxyallyl cations as the 3-atom units have emerged as a powerful method for the synthesis of nitrogen-containing heterocycles. In this feature article, we highlight recent advances in this rapidly growing area, mainly focusing on the reaction design as well as the reaction mechanism.

Synthesis and Biological Evaluation of Ru(II) and Pt(II) Complexes Bearing Carboxyl Groups as Potential Anticancer Targeted Drugs.

Science.gov (United States)

Martínez, Ma Ángeles; Carranza, M Pilar; Massaguer, Anna; Santos, Lucia; Organero, Juan A; Aliende, Cristina; de Llorens, Rafael; Ng-Choi, Iteng; Feliu, Lidia; Planas, Marta; Rodríguez, Ana M; Manzano, Blanca R; Espino, Gustavo; Jalón, Félix A

2017-11-20

The synthesis and characterization of Pt(II) (1 and 2) and Ru(II) arene (3 and 4) or polypyridine (5 and 6) complexes is described. With the aim of having a functional group to form bioconjugates, one uncoordinated carboxyl group has been introduced in all complexes. Some of the complexes were selected for their potential in photodynamic therapy (PDT). The molecular structures of complexes 2 and 5, as well as that of the sodium salt of the 4'-(4-carboxyphenyl)-2,2':6',2″-terpyridine ligand (cptpy), were determined by X-ray diffraction. Different techniques were used to evaluate the binding capacity to model DNA molecules, and MTT cytotoxicity assays were performed against four cell lines. Compounds 3, 4, and 5 showed little tendency to bind to DNA and exhibited poor biological activity. Compound 2 behaves as bonded to DNA probably through a covalent interaction, although its cytotoxicity was very low. Compound 1 and possibly 6, both of which contain a cptpy ligand, were able to intercalate with DNA, but toxicity was not observed for 6. However, compound 1 was active in all cell lines tested. Clonogenic assays and apoptosis induction studies were also performed on the PC-3 line for 1. The photodynamic behavior for complexes 1, 5, and 6 indicated that their nuclease activity was enhanced after irradiation at λ = 447 nm. The cell viability was significantly reduced only in the case of 5. The different behavior in the absence or presence of light makes complex 5 a potential prodrug of interest in PDT. Molecular docking studies followed by molecular dynamics simulations for 1 and the counterpart without the carboxyl group confirmed the experimental data that pointed to an intercalation mechanism. The cytotoxicity of 1 and the potential of 5 in PDT make them good candidates for subsequent conjugation, through the carboxyl group, to "selected peptides" which could facilitate the selective vectorization of the complex toward receptors that are overexpressed in

Silver nanoparticles decorated carboxylate functionalized SiO2, New nanocomposites for non-enzymatic detection of glucose and hydrogen peroxide

International Nuclear Information System (INIS)

Ensafi, Ali A.; Zandi-Atashbar, N.; Rezaei, B.; Ghiaci, M.; Taghizadeh, M.

2016-01-01

Highlights: • Silver nanoparticles decorated carboxylates functionalized SiO 2 were prepared. • Ligands are bonding to silica support as SiO 2 –pro–NH 2 and SiO 2 –pro–NH–cyanuric–NH 2 . • These nanomaterials were used as electrochemical sensors for H 2 O 2 and glucose detection. • H 2 O 2 and glucose could be detected as low as 0.094 and 0.33 μmol L −1 , respectively. - Abstract: Here, two different nanocomposites are prepared based on the decoration of silver nanoparticles (AgNPs) on carboxylated SiO 2 . SiO 2 was functionalized with two different carboxylate ligands to stabilize silver nanoparticles on them, using two different organic bondings. Then, AgNPs were decorated successfully on the surface of the functionalized SiO 2 . The functionalized SiO 2 and AgNPs-functionalized SiO 2 were characterized using Fourier transform infrared spectroscopy, elemental analyses, and Transmission electron microscopy (TEM). For further characterization, the generated nanoparticles were employed as modifiers in the preparation of carbon paste electrodes (CPEs). Then, cyclic voltammetry and electrochemical impedance spectroscopy were used to study their electrochemical behavior. The electrochemical data exhibited that the modifications of CPE led to easier electron transfers rather than the bare and unmodified SiO 2 /CPE due to the presence of functionalized SiO 2 in accompany with electrocatalytic effects of the decorated silver nanoparticles. Furthermore, the modified–CPEs were examined as non–enzymatic H 2 O 2 and glucose sensors using electrochemical techniques including cyclic voltammetry and hydrodynamic chronoamperometric. Electrochemical results represented that the modified-CPE is efficient and sensitive for H 2 O 2 and glucose detection as low as 0.094 and 0.33 μmol L −1 , respectively. At last, the practical applications of these sensors were also evaluated by analyzing H 2 O 2 and glucose in the presence of common interfering species

Lactoperoxidase, an Antimicrobial Milk Protein, as a Potential Activator of Carcinogenic Heterocyclic Amines in Breast Cancer.

Science.gov (United States)

Sheikh, Ishfaq Ahmad; Jiffri, Essam Hussain; Kamal, Mohammad Amjad; Ashraf, Ghulam Md; Beg, Mohd Amin

2017-11-01

Lactoperoxidase (LPO) is an antimicrobial protein secreted from mammary, salivary and other mucosal glands. It is an important member of heme peroxidase enzymes and the primary peroxidase enzyme present in breast tissues. In addition to the antimicrobial properties, LPO has been shown to be associated with breast cancer etiology. Heterocyclic amines, an important class of environmental and dietary carcinogens, have been increasingly associated with breast cancer etiology. Heterocyclic amines undergo activation in breast tissue as a result of oxidation by LPO. The current study includes three important heterocyclic amines, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methy-6-phenylimidazo[4,5-b]-pyridine (PhIP), that have carcinogenic activity. The structural binding characterization of IQ, MeIQx and PhIP with LPO was done using in silico approaches. Their binding pattern and interactions with LPO amino acid residues were analyzed. The three compounds bound in the distal heme cavity of LPO without replacing the important water molecule required for oxidation of substrate compounds. PhIP displayed lesser binding affinity for LPO in comparison to IQ and MeIQx. The binding mode of heterocyclic amines in distal heme cavity of LPO resembled to that of substrate binding pattern. The three heterocyclic amines are suggested to act as LPO substrate. The undisturbed water molecule present in distal heme cavity of the LPO is expected to facilitate the oxidation and activation of the three heterocyclic amines. These activated compounds may potentially bind with DNA in breast tissues forming DNA adducts and may subsequently lead to breast cancer initiation. Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

Cyclometalation and coupling of a rigid 4,5-bis(imino)acridanide pincer ligand on yttrium.

Science.gov (United States)

Wong, Edwin W Y; Emslie, David J H

2015-07-07

An extremely rigid NNN-donor proligand, 4,5-bis{(diphenylmethylene)amino}-2,7,9,9-tetramethylacridan, H[AIm2] was prepared in five steps starting from 5-methyl-2-aminobenzoic acid and 4-bromotoluene. Reaction of intensely orange H[AIm2] with LiCH2SiMe3 formed deep blue Li(x)[AIm2]x (x = 2 in the solid state), while reaction with [Y(CH2SiMe3)3(THF)2] (0.5 equiv.) afforded deep blue [Y(AIm2)(AIm)] (1; AIm = an AIm2 ligand cyclometalated at the ortho-position of one of the phenyl rings). Compound 1 slowly isomerizes to form green-brown 2, which contains a single trianionic, hexadentate ligand that features one amine, two imine, and three amido donors. The acridanide backbone and one imine group in each of the original AIm2 ligands is intact, but the two acridanide backbones are now linked by an isoindoline heterocycle. Yttrium in 2 is coordinated to six nitrogen donors and the ortho carbon of an isoindoline phenyl substituent. The intense colours of H[AIm2], Li(x)[AIm2]x and 1 were shown by TD-DFT calculations to arise from charge transfer transitions from the HOMO, which is localized on the acridanide ligand backbone, to the LUMO and LUMO+1, which are localized on the imine substituents. The conversion of 1 to 2 was studied by UV-Visible absorption spectroscopy and is first-order with a half-life of 7.8 hours at room temperature.

Rh(I)-Catalyzed Arylation of Heterocycles via C-H Bond Activation: Expanded Scope Through Mechanistic Insight

Energy Technology Data Exchange (ETDEWEB)

Lewis, Jared; Berman, Ashley; Bergman, Robert; Ellman, Jonathan

2007-07-18

A practical, functional group tolerant method for the Rh-catalyzed direct arylation of a variety of pharmaceutically important azoles with aryl bromides is described. Many of the successful azole and aryl bromide coupling partners are not compatible with methods for the direct arylation of heterocycles using Pd(0) or Cu(I) catalysts. The readily prepared, low molecular weight ligand, Z-1-tert-butyl-2,3,6,7-tetrahydrophosphepine, which coordinates to Rh in a bidentate P-olefin fashion to provide a highly active yet thermally stable arylation catalyst, is essential to the success of this method. By using the tetrafluoroborate salt of the corresponding phosphonium, the reactions can be assembled outside of a glove box without purification of reagents or solvent. The reactions are also conducted in THF or dioxane, which greatly simplifies product isolation relative to most other methods for direct arylation of azoles employing high-boiling amide solvents. The reactions are performed with heating in a microwave reactor to obtain excellent product yields in two hours.

Mn(III-Initiated Facile Oxygenation of Heterocyclic 1,3-Dicarbonyl Compounds

Directory of Open Access Journals (Sweden)

Md. Aminul Haque

2011-11-01

Full Text Available The Mn(III-initiated aerobic oxidation of heterocyclic 1,3-dicarbonyl compounds, such as 4-alkyl-1,2-diphenylpyrazolidine-3,5-diones, 1,3-dialkylpyrrolidine-2,4-diones, 3-alkyl-1,5-dimethylbarbituric acids, and 3-butyl-4-hydroxy-2-quinolinone gave excellent to good yields of the corresponding hydroperoxides, which were gradually degraded by exposure to the metal initiator after the reaction to afford the corresponding alcohols. The synthesis of 30 heterocyclic 1,3-dicarbonyl compounds, the corresponding hydroperoxides and the 10 alcohols, their characterization, and the limitations of the procedure are described. In addition, the mechanism of the hydroperoxidation and the redox decomposition of the hydroperoxides are discussed.

Nitrogen-rich heterocycles as reactivity retardants in shocked insensitive explosives.

Science.gov (United States)

Manaa, M Riad; Reed, Evan J; Fried, Laurence E; Goldman, Nir

2009-04-22

We report the first quantum-based multiscale simulations to study the reactivity of shocked perfect crystals of the insensitive energetic material triaminotrinitrobenzene (TATB). Tracking chemical transformations of TATB experiencing overdriven shock speeds of 9 km/s for up to 0.43 ns and 10 km/s for up to 0.2 ns reveal high concentrations of nitrogen-rich heterocyclic clusters. Further reactivity of TATB toward the final decomposition products of fluid N(2) and solid carbon is inhibited due to the formation of these heterocycles. Our results thus suggest a new mechanism for carbon-rich explosive materials that precedes the slow diffusion-limited process of forming the bulk solid from carbon clusters and provide fundamental insight at the atomistic level into the long reaction zone of shocked TATB.

Tris(1,10-phenanthroline-κ2N,N′zinc(II chloride 2-phenyl-4-selenazole-5-carboxylate decahydrate

Directory of Open Access Journals (Sweden)

Jin-Bei Shen

2011-02-01

Full Text Available The asymmetric unit of the title salt, [Zn(C12H8N23](C10H6NO2SeCl·10H2O, contains a [Zn(phen3]2+ cation (phen is 1,10-phenanthroline, uncoordinated chloride and 2-phenyl-4-selenazole-5-carboxylate anions and ten uncoordinated water molecules. The central ZnII ion is six-coordinated by six N atoms from three phen ligands in a distorted octahedral geometry. An extensive O—H...O, O—H...N and O—H...Cl hydrogen-bonding network stabilizes the crystal structure.

Enantioselective construction of quaternary N-heterocycles by palladium-catalysed decarboxylative allylic alkylation of lactams

KAUST Repository

Behenna, Douglas C.

2011-12-18

The enantioselective synthesis of nitrogen-containing heterocycles (N-heterocycles) represents a substantial chemical research effort and resonates across numerous disciplines, including the total synthesis of natural products and medicinal chemistry. In this Article, we describe the highly enantioselective palladium-catalysed decarboxylative allylic alkylation of readily available lactams to form 3,3-disubstituted pyrrolidinones, piperidinones, caprolactams and structurally related lactams. Given the prevalence of quaternary N-heterocycles in biologically active alkaloids and pharmaceutical agents, we envisage that our method will provide a synthetic entry into the de novo asymmetric synthesis of such structures. As an entry for these investigations we demonstrate how the described catalysis affords enantiopure quaternary lactams that intercept synthetic intermediates previously used in the synthesis of the Aspidosperma alkaloids quebrachamine and rhazinilam, but that were previously only available by chiral auxiliary approaches or as racemic mixtures. © 2012 Macmillan Publishers Limited. All rights reserved.

Greener Alternatives to Expedient Synthesis of Heterocycles and Nanomaterial

Science.gov (United States)

A brief account of reactions involving microwave (MW) exposure of neat reactants or catalyzed by mineral support surfaces, such as alumina, silica, clay, or their ‘doped’ versions, for the rapid one-pot assembly of heterocyclic compounds [1] from in situ generated reactive interm...

Preparation, characterization and biological evaluation of fac(M(CO)3)+ labeled amino carboxy ligands

International Nuclear Information System (INIS)

Baishya, Rinku; Halder, K.K.; Debnath, M.C.

2010-01-01

Full text: The objective of this study is to radiolabel various amino carboxy based chelating ligands with fac(M(CO) 3 )+ core, their physicochemical and biological characterization so that they can be used as bifunctional chelators and could be incorporated into biomolecules. Introduction: Amino acids as a class attract considerable physiological interest because of their participation in many vital processes associated with the living system. Some amino acids express in some particular organ like glutamic acid acts as excitatory neurotransmitter in mammalian brain. Histidine, methionine, tryptophan express in the tumor cell. Amino acids also play an important role for development of a new series of chelate complexes of 99m Tc that can direct the biodistribution of the radiotracer for purposes in diagnostic nuclear medicine. Various 99m Tc-amino acid chelates based on (Tc(V)O) 3 + core were reported from this laboratory some of which exhibited high renal specificity in animals. The structural requirements favouring this biological behaviour could be the oxotechnetium glycine sequence (TcO-NH-CH 2 -COOH) resembling the -CO-glycine sequence of hippurate. In recent years with the development of organometallic chemistry of technetium and rhenium for biological application intensive efforts have been executed on designing of the bifunctional chelator for effective coordination to (M(CO) 3 )+ core. The suitability and stability of the metal carbonyl core has given rise to a new platform for the preparation of the metal complexes of biologically active peptide in macroscopic quantity using the solid phase synthetic approach. Materials and Methods: We chelated different amino carboxy based ligands with ( 99m Tc(CO) 3 )+ and (Re(CO) 3 )+ core. The choice of amino acid was made by taking representative members from various groupings such as mono amino mono carboxylate, mono amino poly carboxylate, poly amino mono carboxylate and sulfur containing amino carboxylates. The

Mercury coordination polymers with flexible ethane-1,2-diyl-bis-(pyridyl-3-carboxylate): Synthesis, structures, thermal and luminescent properties

Energy Technology Data Exchange (ETDEWEB)

Vallejos, Javier [Departamento de Química, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta (Chile); Brito, Iván, E-mail: ivanbritob@yahoo.com [Departamento de Quimica, Universidad de Antofagasta, Av. Angamos 601, Antofagasta (Chile); Cárdenas, Alejandro [Departamento de Física, Universidad de Antofagasta, Av. Angamos 601, Antofagasta (Chile); Llanos, Jaime [Departamento de Química, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta (Chile); Bolte, Michael [Institut für Anorganische Chemie der Goethe—Universität Frankfurt, Max-von-Laue-Strasse 7, D-60438 Frankfurt am Main (Germany); López-Rodríguez, Matías [Instituto de Bio-Orgánica “Antonio González”, Universidad de La Laguna, Astrofísico Francisco Sánchez N° 2, La Laguna, Tenerife (Spain)

2015-03-15

The reaction of the flexible ligand, ethane-1,2-diyl-bis-(pyridyl-3-carboxylate), (L) with HgI{sub 2} and HgBr{sub 2} salts under the same experimental conditions leads to the formation of two coordination polymers with different motifs: ([Hg(L)(Br{sub 2})]){sub n}(1) and ([Hg(L)(I{sub 2})]){sub n}(2). In both compounds, the ligand, (L) acts in a μ2-N:N′-bidentate fashion to link HgBr{sub 2} and HgI{sub 2} units to form a linear and helical chain motif, along [1 0 0] for (1) and [0 0 1] for (2). The ethylene moiety of (L) has gauche and trans conformation in compounds (1) and (2), respectively. The flexible conformation of L produces differences in the optical and crystal properties of the two compounds. - Graphical abstract: This work demonstrates how the HgX{sub 2} units are coordinates by bi-dentate ligand forming polymeric coordination complexes by self-assembly of both chemical units.- Highlights: • News 1-D d{sup 10} transition metal coordination polymers. • The photoluminescent properties have been measured. • The thermal properties have been measured.

Synthesis, structure and photoluminescence of novel lanthanide (Tb(III), Gd(III)) complexes with 6-diphenylamine carbonyl 2-pyridine carboxylate

International Nuclear Information System (INIS)

An Baoli; Gong Menglian; Cheah, Kok-Wai; Wong, Wai-Kwok; Zhang Jiming

2004-01-01

A novel organic ligand, 6-diphenylamine carbonyl 2-pyridine carboxylic acid (HDPAP), and the corresponding lanthanide complexes, tris(6-diphenylamine carbonyl 2-pyridine carboxylato) terbium(III) (Tb-DPAP) and tris(6-diphenylamine carbonyl 2-pyridine carboxylato) gadolinium(III) (Gd-DPAP) have been designed and synthesized. The crystal structure and photoluminescence of Tb-DPAP and Gd-DPAP have been studied. The results showed that the lanthanide complexes have electroneutral structures, and the solid terbium complex emits characteristic green fluorescence of Tb(III) ions at room temperature while the gadolinium complex emits the DPAP ligand phosphorescence. The lowest triplet level of DPAP ligand was calculated from the phosphorescence spectrum of Gd-DPAP in N,N-dimethyl formamide (DMF) dilute solution determined at 77 K, and the energy transfer mechanisms in the lanthanide complexes were discussed. The lifetimes of the 5 D 4 levels of Tb 3+ ions in the terbium complex were examined using time-resolved spectroscopy, and the values are 0.0153±0.0001 ms for solid Tb(DPAP) 3 ·11.5H 2 O and 0.074±0.007 ms for 2.5x10 -5 mol/l Tb-DPAP ethanol solution

Preparation of highly-oxidized starch using hydrogen peroxide and its application as a novel ligand for zirconium tanning of leather.

Science.gov (United States)

Yu, Yue; Wang, Ya-Nan; Ding, Wei; Zhou, Jianfei; Shi, Bi

2017-10-15

A series of highly-oxidized starch (HOS) were prepared using H 2 O 2 and a copper-iron catalyst as a desired ligand for zirconium tanning of leather. The effects of catalyst and H 2 O 2 dosages, and reaction temperature on the oxidation degree (OD, represented as the amount of carbonyl and carboxyl groups derived) of starch were investigated. The OD reached 76.2% when oxidation was conducted using 60% H 2 O 2 and 0.015% catalyst at 98°C for 2h. 13 C NMR and FT-IR illustrated carbonyl and carboxyl groups were formed in HOS after oxidation. GPC and laser particle size analyses indicated the decrease of HOS molecular size with increasing H 2 O 2 dosage and OD. HOS with moderate OD and molecular weight was able to coordinate with zirconium and remarkably improve tanning process. Leather tanned by Zr complexes using HOS-60 (60% H 2 O 2 , Mn 3516g/mol) as ligand presented considerably better physical and organoleptic properties than those of traditional Zr-tanned leather. Copyright © 2017 Elsevier Ltd. All rights reserved.

Selective Access to Heterocyclic Sulfonamides and Sulfonyl Fluorides via a Parallel Medicinal Chemistry Enabled Method.

Science.gov (United States)

Tucker, Joseph W; Chenard, Lois; Young, Joseph M

2015-11-09

A sulfur-functionalized aminoacrolein derivative is used for the efficient and selective synthesis of heterocyclic sulfonyl chlorides, sulfonyl fluorides, and sulfonamides. The development of a 3-step parallel medicinal chemistry (PMC) protocol for the synthesis of pyrazole-4-sulfonamides effectively demonstrates the utility of this reagent. This reactivity was expanded to provide rapid access to other heterocyclic sulfonyl fluorides, including pyrimidines and pyridines, whose corresponding sulfonyl chlorides lack suitable chemical stability.

Pyrolysis of high-ash sewage sludge in a circulating fluidized bed reactor for production of liquids rich in heterocyclic nitrogenated compounds.

Science.gov (United States)

Zuo, Wu; Jin, Baosheng; Huang, Yaji; Sun, Yu; Li, Rui; Jia, Jiqiang

2013-01-01

A circulating fluidized bed reactor was used for pyrolyzing sewage sludge with a high ash content to produce liquids rich in heterocyclic nitrogenated compounds. GC/MS and FTIR analyses showed that heterocyclic nitrogenated compounds and hydrocarbons made up 38.5-61.21% and 2.24-17.48% of the pyrolysis liquids, respectively. A fluidized gas velocity of 1.13 m/s, a sludge feed rate of 10.78 kg/h and a particle size of 1-2mm promoted heterocyclic nitrogenated compound production. Utilizing heterocyclic nitrogenated compounds as chemical feedstock could be a way for offsetting the cost of sewage sludge treatment. Copyright © 2012 Elsevier Ltd. All rights reserved.

Rhodium-catalyzed regioselective olefination directed by a carboxylic group.

Science.gov (United States)

Mochida, Satoshi; Hirano, Koji; Satoh, Tetsuya; Miura, Masahiro

2011-05-06

The ortho-olefination of benzoic acids can be achieved effectively through rhodium-catalyzed oxidative coupling with alkenes. The carboxylic group is readily removable to allow ortho-olefination/decarboxylation in one pot. α,β-Unsaturated carboxylic acids such as methacrylic acid also undergo the olefination at the β-position. Under the rhodium catalysis, the cine-olefination of heteroarene carboxylic acids such as thiophene-2-carboxylic acid proceeds smoothly accompanied by decarboxylation to selectively produce the corresponding vinylheteroarene derivatives. © 2011 American Chemical Society

New synthesis of photocurable silanes and polysiloxanes bearing heterocyclic or olefinic functions

International Nuclear Information System (INIS)

Youssef, B.; Lecamp, L.; Garin, S.; Bunel, C.

1999-01-01

In this work, we described the synthesis of silanes and polysiloxanes bearing cationic photopolymerizable groups. Two new methods were used. The first one is the reaction between 3-mercapto-propyl-1-triethoxysilane (1) and chloromethylated olefins by a phase transfer catalysis. The second one is the radical addition of (1) or poly(dimethylsiloxane-co-methylmercaptopropylsiloxane) (9) to allyl or vinyl substituted heterocyclic monomers. These methods led to the expected adducts with an excellent yield. The polysiloxanes bearing heterocyclic functional groups linked through thioether bonds were photocurable by cationic route. Under UV light intensity of 17.5 mW/cm 2 , these polymers harden after 15 or 20 s

Structure of radicals produced by γ radiolysis. Part 4. Adamantane matrices doped with various 5-membered heterocyclic molecules

International Nuclear Information System (INIS)

Winters, D.L.; Ling, A.C.

1976-01-01

The effects of γ-radiolysis at room temperature on adamantane and adamantane-d 16 matrices doped with 5-membered heterocyclic molecules has been examined by X-band electron spin resonance (esr) spectrometry. Radical structures formed from heterocyclic solute molecules are discussed and tentative assignments made. Discussion of possible radical structures derived from selected heterocyclic compounds is included, but unambiguous assignmens of structure cannot be made for these compounds from the esr data obtained. It was noted that perdeuterated adamantane matrices provided superior resolution for esr spectra derived from radicals with a delocalized spin center such as allyl or allenyl species. (author)

Formation and ecotoxicity of N-heterocyclic compounds on ammoxidation of mono- and polysaccharides.

Science.gov (United States)

Klinger, Karl Michael; Liebner, Falk; Fritz, Ines; Potthast, Antje; Rosenau, Thomas

2013-09-25

Ammoxidation of technical lignins under mild conditions is a suitable approach to artificial humic substances. However, carbohydrates as common minor constituents of technical lignins have been demonstrated to be a potential source of N-heterocyclic ecotoxic compounds. Ethyl acetate extracts of ammoxidation mixtures of the monosaccharides glucose and xylose exhibited considerable growth inhibiting activity in the OECD 201 test, with 4-methyl-1H-imidazole, 4-(hydroxymethyl)-1H-imidazole, and 3-hydroxypyridine being the most active compounds. The amount of N-heterocyclic compounds formed at moderate ammoxidation conditions (70 °C, 0.2 MPa O2, 3 h) was significantly lower for the polysaccharides cellulose and xylan (16-30 μg/g of educt) compared to glucose (15.4 mg). Ammoxidation at higher temperature is not recommendable for carbohydrate-rich materials as much higher amounts of N-heterocyclic compounds were formed from both monosaccharides (100 °C: 122.4-160.5 mg/g of educt) and polysaccharides (140 °C: 5.52-16.03 mg/g of educt).

Effects of nitro-heterocyclic derivatives against Leishmania (Leishmania) infantum promastigotes and intracellular amastigotes.

Science.gov (United States)

Petri e Silva, Simone Carolina Soares; Palace-Berl, Fanny; Tavares, Leoberto Costa; Soares, Sandra Regina Castro; Lindoso, José Angelo Lauletta

2016-04-01

Leishmaniasis is an overlooked tropical disease affecting approximately 1 million people in several countries. Clinical manifestation depends on the interaction between Leishmania and the host's immune response. Currently available treatment options for leishmaniasis are limited and induce severe side effects. In this research, we tested nitro-heterocyclic compounds (BSF series) as a new alternative against Leishmania. Its activity was measured in Leishmania (Leishmania) infantum promastigotes and intracellular amastigotes using MTT colorimetric assay. Additionally, we assessed the phosphatidylserine exposure by promastigotes, measured by flow cytometry, as well as nitric oxide production, measured by Griess' method. The nitro-heterocyclic compounds (BSF series) showed activity against L. (L.) infantum promastigotes, inducting the phosphatidylserine exposition by promastigotes, decreasing intracellular amastigotes and increasing oxide nitric production. The selectivity index was more prominent to Leishmania than to macrophages. Compared to amphotericin b, our compounds presented higher IC50, however the selectivity index was more specific to parasite than to amphotericin b. In conclusion, these nitro-heterocyclic compounds showed to be promising as an anti-Leishmania drug, in in vitro studies. Copyright © 2016 Elsevier Inc. All rights reserved.

Enantioselective [3+3] atroposelective annulation catalyzed by N-heterocyclic carbenes

KAUST Repository

Zhao, Changgui; Guo, Donghui; Munkerup, Kristin; Huang, Kuo-Wei; Li, Fangyi; Wang, Jian

2018-01-01

on the transition-metal-catalyzed transformations. Here, we report the enantioselective NHC-catalyzed (NHC: N-heterocyclic carbenes) atroposelective annulation of cyclic 1,3-diones with ynals. In the presence of NHC precatalyst, base, Lewis acid and oxidant, a

Synthesis of heterocycles via transition-metal-catalyzed hydroarylation of alkynes.

Science.gov (United States)

Yamamoto, Yoshihiko

2014-03-07

Transition-metal (TM)-catalyzed hydroarylation reactions of alkynes have received much attention, because they enable the net insertion of alkyne C-C triple bonds into C-H bonds of aromatic precursors, resulting in regio- and stereo-selective formation of synthetically useful arylalkenes. Taking advantage of this feature, TM-catalyzed alkyne hydroarylations have been successfully used for the synthesis of heterocycles. TM-catalyzed alkyne hydroarylations can be classified into three major categories depending on the type of reaction and precursors involved: (1) palladium-catalyzed reductive Heck reactions of alkynes with aryl halides, (2) TM-catalyzed conjugate arylation reactions of activated alkynes with arylboronic acids, and (3) TM-catalyzed aromatic C-H alkenylations with alkynes. This review surveys heterocycle synthesis via TM-catalyzed hydroarylation of alkynes according to the above classification, with an emphasis on the scope and limitations, as well as the underlying mechanisms.

A relativistic density functional study of uranyl hydrolysis and complexation by carboxylic acids in aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Ray, Rupashree Shyama

2009-02-10

In this work, the complexation of uranium in its most stable oxidation state VI in aqueous solution was studied computationally, within the framework of density functional (DF) theory. The thesis is divided into the following parts: Chapter 2 briefly summarizes the relevant general aspects of actinide chemistry and then focuses on actinide environmental chemistry. Experimental results on hydrolysis, actinide complexation by carboxylic acids, and humic substances are presented to establish a background for the subsequent discussion. Chapter 3 describes the computational method used in this work and the relevant features of the parallel quantum chemistry code PARAGAUSS employed. First, the most relevant basics of the applied density functional approach are presented focusing on relativistic effects. Then, the treatment of solvent effects, essential for an adequate modeling of actinide species in aqueous solution, will be introduced. At the end of this chapter, computational parameters and procedures will be summarized. Chapter 4 presents the computational results including a comparison to available experimental data. In the beginning, the mononuclear hydrolysis product of UO{sub 2}{sup 2+}, [UO{sub 2}OH]{sup +}, will be discussed. The second part deals with actinide complexation by carboxylate ligands. First of all the coordination number for uranylacetate will be discussed with respect to implications for the complexation of actinides by humic substances followed by the uranyl complexation of aromatic carboxylic acids in comparison to earlier results for aliphatic ones. In the end, the ternary uranyl-hydroxo-acetate are discussed, as models of uranyl humate complexation at ambient condition.

Recovery and esterification of aqueous carboxylates by using CO

NARCIS (Netherlands)

Cabrera-Rodríguez, Carlos I.; Paltrinieri, Laura; Smet, De Louis C.P.M.; Wielen, Van Der Luuk A.M.; Straathof, Adrie J.J.

2017-01-01

The recovery of carboxylic acids from fermentation broth is one of the main bottlenecks for the industrial production of bio-based esters. This paper proposes an alternative for the recovery of carboxylates produced by fermentations at pH values above the pKa of the carboxylic acid. In this

5D-QSAR for spirocyclic sigma1 receptor ligands by Quasar receptor surface modeling.

Science.gov (United States)

Oberdorf, Christoph; Schmidt, Thomas J; Wünsch, Bernhard

2010-07-01

Based on a contiguous and structurally as well as biologically diverse set of 87 sigma(1) ligands, a 5D-QSAR study was conducted in which a quasi-atomistic receptor surface modeling approach (program package Quasar) was applied. The superposition of the ligands was performed with the tool Pharmacophore Elucidation (MOE-package), which takes all conformations of the ligands into account. This procedure led to four pharmacophoric structural elements with aromatic, hydrophobic, cationic and H-bond acceptor properties. Using the aligned structures a 3D-model of the ligand binding site of the sigma(1) receptor was obtained, whose general features are in good agreement with previous assumptions on the receptor structure, but revealed some novel insights since it represents the receptor surface in more detail. Thus, e.g., our model indicates the presence of an H-bond acceptor moiety in the binding site as counterpart to the ligands' cationic ammonium center, rather than a negatively charged carboxylate group. The presented QSAR model is statistically valid and represents the biological data of all tested compounds, including a test set of 21 ligands not used in the modeling process, with very good to excellent accuracy [q(2) (training set, n=66; leave 1/3 out) = 0.84, p(2) (test set, n=21)=0.64]. Moreover, the binding affinities of 13 further spirocyclic sigma(1) ligands were predicted with reasonable accuracy (mean deviation in pK(i) approximately 0.8). Thus, in addition to novel insights into the requirements for binding of spirocyclic piperidines to the sigma(1) receptor, the presented model can be used successfully in the rational design of new sigma(1) ligands. Copyright (c) 2010 Elsevier Masson SAS. All rights reserved.

Bent Shaped 1,3,4-Oxadiazole/Thiadiazole heterocyclic rings ...

Indian Academy of Sciences (India)

Two series of bent shaped 1,3,4-oxadiazole/thiadiazole heterocyclic ring containing liquid crystalline (LC) compounds were synthesized and characterized by FT-IR, 1H, 13C-NMR and ESI-Mass spectro-scopic techniques. Liquid crystal properties were investigated by polarized optical microscopy and differential scanning ...

Synthesis, characterization and applications of some novel mordent and heterocyclic disperse dyes on polyester and wool fibers

Directory of Open Access Journals (Sweden)

Hitendra Mangubhai Patel

2012-10-01

Full Text Available The novel mordent and disperse heterocyclic dyes were prepared by coupling of various diazo solution of aromatic amines with 1-[(2-butyl-2,3-dihydrobenzofuran-3-yl]-1-(4-hydroxyphenylmethanone. The resultant mordent and disperse heterocyclic dyes were characterized by elemental analyses, IR and 1H-NMR and 13C-NMR spectral studies. The UV-visible spectral data have also been discussed in terms of structural property relationship. The dyeing assessment of all the mordent and disperse heterocyclic dyes was evaluated on wool and polyester textile fibers. The results of antibacterial studies of chrome pretreated fabrics revealed that the toxicity of mordented dyes against Escherichia coli, Staphylococcus aureus, Salmonella typhi, Bacillus subtilis bacteria was fairly good.

New trends and applications in carboxylation for isotope chemistry.

Science.gov (United States)

Bragg, Ryan A; Sardana, Malvika; Artelsmair, Markus; Elmore, Charles S

2018-05-08

Carboxylations are an important method for the incorporation of isotopically labeled 14 CO 2 into molecules. This manuscript will review labeled carboxylations since 2010 and will present a perspective on the potential of recent unlabeled methodology for labeled carboxylations. The perspective portion of the manuscript is broken into 3 major sections based on product type, arylcarboxylic acids, benzylcarboxylic acids, and alkyl carboxylic acids, and each of those sections is further subdivided by substrate. © 2018 AstraZeneca. Journal of Labelled Compounds and Radiopharmaceuticals Published by John Wiley & Sons, Ltd.

Carboxyl-terminated butadiene-acrylonitrile-toughened epoxy/carboxyl-modified carbon nanotube nanocomposites: Thermal and mechanical properties

Directory of Open Access Journals (Sweden)

H. F. Xie

2012-09-01

Full Text Available Carboxyl-modified multi-walled carbon nanotubes (MWCNT–COOHs as nanofillers were incorporated into diglycidyl ether of bisphenol A (DGEBA toughened with carboxyl-terminated butadiene-acrylonitrile (CTBN. The carboxyl functional carbon nanotubes were characterized by Fourier-transform infrared spectroscopy and thermogravimetric analysis. Furthermore, cure kinetics, glass transition temperature (Tg, mechanical properties, thermal stability and morphology of DGEBA/CTBN/MWCNT–COOHs nanocomposites were investigated by differential scanning calorimetry (DSC, dynamic mechanical analysis (DMA, universal test machine, thermogravimetric analysis and scanning electron microscopy (SEM. DSC kinetic studies showed that the addition of MWCNT–COOHs accelerated the curing reaction of the rubber-toughened epoxy resin. DMA results revealed that Tg of rubber-toughened epoxy nanocomposites lowered with MWCNT–COOH contents. The tensile strength, elongation at break, flexural strength and flexural modulus of DGEBA/CTBN/MWCNT-COOHs nanocomposites were increased at lower MWCNT-COOH concentration. A homogenous dispersion of nanocomposites at lower MWCNT–COOH concentration was observed by SEM.

Greener and Expeditious Synthesis of Bioactive Heterocycles using Microwave Irradiation

Science.gov (United States)

The utilization of green chemistry techniques is dramatically reducing chemical waste and reaction times as has recently been proven in several organic syntheses and chemical transformations. To illustrate these advantages in the synthesis of bio-active heterocycles, we have stud...

Theoretical NMR spectroscopy of N-heterocyclic carbenes and their metal complexes

KAUST Repository

Falivene, Laura; Cavallo, Luigi

2016-01-01

Recent theoretical analysis of the NMR properties of free N-heterocyclic carbenes (NHC) and Metal-NHC complexes has complemented experiments, allowing the establishment of structure/property relationships and the rationalization of otherwise

Impact of environmental exposures on the mutagenicity/carcinogenicity of heterocyclic amines

Energy Technology Data Exchange (ETDEWEB)

Felton, James S; Knize, Mark G; Bennett, L Michelle; Malfatti, Michael A; Colvin, Michael E; Kulp, Kristen S

2004-05-20

Carcinogenic heterocyclic amines are produced from overcooked foods and are highly mutagenic in most short-term test systems. One of the most abundant of these amines, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), induces breast, colon and prostate tumors in rats. Human dietary epidemiology studies suggest a strong correlation between either meat consumption or well-done muscle meat consumption and cancers of the colon, breast, stomach, lung and esophagus. For over 20 years our laboratory has helped define the human exposure to these dietary carcinogens. In this report we describe how various environmental exposures may modulate the risk from exposure to heterocyclic amines, especially PhIP. To assess the impact of foods on PhIP metabolism in humans, we developed an LC/MS/MS method to analyze the four major PhIP urinary metabolites following the consumption of a single portion of grilled chicken. Adding broccoli to the volunteers' diet altered the kinetics of PhIP metabolism. At the cellular level we have found that PhIP itself stimulates a significant estrogenic response in MCF-7 cells, but even more interestingly, co-incubation of the cells with herbal teas appear to enhance the response. Numerous environmental chemicals found in food or the atmosphere can impact the exposure, metabolism, and cell proliferation response of heterocyclic amines.

Impact of environmental exposures on the mutagenicity/carcinogenicity of heterocyclic amines

International Nuclear Information System (INIS)

Felton, James S.; Knize, Mark G.; Bennett, L. Michelle; Malfatti, Michael A.; Colvin, Michael E.; Kulp, Kristen S.

2004-01-01

Carcinogenic heterocyclic amines are produced from overcooked foods and are highly mutagenic in most short-term test systems. One of the most abundant of these amines, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), induces breast, colon and prostate tumors in rats. Human dietary epidemiology studies suggest a strong correlation between either meat consumption or well-done muscle meat consumption and cancers of the colon, breast, stomach, lung and esophagus. For over 20 years our laboratory has helped define the human exposure to these dietary carcinogens. In this report we describe how various environmental exposures may modulate the risk from exposure to heterocyclic amines, especially PhIP. To assess the impact of foods on PhIP metabolism in humans, we developed an LC/MS/MS method to analyze the four major PhIP urinary metabolites following the consumption of a single portion of grilled chicken. Adding broccoli to the volunteers' diet altered the kinetics of PhIP metabolism. At the cellular level we have found that PhIP itself stimulates a significant estrogenic response in MCF-7 cells, but even more interestingly, co-incubation of the cells with herbal teas appear to enhance the response. Numerous environmental chemicals found in food or the atmosphere can impact the exposure, metabolism, and cell proliferation response of heterocyclic amines

Remote control of SMM behaviour via DTE ligands.

Science.gov (United States)

Cosquer, Goulven; Breedlove, Brian K; Yamashita, Masahiro

2015-02-21

Chemists and physicists are continuously working to understand the mechanisms controlling molecular magnetism, especially single-molecule magnetism, to improve the magnetic properties, such as the blocking temperature. With the current research focused on preparing molecular devices, methods to control the components of the devices are necessary. Extensive research has shown that stimuli, such as light, electric current, etc., can be used to change the properties of the molecules making up the devices. Bis(carboxylato)dithienylethene (DTE) derivatives can be photo-isomerized between open and closed forms, i.e., unconjugated and π-conjugated forms, and because of the carboxylate groups, it can be used to link 3d and/or 4f metal ions. Herein the use of DTE ligands to remotely control the magnetic properties of single-molecule magnets is discussed.

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

Directory of Open Access Journals (Sweden)

Nikzad Nikbin

2011-04-01

Full Text Available This review presents a comprehensive overview on selected synthetic routes towards commercial drug compounds as published in both journal and patent literature. Owing to the vast number of potential structures, we have concentrated only on those drugs containing five-membered heterocycles and focused principally on the assembly of the heterocyclic core. In order to target the most representative chemical entities the examples discussed have been selected from the top 200 best selling drugs of recent years.

Theoretical description of metal-ligand bonding within f-element complexes: A successful and necessary interplay between theory and experiment

International Nuclear Information System (INIS)

Maldivi, P.; Petit, L.; Vetere, V.; Petit, L.; Adamo, C.

2007-01-01

The quantum chemical study presented here shows various aspects of the bonding of lanthanide (La 3+ , Gd 3+ ) and actinide (U 3+ , Am 3+ , Cm 3+ ) ions with N-heterocyclic ligands (poly-azines, BTP: bis(1,2,4-triazinyl)-2,6-pyridine). Several families of complexes, differing by their coordination sphere, have been examined. Clearly, the lanthanide complexes always show a purely ionic bonding. The behaviour of U(III) is also well defined with a more or less strong back bonding interaction whatever the complex is. In contrast, the heavy actinides (Am 3+ and Cm 3+ ) are changeable, with a weak covalent character, going from donation to back donation, depending on the coordination sphere of the complex. (authors)

Role of certain plant natural products or gamma radiation in the control of mutagenic activity of some heterocyclic amines

International Nuclear Information System (INIS)

Abu Ghadeer, A.R.M.; El-Sedeek, A.B.A.; Salem, A.M.; Abu Zaid, M.M.

1999-01-01

The present study was designed to use ames test to evaluate the antimutagenic effect of some natural products on the lever microsomes extracted from rats and incubated with some chemical mutagens (heterocyclic compounds). Male swiss albino rats (120-140 g) were used as the source of liver microsomes. Three natural products (Nigella extract, garlic powder and sesame oil) were used to evaluate their antimutagenic activities on six heterocyclic amines. All the tested natural products exhibited their antimutagenic activities when added to the investigated heterocyclic compounds and the most effective product was nigella sativa. another group of rats was exposed to gamma-radiation (6.5 Gy) for testing the validity of ames test in quantitating mutagenicity using liver microsomes of irradiated rats. Liver microsomes from irradiated rats showed to lose ability for metabolic activation needed for heterocyclic amines to exert their mutagenic effect on salmonella typhimurium

Synthesis and decomposition of a novel carboxylate precursor to indium oxide

Science.gov (United States)

Hepp, Aloysius F.; Andras, Maria T.; Duraj, Stan A.; Clark, Eric B.; Hehemann, David G.; Scheiman, Daniel A.; Fanwick, Phillip E.

1994-01-01

Reaction of metallic indium with benzoyl peroxide in 4-1 methylpyridine (4-Mepy) at 25 C produces an eight-coordinate mononuclear indium(III) benzoate, In(eta(sup 2)-O2CC6H5)3(4-Mepy)2 4H2O (I), in yields of up to 60 percent. The indium(III) benzoate was fully characterized by elemental analysis, spectroscopy, and X-ray crystallography; (I) exists in the crystalline state as discrete eight-coordinate molecules; the coordination sphere around the central indium atom is best described as pseudo-square pyramidal. Thermogravimetric analysis of (I) and X-ray diffraction powder studies on the resulting pyrolysate demonstrate that this new benzoate is an inorganic precursor to indium oxide. Decomposition of (I) occurs first by loss of 4-methylpyridine ligands (100 deg-200 deg C), then loss of benzoates with formation of In2O3 at 450 C. We discuss both use of carboxylates as precursors and our approach to their preparation.

Genetically modified CHO cells for studying the genotoxicity of heterocyclic amines from cooked foods

International Nuclear Information System (INIS)

Thompson, L.H.; Wu, R.W.; Felton, J.S.

1995-07-01

We have developed metabolically competent CHO cells to evaluate the genotoxicity associated with heterocyclic amines, such as those that are present in cooked foods. Into repair-deficient UV5 cells we introduced cDNAs for expressing cytochrome P450IA2 and acetyltransferases. We then genetically reverted these transformed lines to obtain matched metabolically competent repair-deficient/proficient lines. For a high mutagenic response, we find a requirement for acetyltransferase with IQ but not with PhIP. This system allows for both quantifying mutagenesis and analyzing the mutational spectra produced by heterocyclic amines

A comprehensive evaluation of the toxicology of cigarette ingredients: heterocyclic nitrogen compounds.

Science.gov (United States)

Coggins, Christopher R E; Merski, Jerome A; Oldham, Michael J

2011-06-01

Three heterocyclic nitrogen compounds, 2,3-diethylpyrazine (DEP), 2,3,5,6-tetramethylpyrazine (TMP), and 2-acetyl pyridine (AP), are naturally present in tobacco and are also added to tobacco as flavor ingredients. A battery of tests was used to compare the toxicity of mainstream smoke from experimental cigarettes containing the three heterocyclic nitrogen compounds added individually at three different levels. The lowest target inclusion level of the ingredient was 10 ppm, and the highest was 10,000 ppm. Smoke from experimental and control cigarettes was evaluated in analytical smoke chemistry, in vitro cytotoxicity, and mutagenicity assays. The cigarettes with added DEP produced some minor (approximately 10%) changes in smoke chemistry when compared with the cigarettes containing no DEP. Smoke chemistry was effectively unchanged by the addition of either AP or TMP. Cytotoxicity, assessed by the neutral red uptake assay using both gas-vapor and particulate phases of smoke, was unaffected by the addition of any of the test ingredients. Mutagenicity, assessed in five strains of Salmonella treated with mainstream cigarette smoke condensate, also was unaffected by any of the test ingredients. Despite the exaggerated ingredient levels relative to commercial-use levels, there was a lack of a toxicological response for the three heterocyclic nitrogen compounds in the test systems used.

Active sites of ligand-protected Au25 nanoparticle catalysts for CO2 electroreduction to CO

Science.gov (United States)

Alfonso, Dominic R.; Kauffman, Douglas; Matranga, Christopher

2016-05-01

Recent experimental studies have reported the electrochemical reduction of carbon dioxide (CO2) into CO at atomically precise negatively charged Au25- nanoclusters. The studies showed CO2 conversion at remarkably low overpotentials, but the exact mechanisms and nature of the active sites remain unclear. We used first-principles density functional theory and continuum solvation models to examine the role of the cluster during electrochemical CO2 reduction and analyze the free energies of proposed intermediate species. Contrary to previous assumptions, our results show that the fully ligand protected cluster is not an active CO2 reduction catalyst because formation of the crucial carboxyl intermediate required very high electrochemical potentials. Instead, our calculations suggest that the reduction process likely occurs on a dethiolated gold site, and adsorbed carboxyl intermediate formation was significantly stabilized at dethiolated gold sites. These findings point to the crucial role of exposed metal sites during electrochemical CO2 reduction at gold nanocluster catalysts.

Architecture effects on multivalent interactions by polypeptide-based multivalent ligands

Science.gov (United States)

Liu, Shuang

protein materials, including structural as well as functional proteins. Therefore, polypeptide-based multivalent scaffolds are used to display ligands to assess the contribution of different architectural parameters to the multivalent binding events. In this work, a family of alanine-rich alpha-helical glycopolypeptides was designed and synthesized by a combination of protein engineering and chemical coupling, to display two types of saccharide ligands for two different multivalent binding systems. The valencies, chain length and spacing between adjacent ligands of these multivalent ligands were designed in order to study architecture effects on multivalent interactions. The polypeptides and their glycoconjugates were characterized via various methods, including SDS-PAGE, NMR, HPLC, amino acid analysis (AAA), MALDI, circular dichroism (CD) and GPC. In the first multivalent binding system, cholera toxin B pentamer (CT B5) was chosen to be the protein receptor due to its well-characterized structure, lack of significant steric interference of binding to multiple binding sites, and requirement of only simple monosaccharide as ligands. Galactopyranoside was incorporated into polypeptide scaffolds through amine-carboxylic acid coupling to the side chains of glutamic acid residues. The inhibition and binding to CT B5 of these glycopolypeptide ligands were evaluated by direct enzyme-linked assay (DELA). As a complement method, weak affinity chromatography (WAC) was also used to evaluate glycopolypeptides binding to a CT B5 immobilized column. The architecture effects on CT B 5 inhibition are discussed. In the second system, cell surface receptor L-selectin was targeted by polypeptide-based multivalent ligands containing disulfated galactopyranoside ligands, due to its important roles in various immunological activities. The effects of glycopolypeptide architectural variables L-selectin shedding were evaluated via ELISA-based assays. These polypeptide-based multivalent ligands

Human Cells as Platform to Produce Gamma-Carboxylated Proteins.

Science.gov (United States)

de Sousa Bomfim, Aline; de Freitas, Marcela Cristina Corrêa; Covas, Dimas Tadeu; de Sousa Russo, Elisa Maria

2018-01-01

The gamma-carboxylated proteins belong to a family of proteins that depend on vitamin K for normal biosynthesis. The major representative gamma-carboxylated proteins are the coagulation system proteins, for example, factor VII, factor IX, factor X, prothrombin, and proteins C, S, and Z. These molecules have harbored posttranslational modifications, such as glycosylation and gamma-carboxylation, and for this reason they need to be produced in mammalian cell lines. Human cells lines have emerged as the most promising alternative to the production of gamma-carboxylated proteins. In this chapter, the methods to generate human cells as a platform to produce gamma-carboxylated proteins, for example the coagulation factors VII and IX, are presented. From the cell line modification up to the vitamin K adaptation of the produced cells is described in the protocols presented in this chapter.

N- AND O-HETEROCYCLES PRODUCED FROM THE IRRADIATION OF BENZENE AND NAPHTHALENE IN H2O/NH3-CONTAINING ICES

International Nuclear Information System (INIS)

Materese, Christopher K.; Nuevo, Michel; Sandford, Scott A.

2015-01-01

Aromatic heterocyclic molecules are an important class of molecules of astrophysical and biological significance that include pyridine, pyrimidine, and their derivatives. Such compounds are believed to exist in interstellar and circumstellar environments, though they have never been observed in the gas phase. Regardless of their presence in the gas phase in space, numerous heterocycles have been reported in carbonaceous meteorites, which indicates that they are formed under astrophysical conditions. The experimental work described here shows that N- and O-heterocyclic molecules can form from the ultraviolet (UV) irradiation of the homocyclic aromatic molecules benzene (C 6 H 6 ) or naphthalene (C 10 H 8 ) mixed in ices containing H 2 O and NH 3 . This represents an alternative way to generate aromatic heterocycles to those considered before and may have important implications for astrochemistry and astrobiology

In situ Generated Ruthenium Catalyst Systems Bearing Diverse N-Heterocyclic Carbene Precursors for Atom-Economic Amide Synthesis from Alcohols and Amines.

Science.gov (United States)

Cheng, Hua; Xiong, Mao-Qian; Cheng, Chuan-Xiang; Wang, Hua-Jing; Lu, Qiang; Liu, Hong-Fu; Yao, Fu-Bin; Chen, Cheng; Verpoort, Francis

2018-02-16

The transition-metal-catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom-economic process. Among various catalyst systems, in situ generated N-heterocyclic carbene (NHC)-based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active in situ catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron-deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR-scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=-7.8 ppm in the 1 H NMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the in situ generated catalyst system. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Complexes of technetium with polyhydric ligands

International Nuclear Information System (INIS)

Hwang, L.L.Y.; Ronca, N.; Solomon, N.A.; Steigman, J.

1985-01-01

Polyhydric complexes of Tc(V) show absorption bands near 500 nm, with molar absorptivity coefficients of about 100. The shorter-chain compounds like ethylene glycol produce complexes which quickly disproportionate to Tc(IV) (as TcO 2 ) and Tc(VII) (as TcO 4 - ) on acidification. The longer-chain ligands like mannitol and gluconate do not. However, while the mannitol complex shows no change in spectrum from pH 12 to pH 3, the gluconate and glucoheptonate compounds show a definite spectral change on acidification, starting at pH 5. Electrophoresis similarity showed a change in mobility with pH for Tc-glucoheptonate, but none for Tc-mannitol. It was concluded that the carboxylic acid group of glucoheptonate was not binding the technetium. In 25 molal choline chloride the glucoheptonate-Tc mole ratio was 1:1 or less. A similar result emerged from a similar experiment in methylcellosolve as solvent. (author)

Novel Polymers with Carboxylic Acid Loading

DEFF Research Database (Denmark)

Thomsen, Anders Daugaard; Malmström, Eva; Hvilsted, Søren

2006-01-01

Click chemistry has been used to prepare a range of novel polymers with pendant carboxylic acid side groups. Four azido carboxylic acids, either mono- or difunctional and aliphatic or aromatic, have been prepared and thoroughly characterized. Extensive model reactions with 1-ethyl-4-hydroxybenzene......, the simplest model for poly(4-hydroxystyrene), and the four azido carboxylic acids have been conducted to establish the proper reaction conditions and provide an analytical frame for the corresponding polymers. Poly(4-hydroxystyrene) moieties in three different polymers—poly(4-hydroxystyrene), poly(4...... the polymers in general exhibit [when poly(4-hydroxystyrene) is a substantial part] significant changes in the glass-transition temperature from the polar poly(4-hydroxystyrene) (120–130 °C) to the much less polar alkyne polymers (46–60 °C). A direct correlation between the nature of the pendant groups...

Enhancement of electroluminescence in zirconium poly carboxylic acid-based light emitting diodes by bathophenanthroline ligand.

Science.gov (United States)

Shahroosvand, Hashem; Nasouti, Fahimeh; Sousaraei, Ahmad; Mohajerani, Ezeddin; Khabbazi, Amir

2013-06-28

The reactions of a zirconium salt with 1,2,4,5-benzenetetracarboxylate (btec), bathophenanthroline (Bphen) and thiocyanate ions were synthesized and studied by changing the mole ratio, the order of reactant and their pH. It is found that the coordination mode of btec acid depends on the control of reaction conditions. Monodentate, bidentate and bridging modes were investigated by FT-IR spectroscopy. The structures of Zr(btec) and Zr(btec)(Bphen) complexes were also characterized by UV-Vis, CHN, ICP-AES, (1)H NMR and cyclic voltammetry. The role of Bphen ligand in the photopysical properties of Zr(btec)(Bphen) complexes was investigated by DFT calculation. The photoluminescence (PL) emission of nine Zr(btec) complexes that have two peaks, a sharp and intense band for the first peak from 320 to 430 nm in comparison to the second peak with a less intensity and broadened in the regions of 650-780 nm. PL spectra of twelve Zr(btec)(Bphen) complexes also showed bands at 450, 550, 625 nm. LED devices with Zr complex as emitter layer and the structure ITO/PEDOT:PSS/PVK:PBD/zirconium complex/Al emitted a broad band centered at 550 and 650 originating from the Zr complexes. The EL spectra of Zr(btec) and Zr(btec)(Bphen) complexes indicated a long red shift rather than PVK:PBD blend. We believe that the electroplex occurring at PVK-Zr complexes interface is responsible for the green-red emission in the EL of the device. These observations suggest an important role for the Bphen ligand to improve EL performance.

Synthesis and crystal structure of novel fluorescent 1,3,4-oxadiazole-containing carboxylate ligands

Science.gov (United States)

Mikhailov, Igor E.; Popov, Leonid D.; Tkachev, Valery V.; Aldoshin, Sergey M.; Dushenko, Galina A.; Revinskii, Yurii V.; Minkin, Vladimir I.

2018-04-01

Novel chelating ligands, 3-(5-aryl-1,3,4-oxadiazol-2-yl)acrylic acids and their zinc complexes were synthesized and their spectral and luminescent properties studied. The compounds intensively (quantum efficiencies φ = 0.18-0.76) luminesce in nonpolar solvents in the blue-green region (λmaxPL = 458-504 nm) of the spectrum. Molecular and crystal structures of 3-[5-(4-dimethylaminophenyl)-1,3,4-oxadiazol-2-yl]acrylic acid were established using X-ray crystallography. In crystal, the infinite chains of the molecules lie in the parallel planes and are arranged by the "head to tail" type to provide for strong π-π stacking interactions between the layers facilitating appearance of high electron transport properties and formation of excimers.

Auspicious role of the steroidal heterocyclic derivatives as a platform for anti-cancer drugs.

Science.gov (United States)

Tantawy, Mohamed A; Nafie, Mohamed S; Elmegeed, Gamal A; Ali, Ibrahim A I

2017-08-01

Steroids are polycyclic compounds that have a wide range of biological activities. They are bio-synthesized from cholesterol through a series of enzyme-mediated transformations, so they are highly lipophilic and readily enter most cells to interact with intracellular receptors, making them ideal vehicles for targeting a broad array of pathologies. New curative agents for cancers have been developed from several steroidal derivatives. Some biologically important properties of modified steroids are dependent on structural features of the steroid moiety and their side chains. Therefore, chemical derivatization of steroids provides a way to modify their function, and many structure-activity relationships have been confirmed by such synthetic modifications. Several studies demonstrate that steroidal heterocyclic derivatives can be effective in the prevention and treatment of many types of hormone-dependent cancers. The present review is a concise report on steroidal heterocyclic derivatives, with special emphasis on steroid heterocyclic derivatives with 5 membered rings or six-membered rings having interesting therapeutic potential as enzyme inhibitors and cytotoxic drugs to be used as candidates for anti-cancer drug development. Copyright © 2017 Elsevier Inc. All rights reserved.

Azido, triazolyl, and alkynyl complexes of gold(I): syntheses, structures, and ligand effects.

Science.gov (United States)

Robilotto, Thomas J; Deligonul, Nihal; Updegraff, James B; Gray, Thomas G

2013-08-19

Gold(I) triazolyl complexes are prepared in [3 + 2] cycloaddition reactions of (tertiary phosphine)gold(I) azides with terminal alkynes. Seven such triazolyl complexes, not previously prepared, are described. Reducible functional groups are accommodated. In addition, two new (N-heterocyclic carbene)gold(I) azides and two new gold(I) alkynyls are described. Eight complexes are crystallographically authenticated; aurophilic interactions appear in one structure only. The packing diagrams of gold(I) triazolyls all show intermolecular hydrogen bonding between N-1 of one molecule and N-3 of a neighbor. This hydrogen bonding permeates the crystal lattice. Density-functional theory calculations of (triphenylphosphine)gold(I) triazolyls and the corresponding alkynyls indicate that the triazolyl is a stronger trans-influencer than is the alkynyl, but the alkynyl is more electron-releasing. These results suggest that trans-influences in two-coordinate gold(I) complexes can be more than a simple matter of ligand donicity.

Determination of carboxyl groups in wood fibers by headspace gas chromatography

Science.gov (United States)

X.-S. Chai; Q.X. Hou; J.Y. Zhu; S.-L. Chen; S.F. Wang; L. Lucia

2003-01-01

The phase reaction conversion (PRC) headspace gas chromatographic (HSGC) technique was employed to develop a method for the determination of the content of carboxyl groups in wood fibers. Acid treatment of the wood fibers using hydrochloric was applied to convert carboxyl groups to carboxyl acids. Bicarbonate solution is then used to react with carboxyl acids on the...

Studies of effect of heterocyclic dyes in photogalvanic cells for solar ...

Indian Academy of Sciences (India)

Unknown

Studies of effect of heterocyclic dyes in photogalvanic cells for solar ... observed and current–voltage characteristics of the cell studied, and a mechanism has been proposed for the generation ... dye work effectively in the strong alkaline range.

Carboxylate and amino group coated silver nanoparticles as joining materials for copper-to-copper silver joints.

Science.gov (United States)

Oestreicher, A; Röhrich, T; Lerch, M

2012-12-01

Organic silver complexes are introduced where silver is linked either with a carboxyl group or with an amino group. Upon heating, nanoparticles are generated if the respective ligands are long enough to act as stabilizing agents in the nanoparticulate regime. With decomposition and volatilization of the organic material, the sintering of silver occurs. The thermal characteristics of the carboxylates silver-n-octanoate, silver-n-decanoate, and AgOOC(CH2OCH2)2CH2OCH3 are compared with silver-n-alkylamines (n = 8, 9, and 12), and their thermal behavior is discussed based on thermogravimetry (TG) measurements. The consecutive stages of a metallization process are addressed based on the properties of AgOOC(CH2OCH2)2CH2OCH3, and the usable effects of the individual phases of this metal organic compound are analyzed by cross-sectional scanning electron microscope (SEM) images of silver joints. Selection criteria are addressed based on the thermal behavior. A mechanism for the joining process is proposed, considering formation and sintering of the nanoparticles. It was found that the bulk material can be used for low-temperature joining processes. Strong adherence to copper as a basic material can be achieved.

Toxicity of six heterocyclic nitrogen compounds to Daphnia pulex

Science.gov (United States)

Perry, Cynthia M.; Smith, Stephen B.

1988-01-01

We determined the relative toxicities to the aquatic crustacean Daphniz pulex of six heterocyclic nitrogen compunds. These compounds were selected because they were detected in lake trout or walleyes and were commercially available. Stress to the daphnid populations may affect forage fish populations that depend either directly or indirectly on zooplankton as a food source in the Great Lakes.

N-Heterocyclic carbene functionalized goup 7-9 transition metal

NARCIS (Netherlands)

Aktas, H.; Slootweg, J.C.; Ehlers, A.W.; Lutz, M.; Spek, A.L.; Lammertsma, K.

2009-01-01

The N-heterocyclic carbene (NHC) functionalized phosphinidene complexes [(pCy)(IiPr2Me2)- RudPMes*] (4), [(pCy)(IiPr2Me2)OsdPMes*] (6), and [(Cp*)(IiPr2Me2)RhdPMes*] (7) were generated by a double-dehydrohalogenation-ligation sequence of the corresponding primary phosphine complexes with 3 equiv of

Synthesis and properties of nitrogenous heterocycles containing a spiro-fused cyclopropane fragment

International Nuclear Information System (INIS)

Tomilov, Yury V; Nefedov, Oleg M; Kostyuchenko, Irina V

2000-01-01

The published data on the methods of synthesis and chemical transformations of nitrogenous heterocyclic compounds spiro-fused with a cyclopropane fragment are described systematically and generalised. The bibliography includes 146 references.

Physicochemical Mechanisms of Synergistic Biological Action of Combinations of Aromatic Heterocyclic Compounds

OpenAIRE

Evstigneev, Maxim P.

2013-01-01

The mechanisms of synergistic biological effects observed in the simultaneous use of aromatic heterocyclic compounds in combination are reviewed, and the specific biological role of heteroassociation of aromatic molecules is discussed.

40 CFR 721.4663 - Fluorinated carboxylic acid alkali metal salts.

Science.gov (United States)

2010-07-01

... Specific Chemical Substances § 721.4663 Fluorinated carboxylic acid alkali metal salts. (a) Chemical... fluorinated carboxylic acid alkali metal salts (PMNs P-95-979/980/981) are subject to reporting under this... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Fluorinated carboxylic acid alkali...

Equilibrium studies of ternary systems containing some selected transition metal ions, triazoles and aromatic carboxylic acids

Energy Technology Data Exchange (ETDEWEB)

Khalil, Mohamed Magdy; Radalla, Abd-Elatty; Qasem, Fatma; Khaled, Rehab [Beni-Suef University, Beni-Suef (Egypt)

2014-01-15

Solution equilibria of the binary and ternary complex systems of the divalent transition metal ions Cu{sup 2+}, Ni{sup 2+}, Zn{sup 2+}, and Co{sup 2+} with 1,2,4-triazole (TRZ), 3-mercapto-1,2,4-triazole (TRZSH), and 3-amino-1,2,4-triazole (TRZAM) and aromatic carboxylic acids (phthalic, anthranilic, salicylic, and 5-sulfosalicylic acid) have been studied pH-metrically at (25.0±0.1) .deg. C, and a constant ionic strength I=1x10{sup -1} mol L{sup -1} NaNO{sub 3} in an aqueous medium. The potentiometric titration curves show that binary and ternary complexes of these ligands are formed in solution. The stability constants of the different binary and ternary complexes formed were calculated on the basis of computer analysis of the titration data. The relative stability of the different ternary complex species is expressed in terms of Δ log K values, log X and R. S.% parameters. The effect of temperature of the medium on both the proton-ligand equilibria for TRZAM and phthalic acid and their metal-ligand equilibria with Cu{sup 2+}, Ni{sup 2+}, and Co{sup 2+} has been studied along with the corresponding thermodynamic parameters. The complexation behavior of ternary complexes is ascertained using conductivity measurements. In addition, the formation of ternary complexes in solution has been confirmed by using UV-visible spectrophotometry.

Recyclisation of carbo- and heterocyclic compounds involving malononitrile and its derivatives

International Nuclear Information System (INIS)

Litvinov, Victor P

1999-01-01

Published data on recyclisation reactions of carbo- and heterocycles with participation of malononitrile and recyclisation of compounds containing a malononitrile fragment or fragments with malononitrile as a synthon are surveyed, described systematically and analysed. The bibliography includes 206 references.

Identification of sulfur heterocycles in coal liquids and shale oils. Technical progress report, August 1, 1980-May 1, 1981

Energy Technology Data Exchange (ETDEWEB)

Lee, M. L.; Castle, R. N.

1981-01-01

The sulfur heterocycle separation scheme which was described in the last progress report was evaluated for quantitative recovery of individual components. The results indicate that recoveries can range from 10% to approx. 30% depending on the structure of the compound. During this period, 23 unsubstituted sulfur-containing heterocyclic ring systems were synthesized in oder to confirm GC/MS identifications and for biological testing. The four possible 3-ring heterocycles and the thirteen possible 4-ring heterocycles were tested for mutagenic activity in the histidine reversion (Ames assay) system. One of the 3-ring isomers, naphtho(1,2-b)-thiophene, and six of the 4-ring isomers induced mutations in Salmonella test strains. One of these compounds, phenanthro(3,4-b)thiophene, displayed approximately the same mutagenic activity as benzo(a)pyrene. A two-step adsorption chromatographic procedure was developed in order to fractionate synthetic fuels into various chemical-type classes for studying the relative concentrations and mutagenic activities of the various types. An SRC-II Heavy Distillate was fractionated into aliphatic hydrocarbons, polycyclic aromatic hydrocarbons, sulfur heterocycles, indoles and carbazoles, azaarenes, and amino polycyclic aromatic hydrocarbons. It was found that the amino-PAH fraction contained most of the mutagenic activity. A survey was made for compounds containing both nitrogen and sulfur heteroatoms in their structures. A number of these compounds were detected by GC using nitrogen- and sulfur-selective detection.

Modulating p-hydroxycinnamate behavior as a ditopic linker or photoacid in copper(ii) complexes with an auxiliary pyridine ligand.

Science.gov (United States)

Soldevila-Sanmartín, Joan; Calvet, Teresa; Font-Bardia, Merce; Domingo, Concepción; Ayllón, José A; Pons, Josefina

2018-05-08

The reaction of copper(ii) acetate monohydrate with p-hydroxycinnamic acid (HpOHcinn) and different pyridine derivatives (4-tert-butylpyridine, 4-tBupy; 4-acetylpyridine, 4-Acpy; 3-phenylpyridine, 3-Phpy; 4-phenylpyridine, 4-Phpy) was essayed in methanol solvent at room temperature. The crystal structures of the resulting compounds were elucidated. Their analysis shows that the choice of pyridine ligands determines different coordination modes of the pOHcinn ligand and the Cu(ii) coordination, nuclearity and geometry. The pOHcinn acts as a monodentate carboxylate ligand in combination with 4-tBupy or 4-Phpy, yielding monomers and dimers, associated by hydrogen bonds into supramolecular networks in which the phenol group plays a key role. Conversely, in combination with 4-Acpy or 3-Phpy, the phenol group coordinates directly to the Cu(ii), acting as a ditopic ligand and yielding 2D coordination polymers. The compound containing 3-Phpy shows interesting MeOH-H2O reversible exchange behavior. Not only has the pyridine auxiliary ligand had a tremendous effect on the coordination mode of pOHcinn, but also its reactivity is influenced. Particularly, in the case of the compound containing 4-Phpy, it undergoes a photoinduced process, in which the phenol group deprotonates and coordinates to Cu(ii) as a phenoxy ligand. This yields a coordination polymer in which two different dimers alternate, bridged by the resulting pOcinn ligand. The magneto-structural correlation of this compound is also discussed.

General and efficient one-pot synthesis of novel sugar/heterocyclic(aryl) 1,2-diketones from sugar terminal alkynes by Sonogashira/tetra-n- butylammonium permanganate oxidation.

Science.gov (United States)

Zhang, Fuyi; Wu, Xiaopei; Wang, Liming; Liu, Hong; Zhao, Yufen

2015-11-19

A new approach for one-pot synthesis of novel sugar/heterocyclic(aryl) 1,2-diketones has been achieved by the reaction of various sugar terminal alkynes with heterocyclic(aryl) iodides at room temperature. This one-pot protocol includes Sonogashira coupling and mild n-Bu4NMnO4 oxidation reaction. This method is mild, general and efficient. Fifty-six examples have been given and the sugar/heterocyclic(aryl) 1,2-diketones were obtained in 71-94% yields. The sugar terminal alkynes include 9 structurally different sugars in pyranose, furanose, and acyclic form which have various protecting groups, sensitive groups, and sterically bulky substituents. The heterocyclic(aryl) iodides include sterically bulky heterocyclic compounds and iodobenzenes with electron-donating, electron-neutral, and electron-withdrawing substituents. Copyright © 2015 Elsevier Ltd. All rights reserved.

Synthesis of boron-containing heterocyclic compounds

International Nuclear Information System (INIS)

Azev, Yuri; Slepukhina, Irina; Gabel, Detlef

2004-01-01

The synthesis of boron-containing 1,3,5-triazines and 1,2,4-triazines is described. Derivatives of 1,3,5-triazine containing the o-carborane cluster have been obtained by reacting the corresponding propargyl derivatives with B 10 H 14 . Derivatives of 1,2,4-triazine containing the B 12 H 12 2- cluster have been obtained by nucleophilic substitution of ethylsulfone derivatives with B 12 H 11 SH 2- . They have been isolated in their ring-protonated form. Reaction of RNH 2 -B 8 H 11 NH-R with stericly demanding heterocycles failed, either for steric or for solubility reasons

Unusual metal-ligand charge transfer in ferrocene functionalized μ3-O iron carboxylates observed with Mössbauer spectroscopy

International Nuclear Information System (INIS)

Mereacre, Valeriu; Schlageter, Martin; Eichhöfer, Andreas; Bauer, Thomas; Wolny, Juliusz A.; Schünemann, Volker; Powell, Annie K.

2016-01-01

Temperature dependent Mössbauer studies of two ferrocenecarboxylate functionalized {Fe 3 O} complexes in solid state are reported. It was found that conjugation of ferrocene ring orbitals with the π orbitals of the adjacent carboxylic group promotes a shift of electron density from the ferrocene Fe II ion to the cyclopentadienide rings with π-orbital character giving rise to a new type of mixed-valence compound. - Highlights: • In this manuscript we describe a mechanism of electron density shift which stabilizes the trapped mixed-valence state. • The coexistence of ferrocene and ferrocenium in solid state was determined. • A mixed-valence state at room-temperature and a thermally induced electron transfer with gradual interconversion were observed.

Bis-ligated Ti and Zr complexes of chelating N-heterocyclic carbenes

KAUST Repository

El-Batta, Amer; Waltman, Andrew W.; Grubbs, Robert H.

2011-01-01

In this communication we report the synthesis of novel titanium and zirconium complexes ligated by bidentate "salicylaldimine-like" N-heterocyclic carbenes (NHC). Double addition of the NHC chelate to either TiCl4(thf)2 or ZrCl4 forms bis

Quenching of excited uranyl ion during its photochemical reduction with triphenyl-phosphine : Part IV - effect of heterocyclic molecules

International Nuclear Information System (INIS)

Sidhu, M.S.; Bhatia, P.V.K.

1994-01-01

The presence of heterocyclic compounds triggers off a competition between photophysical and photochemical annihilation of excited uranyl ion during its photochemical reduction with triphenylphosphine. This competition is used to measure Stern-Volmer constant using UV visible spectrophotometer for quenching the uranyl ion luminescence with a number of heterocyclic molecules viz., pyridine, thiophene bipyridyl, tetrahydrofuran and piperidine. (author). 7 refs., 2 figs., 1 tab

Synthesis, characterization and dyeing behavior of heterocyclic acid dyes and mordent acid dyes on wool and silk fabrics

Directory of Open Access Journals (Sweden)

Patel Hitendra M.

2012-01-01

Full Text Available Novel heterocyclic acid and mordent acid dyes were synthesized by the coupling of diazonium salt solution of different aromatic amines with 2- butyl-3-(4-hydroxybenzoylbenzofuran. The resulting heterocyclic acid dyes were characterized by spectral techniques, i.e., elemental analysis, IR, 1HNMR, 13C-NMR spectral studies and UV- visible spectroscopy. The dyeing performance of all the heterocyclic acid dyes was evaluated on wool and silk fabrics. The dyeing of chrome pre treated wool and silk fabrics showed better hues on mordented fabrics. Dyeing of wool and silk fabrics resulted in pinkish blue to red shades with very good depth and levelness. The dyed fabrics showed excellent to very good light, washing, perspiration, sublimation and rubbing fastness.

Effect of cooking time and temperature on the heterocyclic amine content of fried beef patties.

Science.gov (United States)

Knize, M G; Dolbeare, F A; Carroll, K L; Moore, D H; Felton, J S

1994-07-01

The mutagenic heterocyclic amines 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) were measured in ground-beef patties fried at 150, 190 and 230 degrees C for 2-10 min on each side. Heterocyclic amines were purified using solid-phase extraction and analysed by HPLC. Recovery-corrected amounts of each heterocyclic amine were determined by the method of standard addition based on spiked samples with recoveries ranging from 40 to 70%. Mutagenic activity measured by the Ames/Salmonella test was determined for each sample. The amounts of MeIQx, PhIP, DiMeIQx and IQ increased with time and temperature of cooking. 3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and 2-amino-9H-pyrido[2,3-b]indole (A alpha C) were not detected in any sample. The mutagenic activity response measured for the meat extracts (TA98 revertants) was similar to the mutagenic activity calculated from the mass of heterocyclic amines present. The rate of formation of PhIP in a model system containing creatinine and phenylalanine heated in 80% diethylene glycol was compared with PhIP formation during meat frying. The apparent heats of activation were 6.5 kcal/mol in the model system compared with 6.0 kcal/mol in the fried meat patties. The increase in PhIP and MeIQx formation fitted an exponential function over the range 0 to 11 min and from 150 to 230 degrees C. This report shows clearly that increases in cooking temperature and time can have a profound effect on the amounts of heterocyclic amines generated and subsequently consumed in the diet.

Polar metabolites of polycyclic aromatic compounds from fungi are potential soil and groundwater contaminants

DEFF Research Database (Denmark)

Boll, Esther Sørensen; Johnsen, Anders R.; Christensen, Jan H.

2015-01-01

and either hydroxylated or oxidized to carboxylic acids at the methyl group. The metabolism of the sulfur-containing heterocyclic PAC resulted in sulfate conjugates. The sorption of the PAC metabolites to three soils was determined using a batch equilibrium method, and partition coefficients (Kd's) were......-methylphenanthrene, 1-methylpyrene), and one sulfur-containing heterocyclic PAC (dibenzothiophene). Fifty-eight metabolites were tentatively identified; metabolites from the un-substituted PACs were hydroxylated and sulfate conjugated, whereas metabolites from alkyl-substituted PACs were sulfate conjugated...... calculated for fourteen representative metabolites. Sulfate conjugated metabolites displayed Kd's below 70 whereas the metabolites with both a sulfate and a carboxylic acid group had Kd's below 2.8. The low Kd's of water-soluble PAC metabolites indicate high mobility in soil and a potential for leaching...

Formation of Haloacetonitriles, Haloacetamides, and Nitrogenous Heterocyclic Byproducts by Chloramination of Phenolic Compounds.

Science.gov (United States)

Nihemaiti, Maolida; Le Roux, Julien; Hoppe-Jones, Christiane; Reckhow, David A; Croué, Jean-Philippe

2017-01-03

The potential formation of nitrogenous disinfection byproducts (N-DBPs) was investigated from the chloramination of nitrogenous and non-nitrogenous aromatic compounds. All molecules led to the formation of known N-DBPs (e.g., dichloroacetonitrile, dichloroacetamide) with various production yields. Resorcinol, a major precursor of chloroform, also formed di/trichloroacetonitrile, di/trichloroacetamide, and haloacetic acids, indicating that it is a precursor of both N-DBPs and carbonaceous DBPs (C-DBPs) upon chloramination. More detailed experiments were conducted on resorcinol to understand N-DBPs formation mechanisms and to identify reaction intermediates. Based on the accurate mass from high resolution Quadrupole Time-of-Flight GC-MS (GC-QTOF) and fragmentation patterns from electronic impact and positive chemical ionization modes, several products were tentatively identified as nitrogenous heterocyclic compounds (e.g., 3-chloro-5-hydroxy-1H-pyrrole-2-one with dichloromethyl group, 3-chloro-2,5-pyrroledione). These products were structurally similar to the heterocyclic compounds formed during chlorination, such as the highly mutagenic MX (3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone) or halogenated pyrroles. To our knowledge, this is the first time that the formation of halogenated nitrogenous heterocyclic compounds is reported from chloramination process. The formation of these nitrogenous byproducts during chloramination might be of concern considering their potential toxicity.

Recent advances in novel heterocyclic scaffolds for the treatment of drug-resistant malaria.

Science.gov (United States)

Kumar, Sahil; Singh, Rajesh K; Patial, Babita; Goyal, Sachin; Bhardwaj, T R

2016-01-01

Malaria is a major public health problem all over the world, particularly in tropical and subtropical countries due to the development of resistance and most deadly infection is caused by Plasmodium falciparum. There is a direct need for the discovery of new drugs with unique structures and mechanism of action to treat sensitive and drug-resistant strains of various plasmodia for radical cure of this disease. Traditional compounds such as quinine and related derivatives represent a major source for the development of new drugs. This review presents recent modifications of 4-aminoquinoline and 8-aminoquinolone rings as leads to novel active molecules which are under clinical trials. The review also encompasses the other heterocyclic compounds emerged as potential antimalarial agents with promising results such as acridinediones and acridinone analogues, pyridines and quinolones as antimalarials. Miscellaneous heterocyclics such as tetroxane derivatives, indole derivatives, imidazolopiperazine derivatives, biscationic choline-based compounds and polymer-linked combined antimalarial drugs are also discussed. At last brief introduction to heterocyclics in natural products is also reviewed. Most of them have been under clinical trials and found to be promising in the treatment of drug-resistant strains of Plasmodium and others can be explored for the same purpose.

Manganese(II), iron(II), and mixed-metal metal-organic frameworks based on chains with mixed carboxylate and azide bridges: magnetic coupling and slow relaxation.

Science.gov (United States)

Wang, Yan-Qin; Yue, Qi; Qi, Yan; Wang, Kun; Sun, Qian; Gao, En-Qing

2013-04-15

Mn(II) and Fe(II) compounds derived from azide and the zwitterionic 1-carboxylatomethylpyridinium-4-carboxylate ligand are isomorphous three-dimensional metal-organic frameworks (MOFs) with the sra net, in which the metal ions are connected into anionic chains by mixed (μ-1,1-azide)bis(μ-carboxylate) triple bridges and the chains are cross-linked by the cationic backbones of the zwitterionic ligands. The Mn(II) MOFs display typical one-dimensional antiferromagnetic behavior. In contrast, with one more d electron per metal center, the Fe(II) counterpart shows intrachain ferromagnetic interactions and slow relaxation of magnetization attributable to the single-chain components. The activation energies for magnetization reversal in the infinite- and finite-chain regimes are Δτ1 = 154 K and Δτ2 = 124 K, respectively. Taking advantage of the isomorphism between the Mn(II) and Fe(II) MOFs, we have prepared a series of mixed-metal Mn(II)(1-x)Fe(II)(x) MOFs with x = 0.41, 0.63, and 0.76, which intrinsically feature random isotropic/anisotropic sites and competing antiferromagnetic-ferromagnetic interactions. The materials show a gradual antiferromagnetic-to-ferromagnetic evolution in overall behaviors as the Fe(II) content increases, and the Fe-rich materials show complex relaxation processes that may arise for mixed SCM and spin-glass mechanisms. A general trend is that the activation energy and the blocking temperature increase with the Fe(II) content, emphasizing the importance of anisotropy for slow relaxation of magnetization.

Ligand-accelerated non-directed C-H functionalization of arenes

Science.gov (United States)

Wang, Peng; Verma, Pritha; Xia, Guoqin; Shi, Jun; Qiao, Jennifer X.; Tao, Shiwei; Cheng, Peter T. W.; Poss, Michael A.; Farmer, Marcus E.; Yeung, Kap-Sun; Yu, Jin-Quan

2017-11-01

The directed activation of carbon-hydrogen bonds (C-H) is important in the development of synthetically useful reactions, owing to the proximity-induced reactivity and selectivity that is enabled by coordinating functional groups. Palladium-catalysed non-directed C-H activation could potentially enable further useful reactions, because it can reach more distant sites and be applied to substrates that do not contain appropriate directing groups; however, its development has faced substantial challenges associated with the lack of sufficiently active palladium catalysts. Currently used palladium catalysts are reactive only with electron-rich arenes, unless an excess of arene is used, which limits synthetic applications. Here we report a 2-pyridone ligand that binds to palladium and accelerates non-directed C-H functionalization with arene as the limiting reagent. This protocol is compatible with a broad range of aromatic substrates and we demonstrate direct functionalization of advanced synthetic intermediates, drug molecules and natural products that cannot be used in excessive quantities. We also developed C-H olefination and carboxylation protocols, demonstrating the applicability of our methodology to other transformations. The site selectivity in these transformations is governed by a combination of steric and electronic effects, with the pyridone ligand enhancing the influence of sterics on the selectivity, thus providing complementary selectivity to directed C-H functionalization.

Elucidating the role of surface passivating ligand structural parameters in hole wave function delocalization in semiconductor cluster molecules.

Science.gov (United States)

Teunis, Meghan B; Nagaraju, Mulpuri; Dutta, Poulami; Pu, Jingzhi; Muhoberac, Barry B; Sardar, Rajesh; Agarwal, Mangilal

2017-09-28

This article describes the mechanisms underlying electronic interactions between surface passivating ligands and (CdSe) 34 semiconductor cluster molecules (SCMs) that facilitate band-gap engineering through the delocalization of hole wave functions without altering their inorganic core. We show here both experimentally and through density functional theory calculations that the expansion of the hole wave function beyond the SCM boundary into the ligand monolayer depends not only on the pre-binding energetic alignment of interfacial orbitals between the SCM and surface passivating ligands but is also strongly influenced by definable ligand structural parameters such as the extent of their π-conjugation [π-delocalization energy; pyrene (Py), anthracene (Anth), naphthalene (Naph), and phenyl (Ph)], binding mode [dithiocarbamate (DTC, -NH-CS 2 - ), carboxylate (-COO - ), and amine (-NH 2 )], and binding head group [-SH, -SeH, and -TeH]. We observe an unprecedentedly large ∼650 meV red-shift in the lowest energy optical absorption band of (CdSe) 34 SCMs upon passivating their surface with Py-DTC ligands and the trend is found to be Ph- wave function delocalization rather than carrier trapping and/or phonon-mediated relaxation. Taken together, knowledge of how ligands electronically interact with the SCM surface is crucial to semiconductor nanomaterial research in general because it allows the tuning of electronic properties of nanomaterials for better charge separation and enhanced charge transfer, which in turn will increase optoelectronic device and photocatalytic efficiencies.

Two-dimensional inorganic–organic hybrid semiconductors composed of double-layered ZnS and monoamines with aromatic and heterocyclic aliphatic rings: Syntheses, structures, and properties

International Nuclear Information System (INIS)

Wang, Sujing; Li, Jing

2015-01-01

As an addition to the II–VI based inorganic–organic hybrid semiconductor family, five new two-dimensional (2D) double-layered structures have been synthesized employing monoamines with different aromatic or heterocyclic aliphatic rings. Zn 2 S 2 (bza) (1), Zn 2 S 2 (mbza) (2), Zn 2 S 2 (fbza) (3), Zn 2 S 2 (pca) (4), and Zn 2 S 2 (thfa) (5) (bza=benzylamine, mbza=4-methoxybenzylamine, fbza=4-flurobenzylamine, pca=3-picolylamine, and thfa=tetrahydrofurfurylamine) are prepared by solvothermal reactions and characterized by different analytical methods, including powder X-ray diffraction, optical diffuse reflection, thermogravimetric analysis and photoluminescence spectroscopy. The powder X-ray diffraction patterns show that all five compounds adopt 2D double-layered structures. Optical diffuse reflectance spectra of these compounds suggest that they have notably lower band gaps than those of the similar compounds composed of aliphatic alkyl amines. Their photoluminescence properties and thermal stability are also analyzed. - Graphical abstract: Five new members of two-dimensional double-layered 2D-Zn 2 S 2 (L) (L=Ligand) structures employing monoamines with different aromatic or heterocyclic aliphatic rings have been designed, synthesized, and characterized. - Highlights: • A new sub-family of II-VI based hybrid semiconductors are designed, synthesized, and structurally characterized using amines with aromatic or aliphatic cyclic rings. • These compounds have notably lower band gaps than those made of aliphatic alkyl amines, greatly broadening the range of band gaps of this material family. • They emit strongly with systematically tunable emission intensity and energy

Two food-borne heterocyclic amines: Metabolism and DNA adduct formation of amino-alpha-carbolines

DEFF Research Database (Denmark)

Frederiksen, Hanne

2005-01-01

or proteins of animal or vegetable origin, furthermore they are found in many cooked foods, such as fish, meat, and chicken. The specific mutagenicity of the amino-a-carbolines are lower in the Ames Salmonella assay than other heterocyclic amines, but in rodent studies the carcinogenicity of the aminoa, alpha......The amino-alpha-carbolines 2-amino-9H-pyrido[2,3-b]indole (A alpha C) and 2-amino-3-methyl-9H-pyrido-[2,3-b]indole (MeA alpha C) are two mutagenic and carcinogenic heterocyclic amines formed during ordinary cooking. Amino-alpha-carbolines can be formed in model systems by pyrolyzing tryptophan...

An endogenous aryl hydrocarbon receptor ligand acts on dendritic cells and T cells to suppress experimental autoimmune encephalomyelitis

Science.gov (United States)

Quintana, Francisco J.; Murugaiyan, Gopal; Farez, Mauricio F.; Mitsdoerffer, Meike; Tukpah, Ann-Marcia; Burns, Evan J.; Weiner, Howard L.

2010-01-01

The ligand-activated transcription factor aryl hydrocarbon receptor (AHR) participates in the differentiation of FoxP3+ Treg, Tr1 cells, and IL-17–producing T cells (Th17). Most of our understanding on the role of AHR on the FoxP3+ Treg compartment results from studies using the toxic synthetic chemical 2,3,7,8-tetrachlorodibenzo-p-dioxin. Thus, the physiological relevance of AHR signaling on FoxP3+ Treg in vivo is unclear. We studied mice that carry a GFP reporter in the endogenous foxp3 locus and a mutated AHR protein with reduced affinity for its ligands, and found that AHR signaling participates in the differentiation of FoxP3+ Treg in vivo. Moreover, we found that treatment with the endogenous AHR ligand 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) given parenterally or orally induces FoxP3+ Treg that suppress experimental autoimmune encephalomyelitis. ITE acts not only on T cells, but also directly on dendritic cells to induce tolerogenic dendritic cells that support FoxP3+ Treg differentiation in a retinoic acid-dependent manner. Thus, our work demonstrates that the endogenous AHR ligand ITE promotes the induction of active immunologic tolerance by direct effects on dendritic and T cells, and identifies nontoxic endogenous AHR ligands as potential unique compounds for the treatment of autoimmune disorders. PMID:21068375

Tuning optoelectronic properties of small semiconductor nanocrystals through surface ligand chemistry

Science.gov (United States)

Lawrence, Katie N.

Semiconductor nanocrystals (SNCs) are a class of material with one dimension wave function 1) into the ligand monolayer using metal carboxylates and 2) beyond the ligand monolayer to provide strong inter-SNC electronic coupling using poly(ethylene) glycol (PEG)-thiolate was explored. Passivation of the Se sites of metal chalcogenide SNCs by metal carboxylates provided a two-fold outcome: (1) facilitating the delocalization of exciton wave functions into ligand monolayers (through appropriate symmetry matching and energy alignment) and (2) increasing fluorescence quantum yield (through passivation of midgap trap states). An ˜240 meV red-shift in absorbance was observed upon addition of Cd(O2CPh)2, as well as a ˜260 meV shift in emission with an increase in PL-QY to 73%. Through a series of control experiments, as well as full reversibility of our system, we were able to conclude that the observed bathochromic shifts were the sole consequence of delocalization, not a change in size or relaxation of the inorganic core, as previously reported. Furthermore, the outstanding increase in PL-QY was found to be a product of both passivation and delocalization effects. Next we used poly(ethylene) glycol (PEG)-thiolate ligands to passivate the SNC and provide unique solubility properties in both aqueous and organic solvents as well as utilized their highly conductive nature to explore inter-SNC electronic coupling. The electronic coupling was studied: 1) as a function of SNC size where the smallest SNC exhibited the largest coupling energy (170 meV) and 2) as a function of annealing temperature, where an exceptionally large (˜400 meV) coupling energy was observed. This strong electronic coupling in self-organized films could facilitate the large-scale production of highly efficient electronic materials for advanced optoelectronic device applications. Strong inter-SNC electronic coupling together with high solubility, such as that provided by PEG-thiolate-coated CdSe SNCs

Supramolecular Isomers of Metal-Organic Frameworks Derived from a Partially Flexible Ligand with Distinct Binding Motifs

KAUST Repository

Abdul Halim, Racha Ghassan

2016-01-04

Three novel metal-organic frameworks (MOFs) were isolated upon reacting a heterofunctional ligand 4 (pyrimidin-5 yl)benzoic acid (4,5-pmbc) with mixed valence Cu(I,II) under solvothermal conditions. X-ray crystal structural analysis reveals that the first compound is a layered structure composed of one type of inorganic building block, dinuclear paddlewheel [Cu2(O2C–)4], which are linked through 4,5-pmbc ligands. The two other supramolecular isomers are composed of the same Cu(II) dinuclear paddlewheel and a dinuclear Cu2I2 cluster, which are linked via the 4,5-pmbc linkers to yield two different 3-periodic frameworks with underlying topologies related to lvt and nbo. The observed structural diversity in these structures is due to the distinct coordination modes of the two coordinating moieties (the carboxylate group on the phenyl ring and the N-donor atoms from the pyrimidine moiety).

Supramolecular Isomers of Metal-Organic Frameworks Derived from a Partially Flexible Ligand with Distinct Binding Motifs

KAUST Repository

AbdulHalim, Rasha; Shkurenko, Aleksander; Al Kordi, Mohamed; Eddaoudi, Mohamed

2016-01-01

Three novel metal-organic frameworks (MOFs) were isolated upon reacting a heterofunctional ligand 4 (pyrimidin-5 yl)benzoic acid (4,5-pmbc) with mixed valence Cu(I,II) under solvothermal conditions. X-ray crystal structural analysis reveals that the first compound is a layered structure composed of one type of inorganic building block, dinuclear paddlewheel [Cu2(O2C–)4], which are linked through 4,5-pmbc ligands. The two other supramolecular isomers are composed of the same Cu(II) dinuclear paddlewheel and a dinuclear Cu2I2 cluster, which are linked via the 4,5-pmbc linkers to yield two different 3-periodic frameworks with underlying topologies related to lvt and nbo. The observed structural diversity in these structures is due to the distinct coordination modes of the two coordinating moieties (the carboxylate group on the phenyl ring and the N-donor atoms from the pyrimidine moiety).

MICROWAVE IRRADIATION IN BENIGN SYNTHESIS OF HETEROCYCLES, NOBLE NANOMETALS AND NANOCOMPOSITES

Science.gov (United States)

A brief historic account of reactions involving microwave (MW) exposure of neat reactants or catalyzed by mineral support surfaces, such as alumina, silica, clay, or their ‘doped’ versions, for the rapid one-pot assembly of heterocyclic compounds [1] from in situ generated reacti...

Expedient Access to an N -phenylpyrrolidin-2-yl Heterocycle via a ...

African Journals Online (AJOL)

Expedient Access to an N -phenylpyrrolidin-2-yl Heterocycle via a Base-Induced Intramolecular aza -Michael Reaction. ... in good overall yield when employing a stoichiometric amount of base to facilitate the intramolecular aza-Michael reaction. Keywords: aza Michael, intramolecular, catalysed, piperidine, pyrrolidine, base ...

Effects of Mutations and Ligands on the Thermostability of the l-Arginine/Agmatine Antiporter AdiC and Deduced Insights into Ligand-Binding of Human l-Type Amino Acid Transporters

Directory of Open Access Journals (Sweden)

Hüseyin Ilgü

2018-03-01

Full Text Available The l-arginine/agmatine transporter AdiC is a prokaryotic member of the SLC7 family, which enables pathogenic enterobacteria to survive the extremely acidic gastric environment. Wild-type AdiC from Escherichia coli, as well as its previously reported point mutants N22A and S26A, were overexpressed homologously and purified to homogeneity. A size-exclusion chromatography-based thermostability assay was used to determine the melting temperatures (Tms of the purified AdiC variants in the absence and presence of the selected ligands l-arginine (Arg, agmatine, l-arginine methyl ester, and l-arginine amide. The resulting Tms indicated stabilization of AdiC variants upon ligand binding, in which Tms and ligand binding affinities correlated positively. Considering results from this and previous studies, we revisited the role of AdiC residue S26 in Arg binding and proposed interactions of the α-carboxylate group of Arg exclusively with amide groups of the AdiC backbone. In the context of substrate binding in the human SLC7 family member l-type amino acid transporter-1 (LAT1; SLC7A5, an analogous role of S66 in LAT1 to S26 in AdiC is discussed based on homology modeling and amino acid sequence analysis. Finally, we propose a binding mechanism for l-amino acid substrates to LATs from the SLC7 family.

D-piece modifications of the hemiasterlin analog HTI-286 produce potent tubulin inhibitors.

Science.gov (United States)

Zask, Arie; Birnberg, Gary; Cheung, Katherine; Kaplan, Joshua; Niu, Chuan; Norton, Emily; Yamashita, Ayako; Beyer, Carl; Krishnamurthy, Girija; Greenberger, Lee M; Loganzo, Frank; Ayral-Kaloustian, Semiramis

2004-08-16

Modifications of the D-piece carboxylic acid group of the hemiasterlin analog HTI-286 gave tubulin inhibitors which were potent cytotoxic agents in taxol resistant cell lines expressing P-glycoprotein. Amides derived from proline had potency comparable to HTI-286. Reduction of the carboxylic acid to ketones and alcohols or its conversion to acidic heterocycles also gave potent analogs. Synthetic modifications of the carboxylic acid could be carried out selectively using a wide range of synthetic reagents. Proline analog 3 was found to be effective in a human xenograft model in athymic mice.

Self-assembled arene-ruthenium-based rectangles for the selective sensing of multi-carboxylate anions.

Science.gov (United States)

Vajpayee, Vaishali; Song, Young Ho; Lee, Min Hyung; Kim, Hyunuk; Wang, Ming; Stang, Peter J; Chi, Ki-Whan

2011-07-04

Novel arene-ruthenium [2+2] metalla-rectangles 4 and 5 have been synthesized by self-assembly using dipyridyl amide ligand 3 and arene-ruthenium acceptors (arene: benzoquinone (1), naphthacenedione (2)) and characterized by NMR spectroscopy and ESI-MS. The solid-state structure of 5 was determined by X-ray diffraction and shows encapsulated diethyl ether molecule in the rectangular cavity of 5. The luminescent 5 was further used for anion sensing with the amidic linkage serving as a hydrogen-bond donor site for anions and the ruthenium moiety serving as a signaling unit. A UV/Vis titration study demonstrated that although 5 interacts very weakly with common monoanions as well as with flexible dicarboxylate anions such as malonate and succinate, it displays significant binding affinity (K>10(3) in MeOH) for rigid multi-carboxylate anions such as oxalate, citrate, and tartrate, exhibiting a 1:1 stoichiometry. It has been suggested that 1:1 bidentate hydrogen bonding assisted by appropriate geometrical complementarity is mainly responsible for the increased affinity of 5 towards such anions. A fluorescence titration study revealed a large fluorescence enhancement of 5 upon binding to multi-carboxylate anions, which can be attributed to the blocking of the photoinduced electron-transfer process from the arene-Ru moiety to the amidic donor in 5 as a result of hydrogen bonding between the donor and the anion. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

N- AND O-HETEROCYCLES PRODUCED FROM THE IRRADIATION OF BENZENE AND NAPHTHALENE IN H{sub 2}O/NH{sub 3}-CONTAINING ICES

Energy Technology Data Exchange (ETDEWEB)

Materese, Christopher K.; Nuevo, Michel; Sandford, Scott A., E-mail: christopher.k.materese@nasa.gov [NASA Ames Research Center, Moffett Field, CA 94035 (United States)

2015-02-20

Aromatic heterocyclic molecules are an important class of molecules of astrophysical and biological significance that include pyridine, pyrimidine, and their derivatives. Such compounds are believed to exist in interstellar and circumstellar environments, though they have never been observed in the gas phase. Regardless of their presence in the gas phase in space, numerous heterocycles have been reported in carbonaceous meteorites, which indicates that they are formed under astrophysical conditions. The experimental work described here shows that N- and O-heterocyclic molecules can form from the ultraviolet (UV) irradiation of the homocyclic aromatic molecules benzene (C{sub 6}H{sub 6}) or naphthalene (C{sub 10}H{sub 8}) mixed in ices containing H{sub 2}O and NH{sub 3}. This represents an alternative way to generate aromatic heterocycles to those considered before and may have important implications for astrochemistry and astrobiology.

The effect of organic ligands on the crystallinity of calcium phosphate

Science.gov (United States)

van der Houwen, Jacqueline A. M.; Cressey, Gordon; Cressey, Barbara A.; Valsami-Jones, Eugenia

2003-03-01

Calcium phosphate phases precipitated under critical supersaturation were identified and studied in detail using X-ray powder diffraction, electron probe microanalysis, infrared spectroscopy (IR) and transmission electron microscopy. These synthetic calcium phosphates formed by spontaneous precipitation at pH 7, 25°C and 0.1 M ionic strength (NaCl as the background electrolyte). The combination of several methods allowed detailed characterisation of the calcium phosphates. The purpose of the work was to assess the influence of carboxylate ligands, specifically acetate and citrate, on the quality of the calcium phosphate precipitate. All precipitates were identified as non-stoichiometric, calcium-deficient hydroxylapatites (HAPs), containing carbonate, HPO 42-, sodium and chloride impurities. No other phases were found to be present in any of the precipitates. The presence of citrate resulted in a decrease in crystal size and a higher degree of apatite lattice imperfection in the precipitated HAP. Furthermore, IR spectroscopy showed a higher amount of carbonate present in that HAP, compared with the ones formed in the control and acetate experiments. An additional absorption band, in the infrared spectrum of the HAP formed in the presence of citrate, was observed at 1570 cm -1; this is interpreted as carboxyl groups bound to HAP.

Fluoroalkyl Amino Reagents (FARs: A General Approach towards the Synthesis of Heterocyclic Compounds Bearing Emergent Fluorinated Substituents

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Bruno Commare

2017-06-01

Full Text Available Fluorinated heterocycles are important building blocks in pharmaceutical, agrochemical and material sciences. Therefore, organofluorine chemistry has witnessed high interest in the development of efficient methods for the introduction of emergent fluorinated substituents (EFS onto heterocycles. In this context, fluoroalkyl amino reagents (FARs—a class of chemicals that was slightly forgotten over the last decades—has emerged again recently and proved to be a powerful tool for the introduction of various fluorinated groups onto (heteroaromatic derivatives.

Fluoroalkyl Amino Reagents (FARs): A General Approach towards the Synthesis of Heterocyclic Compounds Bearing Emergent Fluorinated Substituents.

Science.gov (United States)

Commare, Bruno; Schmitt, Etienne; Aribi, Fallia; Panossian, Armen; Vors, Jean-Pierre; Pazenok, Sergiy; Leroux, Frédéric R

2017-06-12

Fluorinated heterocycles are important building blocks in pharmaceutical, agrochemical and material sciences. Therefore, organofluorine chemistry has witnessed high interest in the development of efficient methods for the introduction of emergent fluorinated substituents (EFS) onto heterocycles. In this context, fluoroalkyl amino reagents (FARs)-a class of chemicals that was slightly forgotten over the last decades-has emerged again recently and proved to be a powerful tool for the introduction of various fluorinated groups onto (hetero)aromatic derivatives.

Direct synthesis of aqueous quantum dots through 4,4'-bipyridine-based twin ligand strategy.

Science.gov (United States)

Kalita, Mausam; Cingarapu, Sreeram; Roy, Santanu; Park, Seok Chan; Higgins, Daniel; Jankowiak, Ryszard; Chikan, Viktor; Klabunde, Kenneth J; Bossmann, Stefan H

2012-04-16

We report a new class of derivatized 4,4'-bipyridinium ligands for use in synthesizing highly fluorescent, extremely stable, water-soluble CdSe and CdTe quantum dots (QDs) for bioconjugation. We employed an evaporation-condensation technique, also known as solvated metal atom dispersion (SMAD), followed by a digestive ripening procedure. This method has been used to synthesize both metal nanoparticles and semiconductors in the gram scale with several stabilizing ligands in various solvents. The SMAD technique comprised evaporation condensation and stabilization of CdSe or CdTe in tetrahydrofuran. The as-prepared product was then digestively ripened in both water and dimethyl formamide, leading to narrowing of the particle size distributions. The ligands were synthesized by nucleophilic substitution (S(N)2) reactions using 4,4'-bipyridine as a nucleophile. Confocal microscopy images revealed the orange color of the nanocrystalline QDs with diameters of ~5 nm. The size has been confirmed by using transmission electron microscopy. As a part of our strategy, 85% of the 4,4'-bipyridinium salt was synthesized as propionic acid derivative and used to both stabilize the QDs in water and label basic amino acids and different biomarkers utilizing the carboxylic acid functional group. Fifteen percent of the 4,4'-bipyridinium salt was synthesized as N-propyl maleimide and used as a second ligand to label any protein containing the amino acid cysteine by means of a 1,4-Michael addition. © 2012 American Chemical Society

Thermally Stable Heterocyclic Imines as New Potential Nonlinear Optical Materials

Science.gov (United States)

Nesterov, Volodymyr V.; Antipin, Mikhail Y.; Nesterov, Vladimir N.; Moore, Craig E.; Cardelino, Beatriz H.; Timofeeva, Tatiana V.

2004-01-01

In the course of a search for new thermostable acentric nonlinear optical crystalline materials, several heterocyclic imine derivatives were designed, with the general structure D-pi-A(D'). Introduction of a donor amino group (D') into the acceptor moiety was expected to bring H-bonds into their crystal structures, and so to elevate their melting points and assist in an acentric molecular packing. Six heterocycle-containing compounds of this type were prepared, single crystals were grown for five of them, and these crystals were characterized by X-ray analysis. A significant melting temperature elevation was found for all of the synthesized compounds. Three of the compounds were also found to crystallize in acentric space groups. One of the acentric compounds is built as a three-dimensional H-bonded molecular network. In the other two compounds, with very similar molecular structure, the molecules form one-dimensional H-bonded head-to-head associates (chains). These chains are parallel in two different crystallographic directions and form very unusual interpenetrating chain patterns in an acentric crystal. Two of the compounds crystallized with centrosymmetric molecular packing.

Analysis of heterocyclic amines in hair by on-line in-tube solid-phase microextraction coupled with liquid chromatography−tandem mass spectrometry

International Nuclear Information System (INIS)

Kataoka, Hiroyuki; Inoue, Tsutomu; Saito, Keita; Kato, Hisato; Masuda, Kazufumi

2013-01-01

Graphical abstract: Mutagenic and carcinogenic heterocyclic amines are accumulated in the hair of smoker. -- Highlights: •On-line in-tube solid-phase microextraction of heterocyclic amines was optimized. •Fourteen heterocyclic amines were simultaneously determined by LC–MS/MS. •Pico gram levels of heterocyclic amines could be easily analyzed within 15 min. •Heterocyclic amines could be quantitatively analyzed from several milligrams of hair. •The method is useful for the assessment of long-term exposure to heterocyclic amines. -- Abstract: Mutagenic and carcinogenic heterocyclic amines (HCAs) are formed during heating of various proteinaceous foods, but human exposure to HCAs has not yet been elucidated in detail. To assess long-term exposure to HCAs, we developed a simple and sensitive method for measuring HCAs in hair by automated on-line in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS). Using a Zorbax Eclipse XDB-C8 column, 16 HCAs were analyzed within 15 min. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL sample at a flow rate of 200 μL min −1 using a Supel-Q PLOT capillary column as an extraction device. The extracted HCAs were easily desorbed from the column by passage of the mobile phase, with no carryover observed. This in-tube SPME LC–MS/MS method showed good linearity for HCAs in the range of 10–2000 pg mL −1 , with correlation coefficients above 0.9989 (n = 18), using stable isotope-labeled HCA internal standards. The detection limits (S/N = 3) of 14 HCAs except for MeAαC and Glu-P-1 were 0.10–0.79 pg mL −1 . This method was successfully utilized to analyze 14 HCAs in hair samples without any interference peaks, with quantitative limits (S/N = 10) of about 0.17–1.32 pg mg −1 hair. Using this method, we evaluated the exposure to HCAs in cigarette smoke and the suitability of using hair HCAs as exposure biomarkers

Recent advances in the research of heterocyclic compounds as antitubercular agents.

Science.gov (United States)

Yan, Mi; Ma, Shutao

2012-12-01

Tuberculosis (TB) is a major health problem, with approximately one-third of the world's population infected with Mycobacterium tuberculosis, eight million people in the active disease state, and two million dying annually. Furthermore, the prevalence of TB/HIV co-infection, and the emergence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) have further aggravated the spread of this disease and thus mortality by it. There is an urgent need for novel antitubercular agents with improved properties, such as lower toxicity, shortened duration of therapy, rapid bactericidal action, and enhanced activity against MDR strains. Fortunately, a number of new potential antitubercular candidate drugs with heterocyclic rings, which are most likely to be effective against resistant strains, have entered clinical trials in recent years. This review highlights recent advances in the research of novel heterocyclic compounds, with particular focus on their antimycobacterial activity, mechanisms of action, toxicity, and structure-activity relationships (SARs). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Natural bond orbital analysis of molecular interactions: Theoretical study of W(CO)5 complexes with E(PH3)2 and NHEMe ligands (E=C, Si, Ge, Sn, Pb)

International Nuclear Information System (INIS)

Nguyen Thi Ai Nhung; Huynh Thi Phuong Loan; Duong Tuan Quang; Pham Van Tat

2014-01-01

The complexes with ligands carbodiphosphorane-analogues (called tetrylones) [(CO) 5 W-{E(PH 3 ) 2 }] (W5-EP 2 ) and N-heterocyclic carbene-analogues (called tetrylenes) [(CO) 5 W-{NHE Me }] (W5-NHE Me ) when E=C-Pb have been studied using natural bond orbital (NBO) method. The NBO analysis provides a consistent picture of the chemical bonding is two entire families of transition metal complexes of tetrylone and tetrylene ligands in term of donor-acceptor interactions, showing the correlation of these interactions with Wiberg bond indies (WBI), natural partial charges, and the energetically highest lying occupied molecular orbitals for σ and π orbitals of free ligands E(PH 3 ) 2 and NHE Me . Analysis of the bonding situation reveals that in E(PH 3 ) 2 and NHE Me ligands, the energy level of the π orbital rises, whereas that of the σ orbital decreases as atom E becomes heavier. The complexes with head-on-bonded ligands have (CO) 5 W←E donation which comes from the σ-lone-pair orbital of E(PH 3 ) 2 and NHE Me where E=C for tetrylones and E=C, Si, Ge for tetrylenes, whereas the (CO) 5 W←E donation in the side-on bonded complexes when E becomes heavier arises from the π-lone-pair orbital of E(PH 3 ) 2 and NHE Me ligands which is the HOMO of the free ligands. This makes the heavier adducts of tetrylones and tetrylenes become stronger donors than the lighter systems. The NBO analysis suggests that the E(PH 3 ) 2 ligands are strong σ-donors and strong π-acceptors while the NHE Me ligands are strong σ-donors and weak π-acceptors. This is possible for tetrylones that have two lone-pair orbitals available for donation, whereas the tetrylenes have only one lone-pair orbital available for donation. (author)

Development and validation of method for heterocyclic compounds in wine: optimization of HS-SPME conditions applying a response surface methodology.

Science.gov (United States)

Burin, Vívian Maria; Marchand, Stéphanie; de Revel, Gilles; Bordignon-Luiz, Marilde T

2013-12-15

Considering the importance of the heterocyclic compounds in terms of wine flavor, this study aims to propose a new rapid and solvent free method to quantify different classes of heterocyclic compounds, such as furans, thiophenes, thiazols and pyrazines, which are products of the Maillard reaction, in wines. The use of a central composite design and the response surface methodology to determine the best conditions allows the optimum combination of analytical variables (pH, NaCl and extraction time) to be identified. The validation was carried out using several types of wine as matrices. The method shows satisfactory repeatability (2.7%heterocyclic compounds were determined, mainly for red wines. © 2013 Elsevier B.V. All rights reserved.

Biotransformation of heterocyclic dinitriles by Rhodococcus erythropolis and fungal nitrilases

Czech Academy of Sciences Publication Activity Database

Vejvoda, Vojtěch; Šveda, Ondřej; Kaplan, Ondřej; Přikrylová, Věra; Elišáková, Veronika; Himl, Michal; Kubáč, David; Pelantová, Helena; Kuzma, Marek; Křen, Vladimír; Martínková, Ludmila

2007-01-01

Roč. 29, č. 7 (2007), s. 1119-1124 ISSN 0141-5492 R&D Projects: GA AV ČR IAA500200708; GA MŠk LC06010; GA MŠk OC D25.001 Institutional research plan: CEZ:AV0Z50200510 Keywords : amidase * arpegillus nniger * heterocyclic Subject RIV: EE - Microbiology, Virology Impact factor: 1.222, year: 2007

Prediction model of biocrude yield and nitrogen heterocyclic compounds analysis by hydrothermal liquefaction of microalgae with model compounds.

Science.gov (United States)

Sheng, Lili; Wang, Xin; Yang, Xiaoyi

2018-01-01

The model of biocrude yield and the nitrogen heterocyclic compounds in biocrude of microalgae hydrothermal liquefaction are two of the most concerned issues in this field at present. This study explored a hydrothermal liquefaction biocrude yield model involved in the interaction among biochemical compounds in microalgae and analysed nitrogen heterocyclic compounds in biocrude. The model compound (castor oil, soya protein and glucose) and Nanochloropsis were liquefied at 280°C for 1h. The products were analyzed by GC-MS, element analysis and FTIR. The results suggested that interactions among different components in microalgae enhanced biocrude yield. The biocrude yield prediction model involved cross-interactions performed more accurate than previous models.When the ratio of protein and carbohydrate around 3, the cross-interaction and nitrogen heterocyclic compounds in biocrude would both reach the highest extent. Copyright © 2017. Published by Elsevier Ltd.

Some regularities in formation and solvent extraction of complexes in metal-salicylic acid or its derivative- organic base systems

International Nuclear Information System (INIS)

Alimarin, I.P.; Fadeeva, V.I.; Tikhomirova, T.I.

1982-01-01

The influence of concentrations of the reagents, pH and solvent on the conditions for the formation and extraction of Sc, Ti, Zr, Hf, Th complexes has been examined in salicylic acid (H 2 Sal)-heterocyclic amine systems. The extraction chemism and factors, which affect the reactions between the metal ions and the ligands, are discussed. It has been shown that Zr, Hf, Ti form species of ion associate type, Sc and Th form different-ligand complexes under conditions for interphase equilibrium in a Me-H 2 Sal-heterocyclic amine system

Discovery of peroxisome proliferator-activated receptor α (PPARα) activators with a ligand-screening system using a human PPARα-expressing cell line.

Science.gov (United States)

Tachibana, Keisuke; Yuzuriha, Tomohiro; Tabata, Ryotaro; Fukuda, Syohei; Maegawa, Takashi; Takahashi, Rika; Tanimoto, Keiichi; Tsujino, Hirofumi; Nunomura, Kazuto; Lin, Bangzhong; Matsuura, Yoshiharu; Tanaka, Toshiya; Hamakubo, Takao; Sakai, Juro Js; Kodama, Tatsuhiko; Kobayashi, Tadayuki; Ishimoto, Kenji; Miyachi, Hiroyuki; Doi, Takefumi

2018-05-15

Peroxisome proliferator-activated receptor alpha (PPARα) is a ligand-activated transcription factor that belongs to the superfamily of nuclear hormone receptors. PPARα is mainly expressed in the liver, where it activates fatty acid oxidation and lipoprotein metabolism and improves plasma lipid profiles. Therefore, PPARα activators are often used to treat patients with dyslipidemia. To discover additional PPARα activators as potential compounds for use in hypolipidemic drugs, here we established human hepatoblastoma cell lines with luciferase reporter expression from the promoters containing peroxisome proliferator responsive elements (PPRE) and tetracycline-regulated expression of full-length human PPARα to quantify the effects of chemical ligands on PPARα activity. Using the established cell-based PPARα-activator screening system to screen a library of > 12,000 chemical compounds, we identified several hit compounds with basic chemical skeletons different from those of known PPARα agonists. One of the hit compounds, a 1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid derivative we termed compound 3, selectively up-regulated PPARα transcriptional activity, leading to PPARα target gene expression both in vitro and in vivo. Of note, the half-maximal effective concentrations of the hit compounds were lower than that of the known PPARα ligand fenofibrate. Finally, fenofibrate or compound 3 treatment of high fructose-fed rats having elevated plasma triglyceride levels for 14 days indicated that compound 3 reduces plasma triglyceride levels with similar efficiency as fenofibrate. These observations raise the possibility that 1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid derivatives might be effective drug candidates for selective targeting of PPARα to manage dyslipidemia. Published under license by The American Society for Biochemistry and Molecular Biology, Inc.

Abiotic synthesis of purines and other heterocyclic compounds by the action of electrical discharges

Science.gov (United States)

Yuasa, S.; Flory, D.; Basile, B.; Oro, J.

1984-01-01

The synthesis of purines and pyrimidines using Oparin-Urey-type primitive earth atmospheres has been demonstrated by reacting methane, ethane, and ammonia in electrical discharges. Adenine, guaine, 4-aminoimidazole-5-carboxamide (AICA), and isocytosine have been identified by UV spectrometry and paper chromatography as the products of the reaction. The total yields of the identified heterocyclic compounds are 0.0023 percent. It is concluded that adenine synthesis occurs at a much lower concentration of hydrogen cyanide than has been shown by earlier studies. Pathways for the synthesis of purines from hydrogen cyanide are discussed, and a comparison of the heterocyclic compounds that have been identified in meteorites and in prebiotic reactions is presented.

Synthesis and characterization of carboxylic acid functionalized silicon nanoparticles

Science.gov (United States)

Shaner, Ted V.

Silicon nanoparticles are of great interest in a great number of fields. Silicon nanoparticles show great promise particularly in the field of bioimaging. Carboxylic acid functionalized silicon nanoparticles have the ability to covalently bond to biomolecules through the conjugation of the carboxylic acid to an amine functionalized biomolecule. This thesis explores the synthesis of silicon nanoparticles functionalized by both carboxylic acids and alkenes and their carboxylic acid functionality. Also discussed is the characterization of the silicon nanoparticles by the use of x-ray spectroscopy. Finally, the nature of the Si-H bond that is observed on the surface of the silicon nanoparticles will be investigated using photoassisted exciton mediated hydrosilation reactions. The silicon nanoparticles are synthesized from both carboxylic acids and alkenes. However, the lack of solubility of diacids is a significant barrier to carboxylic acid functionalization by a mixture of monoacids and diacids. A synthesis route to overcome this obstacle is to synthesize silicon nanoparticles with terminal vinyl group. This terminal vinyl group is distal to the surface of the silicon nanoparticle. The conversion of the vinyl group to a carboxylic acid is accomplished by oxidative cleavage using ozonolysis. The carboxylic acid functionalized silicon nanoparticles were then successfully conjugated to amine functionalized DNA strand through an n-hydroxy succinimide ester activation step, which promotes the formation of the amide bond. Conjugation was characterized by TEM and polyacrylamide gel electrophoresis (PAGE). The PAGE results show that the silicon nanoparticle conjugates move slower through the polyacrylamide gel, resulting in a significant separation from the nonconjugated DNA. The silicon nanoparticles were then characterized by the use of x-ray absorption near edge spectroscopy (Xanes) and x-ray photoelectron spectroscopy (XPS) to investigate the bonding and chemical

Unusual metal-ligand charge transfer in ferrocene functionalized μ{sub 3}-O iron carboxylates observed with Mössbauer spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Mereacre, Valeriu, E-mail: valeriu.mereacre@kit.edu [Institut für Anorganische Chemie, Karlsruher Institut für Technologie, D-76131 Karlsruhe (Germany); Schlageter, Martin; Eichhöfer, Andreas [Institut für Nanotechnologie, Karlsruher Institut für Technologie, D-76344 Eggenstein-Leopoldshafen (Germany); Bauer, Thomas; Wolny, Juliusz A.; Schünemann, Volker [Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern (Germany); Powell, Annie K., E-mail: annie.powell@kit.edu [Institut für Anorganische Chemie, Karlsruher Institut für Technologie, D-76131 Karlsruhe (Germany); Institut für Nanotechnologie, Karlsruher Institut für Technologie, D-76344 Eggenstein-Leopoldshafen (Germany)

2016-06-01

Temperature dependent Mössbauer studies of two ferrocenecarboxylate functionalized {Fe_3O} complexes in solid state are reported. It was found that conjugation of ferrocene ring orbitals with the π orbitals of the adjacent carboxylic group promotes a shift of electron density from the ferrocene Fe{sup II} ion to the cyclopentadienide rings with π-orbital character giving rise to a new type of mixed-valence compound. - Highlights: • In this manuscript we describe a mechanism of electron density shift which stabilizes the trapped mixed-valence state. • The coexistence of ferrocene and ferrocenium in solid state was determined. • A mixed-valence state at room-temperature and a thermally induced electron transfer with gradual interconversion were observed.

Secbase: database module to retrieve secondary structure elements with ligand binding motifs.

Science.gov (United States)

Koch, Oliver; Cole, Jason; Block, Peter; Klebe, Gerhard

2009-10-01

Secbase is presented as a novel extension module of Relibase. It integrates the information about secondary structure elements into the retrieval facilities of Relibase. The data are accessible via the extended Relibase user interface, and integrated retrieval queries can be addressed using an extended version of Reliscript. The primary information about alpha-helices and beta-sheets is used as provided by the PDB. Furthermore, a uniform classification of all turn families, based on recent clustering methods, and a new helix assignment that is based on this turn classification has been included. Algorithms to analyze the geometric features of helices and beta-strands were also implemented. To demonstrate the performance of the Secbase implementation, some application examples are given. They provide new insights into the involvement of secondary structure elements in ligand binding. A survey of water molecules detected next to the N-terminus of helices is analyzed to show their involvement in ligand binding. Additionally, the parallel oriented NH groups at the alpha-helix N-termini provide special binding motifs to bind particular ligand functional groups with two adjacent oxygen atoms, e.g., as found in negatively charged carboxylate or phosphate groups, respectively. The present study also shows that the specific structure of the first turn of alpha-helices provides a suitable explanation for stabilizing charged structures. The magnitude of the overall helix macrodipole seems to have no or only a minor influence on binding. Furthermore, an overview of the involvement of secondary structure elements with the recognition of some important endogenous ligands such as cofactors shows some distinct preference for particular binding motifs and amino acids.

Componentes voláteis do café torrado. Parte I: compostos heterocíclicos Volatile components in roasted coffee. Part I: heterocyclic compounds

Directory of Open Access Journals (Sweden)

Carlos Alberto Bastos De Maria

1999-04-01

Full Text Available A review of heterocyclic compounds in roasted coffee is presented. The contents, precursors and sensorial properties of furans, pyrroles, oxazoles, thiazoles, thiophenes, pyrazines and pyridines are discussed. The impact heterocyclic compounds of coffee aroma are described.

Synthesis, spectroscopic characterization, solid state d.c. electrical conductivity and biological studies of some lanthanide(III chloride complexes with a heterocyclic Schiff base ligand

Directory of Open Access Journals (Sweden)

K. Mohanan

2016-07-01

Full Text Available Condensation of 2-hydroxy-1-naphthaldehyde with 2-amino-3-carboxyethyl-4,5-dimethylthiophene in 1:1 molar ratio, yielded a potentially tridentate Schiff base viz. 2-[N-(2′-hydroxy-1-naphthylideneamino]-3-carboxyethyl-4,5-dimethylthiophene (HNAT. This ligand formed complexes with lanthanum(III, cerium(III, praseodymium(III, neodymium(III, samarium(III, europium(III and gadolinium(III chloride under well defined conditions. These complexes were characterized through elemental analysis, molar conductance, magnetic moment measurements, IR, UV–Vis, FAB mass and 1H NMR spectral studies. Analytical data showed that all the metal complexes exhibited 1:1 metal–ligand ratio. Molar conductance values adequately confirmed the non-electrolytic nature of the metal complexes. The proton NMR spectral observations supplement the IR spectral assignments. The spectral data revealed that the ligand acted as neutral tridentate, coordinating to the metal ion through azomethine nitrogen, ester carbonyl and naphtholate oxygen without deprotonation. The ligand and its lanthanum(III chloride complex were subjected to XRD studies. The lanthanum(III chloride complex has undergone a facile transesterification reaction. The solid state d.c. electrical conductivity of some selected complexes were measured as a function of temperature, indicating the semiconducting nature of the metal complexes. The antimicrobial activities were examined by disk diffusion method against some pathogenic bacterial and fungal species.

Adsorption of UO2+2 by polyethylene adsorbents with amidoxime, carboxyl, and amidoxime/carboxyl group

International Nuclear Information System (INIS)

Choi, Seong-Ho; Nho, Young Chang

2000-01-01

The polyethylene (PE) adsorbents were prepared by a radiation-induced grafting of acrylonitrile (AN), acrylic acid (AA), and the mixture of AN/AA onto PE film, and by subsequent amidoximation of cyano groups of poly-AN graft chains. With an increase of AA composition in AN/AA monomer mixture, the water uptake of the grafted polyethylene film increased. In AN/AA mixture, the maximum adsorption of UO 2+ 2 was observed in the adsorbent with a ratio of AN/AA (50/50, mol%) in copolymer. The amidoxime, carboxyl, and amidoxime/carboxyl groups onto PE acted as a chelating site for the selected UO 2+ 2 . The complex structure of polyethylene with three functional groups and UO 2+ 2 was confirmed by Fourier Transform Infrared (FTIR) spectroscopy. (author)

Polar and non-polar heterocyclic amines in cooked fish and meat products and their corresponding pan residues.

Science.gov (United States)

Skog, K; Augustsson, K; Steineck, G; Stenberg, M; Jägerstad, M

1997-06-01

Fourteen cooked dishes with their corresponding pan residues were analysed for polar and non-polar heterocyclic amines using HPLC. The choice of foods, including beef, pork, poultry, game, fish, egg and sausages, was based on an investigation of an elderly population in Stockholm participating in an analytical epidemiological case-control study on cancer risks after intake of heterocyclic amines. The food items were prepared using normal household cooking practices, and to reflect the wide range of surface browning of the cooked dishes that would be encountered in this population, four cooking temperatures were used in the range 150-225 degrees C. For all food samples, the total amount of heterocyclic amines formed at 150 degrees C was less than 1 ng/g cooked product, and at 175 degrees C less than 2 ng/g. The highest concentrations of heterocyclic amines were detected in fillet of pork, reindeer meat and chicken breast fried at 200 and 225 degrees C and their corresponding pan residues. The total sum of 2-amino-3,8-dimethylimidazo-[4,5-f]quinoxaline, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine was about 1 microgram per 100 g portion (including pan residues) for reindeer meat and chicken breast, and between 1.9 and 6.3 micrograms per 100-g portion for fillet of pork. PhIP was the most abundant heterocyclic amine, identified in 73 of 84 samples, and the highest concentration of PhIP, 32.0 ng/g, was found in the pan residue from fillet of pork cooked at 225 degrees C. The non-polar heterocyclic amines 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole and 3-amino-1-methyl-5H-pyrido[4,3-b]indole were detected in the range of 0.5-7.4 ng/g in most foods cooked at 225 degrees C, and also in meat sauce prepared at 200 and 175 degrees C. The other heterocyclic amines tested for: 2-amino-3-methylimidazo-[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, 2-amino-6-methyl-pyrido-[1,2-a:3',2'-d]-imidazole and 2

Quantum-chemical investigation of the 1,2-proton shift in protonated five-membered aromatic heterocycles

International Nuclear Information System (INIS)

Abronin, I.A.; Gorb, L.G.; Litvinov, V.P.

1985-01-01

Calculations of the energetics of the 1,2-proton shift in protonated five-membered aromatic heterocycles - pyrrole, furan, and thiophene - have been carried out by the SCF MO LCAO method in the MINDO/3 approximation and nonempirically on the OST-3GF (OST-3GF) basis. The general features of this process, and also the influence of solvation and of taking into account the vacant d-AOs of the sulfur atom in the protonated form of thiophene on the results of the calculation are considered. The results obtained have been used for a discussion of the activity and selectivity of the heterocycles considered in aromatic electrophilic substitution reactions

Greener Synthesis of N-Heterocycles via Sustainable Applications of Nano-Catalysts

Science.gov (United States)

A brief historic account of reactions involving microwave (MW) exposure of neat reactants or catalysis by mineral surfaces, such as alumina, silica, clay, or their ‘doped’ versions, for the rapid one-pot assembly of heterocyclic compounds from in situ generated reactive intermedi...

Reaction of vanadocene and its monochloride with salts of nitrogen-containing heterocycles

International Nuclear Information System (INIS)

Gordetsov, A.S.; Pereshein, V.V.; Lyatyaeva, V.N.; Mar'in, V.P.; Rukevich, OS.; Zakharova, E.S.

1985-01-01

The reaction of bis(eta 5 -cyclopentadienyl) vanadium (Cp 2 V) and its monochloride with diallyl isocyanurates of Ag and alkali metals and with Ag salt of succinimide is used for preparing almost inaccessible Cp 2 V-substituted nitrogen-containing heterocycles. The reactions have been performed in toluene in an evacuated ampoule at room temperature and at 120-130 deg C in case of diallyl isocyanurates of alkali metals. Reaction yields element analysis data, DTA, IR spectra and ESR spectra. Cp 2 V easily reduces Ag from its salts with nitrogen-containing heterocycles oxidizing with production of V(3) sandwich derivatives In exchange reactions of Cp 2 VCl with diallyl isocyanurate salts of alkali metals and silver Cp 2 V-diallyl isocyanurate with an oxo-structure is prosduced as well. The produced AgCl subsequently oxidizers Cp 2 VCl up to Cp 2 VCl 2

Converging ligand-binding free energies obtained with free-energy perturbations at the quantum mechanical level.

Science.gov (United States)

Olsson, Martin A; Söderhjelm, Pär; Ryde, Ulf

2016-06-30

In this article, the convergence of quantum mechanical (QM) free-energy simulations based on molecular dynamics simulations at the molecular mechanics (MM) level has been investigated. We have estimated relative free energies for the binding of nine cyclic carboxylate ligands to the octa-acid deep-cavity host, including the host, the ligand, and all water molecules within 4.5 Å of the ligand in the QM calculations (158-224 atoms). We use single-step exponential averaging (ssEA) and the non-Boltzmann Bennett acceptance ratio (NBB) methods to estimate QM/MM free energy with the semi-empirical PM6-DH2X method, both based on interaction energies. We show that ssEA with cumulant expansion gives a better convergence and uses half as many QM calculations as NBB, although the two methods give consistent results. With 720,000 QM calculations per transformation, QM/MM free-energy estimates with a precision of 1 kJ/mol can be obtained for all eight relative energies with ssEA, showing that this approach can be used to calculate converged QM/MM binding free energies for realistic systems and large QM partitions. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

Uranium (IV) carboxylates - I

Energy Technology Data Exchange (ETDEWEB)

Satpathy, K C; Patnaik, A K [Sambalpur Univ. (India). Dept. of Chemistry

1975-11-01

A few uranium(IV) carboxylates with monochloro and trichloro acetic acid, glycine, malic, citric, adipic, o-toluic, anthranilic and salicylic acids have been prepared by photolytic methods. The I.R. spectra of these compounds are recorded and basing on the spectral data, structure of the compounds have been suggested.

Sorption of Heterocyclic Organic Compounds to Multiwalled Carbon Nanotubes.

Science.gov (United States)

Metzelder, Florian; Funck, Matin; Schmidt, Torsten C

2018-01-16

Sorption is an important natural and technical process. Sorption coefficients are typically determined in batch experiments, but this may be challenging for weakly sorbing compounds. An alternative method enabling analysis of those compounds is column chromatography. A column packed with the sorbent is used and sorption data are determined by relating sorbate retention to that of a nonretarded tracer. In this study, column chromatography was applied for the first time to study sorption of previously hardly investigated heterocyclic organic compounds to multiwalled carbon nanotubes (MWCNTs). Sorption data for these compounds are very limited in literature, and weak sorption is expected from predictions. Deuterium oxide was used as nonretarded tracer. Sorption isotherms were well described by the Freundlich model and data showed reasonable agreement with predicted values. Sorption was exothermic and physisorption was observed. H-bonding may contribute to overall sorption, which is supported by reduced sorption with increasing ionic strength due to blocking of functional groups. Lowering pH reduced sorption of ionizable compounds, due to electrostatic repulsion at pH 3 where sorbent as well as sorbates were positively charged. Overall, column chromatography was successfully used to study sorption of heterocyclic compounds to MWCNTs and could be applied for other carbon-based sorbents.

Ru(II)-Catalyzed Oxidative Heck-Type Olefination of Aromatic Carboxylic Acids with Styrenes through Carboxylate-Assisted C-H Bond Activation.

Science.gov (United States)

Dana, Suman; Mandal, Anup; Sahoo, Harekrishna; Mallik, Sumitava; Grandhi, Gowri Sankar; Baidya, Mahiuddin

2018-02-02

A straightforward synthesis of 2-styrylbenzoic acids from aryl carboxylic acids is disclosed through a carboxylate-assisted coupling under Ru(II) catalysis. This protocol is simple and exhibits broad scope with high tolerance of common organic functional groups, providing good to excellent yields of diverse olefinated products. The efficacy of this protocol has been showcased through sequential syntheses of isochromanone, isocoumarin, and formal synthesis of anacardic acid derivative in good yields.

Pd(II)/Bipyridine-Catalyzed Conjugate Addition of Arylboronic Acids to α,β-Unsaturated Carboxylic Acids. Synthesis of β-Quaternary Carbons Substituted Carboxylic Acids.

Science.gov (United States)

Liu, Rui; Yang, Zhenyu; Ni, Yuxin; Song, Kaixuan; Shen, Kai; Lin, Shaohui; Pan, Qinmin

2017-08-04

Pd(II)/bipyridine-catalyzed conjugate addition of arylboronic acids to α,β-unsaturated carboxylic acids (including β,β-disubstituted acrylic acids) was developed and optimized, which provided a mild and convenient method for the highly challenging synthesis of β-quaternary carbons substituted carboxylic acids.

Radiolabeled derivatives of folic acid

International Nuclear Information System (INIS)

1980-01-01

Derivatives of folic acid are described, in which the α-carboxyl group is substituted with an amino compound having an aromatic or heterocyclic ring substituent which is capable of being radiolabelled. Particularly mentioned as a radiolabel is 125 I. (author)

Biochemical interpretation of quantitative structure-activity relationships (QSAR) for biodegradation of N-heterocycles: a complementary approach to predict biodegradability.

Science.gov (United States)

Philipp, Bodo; Hoff, Malte; Germa, Florence; Schink, Bernhard; Beimborn, Dieter; Mersch-Sundermann, Volker

2007-02-15

Prediction of the biodegradability of organic compounds is an ecologically desirable and economically feasible tool for estimating the environmental fate of chemicals. We combined quantitative structure-activity relationships (QSAR) with the systematic collection of biochemical knowledge to establish rules for the prediction of aerobic biodegradation of N-heterocycles. Validated biodegradation data of 194 N-heterocyclic compounds were analyzed using the MULTICASE-method which delivered two QSAR models based on 17 activating (OSAR 1) and on 16 inactivating molecular fragments (GSAR 2), which were statistically significantly linked to efficient or poor biodegradability, respectively. The percentages of correct classifications were over 99% for both models, and cross-validation resulted in 67.9% (GSAR 1) and 70.4% (OSAR 2) correct predictions. Biochemical interpretation of the activating and inactivating characteristics of the molecular fragments delivered plausible mechanistic interpretations and enabled us to establish the following biodegradation rules: (1) Target sites for amidohydrolases and for cytochrome P450 monooxygenases enhance biodegradation of nonaromatic N-heterocycles. (2) Target sites for molybdenum hydroxylases enhance biodegradation of aromatic N-heterocycles. (3) Target sites for hydratation by an urocanase-like mechanism enhance biodegradation of imidazoles. Our complementary approach represents a feasible strategy for generating concrete rules for the prediction of biodegradability of organic compounds.

Two-dimensional inorganic–organic hybrid semiconductors composed of double-layered ZnS and monoamines with aromatic and heterocyclic aliphatic rings: Syntheses, structures, and properties

Energy Technology Data Exchange (ETDEWEB)

Wang, Sujing; Li, Jing, E-mail: jingli@rutgers.edu

2015-04-15

As an addition to the II–VI based inorganic–organic hybrid semiconductor family, five new two-dimensional (2D) double-layered structures have been synthesized employing monoamines with different aromatic or heterocyclic aliphatic rings. Zn{sub 2}S{sub 2}(bza) (1), Zn{sub 2}S{sub 2}(mbza) (2), Zn{sub 2}S{sub 2}(fbza) (3), Zn{sub 2}S{sub 2}(pca) (4), and Zn{sub 2}S{sub 2}(thfa) (5) (bza=benzylamine, mbza=4-methoxybenzylamine, fbza=4-flurobenzylamine, pca=3-picolylamine, and thfa=tetrahydrofurfurylamine) are prepared by solvothermal reactions and characterized by different analytical methods, including powder X-ray diffraction, optical diffuse reflection, thermogravimetric analysis and photoluminescence spectroscopy. The powder X-ray diffraction patterns show that all five compounds adopt 2D double-layered structures. Optical diffuse reflectance spectra of these compounds suggest that they have notably lower band gaps than those of the similar compounds composed of aliphatic alkyl amines. Their photoluminescence properties and thermal stability are also analyzed. - Graphical abstract: Five new members of two-dimensional double-layered 2D-Zn{sub 2}S{sub 2}(L) (L=Ligand) structures employing monoamines with different aromatic or heterocyclic aliphatic rings have been designed, synthesized, and characterized. - Highlights: • A new sub-family of II-VI based hybrid semiconductors are designed, synthesized, and structurally characterized using amines with aromatic or aliphatic cyclic rings. • These compounds have notably lower band gaps than those made of aliphatic alkyl amines, greatly broadening the range of band gaps of this material family. • They emit strongly with systematically tunable emission intensity and energy.

Conductive Supramolecular Architecture Constructed from Polyoxovanadate Cluster and Heterocyclic Surfactant

Directory of Open Access Journals (Sweden)

Toshiyuki Misawa

2018-01-01

Full Text Available Proton-conductive solid electrolytes are significant for fuel-cell battery technology. Especially for use in motor vehicles, proton conductors which work at intermediate temperatures (373–673 K under an anhydrous atmosphere are desired to improve the fuel cell stability and efficiency. Inorganic–organic hybrid supramolecular architectures are a promising option for the realization of highly conductive proton conductors. Here, a hybrid layered crystal was synthesized for the first time by using an proton-containing decavanadate (V10 anion and a heterocyclic surfactant cation. A simple ion-exchange reaction led to the formation of an inorganic–organic hybrid of V10 by using dodecylpyridazinium (C12pda as the heterocyclic surfactant. Single crystal X-ray analyses revealed that four C12pda cations were associated with one V10 anion, which was a diprotonated species forming a one-dimensional infinite chain structure through hydrogen bonds. Anhydrous proton conductivity was investigated by alternating current (AC impedance spectroscopy in the range of 313–393 K, exhibiting a maximum value of 1.7 × 10−5 S cm−1 at 373 K.

Effects of Mutations and Ligands on the Thermostability of the l-Arginine/Agmatine Antiporter AdiC and Deduced Insights into Ligand-Binding of Human l-Type Amino Acid Transporters.

Science.gov (United States)

Ilgü, Hüseyin; Jeckelmann, Jean-Marc; Colas, Claire; Ucurum, Zöhre; Schlessinger, Avner; Fotiadis, Dimitrios

2018-03-20

The l-arginine/agmatine transporter AdiC is a prokaryotic member of the SLC7 family, which enables pathogenic enterobacteria to survive the extremely acidic gastric environment. Wild-type AdiC from Escherichia coli, as well as its previously reported point mutants N22A and S26A, were overexpressed homologously and purified to homogeneity. A size-exclusion chromatography-based thermostability assay was used to determine the melting temperatures ( T m s) of the purified AdiC variants in the absence and presence of the selected ligands l-arginine (Arg), agmatine, l-arginine methyl ester, and l-arginine amide. The resulting T m s indicated stabilization of AdiC variants upon ligand binding, in which T m s and ligand binding affinities correlated positively. Considering results from this and previous studies, we revisited the role of AdiC residue S26 in Arg binding and proposed interactions of the α-carboxylate group of Arg exclusively with amide groups of the AdiC backbone. In the context of substrate binding in the human SLC7 family member l-type amino acid transporter-1 (LAT1; SLC7A5), an analogous role of S66 in LAT1 to S26 in AdiC is discussed based on homology modeling and amino acid sequence analysis. Finally, we propose a binding mechanism for l-amino acid substrates to LATs from the SLC7 family.

Inhibitory effects of pomegranate seed extract on the formation of heterocyclic aromatic amines in beef and chicken meatballs after cooking by four different methods.

Science.gov (United States)

Keşkekoğlu, Hasan; Uren, Ali

2014-04-01

Beef and chicken meatballs with a 0.5% (w/w) pomegranate seed extract were cooked using four different cooking methods (oven roasting, pan cooking, charcoal-barbecue, and deep-fat frying) and six heterocyclic aromatic amines; IQ, MeIQx, 4,8-DiMeIQx, PhIP, norharman, and harman were observed. In the beef meatballs, the highest inhibitory effects of pomegranate seed extract on heterocyclic aromatic amines formation were 68% for PhIP, 24% for norharman, 18% for harman, 45% for IQ, and 57% for MeIQx. Total heterocyclic aromatic amine formation was reduced by 39% and 46% in beef meatballs cooked by charcoal-barbecue and deep-fat frying, respectively. In the chicken meatballs, the highest inhibitory effects were 75% for PhIP, 57% for norharman, 28% for harman, 46% for IQ, and 49% for MeIQx. When the pomegranate seed extract was added to the chicken meatballs cooked by deep-fat frying, the total heterocyclic aromatic amine formation was inhibited by 49%, in contrast the total heterocyclic aromatic amine contents after oven roasting increased by 70%. Copyright © 2013 Elsevier Ltd. All rights reserved.

Spectroscopic Observation of Water-Mediated Deformation of the CARBOXYLATE-M2+ (M= Mg, Ca) Contact Ion Pair

Science.gov (United States)

Kelleher, Patrick J.; DePalma, Joseph W.; Johnson, Mark

2016-06-01

The binding of alkaline earth dications to the biologically relevant carboxylate ligand has previously been studied using vibrational sum frequency generation (VSFG) spectroscopy of the air-water interface, infrared multiple photon dissociation (IRMPD) spectroscopy of clusters, and DFT methods. These results suggest the presence of both monodentate and bidentate binding motifs of the M2+ ions to the cayboxyl head groups depending on the extent of solvation. We revisit these systems using vibrational predissociation spectroscopy to measure the gas-phase vibrational spectra of the D2-tagged microhydrated [MgOAc(H2O)n=1-5]+ and [CaOAc(H2O)n=1-6]+ clusters. The spectra show that [MgOAc(H2O)n]+ switches from bidentate to monodentate binding promptly at n = 5, while [CaOAc(H2O)n]+ retains its bidentate attachment such that the sixth water molecule initiates the second solvation shell. The difference in binding behavior between these two divalent metal ions is analyzed in the context of the local acidity of the solvent water molecules and the strength of the metal-carboxylate and metal-water interactions. This cluster study provides insight into the chemical physics underlying the unique and surprising impacts of Mg2+ and Ca2+ on the chemistry mediated by sea spray aerosols. Funding for this work was provided by the NSF's Center for Aerosol Impacts on Climate and the Environment.

Enaminone in heterocyclic synthesis: synthesis of new pyrazolopyrazole, pyrazolothienooxazine and pyrazolothienopyridine derivatives

International Nuclear Information System (INIS)

Hafiz, I.S.; Rahim, M.A.M.A.

2014-01-01

The chemical reactivity of enaminone 2 toward some nucleophilic and electrophilic reagents was investigated. Enaminone 2 was used as a key precursor for the synthesis of many important heterocyclic compounds. The synthesized compounds were characterized by IR, 1H-NMR, MS spectral and elemental analysis. (author)

Synthesis and Studies of Sulfur-Containing Heterocyclic Molecules for Molecular Electronics

DEFF Research Database (Denmark)

Mazzanti, Virginia

This work describes the synthesis and studies of sulfur containing π conjugated heterocycles, which are considered interesting motifs in the field of molecular electronics. The first project, which is covered in Chapter 1, concerns the functionalization of tetracycle dibenzo[bc,fg][1,4]dithiapent......This work describes the synthesis and studies of sulfur containing π conjugated heterocycles, which are considered interesting motifs in the field of molecular electronics. The first project, which is covered in Chapter 1, concerns the functionalization of tetracycle dibenzo[bc,fg][1......,4]dithiapentalene (DDP). Attempts to prepare the S-O analog are also discussed. Chapter 2, focuses upon the studies performed on DDP and other sulfur containing π conjugated organic molecules. Organic Field Effect Transistor devices were fabricated and their performances were evaluated. Chapter 3 entails...... the synthesis of dimeric structures of redox active system tetrathiafulvalene (TTF). Molecules with different conjugation pathways bridging two TTFs were synthesized and studied using CV and DPV in order to probe the electronic interaction between these two redox units. The last aspect of this thesis, which...

Towards an interpretation of the mechanism of the actinides(III)/lanthanides(III) separation by synergistic solvent extraction with nitrogen-containing polydendate ligands; Vers une interpretation des mecanismes de la separation actinides(III)/lanthanides(III) par extraction liquide-liquide synergique impliquant des ligands polyazotes

Energy Technology Data Exchange (ETDEWEB)

Francois, N [CEA/VALRHO - site de Marcoule, Dept. de Recherche en Retraitement et en Vitrification, (DRRV), 30 - Marcoule (France); Universite Henri Poincare, 54 - Vandoeuvre-les-Nancy (France)

2000-07-01

In the field of the separation of long-lived radionuclides from the wastes produced by nuclear fuel reprocessing, aromatic nitrogen-containing polydendate ligands are potential candidates for the selective extraction, alone or in synergistic mixture with acidic extractants, of trivalent actinides from trivalent lanthanides. The first part of this work deals with the complexation of trivalent f cations with various nitrogen-containing ligands (poly-pyridine analogues). Time-resolved laser-induced fluorimetry (TRLIF) and UV-visible spectrophotometry were used to determine the nature and evaluate the stability of each complex. Among the ligands studied, the least basic Me-Btp proved to be highly selective towards americium(III) in acidic solution. In the second part, two synergistic systems (nitrogen-containing polydendate ligand and lipophilic carboxylic acid) are studied and compared in regard to the extraction and separation of lanthanides(III) and actinides(III). TRLIF and gamma spectrometry allowed the nature of the extracted complexes and the optimal conditions of efficiency of both systems to be determined. Comparison between these different studies showed that the selectivity of complexation of trivalent f cations by a given nitrogen-containing polydendate ligand could not always be linked to the Am(III)Eu(III) selectivity reached in synergistic extraction. The latter depends on the 'balance' between the acid-basic properties on the one hand, and on the hard-soft characteristics on the other hand, of both components of synergistic system. (author)

Towards an interpretation of the mechanism of the actinides(III)/lanthanides(III) separation by synergistic solvent extraction with nitrogen-containing polydendate ligands; Vers une interpretation des mecanismes de la separation actinides(III)/lanthanides(III) par extraction liquide-liquide synergique impliquant des ligands polyazotes

Energy Technology Data Exchange (ETDEWEB)

Francois, N. [CEA/VALRHO - site de Marcoule, Dept. de Recherche en Retraitement et en Vitrification, (DRRV), 30 - Marcoule (France); Universite Henri Poincare, 54 - Vandoeuvre-les-Nancy (France)

2000-07-01

In the field of the separation of long-lived radionuclides from the wastes produced by nuclear fuel reprocessing, aromatic nitrogen-containing polydendate ligands are potential candidates for the selective extraction, alone or in synergistic mixture with acidic extractants, of trivalent actinides from trivalent lanthanides. The first part of this work deals with the complexation of trivalent f cations with various nitrogen-containing ligands (poly-pyridine analogues). Time-resolved laser-induced fluorimetry (TRLIF) and UV-visible spectrophotometry were used to determine the nature and evaluate the stability of each complex. Among the ligands studied, the least basic Me-Btp proved to be highly selective towards americium(III) in acidic solution. In the second part, two synergistic systems (nitrogen-containing polydendate ligand and lipophilic carboxylic acid) are studied and compared in regard to the extraction and separation of lanthanides(III) and actinides(III). TRLIF and gamma spectrometry allowed the nature of the extracted complexes and the optimal conditions of efficiency of both systems to be determined. Comparison between these different studies showed that the selectivity of complexation of trivalent f cations by a given nitrogen-containing polydendate ligand could not always be linked to the Am(III)Eu(III) selectivity reached in synergistic extraction. The latter depends on the 'balance' between the acid-basic properties on the one hand, and on the hard-soft characteristics on the other hand, of both components of synergistic system. (author)

Synthesis and Characterization of Divalent Manganese, Iron, and Cobalt Complexes in Tripodal Phenolate/N-Heterocyclic Carbene Ligand Environments

DEFF Research Database (Denmark)

Käß, Martina; Hohenberger, Johannes; Adelhardt, Mario

2014-01-01

. The complete ligand series offers a convenient way of tuning the electronic and steric environment around the metal center, thus, allowing for control of the complex’s reactivity. This series of divalent complexes of Mn, Fe, and Co was synthesized and characterized by 1H NMR, IR, and UV/vis spectroscopy...... as well as by single-crystal X-ray diffraction studies. Variable-temperature SQUID magnetization measurements in the range from 2 to 300 K confirmed high-spin ground states for all divalent complexes and revealed a trend of increasing zero-field splitting |D| from Mn(II), to Fe(II), to Co(II) complexes...

Microwave-Assisted Synthesis of Bio-Active Heterocycles and Fine Chemicals in Aqueous Media

Science.gov (United States)

Human health, especially in the aging population, mostly depends on various medicines, and researchers are combating against emerging diseases by new drug discovery. Heterocyclic compounds hold a special place among pharmaceutically active natural products as well as synthetic co...

Cyclopentadienyl molybdenum(II/VI) N-heterocyclic carbene complexes: Synthesis, structure, and reactivity under oxidative conditions

KAUST Repository

Li, Shenyu

2010-04-26

A series of N-heterocyclic carbene (NHC) complexes CpMo(CO) 2(NHC)X (NHC = IMe = 1,3-dimethylimidazol-2-ylidene, X = Br, 1; NHC = 1,3-dipropylimidazol-2-ylidene, X = Br, 2; NHC = IMes = 1,3-bis(2,4,6- trimethylphenyl)imidazol-2-ylidene, X = Br, 3; NHC = IBz = 1,3-dibenzylimidazol- 2-ylidene, X = Br, 4a, and X = Cl, 4b; NHC = 1-methyl-3-propylimidazol-2- ylidene, X = Br, 5) and [CpMo(CO)2(IMes)(CH3CN)][BF 4] (6) have been synthesized and fully characterized. The stability of metal-NHC ligand bonds in these compounds under oxidative conditions has been investigated. The thermally stable Mo(VI) dioxo NHC complex [CpMoO 2(IMes)][BF4] (9) has been isolated by the oxidation of the ionic complex 6 by TBHP (tert-butyl hydrogen peroxide). Complex 6 can be applied as a very active (TOFs up to 3400 h-1) and selective olefin epoxidation catalyst. While under oxidative conditions (in the presence of TBHP), compounds 1-5 decompose into imidazolium bromide and imidazolium polyoxomolybdate. The formation of polyoxomolybdate as oxidation products had not been observed in a similar epoxidation catalyzed by Mo(II) and Mo(VI) complexes. DFT studies suggest that the presence of Br- destabilizes the CpMo(VI) oxo NHC carbene species, consistent with the experimental observations. © 2010 American Chemical Society.

High-level production of C-11-carboxyl-labeled amino acids

International Nuclear Information System (INIS)

Washburn, L.C.; Sun, T.T.; Byrd, B.L.; Hayes, R.L.; Butler, T.A.; Callahan, A.P.

1979-01-01

Carbon-11-labeled amino acids have significant potential as agents for positron tomographic functional imaging. We have developed a rapid, high-temperature, high-pressure modification of the Buecherer--Strecker amino acid synthesis and found it to be quite general for the production of C-11-carboxyl-labeled neutral amino acids. Production of C-11-carboxyl-labeled DL-tryptophan requires certain modifications in the procedure. Twelve different amino acids have been produced to date by this technique. Synthesis and chromatographic purification require approximately 40 min, and C-11-carboxyl-labeled amino acids have been produced in yields of up to 425 mCi. Two C-11-carboxyl-labeled amino acids are being investigated clinically for tumor scanning and two others for pancreatic imaging. Over 120 batches of the various agents have been produced for clinical use over a three-year period

Auranofin and N-heterocyclic carbene gold-analogs are potent inhibitors of the bacteria Helicobacter pylori.

Science.gov (United States)

Owings, Joshua P; McNair, Nina N; Mui, Yiu Fung; Gustafsson, Tomas N; Holmgren, Arne; Contel, Maria; Goldberg, Joanna B; Mead, Jan R

2016-07-01

Auranofin is an FDA-approved gold-containing compound used for the treatment of rheumatoid arthritis. Recent reports of antimicrobial activity against protozoa and bacteria indicate that auranofin targets the reductive enzyme thioredoxin reductase (TrxR). We evaluated auranofin as well as five auranofin analogs containing N-heterocyclic carbenes (instead of the triethylphosphane present in auranofin) and five gold-carbene controls for their ability to inhibit or kill Helicobacter pylori in vitro Auranofin completely inhibited bacterial growth at 1.2 μM. Purified H. pylori TrxR was inhibited by auranofin in a cell-free assay (IC50 ∼88 nM). The most active gold(I)-N-heterocyclic carbene compounds exhibited MICs comparable to auranofin against H. pylori (2 μM), while also exhibiting lower toxicities for human embryonic kidney cells (HEK-293T cells). Median toxic concentrations (TC50) were 13-20-fold higher compared to auranofin indicating that they were less cytotoxic. The N-heterocyclic carbene analogs maybe well tolerated, but further evaluation is needed in vivo Finally, auranofin was synergistic with the antibiotic amoxicillin, suggesting that targeting both the reductive enzyme TrxR and cell wall synthesis may be effective against H. pylori infections. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Oxidation of methyl heterocyclic compounds on vanadium oxide catalysts

International Nuclear Information System (INIS)

Shimanskaya, M.V.; Lejtis, L.A.; Iovel', I.G.; Gol'dberg, Yu.Sh.; Skolmejstere, R.A.; Golender, L.O.

1985-01-01

Data on vapor-phase oxidation of methyl derivatives of thiophene, Δ 2 - thiazo line, pyridine, pyrazine and pyramidine on oxide vanadium-molybdenum catalysts to corresponding heterylaldehydes are generalized. The dependence of catalytic properties of oxide vanadium-molybdenum systems in oxidation reactions of methylheterocyclic compounds on V:Mo ratio in the catalyst is revealed. It is shown that heterocyclic compounds are coordinated by a heteroatom on Lewis centres of V-Mo-O-catalyst primarily with partially reduced vanadium ions

2-([1,2,4]triazolo[1,5-c]quinazolin-2-yl-alkyl-(alkaryl-, aryl--amines and their derivatives. (3Н-quinazolin-4-ylidenhydrazides (1,3-dioxo-1,3-dihydro-2H-isoindol-2-ylalkyl-(alkaryl-, aryl-carboxylic acids: features of synthesis, modification and ant

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Yu. V. Martynenko

2016-08-01

Full Text Available The combination of different «pharmacophore» components in one structure connected via «linker» functional groups is one of the major and justified approaches for the synthesis of new biologically active substances. In this area (3Н-quinazoline-4-ylidenhydrazides (1,3-dioxo-1,3-dihydro-2H-іsoindol-2-yl-alkyl-(aralkyl-, aryl-carboxylic acids are the most interesting compounds. They contain quinazoline and іsoindole fragments united through аlkyl, аlkaryl and аryl groups and furthermore can be used for the synthesis of new heterocycles. Aim: The purpose of this work is to find antimicrobial and antifungal agents among (3H-quinazolin-4-ylidenehydrazides (1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl-alkyl-(alkaryl-, aryl-carboxylic acids and their fused derivatives and to establish physical-chemical properties of these compounds and to correlate «structure – activity relationship» for structure optimization. Methods and results. The study of microbiological activity was conducted by disco-diffusion method on Mueller-Hinton agar on the following strains of microorganisms: gram-positive cocci (Staphylococcus aureus ATCC 25923, Enterococcus aeruginosa, E. faecalis ATCC 29212, gram-negative bacteria (Pseudomonas aeruginosa PSS27853, Escherichia coli ATCC 25922, facultative anaerobic gram-negative bacteria (Klebsiella pneumoniaе and fungi (Candida albicans ATCC 885653. Conclusion. The protected aminoacids were used to synthesize unknown (3H-quinazolin-4-ylidenehydrazides (1,3-dioxo-1,3-dihydroisoindolo-2-yl-alkyl-(alkaryl-, aryl-carboxylic acids in the reactions of nucleophilic substitution for the first time. While new [1,2,4]triazolo[1,5-c]quinazolin-2-yl-alkyl-(alkaryl-, aryl-- isoindol-1,3(2H-diones were received by heterocyclization of the last. Structure and identity have been confirmed by elemental analysis, physical and chemical methods (1H NMR spectroscopy, mass-spectrometry. Analysis of the results of microbiological study shows, that

Synthesis of acetylene alcohols of heterocyclic type and the acyl derivatives

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Moldir Dyusebaeva

2015-03-01

Full Text Available A synthesis of potentially biologically active heterocyclic amino alcohols of acetylene (Piperidine and Morpholine under the conditions of Mannich reaction accomplished and received their acyl derivatives. Pharmacological activity (antibacterial and antispasmotic of synthesized compounds, also acute toxicological characteristics studied. The study showed that the combination of DMAE-4 has antispasmodic activity with low toxicity.

The labeling of unsaturated γ-hydroxybutyric acid by heavy isotopes of hydrogen: iridium complex-mediated H/D exchange by C─H bond activation vs reduction by boro-deuterides/tritides.

Science.gov (United States)

Marek, Aleš; Pedersen, Martin H F; Vogensen, Stine B; Clausen, Rasmus P; Frølund, Bente; Elbert, Tomáš

2016-10-01

3-Hydroxycyclopent-1-ene-1-carboxylic acid (HOCPCA (1)) is a potent ligand for high-affinity γ-hydroxybutyric acid binding sites in the central nervous system. Various approaches to the introduction of a hydrogen label onto the HOCPCA skeleton are reported. The outcomes of the feasible C─H activation of olefin carbon (C-2) by iridium catalyst are compared with the reduction of the carbonyl group (C-3) by freshly prepared borodeuterides. The most efficient iridium catalysts proved to be Kerr bulky phosphine N-heterocyclic species providing outstanding deuterium enrichment (up to 91%) in a short period of time. The highest deuterium enrichment (>99%) was achieved through the reduction of ketone precursor 2 by lithium trimethoxyborodeuteride. Hence, analogical conditions were used for the tritiation experiment. [ 3 H]-HOCPCA selectively labeled on the position C-3 was synthetized with radiochemical purity >99%, an isolated yield of 637 mCi and specific activity = 28.9 Ci/mmol. Copyright © 2016 John Wiley & Sons, Ltd.

Crystal structure of a mixed-ligand silver(I complex of the non-steroidal anti-inflammatory drug diclofenac and pyrimidine

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Sevim Hamamci Alisir

2016-10-01

Full Text Available In the title mixed-ligand silver(I coordination polymeric complex with the non-steroidal anti-inflammatory drug diclofenac (C14H11Cl2NO2 (diclH and pyrimidine (pym, namely poly[{μ2-2-[2-(2,6-dichloroanilinophenyl]acetato-κ2O:O′}(μ2-pyrimidine-κ2N1:N3silver(I], [Ag(C14H10Cl2NO2(C4H4N2]n or [Ag(μ-dicl(μ-pym]n, the very distorted tetrahedral AgN2O2 coordination centres comprise two N-atom donors from bridging pym ligands [Ag—N = 2.381 (3 and 2.412 (3 Å] and two carboxylate O-atom donors from dicl ligands [Ag—O = 2.279 (2 and 2.280 (2 Å], which bridge Ag atoms, giving a centrosymmetric dinuclear units with a short Ag...Ag separation [2.8931 (5 Å]. Within the units are short intraligand C—Cl...π(pym interactions [3.6409 (15 Å]. The units are linked through the bridging N atoms of the pym ligand into a two-dimensional sheet–polymer structure lying parallel to (100 and stabilized by inter-ring π–π interactions between the pym ligands [Cg...Cg = 3.4199 (17 Å]. Additional inter-unit C—H...O and C—H...Cg hydrogen-bonding interactions between the sheets give an overall three-dimensional structure.

Methyl 2-Benzamido-2-(1H-benzimidazol-1-ylmethoxyacetate

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Alami Anouar

2012-09-01

Full Text Available The heterocyclic carboxylic α-aminoester methyl 2-benzamido-2-(1H-benzimidazol-1-ylmethoxyacetate is obtained by O-alkylation of methyl α-azido glycinate N-benzoylated with 1H-benzimidazol-1-ylmethanol.

In situ ligand generation for novel Mn(II) and Ni(II) coordination polymers with disulfide ligand: Solvothermal syntheses, structures and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Han, Yinfeng, E-mail: hanyinfeng@gmail.com; Wang, Chang' an; Zheng, Zebao; Sun, Jiafeng; Nie, Kun; Zuo, Jian; Zhang, Jianping

2015-07-15

Two coordination polymers, ([Mn{sub 2}(L1){sub 2}(μ{sub 2}-H{sub 2}O)(H{sub 2}O){sub 4}]·5H{sub 2}O){sub n}1 and ([Ni(L1)(H{sub 2}O){sub 2}]·2H{sub 2}O){sub n}2 (H{sub 2}L1=2,2′-dithiobisnicotinic acid), were prepared by the solvothermal reactions of the Mn(II) or Ni(II) ions with 2-mercaptonanicotinic acid. In 1, the [Mn{sub 2}(COO){sub 4}] units are connected by the 2,2′-dithiobisnicotinic dianion to form a two-dimensional (4,4)-connected network. In 2, the adjacent Ni(II) ions are connected by the carboxyl groups of the 2,2′-dithiobisnicotinic dianion to form an one-dimensional inorganic rod-shaped chain [Ni(COO){sub 2}]{sub n}, which are further interconnected by the 2,2′-dithiobisnicotinic ligand, giving rise to a two-dimensional framework. Variable-temperature magnetic susceptibilities of 1 and 2 exhibit overall weak antiferromagnetic coupling between the adjacent metal ions. - Graphical abstract: Two 2D coordination polymers were synthesized by transition-metal/in-situ oxidation of 2-mercaptonicotinic acid. The compounds pack into 2D frameworks by the carboxyl groups of 2,2′-dithiobisnicotinic dianion and exhibit overall weak antiferromagnetic coupling. - Highlights: • Two 2D coordination polymers containing 2,2′-dithiobisnicotinic dianion. • In situ oxidation and dehydro coupling reaction of 2-mercaptonbenzoic acid. • Two compounds display weak antiferromagnetic exchanges.

Carboxylic acid exchangers in analytical chemistry

International Nuclear Information System (INIS)

Venkateswarlu, Ch.

1976-01-01

The literature on the use of carboxylic acid exchangers in inorganic analytical chemistry is reviewed. It is classified under two heads, based on the ionic form in which the exchanger is employed, viz., the salt form and the acid form. In the salt form, the separations reported in the beginning are mostly carried out in alkaline medium, employing ammonia and its derivatives as complexing agents to hold cations in solution. This was followed by the use of ammonium ion as an eluent from heavy weakly or neutral solutions. There are a few separations reported making use of EDTA as eluent. It appears that separation of some anions from cations can be achieved with greater ease with these exchangers than with sulphonic acid type. Contary to the general belief, carboxylic acid exchangers are used in H + form to achieve some analytical separations of cations of interest. These exchangers exhibit better sorption of some cations in presence of complexing agents containing basic nitrogen as a donor. In fact, a careful study of these exchangers with different matrices might yield really selective exchangers, than the chelating ones known commercially. From the separation cited, carboxylic acid exchangers appear to have greater potentialities in their applications, than what is normally expected. (author)

Reactions of carbonyl compounds with α,β-unsaturated nitriles as a convenient pathway to carbo- and heterocycles

International Nuclear Information System (INIS)

Sharanin, Yu A; Goncharenko, M P; Litvinov, Victor P

1998-01-01

Published data on the methods for synthesis of carbo- and heterocyclic compounds based on reactions of α,β-unsaturated nitriles with carbonyl compounds and activated phenols are surveyed. It is demonstrated that all these reactions occur via nucleophilic addition of the carbanion generated from a carbonyl compound to the double bond of an unsaturated nitrile (the Michael reaction). The main routes of transformation of the adducts into carbo- and heterocyclic compounds are considered. The methods for regioselective preparation of fused 4H-pyrans or 1,4-dihydropyridines by varying conditions of cyclisation of Michael adducts are discussed. The bibliography includes 249 references.

Solid-phase synthesis of compounds of europium and terbium with nitrogen-containing heterocyclic compounds under mechanical activation

International Nuclear Information System (INIS)

Kalinovskaya, I.V.; Karasev, V.E.

2000-01-01

Effect of solvents and parameters of mechanical treatment on basic regularities of synthesis of rare earth compounds with nitrogen-containing heterocyclic compounds is studied. It is shown that interaction on europium (3) and terbium (3) nitrates with nitrogen-containing heterocyclic compounds leads to formation of compounds of Ln(NO 3 )·2D composition, where Ln=Eu, Tb; D=2,2-dipyridyl, 1,10-phenanthroline, diphenylguanidine. Effect of conditions of mechanical treatment and different additions on process and yield of products is studied. Compounds prepared are characterized by the methods of chemical element analysis, IR spectroscopy and luminescent spectroscopy [ru

Application of heterocyclic aldehydes as components in Ugi–Smiles couplings

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Katelynn M. Mason

2016-09-01

Full Text Available Efficient one-pot Ugi–Smiles couplings are reported for the use of furyl-substituted aldehyde components. In the presence of these heterocyclic aldehydes, reactions tolerated variations in amine components and led to either isolated N-arylamide Ugi–Smiles adducts or N-arylepoxyisoindolines, products of tandem Ugi–Smiles Diels–Alder cyclizations, in moderate yields. A thienyl-substituted aldehyde was also a competent component for Ugi–Smiles adduct formation.

Synthesis and Characterization of Acyclic and Cyclic Azabridged Ligands Incorporating 2,2'-Bipyridine Subunits and Their Complexes With Copper(II, Cobalt(II, and Nickel(II