Highly stable [mambf6-n(o/h2o)n(ligand)2(solvent)x]n metal organic frameworks

KAUST Repository

Eddaoudi, Mohamed

2016-10-13

Provided herein are metal organic frameworks having high selectivity and stability in the present of gases and vapors including H2S, H2O, and CO2. Metal organic frameworks can comprise metal nodes and N-donor organic ligands. Further provided are methods of making metal organic frameworks.

Mononuclear mercury(II) complexes containing bipyridine derivatives and thiocyanate ligands: Synthesis, characterization, crystal structure determination, and luminescent properties

Science.gov (United States)

Amani, Vahid; Alizadeh, Robabeh; Alavije, Hanieh Soleimani; Heydari, Samira Fadaei; Abafat, Marzieh

2017-08-01

A series of mercury(II) complexes, [Hg(Nsbnd N)(SCN)2] (Nsbnd N is 4,4‧-dimethyl-2,2‧-bipyridine in 1, 5,5‧-dimethyl-2,2‧-bipyridine in 2, 6,6‧-dimethyl-2,2‧-bipyridine in 3 and 6-methyl-2,2‧-bipyridine in 4), were prepared from the reactions of Hg(SCN)2 with mentioned ligands in methanol. Suitable crystals of these complexes were obtained for X-ray diffraction measurement by methanol diffusion into a DMSO solution. The four complexes were thoroughly characterized by spectral methods (IR, UV-Vis, 13C{1H}NMR, 1H NMR and luminescence), elemental analysis (CHNS) and single crystal X-ray diffraction. The X-ray structural analysis indicated that in the structures of these complexes, the mercury(II) cation is four-coordinated in a distorted tetrahedral configuration by two S atoms from two thiocyanate anions and two N atoms from one chelating 2,2‧-bipyridine derivative ligand. Also, in these complexes intermolecular interactions, for example Csbnd H⋯N hydrogen bonds (in 1-4), Csbnd H⋯S hydrogen bonds (in 1, 2 and 4), π … π interactions (in 2-4), Hg⋯N interactions (in 2) and S⋯S interactions (in 4), are effective in the stabilization of the crystal structures and the formation of the 3D supramolecular complexes. Furthermore, the luminescence spectra of the title complexes show that the intensity of their emission bands are stronger than the emission bands for the free bipyridine derivative ligands.

Crystal and molecular structure of the coordination compounds of Er3+ with 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene [ErL21(NO3)2]2[Er(NO3)2(H2O)5]0.333(NO3)2.333 · 2.833H2O and its ethyl substituted derivative [ErL22(NO3)2][Er(NO3)5]0.5 · 0.5H2O

International Nuclear Information System (INIS)

Polyakova, I. N.; Baulin, V. E.; Ivanova, I. S.; Pyatova, E. N.; Sergienko, V. S.; Tsivadze, A. Yu.

2015-01-01

The coordination compounds of Er 3+ with 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene [ErL 2 1 (NO 3 ) 2 ] 2 [Er(NO 3 ) 2 (H 2 O) 5 ] 0.333 (NO 3 ) 2.333 · 2.833H 2 O (I) and its ethyl substituted derivative [ErL 2 2 (NO 3 ) 2 ][Er(NO 3 ) 5 ] 0.5 · 0.5H 2 O (II) are synthesized and their crystal structures are studied. I and II contain [ErL 2 (NO 3 ) 2 ] + complex cations of identical composition and close structure. The eight-vertex polyhedron of the Er atom in the shape of a distorted octahedron with two split trans vertices is formed by the O atoms of the phosphoryl groups of L ligands and nitrate anions. L ligands close nine-membered metallocycles. The structures contain spacious channels which are populated differently, namely, by disordered [Er(NO 3 ) 2 (H 2 O) 5 ] + complex cations, NO 3 − anions, and crystallization water molecules in I and disordered [Er(NO 3 ) 5 ] 2− complex anions and crystallization water molecules in II. The IR spectra of I and II are studied

Diazadienes in chemistry of lanthanides: latest view on old ligands. Synthesis, structure and properties of complexes {[(R)CNC6H3Pr2i]2}Lu(THF)2(μ-Cl)2Li(THF2 (R=CH3, CH2)

International Nuclear Information System (INIS)

Makhrova, T.V.; Fukin, G.K.; Cherkasov, A.V.; Trifonov, A.A.

2008-01-01

Reaction of dianion derivative [DADLi 2 ] (DAD -1,4-bis(2,6-diisopropylphenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene) prepared in situ by the reduction of corresponding DAD by the excess of metal lithium in THF with anhydrous LuCl 3 (1:1) results in the formation of the metal cyclic complex {[(R)CNC 6 H 3 Pr 2 i ] 2 }Lu(THF) 2 (μ-Cl) 2 Li(THF) 2 (1) containing the fragment N-C(Me)=C(Me)-N. DAD Treatment by two equivalents BuLi in the mixture ether-hexane (20 Deg C) results in the activation of the C-H bond of methyl substitutes at imine carbon. By the reaction of dilithium derivative [DAD - 2 H Li 2 ] formed in situ with LuCl 3 in THF the complex {[(CH 2 )CNC 6 H 3 Pr 2 i ] 2 }Lu(THF) 2 (μ-Cl) 2 Li(THF) 2 (2) with diamide ligand N-C(=CH 2 )-C(=CH 2 )-N was prepared. Structures of 1 and 2 complexes have been established by X-ray structure analysis [ru

Ligand-enabled ortho-C-H olefination of phenylacetic amides with unactivated alkenes.

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Lu, Ming-Zhu; Chen, Xing-Rong; Xu, Hui; Dai, Hui-Xiong; Yu, Jin-Quan

2018-02-07

Although chelation-assisted C-H olefination has been intensely investigated, Pd(ii)-catalyzed C-H olefination reactions are largely restricted to acrylates and styrenes. Here we report a quinoline-derived ligand that enables the Pd(ii)-catalyzed olefination of the C(sp 2 )-H bond with simple aliphatic alkenes using a weakly coordinating monodentate amide auxiliary. Oxygen is used as the terminal oxidant with catalytic copper as the co-oxidant. A variety of functional groups in the aliphatic alkenes are tolerated. Upon hydrogenation, the ortho -alkylated product can be accessed. The utility of this reaction is also demonstrated by the late-stage diversification of drug molecules.

Copper-promoted methylene C-H oxidation to a ketone derivative by O2.

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Deville, Claire; McKee, Vickie; McKenzie, Christine J

2017-01-17

The methylene group of the ligand 1,2-di(pyridin-2-yl)-ethanone oxime (dpeo) is slowly oxygenated by the O 2 in air under ambient conditions when [Cu(dpeo) 2 ](ClO 4 ) 2 is dissolved in ethanol or acetonitrile. An initial transient ketone product, 2-(hydroxyimino)-1,2-di(pyridine-2-yl)ethanone, (hidpe) was characterized in the heteroleptic copper(ii) complex [Cu(bpca)(hidpe)](ClO 4 ). The co-ligand in this complex, N-(2'-pyridylcarbonyl)pyridine-2-carboximidate (bpca - ), is derived from a copper-promoted Beckmann rearrangement of hidpe. In the presence of bromide only [Cu(bpca)Br] is isolated. When significant water is present in reaction mixtures copper complexes of dpeo, hidpe and bpca - are not recovered and [Cu(pic) 2 H 2 O] is isolated. This occurs since two equivalents of picolinate are ultimately generated from one equivalent of oxidized and hydrolysed dpeo. The copper-dependent O 2 activation and consequent stoichiometric dpeo C-H oxidation is reminiscent of the previously observed catalysis of dpeo oxidation by Mn(ii) [C. Deville, S. K. Padamati, J. Sundberg, V. McKee, W. R. Browne, C. J. McKenzie, Angew. Chem., Int. Ed., 2016, 55, 545-549]. By contrast dpeo oxidation is not observed during complexation reactions with other late transition metal(ii) ions (M = Fe, Co, Ni, Zn) under aerobic conditions. In these cases bis and tris complexes of bidentate dpeo are isolated in good yields. It is interesting to note that dpeo is not oxidised by H 2 O 2 in the absence of Cu or Mn, suggesting that metal-based oxidants capable of C-H activation are produced from the dpeo-Cu/Mn systems and specifically O 2 . The metastable copper complexes [Cu(dpeo) 2 ](ClO 4 ) 2 and [Cu(bpca)(hidpe)](ClO 4 ), along with [NiX 2 (dpeo) 2 ] (X = Cl, Br), [Ni(dpeo) 3 ](ClO 4 ) 2 , [Co(dpeo) 3 ](ClO 4 ) 3 and the mixed valence complex [Fe III Fe(dpeo-H) 3 (dpeo) 3 ](PF 6 ) 4 , have been structurally characterized.

Oxygen Atom Exchange between H2O and Non-Heme Oxoiron(IV) Complexes: Ligand Dependence and Mechanism.

Science.gov (United States)

Puri, Mayank; Company, Anna; Sabenya, Gerard; Costas, Miquel; Que, Lawrence

2016-06-20

Detailed studies of oxygen atom exchange (OAE) between H2(18)O and synthetic non-heme oxoiron(IV) complexes supported by tetradentate and pentadentate ligands provide evidence that they proceed by a common mechanism but within two different kinetic regimes, with OAE rates that span 2 orders of magnitude. The first kinetic regime involves initial reversible water association to the Fe(IV) complex, which is evidenced by OAE rates that are linearly dependent on [H2(18)O] and H2O/D2O KIEs of 1.6, while the second kinetic regime involves a subsequent rate determining proton-transfer step between the bound aqua and oxo ligands that is associated with saturation behavior with [H2(18)O] and much larger H2O/D2O KIEs of 5-6. [Fe(IV)(O)(TMC)(MeCN)](2+) (1) and [Fe(IV)(O)(MePy2TACN)](2+) (9) are examples of complexes that exhibit kinetic behavior in the first regime, while [Fe(IV)(O)(N4Py)](2+) (3), [Fe(IV)(O)(BnTPEN)](2+) (4), [Fe(IV)(O)(1Py-BnTPEN)](2+) (5), [Fe(IV)(O)(3Py-BnTPEN)](2+) (6), and [Fe(IV)(O)(Me2Py2TACN)](2+) (8) represent complexes that fall in the second kinetic regime. Interestingly, [Fe(IV)(O)(PyTACN)(MeCN)](2+) (7) exhibits a linear [H2(18)O] dependence below 0.6 M and saturation above 0.6 M. Analysis of the temperature dependence of the OAE rates shows that most of these complexes exhibit large and negative activation entropies, consistent with the proposed mechanism. One exception is complex 9, which has a near-zero activation entropy and is proposed to undergo ligand-arm dissociation during the RDS to accommodate H2(18)O binding. These results show that the observed OAE kinetic behavior is highly dependent on the nature of the supporting ligand and are of relevance to studies of non-heme oxoiron(IV) complexes in water or acetonitrile/water mixtures for applications in photocatalysis and water oxidation chemistry.

H₃O_2-, O₂^2- and O₂•- bridging ligands in cobalt(III) complexes of an acyclic phenolate-hinged dinucleating ligand

DEFF Research Database (Denmark)

Ghiladi, Morten; Gomez, Jonnes T.; Hazell, A.

2003-01-01

The dicobalt(III) complex, [Co2(bpbp)(μ-H3O2)2](ClO4)3 (bpbp− = 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-tert-butylphenolate), obtained by reaction of cobalt(II) perchlorate with Hbpbp under ambient conditions contains two μ-H3O2− bridging ligands. The H-bonded O⋯O distances in this motif are 2...

Epibatidine-derivatives: ligands for the neuronal nicotinic acetylcholine receptor

International Nuclear Information System (INIS)

Westera, G.; Patt, J.T.; Jankowski, K.; Bertrand, D.; Spang, J.; Schubiger, P.A.

1997-01-01

Epibatidine, isolated from the Ecuadorian frog Epipedobates tricolar, has been synthesized. 11 C-N-methyl derivate is investigated as useful nicotinergic receptor ligand by electrophysiological methods and in vivo mice experiments. (author) 2 figs., 7 refs

Synthesis, Characterization, DNA Interaction, and Antitumor Activities of La (III) Complex with Schiff Base Ligand Derived from Kaempferol and Diethylenetriamine.

Science.gov (United States)

Wang, Qin; Huang, Yu; Zhang, Jin-Sheng; Yang, Xin-Bin

2014-01-01

A novel La (III) complex, [LaL(H2O)3]NO3 ·3H2O, with Schiff base ligand L derived from kaempferol and diethylenetriamine, has been synthesized and characterized by elemental analysis, IR, UV-visible, (1)H NMR, thermogravimetric analysis, and molar conductance measurements. The fluorescence spectra, circular dichroism spectra, and viscosity measurements and gel electrophoresis experiments indicated that the ligand L and La (III) complex could bind to CT-DNA presumably via intercalative mode and the La (III) complex showed a stronger ability to bind and cleave DNA than the ligand L alone. The binding constants (K b ) were evaluated from fluorescence data and the values ranged from 0.454 to 0.659 × 10(5) L mol(-1) and 1.71 to 17.3 × 10(5) L mol(-1) for the ligand L and La (III) complex, respectively, in the temperature range of 298-310 K. It was also found that the fluorescence quenching mechanism of EB-DNA by ligand L and La (III) complex was a static quenching process. In comparison to free ligand L, La (III) complex exhibited enhanced cytotoxic activities against tested tumor cell lines HL-60 and HepG-2, which may correlate with the enhanced DNA binding and cleaving abilities of the La (III) complex.

The extracellular loop 2 (ECL2 of the human histamine H4 receptor substantially contributes to ligand binding and constitutive activity.

Directory of Open Access Journals (Sweden)

David Wifling

Full Text Available In contrast to the corresponding mouse and rat orthologs, the human histamine H4 receptor (hH4R shows extraordinarily high constitutive activity. In the extracellular loop (ECL, replacement of F169 by V as in the mouse H4R significantly reduced constitutive activity. Stabilization of the inactive state was even more pronounced for a double mutant, in which, in addition to F169V, S179 in the ligand binding site was replaced by M. To study the role of the FF motif in ECL2, we generated the hH4R-F168A mutant. The receptor was co-expressed in Sf9 insect cells with the G-protein subunits Gαi2 and Gβ1γ2, and the membranes were studied in [3H]histamine binding and functional [35S]GTPγS assays. The potency of various ligands at the hH4R-F168A mutant decreased compared to the wild-type hH4R, for example by 30- and more than 100-fold in case of the H4R agonist UR-PI376 and histamine, respectively. The high constitutive activity of the hH4R was completely lost in the hH4R-F168A mutant, as reflected by neutral antagonism of thioperamide, a full inverse agonist at the wild-type hH4R. By analogy, JNJ7777120 was a partial inverse agonist at the hH4R, but a partial agonist at the hH4R-F168A mutant, again demonstrating the decrease in constitutive activity due to F168A mutation. Thus, F168 was proven to play a key role not only in ligand binding and potency, but also in the high constitutive activity of the hH4R.

Aminosilanes derived from 1H-benzimidazole-2(3H)-thione

International Nuclear Information System (INIS)

Palomo-Molina, Juliana; García-Báez, Efrén V.; Contreras, Rosalinda; Pineda-Urbina, Kayim; Ramos-Organillo, Angel

2015-01-01

In two trimethylsilyl-substituted 1H-benzimidazole-2(3H)-thiones, noncovalent C—H⋯π interactions between the centroid of the benzmidazole system and the SiMe 3 groups form helicoidal arrangements in one, and dimerization results in the formation of R s 2 (8) rings via N—H⋯S interactions, along with parallel π–π interactions between imidazole and benzene rings, in the second compound. Two new molecular structures, namely 1,3-bis(trimethylsilyl)-1H-benzimidazole-2(3H)-thione, C 13 H 22 N 2 SSi 2 , (2), and 1-trimethylsilyl-1H-benzimidazole-2(3H)-thione, C 10 H 14 N 2 SSi, (3), are reported. Both systems were derived from 1H-benzimidazole-2(3H)-thione. Noncovalent C—H⋯π interactions between the centroid of the benzmidazole system and the SiMe 3 groups form helicoidal arrangements in (2). Dimerization of (3) results in the formation of R 2 2 (8) rings via N—H⋯S interactions, along with parallel π–π interactions between imidazole and benzene rings

Targeting the transsulfuration-H2S pathway by FXR and GPBAR1 ligands in the treatment of portal hypertension.

Science.gov (United States)

Fiorucci, Stefano; Distrutti, Eleonora

2016-09-01

Cirrhosis is a end-stage disease of the liver in which fibrogenesis, angiogenesis and distortion of intrahepatic microcirculation lead to increased intrahepatic resistance to portal blood flow, a condition known as portal hypertension. Portal hypertension is maintained by a variety of molecular mechanisms including sinusoidal endothelial cells (LSECs) hyporeactivity, activation of hepatic stellate cells (HSCs), reduction in hepatic endothelial nitric oxide synthase (eNOS) activity along with increased eNOS-derived NO generation in the splanchnic and systemic circulations. A reduction of the expression/function of the two major hydrogen sulfide (H2S)-producing enzymes, cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS), has also been demonstrated. A deficit in the transsulfuration pathway leading to the accumulation of homocysteine might contribute to defective generation of H2S and endothelial hyporeactivity. Bile acids are ligands for nuclear receptors, such as farnesoid X receptor (FXR), and G-protein-coupled receptors (GPCRs), such as the G-protein bile acid receptor 1 (GPBAR1). FXR and GPBAR1 ligands regulate the expression/activity of CSE by both genomic and non-genomic effects and have been proved effective in protecting against endothelial dysfunction observed in rodent models of cirrhosis. GPBAR1, a receptor for secondary bile acids, is selectively expressed by LSECs and its activation increases the expression of CSE and attenuates the production of endotelin-1, a potent vasoconstrictor agent. In vivo GPBAR1 ligand attenuates the imbalance between vasodilatory and vaso-constricting agents, making GPBAR1 a promising target in the treatment of portal hypertension. Copyright © 2016 Elsevier Ltd. All rights reserved.

Aminosilanes derived from 1H-benzimidazole-2(3H)-thione

Energy Technology Data Exchange (ETDEWEB)

Palomo-Molina, Juliana [Facultad de Ciencias Químicas, Universidad de Colima, Carretera Coquimatlán-Colima, Coquimatlán Colima 28400 (Mexico); García-Báez, Efrén V. [Unidad Profesional Interdisciplinaria de Biotecnología, Instituto Politécnico Nacional, Avenida Acueducto s/n, Barrio La Laguna Ticomán, México DF 07340 (Mexico); Contreras, Rosalinda [Departamento de Química, Centro de Investigación y de Estudios Avanzados del IPN, Apartado Postal 14-740, México DF 07000 (Mexico); Barrio La Laguna Ticomán, México DF 07340 (Mexico); Pineda-Urbina, Kayim; Ramos-Organillo, Angel, E-mail: aaramos@ucol.mx [Facultad de Ciencias Químicas, Universidad de Colima, Carretera Coquimatlán-Colima, Coquimatlán Colima 28400 (Mexico)

2015-08-12

In two trimethylsilyl-substituted 1H-benzimidazole-2(3H)-thiones, noncovalent C—H⋯π interactions between the centroid of the benzmidazole system and the SiMe{sub 3} groups form helicoidal arrangements in one, and dimerization results in the formation of R{sub s} {sup 2}(8) rings via N—H⋯S interactions, along with parallel π–π interactions between imidazole and benzene rings, in the second compound. Two new molecular structures, namely 1,3-bis(trimethylsilyl)-1H-benzimidazole-2(3H)-thione, C{sub 13}H{sub 22}N{sub 2}SSi{sub 2}, (2), and 1-trimethylsilyl-1H-benzimidazole-2(3H)-thione, C{sub 10}H{sub 14}N{sub 2}SSi, (3), are reported. Both systems were derived from 1H-benzimidazole-2(3H)-thione. Noncovalent C—H⋯π interactions between the centroid of the benzmidazole system and the SiMe{sub 3} groups form helicoidal arrangements in (2). Dimerization of (3) results in the formation of R{sub 2}{sup 2}(8) rings via N—H⋯S interactions, along with parallel π–π interactions between imidazole and benzene rings.

Phosphinodi(benzylsilane) PhP{(o-C6H4CH2)SiMe2H}2: a versatile "PSi2Hx" pincer-type ligand at ruthenium.

Science.gov (United States)

Montiel-Palma, Virginia; Muñoz-Hernández, Miguel A; Cuevas-Chávez, Cynthia A; Vendier, Laure; Grellier, Mary; Sabo-Etienne, Sylviane

2013-09-03

The synthesis of the new phosphinodi(benzylsilane) compound PhP{(o-C6H4CH2)SiMe2H}2 (1) is achieved in a one-pot reaction from the corresponding phenylbis(o-tolylphosphine). Compound 1 acts as a pincer-type ligand capable of adopting different coordination modes at Ru through different extents of Si-H bond activation as demonstrated by a combination of X-ray diffraction analysis, density functional theory calculations, and multinuclear NMR spectroscopy. Reaction of 1 with RuH2(H2)2(PCy3)2 (2) yields quantitatively [RuH2{[η(2)-(HSiMe2)-CH2-o-C6H4]2PPh}(PCy3)] (3), a complex stabilized by two rare high order ε-agostic Si-H bonds and involved in terminal hydride/η(2)-Si-H exchange processes. A small free energy of reaction (ΔrG298 = +16.9 kJ mol(-1)) was computed for dihydrogen loss from 3 with concomitant formation of the 16-electron species [RuH{[η(2)-(HSiMe2)-CH2-o-C6H4]PPh[CH2-o-C6H4SiMe2]}(PCy3)] (4). Complex 4 features an unprecedented (29)Si NMR decoalescence process. The dehydrogenation process is fully reversible under standard conditions (1 bar, 298 K).

Expanding the Library of Uranyl Amide Derivatives: New Complexes Featuring the tert-Butyldimethylsilylamide Ligand.

Science.gov (United States)

Pattenaude, Scott A; Coughlin, Ezra J; Collins, Tyler S; Zeller, Matthias; Bart, Suzanne C

2018-04-16

New uranyl derivatives featuring the amide ligand, -N(SiHMe 2 ) t Bu, were synthesized and characterized by X-ray crystallography, multinuclear NMR spectroscopy, and absorption spectroscopies. Steric properties of these complexes were also quantified using the computational program Solid-G. The increased basicity of the free ligand -N(SiHMe 2 ) t Bu was demonstrated by direct comparison to -N(SiMe 3 ) 2 , a popular supporting ligand for uranyl. Substitutional lability on a uranyl center was also demonstrated by exchange with the -N(SiMe 3 ) 2 ligand. The increased basicity of this ligand and diverse characterization handles discussed here will make these compounds useful synthons for future reactivity.

Tuning of tantalum alkylidene reactivity with a terdentate arylamine ligand : synthesis, structure and reactivity of [TaCl2{C6H3(CH2NMe2)2-2,6}(CHBu-tert)

NARCIS (Netherlands)

Abbenhuis, H.C.L.; Grove, D.M.; Koten, van G.; Sluijs, van der P.; Spek, A.L.

1990-01-01

The terdentate aryldiamine ligand in the aryltantalum(V) alkylidene complex [TaCl2{C6H3(CH2NMe2)2-2,6}(CHBut)] (1) controls alkylidene reactivity in a range of metal-mediated Wittig reactions. An X-ray diffraction study of (1) shows that the hexacoordinate tantalum centre has a very irregular ligand

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

Directory of Open Access Journals (Sweden)

Andrea Pappalardo

2003-07-01

Full Text Available The synthesis of a series of N,N'-disubstituted acyclic (AL and cyclic (CL aza-bridged ligands incorporating 2,2-pipryidine subunits is described. 1H-NMR and IR spectral data support the proposed ligand structures. Dynamic 1H-NMR studies on diurea and diamide derivatives point to the presence of slowly interconverting conformers on the 1H-NMR time-scale, owing to N−H···N hydrogen bonding and/or a restricted rotation around the amide bonds. The ligands synthesized form 1:1 complexes with divalent transition metal ions. Upon complexation, bis-ester derivatives AL5 and CL5 undergo a metal-induced hydrolysis of the ester groups to carboxyl functions, which act as additional binding sites for the metal ion, as well as hydrogen-bonding donor-acceptor binding site to produce dimeric complexes.

Designer ligands. Part 14. Novel Mn(lI), Ni(II) and Zn(II) complexes of benzamide- and biphenyl-derived ligands

CSIR Research Space (South Africa)

Wellington, Kevin W

2009-01-01

Full Text Available . Results and Discussion The ligands 1a-c (Scheme 1) were prepared by treating benzoic acid with carbonyl diimidazole (CDI)13 in dimethylformamide (DMF), followed by the respective primary amines, histamine, 2- (2-aminoethyl)benzimidazole and 2...-(2-aminoethyl)pyridine. [Histamine had to be released from its dihydrochloride salt by treatment with sodium methoxide, while 2-(2- aminoethyl)benzimidazole was prepared from 1,2-diaminobenzene and β-alanine.16] The synthesis of the biphenyl-derived ligand 2...

New family of lanthanide-based inorganic-organic hybrid frameworks: Ln2(OH)4[O3S(CH2)nSO3]·2H2O (Ln = La, Ce, Pr, Nd, Sm; n = 3, 4) and their derivatives.

Science.gov (United States)

Liang, Jianbo; Ma, Renzhi; Ebina, Yasuo; Geng, Fengxia; Sasaki, Takayoshi

2013-02-18

We report the synthesis and structure characterization of a new family of lanthanide-based inorganic-organic hybrid frameworks, Ln(2)(OH)(4)[O(3)S(CH(2))(n)SO(3)]·2H(2)O (Ln = La, Ce, Pr, Nd, Sm; n = 3, 4), and their oxide derivatives. Highly crystallized samples were synthesized by homogeneous precipitation of Ln(3+) ions from a solution containing α,ω-organodisulfonate salts promoted by slow hydrolysis of hexamethylenetetramine. The crystal structure solved from powder X-ray diffraction data revealed that this material comprises two-dimensional cationic lanthanide hydroxide {[Ln(OH)(2)(H(2)O)](+)}(∞) layers, which are cross-linked by α,ω-organodisulfonate ligands into a three-dimensional pillared framework. This hybrid framework can be regarded as a derivative of UCl(3)-type Ln(OH)(3) involving penetration of organic chains into two {LnO(9)} polyhedra. Substitutional modification of the lanthanide coordination promotes a 2D arrangement of the {LnO(9)} polyhedra. A new hybrid oxide, Ln(2)O(2)[O(3)S(CH(2))(n)SO(3)], which is supposed to consist of alternating {[Ln(2)O(2)](2+)}(∞) layers and α,ω-organodisulfonate ligands, can be derived from the hydroxide form upon dehydration/dehydroxylation. These hybrid frameworks provide new opportunities to engineer the interlayer chemistry of layered structures and achieve advanced functionalities coupled with the advantages of lanthanide elements.

Steric and electronic effects of 1,3-disubstituted cyclopentadienyl ligands on metallocene derivatives of Cerium, Titanium, Manganese, and Iron

Energy Technology Data Exchange (ETDEWEB)

Sofield, Chadwick Dean [Univ. of California, Berkeley, CA (United States)

2000-05-01

Sterically demanding 1,3-disubstituted cyclopentadienyl ligands were used to modify the physical properties of the corresponding metallocenes. Sterically demanding ligands provided kinetic stabilization for trivalent cerium compounds. Tris(di-t-butylcyclopentadienyl)cerium was prepared and anion competition between halides and cyclopentadienyl groups which had complicated synthesis of the tris(cyclopentadienyl)compound was qualitatively examined. Bis(di-t-butylcyclopentadienyl)cerium methyl was prepared and its rate of decomposition, by ligand redistribution, to tris(di-t-butylcyclopentadienyl)cerium was shown to be slower than the corresponding rate for less sterically demanding ligands. Asymmetrically substituted ligands provided a symmetry label for examination of chemical exchange processes. Tris[trimethylsilyl(t-butyl)cyclopentadienyl]cerium was prepared and the rate of interconversion between the C1 and C3 isomers was examined. The enthalpy difference between the two distereomers is 7.0 kJ/mol. The sterically demanding cyclopentadienyl ligands ansa-di-t-butylcyclopentadiene (Me₂Si[(Me₃C)₂C₅H₃]₂), ansa-bis(trimethylsilyl)cyclopentadiene (Me₂Si[(Me₃Si)₂C₅H₃]₂) and tetra-t-butylfulvalene and metallocene derivatives of the ligands were prepared and their structures were examined by single crystal X-ray crystallography. The effect that substituents on the cyclopentadienyl ring have on the pi-electron system of the ligand was examined through interaction between ligand and metal orbitals. A series of 1,3-disubstituted manganocenes was prepared and their electronic states were determined by solid-state magnetic susceptibility, electron paramagnetic resonance, X-ray crystallography, and variable temperature UV-vis spectroscopy. Spin-equilibria in [(Me₃C)₂C₅H₃]₂Mn and [(Me₃

Mixed-Ligand Complexes Of Nickel (II) With 2-Acetylpyridine ...

African Journals Online (AJOL)

The preparation and spectral properties of five nickel (II) mixed-ligands complexes (Ni [2-Actsc.Y]CI2), derived from 2-acetylpyridinethiosermicarbazones and some nitrogen/sulphur monodentate ligands such as thiophene, ammonia, picoline, pyridine and aniline are described. The complexes have been characterized on ...

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.

Major advances in the development of histamine H4 receptor ligands.

Science.gov (United States)

Smits, Rogier A; Leurs, Rob; de Esch, Iwan J P

2009-08-01

The search for new and potent histamine H4 receptor ligands is leading to a steadily increasing number of scientific publications and patent applications. Several interesting and structurally diverse compounds have been found, but fierce IP competition for a preferred 2-aminopyrimidine scaffold is becoming apparent. Recent investigations into the role of the histamine H(4)R in (patho)physiology and the use of H4R ligands in in vivo disease models reveal enormous potential in the field of inflammation and allergy, among others. The development of ligands that display activity at two or more histamine receptor (HR) subtypes is another clinical opportunity that is currently being explored. Taken together, the histamine H4R field is gearing up for clinical studies and has the potential to deliver another generation of blockbuster drugs.

New metal-organic frameworks of [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La, Ce) and [Ce2(C2O4)(C6H6O7)2] . 4H2O

International Nuclear Information System (INIS)

Weng Shengfeng; Wang, Yun-Hsin; Lee, Chi-Shen

2012-01-01

Two novel materials, [M(C 6 H 5 O 7 )(C 6 H 6 O 7 )(C 6 H 7 O 7 )(H 2 O)] . H 2 O (M=La(1a), Ce(1b)) and [Ce 2 (C 2 O 4 )(C 6 H 6 O 7 ) 2 ] . 4H 2 O (2), with a metal-organic framework (MOF) were prepared with hydrothermal reactions and characterized with photoluminescence, magnetic susceptibility, thermogravimetric analysis and X-ray powder diffraction in situ. The crystal structures were determined by single-crystal X-ray diffraction. Compound 1 crystallized in triclinic space group P1-bar (No. 2); compound 2 crystallized in monoclinic space group P2 1 /c (No. 14). The structure of 1 is built from a 1D MOF, composed of deprotonated citric ligands of three kinds. Compound 2 contains a 2D MOF structure consisting of citrate and oxalate ligands; the oxalate ligand arose from the decomposition in situ of citric acid in the presence of Cu II ions. Photoluminescence spectra of compounds 1b and 2 revealed transitions between the 5d 1 excited state and two levels of the 4f 1 ground state ( 2 F 5/2 and 2 F 7/2 ). Compounds 1b and 2 containing Ce III ion exhibit a paramagnetic property with weak antiferromagnetic interactions between the two adjacent magnetic centers. - Graphical Abstract: [M(C 6 H 5 O 7 )(C 6 H 6 O 7 )(C 6 H 7 O 7 )(H 2 O)] . H 2 O (M=La(1a), Ce(1b)) and [Ce 2 (C 2 O 4 )(C 6 H 6 O 7 ) 2 ] . 4H 2 O (2)—with 1D and 2D structures were synthesized and characterized. Highlights: ► Two MOF – [M(C 6 H 5 O 7 )(C 6 H 6 O 7 )(C 6 H 7 O 7 )(H 2 O)] . H 2 O (M=La(1a), Ce(1b)) and [Ce 2 (C 2 O 4 )(C 6 H 6 O 7 ) 2 ] . 4H 2 O (2) – with 1D and 2D structures. ► The adjacent chains of the 1D framework were correlated with each other through an oxalate ligand to form a 2D layer structure. ► The source of the oxalate ligand was the decomposition in situ of citric acid oxidized in the presence of Cu II ions.

Reversibly Switchable, pH-Dependent Peptide Ligand Binding via 3,5-Diiodotyrosine Substitutions.

Science.gov (United States)

Ngambenjawong, Chayanon; Sylvestre, Meilyn; Gustafson, Heather H; Pineda, Julio Marco B; Pun, Suzie H

2018-04-20

Cell type-specific targeting ligands utilized in drug delivery applications typically recognize receptors that are overexpressed on the cells of interest. Nonetheless, these receptors may also be expressed, to varying extents, on off-target cells, contributing to unintended side effects. For the selectivity profile of targeting ligands in cancer therapy to be improved, stimuli-responsive masking of these ligands with acid-, redox-, or enzyme-cleavable molecules has been reported, whereby the targeting ligands are exposed in specific environments, e.g., acidic tumor hypoxia. One possible drawback of these systems lies in their one-time, permanent trigger, which enables the "demasked" ligands to bind off-target cells if released back into the systemic circulation. A promising strategy to address the aforementioned problem is to design ligands that show selective binding based on ionization state, which may be microenvironment-dependent. In this study, we report a systematic strategy to engineer low pH-selective targeting peptides using an M2 macrophage-targeting peptide (M2pep) as an example. 3,5-Diiodotyrosine mutagenesis into native tyrosine residues of M2pep confers pH-dependent binding behavior specific to acidic environment (pH 6) when the amino acid is protonated into the native tyrosine-like state. At physiological pH of 7.4, the hydroxyl group of 3,5-diiodotyrosine on the peptide is deprotonated leading to interruption of the peptide native binding property. Our engineered pH-responsive M2pep (Ac-Y-Î-Î) binds target M2 macrophages more selectively at pH 6 than at pH 7.4. In addition, 3,5-diiodotyrosine substitutions also improve serum stability of the peptide. Finally, we demonstrate pH-dependent reversibility in target binding via a postbinding peptide elution study. The strategy presented here should be applicable for engineering pH-dependent functionality of other targeting peptides with potential applications in physiology-dependent in vivo targeting

Synthesis of new 3-(2-aminothiazol-4-yl-4-hydroxy-2H-chromen-2-one derivatives

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S. SUKDOLAK

2006-06-01

Full Text Available Aminothiazole derivatives of 4-hydroxy-2H-chromen-2-one were prepared by the Hantzsch reaction1 using 3-(2-bromoacetyl-4-hydroxy-2H-chromen-2-one and thiourea derivatives. Starting compound for this synthesis 3-(2-bromoacetyl-4-hydroxy- 2H-chromen-2-one (1 was prepared previously.2 Also, for this synthesis we used thiourea derivatives (2a–j as compounds which possess groups with biological activity. Reactions are carried out in refluxing ethanol for a period of 30 – 45 min. Final products (3a–j are obtained in a high yield. Chemical structure of the obtained compounds was confirmed by elemental and structural analysis (IR and 1H NMR spectroscopy.

Ligand-controlled, tunable silver-catalyzed C-H amination.

Science.gov (United States)

Alderson, Juliet M; Phelps, Alicia M; Scamp, Ryan J; Dolan, Nicholas S; Schomaker, Jennifer M

2014-12-03

The development of readily tunable and regioselective C-H functionalization reactions that operate solely through catalyst control remains a challenge in modern organic synthesis. Herein, we report that simple silver catalysts supported by common nitrogenated ligands can be used to tune a nitrene transfer reaction between two different types of C-H bonds. The results reported herein represent the first example of ligand-controlled and site-selective silver-promoted C-H amination.

The expression of the beta cell-derived autoimmune ligand for the killer receptor nkp46 is attenuated in type 2 diabetes.

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Chamutal Gur

Full Text Available NK cells rapidly kill tumor cells, virus infected cells and even self cells. This is mediated via killer receptors, among which NKp46 (NCR1 in mice is prominent. We have recently demonstrated that in type 1 diabetes (T1D NK cells accumulate in the diseased pancreas and that they manifest a hyporesponsive phenotype. In addition, we found that NKp46 recognizes an unknown ligand expressed by beta cells derived from humans and mice and that blocking of NKp46 activity prevented diabetes development. Here we investigated the properties of the unknown NKp46 ligand. We show that the NKp46 ligand is mainly located in insulin granules and that it is constitutively secreted. Following glucose stimulation the NKp46 ligand translocates to the cell membrane and its secretion decreases. We further demonstrate by using several modalities that the unknown NKp46 ligand is not insulin. Finally, we studied the expression of the NKp46 ligand in type 2 diabetes (T2D using 3 different in vivo models and 2 species; mice and gerbils. We demonstrate that the expression of the NKp46 ligand is decreased in all models of T2D studied, suggesting that NKp46 is not involved in T2D.

A quantum dynamical study of the rotation of the dihydrogen ligand in the Fe(H)2(H2)(PEtPh2)3 coordination complex

Science.gov (United States)

Gonzalez, Megan E.; Eckert, Juergen; Aquino, Adelia J. A.; Poirier, Bill

2018-04-01

Progress in the hydrogen fuel field requires a clear understanding and characterization of how materials of interest interact with hydrogen. Due to the inherently quantum mechanical nature of hydrogen nuclei, any theoretical studies of these systems must be treated quantum dynamically. One class of material that has been examined in this context are dihydrogen complexes. Since their discovery by Kubas in 1984, many such complexes have been studied both experimentally and theoretically. This particular study examines the rotational dynamics of the dihydrogen ligand in the Fe(H)2(H2)(PEtPh2)3 complex, allowing for full motion in both the rotational degrees of freedom and treating the quantum dynamics (QD) explicitly. A "gas-phase" global potential energy surface is first constructed using density functional theory with the Becke, 3-parameter, Lee-Yang-Parr functional; this is followed by an exact QD calculation of the corresponding rotation/libration states. The results provide insight into the dynamical correlation of the two rotation angles as well as a comprehensive analysis of both ground- and excited-state librational tunneling splittings. The latter was computed to be 6.914 cm-1—in excellent agreement with the experimental value of 6.4 cm-1. This work represents the first full-dimensional ab initio exact QD calculation ever performed for dihydrogen ligand rotation in a coordination complex.

Novel 4-phenylpiperidine-2,6-dione derivatives. Ligands for α1-adrenoceptor subtypes

KAUST Repository

Romeo, Giuseppe F.

2011-07-01

A number of new 4-phenylpiperidine-2,6-diones bearing at the 1-position an ω-[4-(substituted phenyl)piperazin-1-yl]alkyl moiety were designed and synthesized as ligands for the α1-adrenergic receptor (α1-AR) subtypes. Some synthesized compounds, tested in binding assays for the human cloned α1A-, α1B-, and α1D-AR subtypes, displayed affinities in the nanomolar range. Highest affinity values were found in derivatives having a butyl connecting chain between the 4-phenylpiperidine-2,6-dione and the phenylpiperazinyl moieties. 1-[4-[4-(2-Methoxyphenyl)piperazin-1-yl]butyl]-4-phenylpiperidine-2,6- dione (34) showed the best affinity for the α1A-AR (pK i = 8.74) and 10-fold selectivity compared to the other two α1-AR subtypes. Some representative compounds were also tested in order to evaluate their effects on the signal transduction pathway coupled to α1-AR subtypes. They all blocked norepinephrine-induced stimulation of inositol phospholipid hydrolysis, thus behaving as antagonists. Binding data were used to refine a previously developed pharmacophoric model for α1D-ARs. The revised model shows a highly predictive power and could be useful for the future design of high affinity α1D-AR ligands. © 2011 Elsevier Masson SAS. All rights reserved.

Novel 4-phenylpiperidine-2,6-dione derivatives. Ligands for α1-adrenoceptor subtypes

KAUST Repository

Romeo, Giuseppe F.; Materia, Luisa; Modica, Maria Nunziata; Pittal, Valeria; Salerno, Loredana; Siracusa, Maria Angela; Manetti, Fabrizio; Botta, Maurizio; Minneman, Kenneth P.

2011-01-01

A number of new 4-phenylpiperidine-2,6-diones bearing at the 1-position an ω-[4-(substituted phenyl)piperazin-1-yl]alkyl moiety were designed and synthesized as ligands for the α1-adrenergic receptor (α1-AR) subtypes. Some synthesized compounds, tested in binding assays for the human cloned α1A-, α1B-, and α1D-AR subtypes, displayed affinities in the nanomolar range. Highest affinity values were found in derivatives having a butyl connecting chain between the 4-phenylpiperidine-2,6-dione and the phenylpiperazinyl moieties. 1-[4-[4-(2-Methoxyphenyl)piperazin-1-yl]butyl]-4-phenylpiperidine-2,6- dione (34) showed the best affinity for the α1A-AR (pK i = 8.74) and 10-fold selectivity compared to the other two α1-AR subtypes. Some representative compounds were also tested in order to evaluate their effects on the signal transduction pathway coupled to α1-AR subtypes. They all blocked norepinephrine-induced stimulation of inositol phospholipid hydrolysis, thus behaving as antagonists. Binding data were used to refine a previously developed pharmacophoric model for α1D-ARs. The revised model shows a highly predictive power and could be useful for the future design of high affinity α1D-AR ligands. © 2011 Elsevier Masson SAS. All rights reserved.

Synthesis and X-ray structure of the dysprosium(III complex derived from the ligand 5-chloro-1,3-diformyl-2-hydroxybenzene-bis-(2-hydroxybenzoylhydrazone [Dy2(C22H16ClN4O53](SCN 3.(H2O.(CH3OH

Directory of Open Access Journals (Sweden)

Aliou H. Barry

2003-12-01

Full Text Available The title compound [Dy2(C22H16ClN4O53](SCN 3.(H2O.(CH3OH has been synthesized and its crystal structure determined by single X-ray diffraction at room temperature. The two nine coordinated Dy(III are bound to three macromolecules ligand through the phenolic oxygens of the p-chlorophenol moieties, the nitrogen atoms and the carbonyl functions of the hydrazonic moieties. The phenolic oxygen atoms of the 2-hydroxybenzoyl groups are not bonded to the metal ions. In the bases of the coordination polyhedra the six Dy-N bonds are in the range 2.563(13-2.656(13 Å and the twelve Dy-O bonds are in the range 2.281(10-2.406(10 Å.

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�

Pd(II)-Catalyzed Ortho- or Meta-C–H Olefination of Phenol Derivatives

Science.gov (United States)

Dai, Hui-Xiong; Li, Gang; Zhang, Xing-Guo; Stepan, Antonia F.

2013-01-01

A combination of weakly coordinating auxiliaries and ligand acceleration allows for the development of both ortho- and meta-selective C–H olefination of phenol derivatives. These reactions demonstrate the feasibility of directing C–H functionalizations when functional groups are distal to target C–H bonds. The meta-C–H functionalization of electron-rich phenol derivatives is unprecedented and orthogonal to previous electrophilic substitution of phenols in terms of regioselectivity. These methods are also applied to functionalize α-phenoxyacetic acids, a fibrate class of drug scaffolds. PMID:23614807

C-H and H-H Bond Activation via Ligand Dearomatization/Rearomatization of a PN3P-Rhodium(I) Complex

KAUST Repository

Huang, Kuo-Wei; Wang, Yuan; Zheng, Bin; Pan, Yupeng; Pan, Chengling; He, Lipeng

2015-01-01

A neutral complex PN3P-Rh(I)Cl (2) was prepared from a reaction of the PN3P pincer ligand (1) with [Rh(COD)Cl]2 (COD = 1,5-cyclooctadiene). Upon treatment with a suitable base, H–H and Csp2–H activation reactions can be achieved through

Tridentate hydrazone metal complexes derived from cephalexin and 2-hydrazinopyridine: Synthesis, characterization and antibacterial activity

Science.gov (United States)

Anacona, J. R.; Rincones, Maria

2015-04-01

Metal(II) coordination compounds of a tridentate hydrazone ligand (HL) derived from the condensation of cephalexin antibiotic with 2-hydrazinopyridine were synthesized. The hydrazone ligand and mononuclear [ML(OAc)(H2O)] (M(II) = Mn, Co, Ni, Cu, Zn, Ag) complexes were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and 1H NMR spectral studies. The cephalexin 2-pyridinylhydrazone ligand HL behaves as a monoanionic tridentate NNO chelating agent. The biological applications of complexes have been studied on three bacteria strains (Escherichia coli, Acinetobacter baumannii and Enterococcus faecalis) by agar diffusion disc method.

Xanthene and Xanthone Derivatives as G-Quadruplex Stabilizing Ligands

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Alessandro Altieri

2013-10-01

Full Text Available Following previous studies on anthraquinone and acridine-based G-quadruplex ligands, here we present a study of similar aromatic cores, with the specific aim of increasing G-quadruplex binding and selectivity with respect to duplex DNA. Synthesized compounds include two and three-side chain xanthone and xanthene derivatives, as well as a dimeric “bridged” form. ESI and FRET measurements suggest that all the studied molecules are good G-quadruplex ligands, both at telomeres and on G-quadruplex forming sequences of oncogene promoters. The dimeric compound and the three-side chain xanthone derivative have been shown to represent the best compounds emerging from the different series of ligands presented here, having also high selectivity for G-quadruplex structures with respect to duplex DNA. Molecular modeling simulations are in broad agreement with the experimental data.

Synthesis of 2-amino-4H-chromene derivatives under microwave ...

Indian Academy of Sciences (India)

ing method to construct the 2-amino-4H-chromene skeleton. 2. Experimental. 2.1 Materials and methods .... ing 2-amino-4H-chromene (3a–r) derivatives in good .... Students. Supplementary information. The electronic supporting information ...

Chemistry of the oxophosphinidene ligand. 2. Reactivity of the anionic complexes [MCp{P(O)R*}(CO)(2)](-) (M = Mo, W; R* = 2,4,6-C(6)H(2)(t)Bu(3)) toward electrophiles based on elements different from carbon.

Science.gov (United States)

Alonso, María; Alvarez, M Angeles; García, M Esther; Ruiz, Miguel A; Hamidov, Hayrullo; Jeffery, John C

2010-12-20

The anionic oxophosphinidene complexes (H-DBU)[MCp{P(O)R*}(CO)(2)] (M = Mo, W; R* = 2,4,6-C(6)H(2)(t)Bu(3); Cp = η(5)-C(5)H(5), DBU = 1,8-diazabicyclo [5.4.0] undec-7-ene) displayed multisite reactivity when faced with different electrophilic reagents. The reactions with the group 14 organochloride compounds ER(4-x)Cl(x) (E = Si, Ge, Sn, Pb) led to either phosphide-like, oxophosphinidene-bridged derivatives [MCp{P(OE')R*}(CO)(2)] (E' = SiMe(3), SiPh(3), GePh(3), GeMe(2)Cl) or to terminal oxophosphinidene complexes [MCp{P(O)R*}(CO)(2)(E')] (E' = SnPh(3), SnPh(2)Cl, PbPh(3); Mo-Pb = 2.8845(4) Å for the MoPb compound). A particular situation was found in the reaction with SnMe(3)Cl, this giving a product existing in both tautomeric forms, with the phosphide-like complex [MCp{P(OSnMe(3))R*}(CO)(2)] prevailing at room temperature and the tautomer [MCp{P(O)R*}(CO)(2)(SnMe(3))] being the unique species present below 203 K in dichloromethane solution. The title anions also showed a multisite behavior when reacting with transition-metal based electrophiles. Thus, the reactions with the complexes [M'Cp(2)Cl(2)] (M' = Ti, Zr) gave phosphide-like derivatives [MCp{P(OM')R*}(CO)(2)] (M = Mo, M' = TiCp(2)Cl, ZrCp(2)Cl; M = W, M' = ZrCp(2)Cl), displaying a bridging κ(1),κ(1)-P,O- oxophosphinidene ligand connecting MCp(CO)(2) and M'Cp(2)Cl metal fragments (W-P = 2.233(1) Å, O-Zr = 2.016(4) Å for the WZr compound]. In contrast, the reactions with the complex [AuCl{P(p-tol)(3)}] gave the metal-metal bonded derivatives trans-[MCp{P(O)R*}(CO)(2){AuP(p-tol)(3)}] (M = Mo, W; Mo-Au = 2.7071(7) Å). From all the above results it was concluded that the terminal oxophosphinidene complexes are preferentially formed under conditions of orbital control, while charge-controlled reactions tend to give derivatives with the electrophilic fragment bound to the oxygen atom of the oxophosphinidene ligand (phosphide-like, oxophosphinidene-bridged derivatives).

Physico-chemical characterization of mixed-ligand complexes of Mn(III based on the acetylacetonate and maleic acid and its hydroxylamine derivative

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Cakić Suzana M.

2005-01-01

Full Text Available Two new Mn(III mixed-ligand complexes with two acetylacetonate (acac ligands and one maleate ligand and its hydroxylamine derivative of the general formula [Mn(C5H7O22L] were prepared. Their structure was established by using elemental analysis, FTIR and UV/VIS spectroscopic methods, as well as magnetic measurement. Replacement of the acetylacetonate ligand by the corresponding acid ligand has been confirmed in Mn(III acetylacetonate. Based on the obtained experimental data and literature indications, structural formulae to these compounds were assigned.

Construction of three metal-organic frameworks based on multifunctional T-shaped tripodal ligands, H3PyImDC

KAUST Repository

Jing, Xuemin

2010-08-04

Three novel metal-organic frameworks (MOFs), |(C3H 7NO)2(H2O)|[Zn3(C10H 5N3O4)3(C3H 7NO)2] (1), |(H2O)5(H 3O)(NO3)|[Nd2(C10H5N 3O4)3(H2O)4] (2), and |(H2O)2|[Nd3(C10H5N 3O4)3(C10H4N 3O4)] (3), based on the T-shaped tripodal ligands 2-(pyridine-4-yl)-1H-4,5-imidazoledicarboxylic acid and 2-(pyridine-3-yl)-1H-4, 5-imidazoledicarboxylic acid (H3PyImDC), have been constructed under solvo-/hydrothermal conditions. The diverse coordination modes of H 3PyImDC ligands have afforded the assembly of three novel compounds. In compound 1, two oxygen atoms and three nitrogen atoms of the H 3PyImDC ligand, a T-shaped linker, coordinate to two zinc centers to form a novel bbm net with two distinct channels along the [100] and [001] directions. In compound 2, H3PyImDC ligands coordinate to neodymium centers to form a ladder-like chain which then interacts with a water molecules chain via hydrogen-bondings to construct a 3D supermolecular structure. In compound 3, H3PyImDC ligands, a T-shaped linker, coordinate to neodymium centers to form a (3,6)-connected net with an ant topology. In compounds 1-3, the two H3PyImDC ligands exhibit different coordination modes with zinc and neodymium centers, which afforded the expected structural diversity. Additionally, all three compounds exhibit strong fluorescence emissions in the solid state at room temperature. © 2010 American Chemical Society.

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)

Chiral ligands derived from monoterpenes: application in the synthesis of optically pure secondary alcohols via asymmetric catalysis.

Science.gov (United States)

El Alami, Mohammed Samir Ibn; El Amrani, Mohamed Amin; Agbossou-Niedercorn, Francine; Suisse, Isabelle; Mortreux, André

2015-01-19

The preparation of optically pure secondary alcohols in the presence of catalysts based on chiral ligands derived from monoterpenes, such as pinenes, limonenes and carenes, is reviewed. A wide variety of these ligands has been synthesized and used in several catalytic reactions, including hydrogen transfer, C-C bond formation via addition of organozinc compounds to aldehydes, hydrosilylation, and oxazaborolidine reduction, leading to high activities and enantioselectivities. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reactions of Cp2MCl2 (M=Ti or Zr with Imine-Oxime Ligands. Formation of Metallacycles

Directory of Open Access Journals (Sweden)

C. Tripathi

2005-07-01

Full Text Available The reactions of bis(cyclopentadienyltitanium(IV/zirconium(IV dichloridewith a series of imine-oxime ligands (LH2, derived by condensing benzil-α-monoxime and2-phenylenediamine, 4-phenylenediamine, 4-methyl-2-phenylenediamine, 2,6-diamino-pyridine, have been studied in anhydrous tetrahydrofuran in the presence of base andmetallocycles of the [Cp2M(L] (M=Ti or Zr type have been isolated. Tentative structureshave been proposed for the products based on elemental analysis, electrical conductance andspectral (electronic, IR and 1H-NMR data. Proton NMR spectra indicate that on the NMRtime scale there is rapid rotation of the cyclopentadienyl ring around the metal-ring axis at25oC. Studies were conducted to assess the growth inhibiting potential of the complexessynthesized and the ligands against various bacterial strains.

Hydrogen/deuterium fractionation factors of the aqueous ligand of cobalt in Co(H2O)62+ and Co(II)-substituted carbonic anhydrase

International Nuclear Information System (INIS)

Kassebaum, J.W.

1988-01-01

The author has measured the hydrogen/deuterium fractionation factor for the rapidly exchanging aqueous ligands of cobalt in Co(H 2 O) 6 2+ and in three Co(II)-substituted isozymes of carbonic anhydrase. The fractionation factor was determined from NMR relaxation rates at 300 MHz of the protons of water in mixed solutions of H 2 O and D 2 O containing these complexes. In each case, the paramagnetic contribution to 1/T 2 was greater than to 1/T 1 , consistent with a chemical shift mechanism affecting 1/T 2 . The fractionation factors obtained from T 2 were 0.73 ± 0.02 for Co(H 2 O) 6 2+ , 0.72 ± 0.02 for Co(II)-substituted carbonic anhydrase I, 0.77 ± 0.01 for Co(II)-substituted carbonic anhydrase II, and 1.00 ± 0.07 for Co(Il)-substituted carbonic anhydrase III. He concluded that fractionation factors in these cases determined from T 1 and T 2 measured isotope preferences for different populations of ligand sites. Since T 2 has a large contribution from a chemical shift mechanism, the fractionation factor determined from T 2 has a large contribution of the fractionation of inner shell ligands. The fractionation factor of Co(H 2 O) 6 2+ was used to interpret the solvent hydrogen isotope effects on the formation of complexes of cobalt with the bidentate ligands glycine, N,N-dimethylglycine, and acetylacetone. The contribution of the fractionation factor of the inner water shell in Co(H 2 O) 6 2+ did not account completely for the measured isotope effect, and that the hydrogen/deuterium fractionation of outer shell water makes a large contribution to the isotope effect on the formation of these complexes

Polymerization of 1,3-butadiene catalyzed by pincer cobalt(II) complexes derived from 2-(1-arylimino)-6-(pyrazol-1-yl)pyridine ligands

KAUST Repository

Gong, Dirong; Jia, Weiguo; Chen, Tao; Huang, Kuo-Wei

2013-01-01

A new class of air stable and structurally well-defined cobalt complexes with unsymmetrical pincer type ligands ([2-(ArNCMe)-6-(Py)C5H 3N]CoCl2) (Ar = C6H5, Py = pyrazol-1-yl, 5a; Ar = 2,4,6-Me3C6H2, Py = pyrazol-1-yl, 5b; Ar = 2,6-iPr2C6H3, Py

C-H and H-H Bond Activation via Ligand Dearomatization/Rearomatization of a PN3P-Rhodium(I) Complex

KAUST Repository

Huang, Kuo-Wei

2015-04-13

A neutral complex PN3P-Rh(I)Cl (2) was prepared from a reaction of the PN3P pincer ligand (1) with [Rh(COD)Cl]2 (COD = 1,5-cyclooctadiene). Upon treatment with a suitable base, H–H and Csp2–H activation reactions can be achieved through the deprotonation/reprotonation of one of the N–H arms and dearomatization/rearomatization of the central pyridine ring with the oxidation state of Rh remaining I.

(E-6-Amino-1,3-dimethyl-5-[(pyridin-2-ylmethylideneamino]pyrimidine-2,4(1H,3H-dione

Directory of Open Access Journals (Sweden)

Irvin Booysen

2011-09-01

Full Text Available In the title compound, C12H13N5O2, a Schiff-base-derived chelate ligand, the non-aromatic heterocycle and its substituents essentially occupy one common plane (r.m.s. of fitted non-H atoms = 0.0503 Å. The N=C bond is E-configured. Intracyclic angles in the pyridine moiety cover the range 117.6 (2–124.1 (2°. Intra- and intermolecular N—H...N and N—H...O hydrogen bonds are observed in the crystal structure, as are intra- and intermolecular C—H...O contacts which, in total, connect the molecules into a three-dimensional network. The shortest ring-centroid-to-ring-centroid distance of 3.5831 (14 Å is between the two different types of six-membered rings.

Spectroscopic and Computational Investigations of Ligand Binding to IspH: Discovery of Non-diphosphate Inhibitors

Energy Technology Data Exchange (ETDEWEB)

O' Dowd, Bing [Department of Chemistry, University of Illinois, 600 South Mathews Avenue Urbana IL 61801 USA; Williams, Sarah [Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla CA 92093 USA; Wang, Hongxin [Department of Chemistry, University of California, 1 Shields Avenue Davis CA 95616 USA; Lawrence Berkeley National Laboratory, 1 Cyclotron Road Berkeley CA 94720 USA; No, Joo Hwan [Center for Biophysics and Computational Biology, Urbana, IL (United States); Rao, Guodong [Department of Chemistry, University of Illinois, 600 South Mathews Avenue Urbana IL 61801 USA; Wang, Weixue [Center for Biophysics and Computational Biology, Urbana, IL (United States); McCammon, J. Andrew [Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla CA 92093 USA; Howard Hughes Medical Institute, University of California at San Diego, La Jolla CA 92093 USA; National Biomedical Computation Resource, University of California at San Diego, La Jolla CA 92093 USA; Cramer, Stephen P. [Department of Chemistry, University of California, 1 Shields Avenue Davis CA 95616 USA; Lawrence Berkeley National Laboratory, 1 Cyclotron Road Berkeley CA 94720 USA; Oldfield, Eric [Department of Chemistry, University of Illinois, 600 South Mathews Avenue Urbana IL 61801 USA

2017-04-07

Isoprenoid biosynthesis is an important area for anti-infective drug development. One isoprenoid target described is (E)-1-hydroxy-2-methyl-but-2-enyl 4-diphosphate (HMBPP) reductase (IspH), which forms isopentenyl diphosphate and dimethylallyl diphosphate from HMBPP in a 2H + /2e - reduction. IspH contains a 4 Fe-4 S cluster, and in this work, we first investigated how small molecules bound to the cluster by using HYSCORE and NRVS spectroscopies. The results of these, as well as other structural and spectroscopic investigations, led to the conclusion that, in most cases, ligands bound to IspH 4 Fe-4 S clusters by η 1 coordination, forming tetrahedral geometries at the unique fourth Fe, ligand side chains preventing further ligand (e.g., H 2 O, O 2 ) binding. Based on these ideas, we used in silico methods to find drug-like inhibitors that might occupy the HMBPP substrate binding pocket and bind to Fe, leading to the discovery of a barbituric acid analogue with a K i value of ≈500 nm against Pseudomonas aeruginosa IspH.

Interactions of ligands with active and inactive conformations of the dopamine D2 receptor.

Science.gov (United States)

Malmberg, A; Mohell, N; Backlund Höök, B; Johansson, A M; Hacksell, U; Nordvall, G

1998-04-10

The affinities of 19 pharmacologically diverse dopamine D2 receptor ligands were determined for the active and inactive conformations of cloned human dopamine D2 receptors expressed in Ltk cells. The agonist [3H]quinpirole was used to selectively label the guanine nucleotide-binding protein-coupled, active receptor conformation. The antagonist [3H]raclopride, in the presence of the non-hydrolysable GTP-analogue Gpp(NH)p and sodium ions and in the absence of magnesium ions, was used to label the free inactive receptor conformation. The intrinsic activities of the ligands were determined in a forskolin-stimulated cyclic AMP assay using the same cells. An excellent correlation was shown between the affinity ratios (KR/KRG) of the ligands for the two receptor conformations and their intrinsic activity (r=0.96). The ligands included eight structurally related and enantiopure 2-aminotetralin derivatives; the enantiomers of 5-hydroxy-2-(dipropylamino)tetralin, 5-methoxy-2-(dipropylamino)tetralin, 5-fluoro-2-(dipropylamino)tetralin and 2-(dipropylamino)tetralin. The (S)-enantiomers behaved as full agonists in the cyclic AMP assay and displayed a large KR/KRG ratio. The (R)-enantiomers were classified as partial agonists and had lower ratios. The structure-affinity relationships of these compounds at the active and the inactive receptor conformations were analysed separately, and used in conjunction with a homology based receptor model of the dopamine D2 receptor. This led to proposed binding modes for agonists, antagonists and partial agonists in the 2-aminotetralin series. The concepts used in this study should be of value in the design of ligands with predetermined affinity and intrinsic activity.

Bis[1,3-bis(2,4,6-trimethylphenyl-2,3-dihydro-1H-imidazol-2-ylidene]dinitrosyl(tetrahydroborato-κ2H,H′tungsten(0

Directory of Open Access Journals (Sweden)

Heinz Berke

2011-01-01

Full Text Available In the title paramagnetic 19-electron neutral complex, [W(BH4(C21H24N22(NO2], the W(0 atom is coordinated by two 1,3-bis(2,4,6-trimethylphenylimidazol-2-ylidene (IMes carbene ligands, two NO groups and two H atoms of an η2-tetrahydroborate ligand. Depending on the number of coordination sites (n assigned to the BH4− ligand, the coordination geometry of the W atom may either be described as approximately trigonal–bipyramidal (n = 1 or as very distorted octahedral with the bridging H atoms filling two coordination positions (n = 2. In the latter case, the coplanar NO groups and bridging H atoms (r.m.s. deviation = 0.032 Å form one octahedral plane, with mutually trans-oriented carbene ligands. In the crystal, molecules are connected via C—H...O interactions.

Probing Ligand Exchange in the P450 Enzyme CYP121 from Mycobacterium tuberculosis: Dynamic Equilibrium of the Distal Heme Ligand as a Function of pH and Temperature.

Science.gov (United States)

Fielding, Andrew J; Dornevil, Kednerlin; Ma, Li; Davis, Ian; Liu, Aimin

2017-12-06

CYP121 is a cytochrome P450 enzyme from Mycobacterium tuberculosis that catalyzes the formation of a C-C bond between the aromatic groups of its cyclodityrosine substrate (cYY). The crystal structure of CYP121 in complex with cYY reveals that the solvent-derived ligand remains bound to the ferric ion in the enzyme-substrate complex. Whereas in the generally accepted P450 mechanism, binding of the primary substrate in the active-site triggers the release of the solvent-derived ligand, priming the metal center for reduction and subsequent O 2 binding. Here we employed sodium cyanide to probe the metal-ligand exchange of the enzyme and the enzyme-substrate complex. The cyano adducts were characterized by UV-vis, EPR, and ENDOR spectroscopies and X-ray crystallography. A 100-fold increase in the affinity of cyanide binding to the enzyme-substrate complex over the ligand-free enzyme was observed. The crystal structure of the [CYP121(cYY)CN] ternary complex showed a rearrangement of the substrate in the active-site, when compared to the structure of the binary [CYP121(cYY)] complex. Transient kinetic studies showed that cYY binding resulted in a lower second-order rate constant (k on (CN) ) but a much more stable cyanide adduct with 3 orders of magnitude slower k off (CN) rate. A dynamic equilibrium between multiple high- and low-spin species for both the enzyme and enzyme-substrate complex was also observed, which is sensitive to changes in both pH and temperature. Our data reveal the chemical and physical properties of the solvent-derived ligand of the enzyme, which will help to understand the initial steps of the catalytic mechanism.

Synthesis and properties of mixed-ligand ruthenium(II) complexes containing 2-(2-pyridyl)-benzimidazole and related ligands

International Nuclear Information System (INIS)

Haga, Masaaki; Tanaka, Toshio.

1979-01-01

Mixed-ligand ruthenium(II) complexes of the [Ru(bpy) 2 L]sup(n+) (ClO 4 )sub(n) type, where bpy= 2,2'-bipyridine; L= 2-(2-pyridyl)-benzimidazole (PBImH) when n= 2, and L= 2-(2-pyridyl)-benzimidazolate (PBIm) and 2-(o-hydroxyphenyl)-benzimidazole (OBImH) when n= 1, were prepared. Anodic peak potentials and ruthenium-to-bipyridine charge transfer bands of these complexes are rationalized in terms of the donor ability of L. (author)

Synthesis and properties of mixed-ligand ruthenium(II) complexes containing 2-(2-pyridyl)-benzimidazole and related ligands

Energy Technology Data Exchange (ETDEWEB)

Haga, M [Mie Univ., Tsu (Japan); Tanaka, T

1979-07-01

Mixed-ligand ruthenium(II) complexes of the (Ru(bpy)/sub 2/L)sup(n+) (ClO/sub 4/)sub(n) type, where bpy= 2,2'-bipyridine; L= 2-(2-pyridyl)-benzimidazole (PBImH) when n= 2, and L= 2-(2-pyridyl)-benzimidazolate (PBIm) and 2-(o-hydroxyphenyl)-benzimidazole (OBImH) when n= 1, were prepared. Anodic peak potentials and ruthenium-to-bipyridine charge transfer bands of these complexes are rationalized in terms of the donor ability of L.

Novel 1H-1,2,3-, 2H-1,2,3-, 1H-1,2,4- and 4H-1,2,4-triazole derivatives: a patent review (2008 - 2011).

Science.gov (United States)

Ferreira, Vitor F; da Rocha, David R; da Silva, Fernando C; Ferreira, Patrícia G; Boechat, Núbia A; Magalhães, Jorge L

2013-03-01

The triazoles represent a class of five-membered heterocyclic compounds of great importance for the preparation of new drugs with diverse biological activities because they may present several structural variations with the same numbers of carbon and nitrogen atoms. Due to the success of various triazoles that entered the pharmaceutical market and are still being used in medicines, many companies and research groups have shown interest in developing new methods of synthesis and biological evaluation of potential uses for these compounds. In this review, the authors explored aspects of patents for the 1H-1,2,3-, 2H-1,2,3-, 1H-1,2,4- and 4H-1,2,4-triazole families, including prototypes being considered in clinical studies between 2008 and 2011. The triazoles have been studied for over a century as an important class of heterocyclic compounds and still attract considerable attention due to their broad range of biological activities. More recently, there has been considerable interest in the development of novel triazoles with anti-inflammatory, antiplatelet, antimicrobial, antimycobacterial, antitumoral and antiviral properties and activity against several neglected diseases. This review emphasizes recent perspective and advances in the therapeutically active 1H-1,2,3-, 2H-1,2,3-, 1H-1,2,4- and 4H-1,2,4-triazole derivative patents between 2008 and 2011, covering the development of new chemical entities and new pharmaceuticals. Many studies have focused on these compounds as target structures and evaluated them in several biological targets. The preparation of 1H-1,2,3-, 2H-1,2,3-, 1H-1,2,4- and 4H-1,2,4-triazole derivatives brings to light several issues. There is a need to find new, more efficient preparations for these triazoles that take into consideration current issues in green chemistry, energy saving and sustainability. New diseases are discovered and new viruses and bacteria continue to challenge mankind, so it is imperative to find new prototypes for these

Diverse CdII coordination complexes derived from bromide isophthalic acid binding with auxiliary N-donor ligands

International Nuclear Information System (INIS)

Tang, Meng; Dong, Bao-Xia; Wu, Yi-Chen; Yang, Fang; Liu, Wen-Long; Teng, Yun-Lei

2016-01-01

The coordination characteristics of 4-bromoisophthalic acid (4-Br-H 2 ip) have been investigated in a series of Cd II -based frameworks. Hydrothermal reactions of Cd II salts and 4-Br-H 2 ip together with flexible or semiflexible N-donor auxiliary ligands resulted in the formation of four three-dimensional coordination complexes with diverse structures: (Cd(bix) 0.5 (bix) 0.5 (4-Br-ip)]·H 2 O) n (1), [Cd(bbi) 0.5 (bbi) 0.5 (4-Br-ip)] n (2), ([Cd(btx) 0.5 (4-Br-ip)(H 2 O)]·0.5CH 3 OH·H 2 O) n (3) and ([Cd(bbt) 0.5 (4-Br-ip)(H 2 O)]·3·5H 2 O) n (4). These compounds were characterized by elemental analyses, IR spectra, single-crystal and powder X-ray diffraction. They displayed diverse structures depending on the configuration of the 4-connected metal node, the coordination mode of the 4-Br-H 2 ip, the coordination ability and conformationally flexibility of the N-donor auxiliary. Compound 1 exhibits 3-fold interpenetrated 6 6 topology and compound 2 has a 4 12 topology. Compounds 3–4 have similar 3D pillar-layered structures based on 3,4-connected binodal net with the Schläfli symbol of (4·3 8 ). The thermal stabilities and photoluminescence properties of them were discussed in detail. - Graphical abstract: Four 3D Cd II coordination complexes on the basis of 4-bromoisophthalic acid (4-Br-H 2 ip) and two types of flexible (bbi, bbt) and semiflexible (bix, btx) N-donor ligands are prepared. They displayed diverse topology structures of 6 6 (1), 4 12 (2) and 4·3 8 (3−4), depending on the configuration of the 4-connected metal node, the coordination mode of the 4-Br-H 2 ip, the coordination ability and conformationally flexibility of the N-donor auxiliary ligand. - Highlights: • Four 3D Cd II coordination complexes based on 4-Br-H 2 ip and flexible/semiflexible N-donor ligands have been synthesized. • They displayed diverse topology structures of 6 6 for 1, 4 12 for 2 and 4·3 8 for 3–4. • The structural diversity depends on the configuration of 4-Br-H

Two novel mixed-ligand complexes containing organosulfonate ligands.

Science.gov (United States)

Li, Mingtian; Huang, Jun; Zhou, Xuan; Fang, Hua; Ding, Liyun

2008-07-01

The structures reported herein, viz. bis(4-aminonaphthalene-1-sulfonato-kappaO)bis(4,5-diazafluoren-9-one-kappa(2)N,N')copper(II), [Cu(C(10)H(8)NO(3)S)(2)(C(11)H(6)N(2)O)(2)], (I), and poly[[[diaquacadmium(II)]-bis(mu-4-aminonaphthalene-1-sulfonato)-kappa(2)O:N;kappa(2)N:O] dihydrate], {[Cd(C(10)H(8)NO(3)S)(2)(H(2)O)(2)].2H(2)O}(n), (II), are rare examples of sulfonate-containing complexes where the anion does not fulfill a passive charge-balancing role, but takes an active part in coordination as a monodentate and/or bridging ligand. Monomeric complex (I) possesses a crystallographic inversion center at the Cu(II) atom, and the asymmetric unit contains one-half of a Cu atom, one complete 4-aminonaphthalene-1-sulfonate (ans) ligand and one 4,5-diazafluoren-9-one (DAFO) ligand. The Cu(II) atom has an elongated distorted octahedral coordination geometry formed by two O atoms from two monodentate ans ligands and by four N atoms from two DAFO molecules. Complex (II) is polymeric and its crystal structure is built up by one-dimensional chains and solvent water molecules. Here also the cation (a Cd(II) atom) lies on a crystallographic inversion center and adopts a slightly distorted octahedral geometry. Each ans anion serves as a bridging ligand linking two Cd(II) atoms into one-dimensional infinite chains along the [010] direction, with each Cd(II) center coordinated by four ans ligands via O and N atoms and by two aqua ligands. In both structures, there are significant pi-pi stacking interactions between adjacent ligands and hydrogen bonds contribute to the formation of two- and three-dimensional networks.

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.

Structure activity relationships of quinoxalin-2-one derivatives as platelet-derived growth factor-beta receptor (PDGFbeta R) inhibitors, derived from molecular modeling.

Science.gov (United States)

Mori, Yoshikazu; Hirokawa, Takatsugu; Aoki, Katsuyuki; Satomi, Hisanori; Takeda, Shuichi; Aburada, Masaki; Miyamoto, Ken-ichi

2008-05-01

We previously reported a quinoxalin-2-one compound (Compound 1) that had inhibitory activity equivalent to existing platelet-derived growth factor-beta receptor (PDGFbeta R) inhibitors. Lead optimization of Compound 1 to increase its activity and selectivity, using structural information regarding PDGFbeta R-ligand interactions, is urgently needed. Here we present models of the PDGFbeta R kinase domain complexed with quinoxalin-2-one derivatives. The models were constructed using comparative modeling, molecular dynamics (MD) and ligand docking. In particular, conformations derived from MD, and ligand binding site information presented by alpha-spheres in the pre-docking processing, allowed us to identify optimal protein structures for docking of target ligands. By carrying out molecular modeling and MD of PDGFbeta R in its inactive state, we obtained two structural models having good Compound 1 binding potentials. In order to distinguish the optimal candidate, we evaluated the structural activity relationships (SAR) between the ligand-binding free energies and inhibitory activity values (IC50 values) for available quinoxalin-2-one derivatives. Consequently, a final model with a high SAR was identified. This model included a molecular interaction between the hydrophobic pocket behind the ATP binding site and the substitution region of the quinoxalin-2-one derivatives. These findings should prove useful in lead optimization of quinoxalin-2-one derivatives as PDGFb R inhibitors.

Synthesis and structure of the extended phosphazane ligand [(1,4-C6H4){N(μ-PN(t)Bu)2N(t)Bu}2](4).

Science.gov (United States)

Sevilla, Raquel; Less, Robert J; García-Rodríguez, Raúl; Bond, Andrew D; Wright, Dominic S

2016-02-07

The reaction of the phenylene-bridged precursor (1,4-C6H4)[N(PCl2)2]2 with (t)BuNH2 in the presence of Et3N gives the new ligand precursor (1,4-C6H4)[N(μ-N(t)Bu)2(PNH(t)Bu)2]2, deprotonation of which with Bu2Mg gives the novel tetraanion [(1,4-C6H4){N(μ-N(t)Bu)2(PN(t)Bu)2}2](4-).

Formation of Mixed-Ligand Complexes of Pd2+ with Nucleoside 5'-Monophosphates and Some Metal-Ion-Binding Nucleoside Surrogates

Directory of Open Access Journals (Sweden)

Oleg Golubev

2014-10-01

Full Text Available Formation of mixed-ligand Pd2+ complexes between canonical nucleoside 5'-monophosphates and five metal-ion-binding nucleoside analogs has been studied by 1H-NMR spectroscopy to test the ability of these nucleoside surrogates to discriminate between unmodified nucleobases by Pd2+-mediated base pairing. The nucleoside analogs studied included 2,6-bis(3,5-dimethylpyrazol-1-yl-, 2,6-bis(1-methylhydrazinyl- and 6-(3,5-dimethylpyrazol-1-yl-substituted 9-(β-d-ribofuranosylpurines 1–3, and 2,4-bis(3,5-dimethylpyrazol-1-yl- and 2,4-bis(1-methylhydrazinyl-substituted 5-(β-d-ribofuranosyl-pyrimidines 4–5. Among these, the purine derivatives 1-3 bound Pd2+ much more tightly than the pyrimidine derivatives 4, 5 despite apparently similar structures of the potential coordination sites. Compounds 1 and 2 formed markedly stable mixed-ligand Pd2+ complexes with UMP and GMP, UMP binding favored by 1 and GMP by 2. With 3, formation of mixed-ligand complexes was retarded by binding of two molecules of 3 to Pd2+.

Synthesis and characterization of the Bis- Cyclometalating Ligand 3,3',5,5'-tetrakis[(dimethylamino)methyl]biphenyl and its use in the preparation of bimetallic M(II), M(IV) (M = Pt, Pd) and mixed-valence Pt(II)-Pt(IV) complexes via a dilithio-derivative. Crystal structure of the Pd dimer [ClPd{2,6-(Me2NCH2)2C6H2}]2,

NARCIS (Netherlands)

Koten, G. van; Lagunas, M.C.; Gossage, R.A.; Spek, A.L.

1998-01-01

The potentially bis-cyclometalating ligand 3,3',5,5'-tetrakis[(dimethylamino)methyl]biphenyl, was prepared from 3,5-(Me2NCH2)2C6H3Br in a one-pot synthesis involving lithium-halogen exchange, transmetalation, and reductive-elimination reactions. This ligand undergoes selective dilithiation in the 4

A pair of novel Cd(II) enantiomers based on lactate derivatives: Synthesis, crystal structures and properties

International Nuclear Information System (INIS)

Xu, Zhong-Xuan; Ao, Ke-Hou; Zhang, Jian

2016-01-01

A pair of novel 3D homochiral metal−organic frameworks (HMOFs), namely [Cd 2.5 ((R)-CIA) 6 (1,4-DIB)(H 2 O) 2 ]·((CH 3 ) 2 NH 2 )·H 2 O (1-D), [Cd 2.5 ((S)-CIA) 6 (1,4-DIB)(H 2 O) 2 ]·((CH 3 ) 2 NH 2 )·H 2 O (1-L), have been synthesized using lactic acid derivative ligands ((R)-H 3 CIA and (S)-H 3 CIA) and 1,4-DIB. Crystallographic analyses indicate that the complexes 1-D and 1-L are packed by cage substructures. Some physical characteristics, such as solid-state circular dichroism (CD), thermal stabilities and photoluminescent properties are also investigated. Our results highlight the effective method to apply lactic acid derivative ligands to form interesting HMOFs. - Graphical abstract: Using lactic acid derivative ligands ((R)-H 3 CIA and (S)-H 3 CIA) and 1,4-DIB to assemble with Cd 2+ ions, a pair of novel 3D homochiral metal-organic frameworks (HMOFs) with cage substructures have been synthesized. Display Omitted - Highlights: • Lactic acid derivative ligands • Cage substructure • Enantiomers

C-H and C-C activation of n -butane with zirconium hydrides supported on SBA15 containing N-donor ligands: [(≡SiNH-)(≡SiX-)ZrH2], [(≡SiNH-)(≡SiX-)2ZrH], and[(≡SiN=)(≡SiX-)ZrH] (X = -NH-, -O-). A DFT study

KAUST Repository

Pasha, Farhan Ahmad

2014-07-01

Density functional theory (DFT) was used to elucidate the mechanism of n-butane hydrogenolysis (into propane, ethane, and methane) on well-defined zirconium hydrides supported on SBA15 coordinated to the surface via N-donor surface pincer ligands: [(≡SiNH-)(≡SiO-)ZrH2] (A), [(≡SiNH-)2ZrH2] (B), [(≡SiNH-)(≡SiO-) 2ZrH] (C), [(≡SiNH-)2(≡SiO-)ZrH] (D), [(≡SiN=)(≡Si-O-)ZrH] (E), and [(≡SiN=)(≡SiNH-)ZrH] (F). The roles of these hydrides have been investigated in C-H/C-C bond activation and cleavage. The dihydride A linked via a chelating [N,O] surface ligand was found to be more active than B, linked to the chelating [N,N] surface ligand. Moreover, the dihydride zirconium complexes are also more active than their corresponding monohydrides C-F. The C-C cleavage step occurs preferentially via β-alkyl transfer, which is the rate-limiting step in the alkane hydrogenolysis. The energetics of the comparative pathways over the potential energy surface diagram (PES) reveals the hydrogenolysis of n-butane into propane and ethane. © 2014 American Chemical Society.

Triosmium cluster compounds containing isocyanide and hydride ligands. Crystal and molecular structures of (μ-H)(H)Os3(CO)10(CN-t-C4H9) and (μ-H)2Os3(CO)9(CN-t-C4H9)

International Nuclear Information System (INIS)

Adams, R.D.; Golembski, N.M.

1979-01-01

The structures of the compounds (μ-H)(H)Os 3 (CO) 10 (CN-t-C 4 H 9 ) and (μ-H) 2 Os 3 (CO) 9 (CN-t-C 4 H 9 ) have been revealed by x-ray crystallographic techniques. For (μ-H)(H)Os 3 (CO) 10 (CN-t-C 4 H 9 ): a = 9.064 (3), b = 12.225 (3), c = 20.364 (4) A; β = 98.73 (3) 0 ; space group P2 1 /c[C/sub 2h/ 5 ], No. 14; Z = 4; d/sub calcd/ = 2.79 g cm -3 . This compound contains a triangular cluster of three osmium atoms; Os(1)--Os(2) = 2.930 (1) A, Os(1)--Os(3) = 2.876 (1) A, and Os(2)--Os(3) = 3.000 (1) A. There are ten linear terminal carbonyl groups and one linear terminal isocyanide ligand which occupies an axial coordination site. The hydrogen atoms were not observed crystallographically, but their positions are strongly inferred from considerations of molecular geometry. For (μ-H) 2 Os 3 (CO) 9 (CN-t-C 4 H 9 ): a = 15.220 (8), b = 12.093 (6), c = 23.454 (5) A; space group Pbcn [D/sub 2h/ 14 ], No. 60; Z = 8; d/sub calcd/ = 2.79 g cm -3 . The compound is analogous to the parent carbonyl (μ-H) 2 Os 3 (CO) 10 and has two normal and one short osmium--osmium bonds: Os(1)--Os(2) = 2.827 (1) A, Os(1)--Os(3) = 2.828 (1) A, Os(2)--Os(3) = 2.691 (1) A. The isocyanide ligand resides in an equatorial coordination site on osmium Os(2). The hydrogen atoms were not observed but are believed to occupy bridging positions as in the parent carbonyl complex. 2 figures, 7 tables

New L-Serine Derivative Ligands as Cocatalysts for Diels-Alder Reaction

Science.gov (United States)

Sousa, Carlos A. D.; Rodríguez-Borges, José E.; Freire, Cristina

2013-01-01

New L-serine derivative ligands were prepared and tested as cocatalyst in the Diels-Alder reactions between cyclopentadiene (CPD) and methyl acrylate, in the presence of several Lewis acids. The catalytic potential of the in situ formed complexes was evaluated based on the reaction yield. Bidentate serine ligands showed good ability to coordinate medium strength Lewis acids, thus boosting their catalytic activity. The synthesis of the L-serine ligands proved to be highly efficient and straightforward. PMID:24383009

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.

N6-Benzyladenosine Derivatives as Novel N-Donor Ligands of Platinum(II Dichlorido Complexes

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Ján Vančo

2013-06-01

Full Text Available The platinum(II complexes trans-[PtCl2(Ln2]∙xSolv 1–13 (Solv = H2O or CH3OH, involving N6-benzyladenosine-based N-donor ligands, were synthesized; Ln stands for N6-(2-methoxybenzyladenosine (L1, involved in complex 1, N6-(4-methoxy-benzyladenosine (L2, 2, N6-(2-chlorobenzyladenosine (L3, 3, N6-(4-chlorobenzyl-adenosine (L4, 4, N6-(2-hydroxybenzyladenosine (L5, 5, N6-(3-hydroxybenzyl-adenosine (L6, 6, N6-(2-hydroxy-3-methoxybenzyladenosine (L7, 7, N6-(4-fluoro-benzyladenosine (L8, 8, N6-(4-methylbenzyladenosine (L9, 9, 2-chloro-N6-(3-hydroxy-benzyladenosine (L10, 10, 2-chloro-N6-(4-hydroxybenzyladenosine (L11, 11, 2-chloro-N6-(2-hydroxy-3-methoxybenzyladenosine (L12, 12 and 2-chloro-N6-(2-hydroxy-5-methylbenzyladenosine (L13, 13. The compounds were characterized by elemental analysis, mass spectrometry, IR and multinuclear (1H-, 13C-, 195Pt- and 15N- and two-dimensional NMR spectroscopy, which proved the N7-coordination mode of the appropriate N6-benzyladenosine derivative and trans-geometry of the title complexes. The complexes 1–13 were found to be non-toxic in vitro against two selected human cancer cell lines (HOS and MCF7; with IC50 > 50.0 µM. However, they were found (by ESI-MS study to be able to interact with the physiological levels of the sulfur-containing biogenic biomolecule L-methionine by a relatively simple 1:1 exchange mechanism (one Ln molecule was replaced by one L-methionine molecule, thus forming a mixed-nitrogen/sulfur-ligand dichlorido-platinum(II coordination species.

Mercury(II) and methylmercury(II) complexes of novel sterically hindered thiolates: 13C and 199Hg NMR studies and the crystal and molecular structures of [MeHg(SC6H2-2,4,6-Pri3)], [Hg(SC6H4-2-SiMe3)2], [Hg(2-SC5H3N-3-SiMe3)2], and [Hg{(2-SC6H4)2SiMe2}]2

International Nuclear Information System (INIS)

Block, E.; Brito, M.; Gernon, M.; McGowty, D.; Kang, Hyunkyu; Zubieta, J.

1990-01-01

Several series of complexes of the types [MeHg(SR)] and [Hg(SR) 2 ] have been synthesized, where the ligands are members of new classes of sterically hindered thiolates, including (triorganosilyl)methanethiols, 2-(triorganosilyl)benzenethiols, 3-(triorganosilyl)pyridine-2-thiols, and bis(2-mercaptophenyl) derivatives. Detailed 1 H, 13 C, and 199 Hg NMR studies revealed several general trends. The 199 Hg chemical shifts moved upfield in the order [MeHg(SR)] 2 ] 2 ] 2 ]. For the [MeHg(SR)] series of complexes, 1 J(Hg-C) correlates with δ( 13 C(methyl)) and with the type of thiolate ligand. Anomalous behavior is observed for oligomeric species. There is only a limited correlation of δ( 199 Hg) with steric cone angles for a subset of the complexes. Crystal data for the complexes are reported. 86 refs., 7 figs., 11 tabs

Synthesis, Characterization, and Cytotoxicity of the First Oxaliplatin Pt(IV Derivative Having a TSPO Ligand in the Axial Position

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Salvatore Savino

2016-06-01

Full Text Available The first Pt(IV derivative of oxaliplatin carrying a ligand for TSPO (the 18-kDa mitochondrial translocator protein has been developed. The expression of the translocator protein in the brain and liver of healthy humans is usually low, oppositely to steroid-synthesizing and rapidly proliferating tissues, where TSPO is much more abundant. The novel Pt(IV complex, cis,trans,cis-[Pt(ethanedioatoCl{2-(2-(4-(6,8-dichloro-3-(2-(dipropylamino-2-oxoethylimidazo[1,2-a]pyridin-2-ylphenoxyacetate-ethanolato}(1R,2R-DACH] (DACH = diaminocyclohexane, has been fully characterized by spectroscopic and spectrometric techniques and tested in vitro against human MCF7 breast carcinoma, U87 glioblastoma, and LoVo colon adenocarcinoma cell lines. In addition, affinity for TSPO (IC50 = 18.64 nM, cellular uptake (ca. 2 times greater than that of oxaliplatin in LoVo cancer cells, after 24 h treatment, and perturbation of cell cycle progression were investigated. Although the new compound was less active than oxaliplatin and did not exploit a synergistic proapoptotic effect due to the presence of the TSPO ligand, it appears to be promising in a receptor-mediated drug targeting context towards TSPO-overexpressing tumors, in particular colorectal cancer (IC50 = 2.31 μM after 72 h treatment.

Ligand-Enabled γ-C(sp(3))-H Olefination of Amines: En Route to Pyrrolidines.

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Jiang, Heng; He, Jian; Liu, Tao; Yu, Jin-Quan

2016-02-17

Pd(II)-catalyzed olefination of γ-C(sp(3))-H bonds of triflyl (Tf) and 4-nitrobenzenesulfonyl (Ns) protected amines is achieved. Subsequent aza-Wacker oxidative cyclization or conjugate addition of the olefinated intermediates provides a variety of C-2 alkylated pyrrolidines. Three pyridine- and quinoline-based ligands are developed to match different classes of amine substrates, demonstrating a rare example of ligand-enabled C(sp(3))-H olefination reactions. The use of Ns protecting group to direct C(sp(3))-H activation of alkyl amines is also a significant step toward practical C-H functionalizations of alkyl amines.

A pair of novel Cd(II) enantiomers based on lactate derivatives: Synthesis, crystal structures and properties

Energy Technology Data Exchange (ETDEWEB)

Xu, Zhong-Xuan, E-mail: xuzhongxuan1974@163.com [Department of Chemistry, Zunyi Normal College, Zunyi, Guizhou 563002 (China); State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, the Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Ao, Ke-Hou [Department of Chemistry, Zunyi Normal College, Zunyi, Guizhou 563002 (China); Zhang, Jian [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, the Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

2016-09-15

A pair of novel 3D homochiral metal−organic frameworks (HMOFs), namely [Cd{sub 2.5}((R)-CIA){sub 6}(1,4-DIB)(H{sub 2}O){sub 2}]·((CH{sub 3}){sub 2}NH{sub 2})·H{sub 2}O (1-D), [Cd{sub 2.5}((S)-CIA){sub 6}(1,4-DIB)(H{sub 2}O){sub 2}]·((CH{sub 3}){sub 2}NH{sub 2})·H{sub 2}O (1-L), have been synthesized using lactic acid derivative ligands ((R)-H{sub 3}CIA and (S)-H{sub 3}CIA) and 1,4-DIB. Crystallographic analyses indicate that the complexes 1-D and 1-L are packed by cage substructures. Some physical characteristics, such as solid-state circular dichroism (CD), thermal stabilities and photoluminescent properties are also investigated. Our results highlight the effective method to apply lactic acid derivative ligands to form interesting HMOFs. - Graphical abstract: Using lactic acid derivative ligands ((R)-H{sub 3}CIA and (S)-H{sub 3}CIA) and 1,4-DIB to assemble with Cd{sup 2+} ions, a pair of novel 3D homochiral metal-organic frameworks (HMOFs) with cage substructures have been synthesized. Display Omitted - Highlights: • Lactic acid derivative ligands • Cage substructure • Enantiomers.

Synthesis and crystal structures of new complexes of Np(V) glycolate with 2,2'-bipyridine, [NpO2(C10H8N2)(OOC2H2OH)].1.5H2O and [NpO2(C10H8N2)(OOC2H2OH)].2.5H2O

International Nuclear Information System (INIS)

Charushnikova, I.A.; Krot, N.N.; Starikova, Z.A.

2009-01-01

Single crystals were prepared, and the structures of two complexes of Np(V) glycolate with 2,2'-bipyridine of the compositions [NpO 2 (C 10 H 8 N 2 )(OOC 2 H 2 OH)].1.5H 2 O (I) and [NpO 2 (C 10 H 8 N 2 )(OOC 2 H 2 OH)]2.5H 2 O (II) were studied. The structures of the compounds are based on neptunyl-glycolate chains in which the glycolate anion manifests its complexation ability in different manner. In structure I, the bidentate-bridging anion links the adjacent NpO 2 - cations through the oxygen atoms of the carboxylate group. The neptunyl-glycolate chains of I exhibits the mutual coordination of the NpO 2 - cations acting toward each other simultaneously as ligands and coordinating centers. In compound II, the glycolate anion is bidentately coordinated to one neptunium atom to form a planar five-membered metallocycle [NpOCCO]. The O atom external with respect to the metallocycle is in the coordination environment of the adjacent neptunyl. The nitrogen-containing molecular ligand Bipy is included into the coordination environment of Np. The coordination polyhedron of the Np atoms in both structures is a pentagonal bipyramid in which the average Np-N bond length is 2.666 Aa (I) and 2.596 Aa (II). (orig.)

Hydrophilic 2,9-bis-triazolyl-1,10-phenanthroline ligands enable selective Am(iii) separation: a step further towards sustainable nuclear energy.

Science.gov (United States)

Edwards, Alyn C; Mocilac, Pavle; Geist, Andreas; Harwood, Laurence M; Sharrad, Clint A; Burton, Neil A; Whitehead, Roger C; Denecke, Melissa A

2017-05-02

The first hydrophilic, 1,10-phenanthroline derived ligands consisting of only C, H, O and N atoms for the selective extraction of Am(iii) from spent nuclear fuel are reported herein. One of these 2,9-bis-triazolyl-1,10-phenanthroline (BTrzPhen) ligands combined with a non-selective extracting agent, was found to exhibit process-suitable selectivity for Am(iii) over Eu(iii) and Cm(iii), providing a clear step forward.

Chemopreventive effect of chalcone derivative, L2H17, in colon cancer development

International Nuclear Information System (INIS)

Xu, Shanmei; Chen, Minxiao; Chen, Wenbo; Hui, Junguo; Ji, Jiansong; Hu, Shuping; Zhou, Jianmin; Wang, Yi; Liang, Guang

2015-01-01

Colon cancer is the third most commonly diagnosed cancer and the second leading cause of cancer mortality worldwide. Chalcone and its derivatives are reported to exhibit anti-cancer effects in several cancer cell lines, including colon cancer cells. In addition, chalcones have advantages such as poor interaction with DNA and low risk of mutagenesity. In our previous study, a group of chalcone derivatives were synthesized and exhibited strong anti-inflammatory activities. In this study, we evaluated the anti-cancer effects of the chalcone derivative, L2H17, in colon cancer cells. The cytotoxicities of L2H17 on various colon cancer cell lines were investigated by MTT and clonogenic assay. Cell cycle and apoptosis analysis were performed to evaluate the molecular mechanism of L2H17-mediated inhibition of tumor growth. Also, scratch wound and matrigel invasion experiments were performed to estimate the cell migration and invasion after L2H17 treatment. Finally, we observed the anti-colon cancer effects of L2H17 in vivo. Our data show that compound L2H17 exhibited selective cytotoxic effect on colon cancer cells, via inducing G0/G1 cell cycle arrest and apoptosis in CT26.WT cells. Furthermore, L2H17 treatment decreased cell migration and invasion of CT26.WT cells. In addition, L2H17 possessed marked anti-tumor activity in vivo. The molecular mechanism of L2H17-mediated inhibition of tumor promotion and progression were function through inactivated NF-κB and Akt signaling pathways. All these findings show that L2H17 might be a potential growth inhibitory chalcones derivative for colon cancer cells

The Evaluation of Novel Camphor-derived Ligands as Catalysts in ...

African Journals Online (AJOL)

The evaluation of a series of camphor-derived ligands as catalysts in the asymmetric Henry reaction is reported. The synthesis of two novel derivatives is detailed and these molecules are also screened as catalysts in this reaction. The single crystal X-ray structure of one of the novel compounds is reported. The reaction is ...

Tris[2-(2H-indazol-2-ylethyl]amine

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Saúl Ovalle

2012-06-01

Full Text Available The title tertiary amine, C27H27N7, a potential tripodal ligand for coordination chemistry, crystallizes with the central N atom located on a threefold axis of a trigonal cell. The gauche conformation of the N(amime—CH2—CH2—N(indazole chain [torsion angle = −64.2 (2°] places the pendant 2H-indazole heterocycles surrounding the symmetry axis, affording a claw-like shaped molecule. Two symmetry-related indazole planes in the molecule make an acute angle of 60.39 (4°. The lone pair of the tertiary N atom is located inside the cavity, and should thus be inactive (as a ligand. In the crystal, neither significant π–π nor C—H...π interactions between molecules are found.

Diamagnetism of the B10H12L2 series compounds

International Nuclear Information System (INIS)

Volkov, V.V.; Ikorskij, V.N.; Dunaev, S.T.

1988-01-01

The method of static magnetic susceptibility is used to study diamagnetic susceptibilities of a number of B 10 H 12 L 2 (where L - nitrogen, sulfur, phosphorus-containing organic ligands) decaborane-derivatives and to draw the increment χ M -125 for the nido cluster (B 10 H 12 ) and boron atomic increment χ bar M -9.0 in this cluster. The absolute value χ B in (B 10 H 12 ) cluster is much higher than χ B for noncluster systems (2.7-7.6). This difference proves electron delocalization in (B 10 H 12 ) and the aromatic nature of this nido-cluster

Derivatized Pentadentate Macrocyclic Ligands and Their Transition Metal Complexes

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Muhammad S. Khan

2002-06-01

Full Text Available The reaction of the pendant hydroxyethyl group in the planar pentadentate macrocyclic ligand,1,11-bis(2’-hydroxyethyl-4,8;12,16;17,21-trinitrilo-1,2,10,11-tetraazacyclohenicosa- 2,4,6,9,12,14,18,20-octaene (L2, derived from the condensation of 2,6-pyridinedialdehyde with 6,6’-bis(2’ hydroxyethylhydrazino -2,2’-bipyridine (L1, has been investigated. Esterification reactions are facile, and the reaction of the hydroxyethyl-substituted macrocycle with thionyl chloride yields a chloroethyl derivative. Metal complexes of the new derivatized macrocyclic ligands L3-6having general formula ML3-6X2.nH2O (M = Mn, Fe, Co, Ni, Cu, Zn are readily prepared.

New lanthanide(III) complexes of chiral nonadendate macrocyclic amine derived from (1R,2R)-1,2-diaminocyclohexane and 2,6-diformyl-4-methylphenol

Energy Technology Data Exchange (ETDEWEB)

Paluch, Marta [Department of Chemistry, University of Wroclaw, 14 F. Joliot-Curie, 50-383 Wroclaw (Poland); Lisowski, Jerzy [Department of Chemistry, University of Wroclaw, 14 F. Joliot-Curie, 50-383 Wroclaw (Poland)], E-mail: jurekl@wchuwr.chem.uni.wroc.pl

2008-02-28

The series of complexes [LnH{sub 4}L(NO{sub 3}){sub 2}](NO{sub 3}){sub 2}.nH{sub 2}O (Ln = La, Ce, Pr, Nd, Gd, Tb, Ho, Er, Tm) of the positively charged protonated form of a chiral macrocyclic amine H{sub 4}L{sup +}, derived from the 3 + 3 condensation product of (1R,2R)-1,2-diaminocyclohexane and 2,6-diformyl-4-methylphenol, have been synthesized. The series of complexes Na{sub x}[LnL](X){sub y}(OH){sub x-y}.n(solv) (X = NO{sup 3-} or Cl{sup -}, and Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) of the deprotonated anionic form of the ligand, L{sup 3-}, have also been synthesised. The complexes have been characterised by elemental analyses, {sup 1}H NMR and ESI MS spectra. The X-ray crystal structures of the [LaH{sub 4}L(NO{sub 3}){sub 2}](NO{sub 3}){sub 2}.5CH{sub 3}OH and [GdH{sub 4}L(NO{sub 3}){sub 2}](NO{sub 3}){sub 2}.5CH{sub 3}OH complexes have been determined. The two complexes are isostructural, and the protonated macrocycle acts as pentadentate ligand. The Ln(III) ion is bound to three phenolate oxygen atoms and two amine nitrogen atoms of the macrocyclic ligand and its coordination sphere is completed by the two axial bidendate nitrate anions.

New pinene-derived pyridines as bidentate chiral ligands

Czech Academy of Sciences Publication Activity Database

Malkov, A. V.; Stewart-Liddon, A.; Teplý, Filip; Kobr, L.; Muir, K. W.; Haigh, D.; Kočovský, P.

2008-01-01

Roč. 64, č. 18 (2008), s. 4011-4025 ISSN 0040-4020 Institutional research plan: CEZ:AV0Z40550506 Keywords : chiral ligands * transition metal catalysis * asymmetric catalysis * pyridine ligands * oxazoline ligands Subject RIV: CC - Organic Chemistry Impact factor: 2.897, year: 2008

5-Chloro-2-(2'-((dimethylamino)methyl)-4'-iodophenylthio)benzenamine: a new serotonin transporter ligand

International Nuclear Information System (INIS)

Oya, Shunichi; Choi, Seok-Rye; Kung, Mei-Ping; Kung, Hank F.

2007-01-01

Two novel ligands with 4' substitution on the Phenyl Ring B of biphenylthiol, 5-chloro-2-(2'-((dimethylamino)methyl)-4'-iodophenylthio)benzenamine (7) and 2-(2'-((dimethylamino)methyl)-4'-methoxyphenylthio)-5-iodobenzenamine (8), were prepared and tested as potential serotonin transporter (SERT) imaging agents. The new ligands displayed extremely high binding affinities to SERT (K i =0.22±0.09 and 0.11±0.04 nM, respectively), with very low binding affinities to dopamine and norepinephrine transporters (K i >1000 nM). The corresponding [ 125 I]7 and [ 125 I]8 were successfully prepared from tri-n-butyltin derivatives. They showed good brain uptakes and prolonged retention after intravenous injection in rats (brain uptake was 1.77% and 0.98% dose/g for [ 125 I]7, and 0.92% and 0.29% dose/g for [ 125 I]8, at 2 and 120 min, respectively). Significantly, [ 125 I]7 showed excellent uptake and prolonged retention in the hypothalamus, where SERT concentration was highest. The hypothalamus/cerebellum (HY/CB) ratios (target/background ratios) were 4.24, 7.10, 8.24 and 12.6 at 2, 4, 6 and 12 h, respectively. The HY/CB ratios for [ 125 I]8 were 3.97, 5.57 and 5.06 at 1, 2 and 4 h, respectively. Adding the 4'-iodo group to the Phenyl Ring B of Compound (7) appeared to reduce the rate of clearance from the brain, and kinetics favored uptake and retention in the hypothalamus. The localization of [ 125 I]7 in the hypothalamus region in the rat brain could be blocked by pretreatment with (+)McN5652, escitalopram and ADAM (2), which are all selective SERT ligands (at 2 mg/kg iv, 5 min pretreatment). Ex vivo autoradiograms of rat brain sections (at 4 h after intravenous injection of [ 125 I]7) showed intense labeling in regions of the brain known to have high SERT density. The excellent selective uptake and retention in the hypothalamus region suggest that [ 123 I]7 is a potential lead compound for developing new imaging agents targeting SERT-binding sites with single

Ligand-Enabled Reactivity and Selectivity in a Synthetically Versatile Aryl C–H Olefination*

Science.gov (United States)

Wang, Dong-Hui; Engle, Keary M.; Shi, Bing-Feng; Yu, Jin-Quan

2010-01-01

The Mizoroki–Heck reaction, which couples aryl halides with olefins, has been widely used to stitch together the carbogenic cores of numerous complex organic molecules. Given that the position-selective introduction of a halide onto an arene is not always straightforward, direct olefination of aryl C–H bonds would obviate the inefficiencies associated with generating halide precursors or their equivalents; however, methods for carrying out such a reaction have suffered from narrow substrate scope and low positional selectivity. Here we report an operationally simple, atom-economical, carboxylate-directed Pd(II)-catalyzed C–H olefination reaction with phenylacetic acid and 3-phenylpropionic acid substrates, using oxygen at atmospheric pressure as the oxidant. The positional selectivity can be tuned by introducing amino acid derivatives as ligands. We demonstrate the versatility of the method through direct elaboration of commercial drug scaffolds and efficient synthesis of 2-tetralone and naphthoic acid natural product cores. PMID:19965380

Self-assembled copper(II) metallacycles derived from asymmetric Schiff base ligands: efficient hosts for ADP/ATP in phosphate buffer.

Science.gov (United States)

Kumar, Amit; Pandey, Rampal; Kumar, Ashish; Gupta, Rakesh Kumar; Dubey, Mrigendra; Mohammed, Akbar; Mobin, Shaikh M; Pandey, Daya Shankar

2015-10-21

Novel asymmetric Schiff base ligands 2-{[3-(3-hydroxy-1-methyl-but-2-enylideneamino)-2,4,6-trimethylphenylimino]-methyl}-phenol (H2L(1)) and 1-{[3-(3-hydroxy-1-methyl-but-2-enylideneamino)-2,4,6-trimethylphenylimino]-methyl}-naphthalen-2-ol (H2L(2)) possessing dissimilar N,O-chelating sites and copper(ii) metallacycles (CuL(1))4 (1) and (CuL(2))4 (2) based on these ligands have been described. The ligands and complexes have been thoroughly characterized by satisfactory elemental analyses, and spectral (IR, (1)H, (13)C NMR, ESI-MS, UV/vis) and electrochemical studies. Structures of H2L(2) and 1 have been unambiguously determined by X-ray single crystal analyses. The crystal structure of H2L(2) revealed the presence of two distinct N,O-chelating sites on dissimilar cores (naphthalene and β-ketoaminato groups) offering a diverse coordination environment. Metallacycles 1 and 2 having a cavity created by four Cu(ii) centres coordinated in a homo- and heteroleptic fashion with respective ligands act as efficient hosts for adenosine-5'-diphosphate (ADP) and adenosine-5'-triphosphate (ATP) respectively, over other nucleoside polyphosphates (NPPs). The disparate sensitivity of these metallacycles toward ADP and ATP has been attributed to the size of the ligands assuming diverse dimensions and spatial orientations. These are attuned for π-π stacking and electrostatic interactions suitable for different guest molecules under analogous conditions, metallacycle 1 offers better orientation for ADP, while 2 for ATP. The mechanism of the host-guest interaction has been investigated by spectral and electrochemical studies and supported by molecular docking studies.

pH-metric studies on the mixed ligand-chelates of oxovanadium(IV) with 2,2'-bipyridyl and dicarboxylic or hydroxy acids

International Nuclear Information System (INIS)

Jain, A.K.; Kumari, V.; Chaturvedi, G.K.

1978-01-01

The interaction of vanadyl ion with 2,2'-bipyridyl and some dicarboxylic or hydroxy acids (where dicarboxylic acid = oxalic (OX), malonic (MALN), phthalic (PHA), maleic (MAL) acids; hydroxy acids salicylic (SA), 5-sulfosalicylic (5-SSA), mandelic (MAND) and glycollic (HG) acids was studied potentiometrically. pH-titrations of the reaction mixtures containing vanadyl sulphate, 2,2'-bipyridyl and one of the dicarboxylic or hydroxy acids (OX, MALN, PHA, MAL, SA, 5-SSA, MAND and HG acids) in equimolar ratio exhibited the formation of 1:1:1 mixed ligand chelates. The formation constants of the resulting biligand chelates were calculated, at 35 + -1 0 and 45 + -1 0 and also the thermodynamic functions viz. ΔF, ΔH and ΔS (μ=0.1M KNO 3 ) (auth.)

Synthesis of Two Potentially Heptadentate (N4O3 Schiff-base Ligands Derived from Condensation of Tris(3-aminopropyl-amine and Salicylaldehyde or 4-Hydroxysalicylaldehyde. Nickel(II and Copper(II Complexes of the Former Ligand

Directory of Open Access Journals (Sweden)

R. V. Parish

2002-02-01

Full Text Available Two potentially heptadentate (N4O3 tripodal Schiff-base ligands: tris(3-(salicylideneiminopropylamine (H3L1 and tris(3-(4’-hydroxysalicylideneimino-propylamine (H3L2 have been prepared and characterized by various spectroscopic methods (IR, FAB-MS, NMR. They are derived from the condensation reactions of tris(3-aminopropylamine (tpt, with 3 equivalents of either salicylaldehyde or the ringsubstituted salicylaldehyde, 4-hydroxysalicylaldehyde. The nickel(II and copper(II complexes of H3L1 were obtained from the its reactions Ni(II and Cu(II salts in absolute methanol. These complexes were studied by IR and FAB-Mass spectrometry.

Chemoenzymatic synthesis of chiral 2,2'-bipyridine ligands and their N-oxide derivatives: applications in the asymmetric aminolysis of epoxides and asymmetric allylation of aldehydes.

Science.gov (United States)

Boyd, D R; Sharma, N D; Sbircea, L; Murphy, D; Malone, J F; James, S L; Allen, C C R; Hamilton, J T G

2010-03-07

A series of enantiopure 2,2'-bipyridines have been synthesised from the corresponding cis-dihydrodiol metabolites of 2-chloroquinolines. Several of the resulting hydroxylated 2,2'-bipyridines were found to be useful chiral ligands for the asymmetric aminolysis of meso-epoxides leading to the formation of enantioenriched amino alcohols (-->84% ee). N-oxide and N,N'-dioxide derivatives of these 2,2'-bipyridines, including separable atropisomers, have been synthesised and used as enantioselective organocatalysts in the asymmetric allylation of aldehydes to give allylic alcohols (-->86% ee).

Synthesis, characterization, crystal structure and HSA binding of two new N,O,O-donor Schiff-base ligands derived from dihydroxybenzaldehyde and tert-butylamine

Science.gov (United States)

Khosravi, Iman; Hosseini, Farnaz; Khorshidifard, Mahsa; Sahihi, Mehdi; Rudbari, Hadi Amiri

2016-09-01

Two new o-hydroxy Schiff-bases compounds, L1 and L2, were derived from the 1:1 M condensation of 2,3-dihydroxybenzaldehyde and 2,4-dihydroxybenzaldehyde with tert-butylamine and were characterized by elemental analysis, FT-IR, 1H and 13C NMR spectroscopies. The crystal structure of L2 was also determined by single crystal X-ray analysis. The crystal structure of L2 showed that the compound exists as a zwitterionic form in the solid state, with the H atom of the phenol group being transferred to the imine N atom. It adopts an E configuration about the central Cdbnd N double bond. Furthermore, binding of these Schiff base ligands to Human Serum Albumin (HSA) was investigated by fluorescence quenching, absorption spectroscopy, molecular docking and molecular dynamics (MD) simulation methods. The fluorescence emission of HSA was quenched by ligands. Also, suitable models were used to analyze the UV-vis absorption spectroscopy data for titration of HSA solution by various amounts of Schiff bases. The spectroscopic studies revealed that these Schiff bases formed 1:1 complex with HSA. Energy transfer mechanism of quenching was discussed and the values of 3.35 and 1.57 nm as the mean distances between the bound ligands and the HSA were calculated for L1 and L2, respectively. Molecular docking results indicated that the main active binding site for these Schiff bases ligands is in subdomain IB. Moreover, MD simulation results suggested that this Schiff base complex can interact with HSA, with a slight modification of its tertiary structure.

Irreversible blockade of the high and low affinity (3H) naloxone binding sites by C-6 derivatives of morphinane-6-ones

International Nuclear Information System (INIS)

Krizsan, D.; Varga, E.; Benyhe, S.; Szucs, M.; Borsodi, A.; Hosztafi, S.

1991-01-01

C-6 derivatives-hydrazones, phenylhydrazones, dinitrophenylhydrazones, oximes and semicarbazones - of morphinane-6-ones were synthesized and their binding characteristics were studied on rat brain membranes. The dihydromorphinone and oxymorphone derivatives compete for the ( 3 H)naloxone binding sites with high affinity, while the dihydrocodeinone and oxycodone derivatives are less potent. The affinity of the new compounds is decreased for the delta sites as compared to the parent ligands. The ligands bearing bulky substituents also bind with low affinity to the kappa sites. The modification decreased the Na + -index of compounds indicating their mixed agonist-antagonist character. The dihydromorphinone derivatives are all capable to block irreversibly the high affinity binding site of ( 3 H)naloxone, whereas the dihydrocodeinone derivatives block irreversibly the low affinity site. A possible mechanism for the inhibition is suggested

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

Synthesis, crystal structures and luminescent properties of zinc(II) metal–organic frameworks constructed from terpyridyl derivative ligand

International Nuclear Information System (INIS)

Yang, Xiao-Le; Shangguan, Yi-Qing; Hu, Huai-Ming; Xu, Bing; Wang, Bao-Cheng; Xie, Juan; Yuan, Fei; Yang, Meng-Lin; Dong, Fa-Xin; Xue, Gang-Lin

2014-01-01

Five zinc(II) metal–organic frameworks, [Zn 3 (344-pytpy) 2 Cl 6 ] n ·n(H 2 O) (1), [Zn(344-pytpy)(ox)] n (2), [Zn 2 (344-pytpy)(bdc) 2 ] n ·1.5n(H 2 O) (3), [Zn 2 (344-pytpy) 2 (sfdb) 2 ] n ·1.5n(H 2 O) (4) and [Zn 3 (344-pytpy) 2 (btc) 2 ] n ·2n(H 2 O) (5), (344-pytpy=4′-(3-pyridyl)-4,2′:6′,4″-terpyridine, H 2 ox=oxalic acid, H 2 bdc=1,4-benzenedi-carboxylic acid, H 2 sfdb=4,4′-sulfonyldibenzoic acid and H 3 btc=1,3,5-benzene-tricarboxylic acid) have been prepared by hydrothermal reactions. Compound 1 is a 1D chain structure, in which 344-pytpy ligand links three Zn II centers through three of terminal N-donors. Compound 2 is a 4-connected 3D framework with the dia topological net and the Schläfli symbol of 6 6 . Compound 3 displays a unusual 3-fold interpenetrating 3D coordination network which exhibits a new intriguing (3,3,4)-connected topological net with the Schläfli symbol of (4.8 2 )(4.8 5 )(8 3 ). Compound 4 features a two-fold interpenetrating 4-connected 2D framework with the sql topological net and the Schläfli symbol of (4 4 .6 2 ). Compound 5 is a new self-interpenetrating (3,3,4,4)-connected topological net with the Schläfli symbol of (6.8 2 ) 2 (6 2 .8 2 .10.12)(6 2 .8 3 .10) 2 (6 2 .8) 2 . The luminescence properties of 1–5 have been investigated by emission spectra and they possess great thermal stabilities which can be stable up to around 400 °C. - Graphical abstract: Five new Zn(II) metal–organic frameworks based on dicarboxylate and terpyridyl derivative ligands have been synthesized by hydrothermal reactions, giving networks from 1D to 3D structures. The thermal stability and luminescent property have been investigated. - Highlights: • Five zinc(II) metal–organic frameworks have been prepared under hydrothermal conditions. • Their crystal and topological structures have been investigated. • The luminescent properties have been investigated. • They possess great thermal stabilities which can be stable up to

Mixed-ligand Ru(II) complexes with 2,2'-bipyridine and aryldiazo-beta-diketonato auxillary ligands: synthesis, physico-chemical study and antitumour properties.

Science.gov (United States)

Mishra, Lallan; Yadaw, Ajay K; Bhattacharya, Subrato; Dubey, Santosh K

2005-05-01

The complexes of Ru(II)-2,2'-bipyridyl with substituted diazopentane-2,4-diones (L1H-L5H) were synthesized and characterized by elemental analyses, conductance, FAB (fast atom bombardment) mass and spectral (IR, UV/Vis (UV/visible), NMR) studies. Molecular geometry optimization of the complexes was also made. None of the complexes luminesce. However, facilitated oxidation of Ru(II) to Ru(III) was evidenced from their lower reduction potential data. The ligands and their complexes were tested for their antitumour activity against a variety of tumour cell lines. Though activity is found to vary with the type of tumour cell lines used, yet complex 5 with naphtyldiazopentane-2,4-dione as co-ligand was found to be a potential compound as it showed in general significant activity against all cell lines studied.

Differential expression of ligands for NKG2D and DNAM-1 receptors by epithelial ovarian cancer-derived exosomes and its influence on NK cell cytotoxicity.

Science.gov (United States)

Labani-Motlagh, Alireza; Israelsson, Pernilla; Ottander, Ulrika; Lundin, Eva; Nagaev, Ivan; Nagaeva, Olga; Dehlin, Eva; Baranov, Vladimir; Mincheva-Nilsson, Lucia

2016-04-01

Cancers constitutively produce and secrete into the blood and other biofluids 30-150 nm-sized endosomal vehicles called exosomes. Cancer-derived exosomes exhibit powerful influence on a variety of biological mechanisms to the benefit of the tumors that produce them. We studied the immunosuppressive ability of epithelial ovarian cancer (EOC) exosomes on two cytotoxic pathways of importance for anticancer immunity-the NKG2D receptor-ligand pathway and the DNAM-1-PVR/nectin-2 pathway. Using exosomes, isolated from EOC tumor explant and EOC cell-line culture supernatants, and ascitic fluid from EOC patients, we studied the expression of NKG2D and DNAM-1 ligands on EOC exosomes and their ability to downregulate the cognate receptors. Our results show that EOC exosomes differentially and constitutively express NKG2D ligands from both MICA/B and ULBP families on their surface, while DNAM-1 ligands are more seldom expressed and not associated with the exosomal membrane surface. Consequently, the NKG2D ligand-bearing EOC exosomes significantly downregulated the NKG2D receptor expression on peripheral blood mononuclear cells (PBMC) while the DNAM-1 receptor was unaffected. The downregulation of NKG2D receptor expression was coupled to inhibition of NKG2D receptor-ligand-mediated degranulation and cytotoxicity measured in vitro with OVCAR-3 and K562 cells as targets. The EOC exosomes acted as a decoy impairing the NKG2D mediated cytotoxicity while the DNAM-1 receptor-ligand system remained unchanged. Taken together, our results support and explain the mechanism behind the recently reported finding that in EOC, NK-cell recognition and killing of tumor cells was mainly dependent on DNAM-1 signaling while the contribution of the NKG2D receptor-ligand pathway was complementary and uncertain.

Benzannulated tris(2-mercapto-1-imidazolyl)hydroborato ligands: tetradentate κ4-S3H binding and access to monomeric monovalent thallium in an [S3] coordination environment.

Science.gov (United States)

Rong, Yi; Palmer, Joshua H; Parkin, Gerard

2014-01-21

The benzannulated tris(mercaptoimidazolyl)borohydride sodium complex, [Tm(Bu(t)Benz)]Na, has been synthesized via the reaction of NaBH4 with 1-tert-butyl-1,3-dihydro-2H-benzimidazole-2-thione, while [Tm(MeBenz)]K has been synthesized via the reaction of KBH4 with 1-methyl-1,3-dihydro-2H-benzimidazole-2-thione. The molecular structures of the solvated adducts, {[Tm(Bu(t)Benz)]Na(THF)}2(μ-THF)2 and [Tm(MeBenz)]K(OCMe2)3, have been determined by X-ray diffraction, which demonstrates that the [Tm(R)] ligands in these complexes adopt different coordination modes to that in {[Tm(MeBenz)]Na}2(μ-THF)3. Specifically, while the [Tm(MeBenz)] ligand of the sodium complex {[Tm(MeBenz)]Na}2(μ-THF)3 adopts a κ(3)-S3 coordination mode, the potassium complex [Tm(MeBenz)]K(OCMe2)3 adopts a most uncommon inverted κ(4)-S3H coordination mode in which the potassium binds to all three sulfur donors and the hydrogen of the B-H group in a linear KH-B manner. Furthermore, the [Tm(Bu(t)Benz)] ligand of {[Tm(Bu(t)Benz)]Na(THF)}2(μ-THF)2 adopts a κ(3)-S2H coordination mode, thereby demonstrating the flexibility of this ligand system. The monovalent thallium compounds, [Tm(MeBenz)]Tl and [Tm(Bu(t)Benz)]Tl, have been obtained via the corresponding reactions of [Tm(MeBenz)]Na and [Tm(Bu(t)Benz)]Na with TlOAc. X-ray diffraction demonstrates that the three sulfur donors of the [Tm(RBenz)] ligands of both [Tm(MeBenz)]Tl and [Tm(Bu(t)Benz)]Tl chelate to thallium. This coordination mode is in marked contrast to that in other [Tm(R)]Tl compounds, which exist as dinuclear molecules wherein two of the sulfur donors coordinate to different thallium centers. As such, this observation provides further evidence that benzannulation promotes κ(3)-S3 coordination in this system.

H2S Sensing by Hybrids Based on Nanocrystalline SnO2 Functionalized with Cu(II Organometallic Complexes: The Role of the Ligand Platform

Directory of Open Access Journals (Sweden)

Marina Rumyantseva

2017-11-01

Full Text Available This paper deals with the functionalization of nanocrystalline SnO2 with Cu(II complexes with organic ligands, aimed at the improvement of sensor selectivity towards gas molecules. For the synthesis of metalorganic/SnO2 hybrid material complexes of Cu(II with phthalocyanine, porphyrinines, bipyridine and azadithiacrown etherwere used. The analysis of gas sensor properties showed the possibility of increasing the sensitivity and selectivity of hybrid materials in H2S detection due to the electron transfer from SnO2 to an adsorbed organic molecule, which changes during the interaction between H2S and Cu(II ions.

Preparation of Rhodium(III) complexes with 2(1H)-quinolinone derivatives and evaluation of their in vitro and in vivo antitumor activity.

Science.gov (United States)

Lu, Xing; Wu, Yi-Ming; Yang, Jing-Mei; Ma, Feng-E; Li, Liang-Ping; Chen, Sheng; Zhang, Ye; Ni, Qing-Ling; Pan, Ying-Ming; Hong, Xue; Peng, Yan

2018-05-10

A series of 2(1H)-quinolinone derivatives and their rhodium (III) complexes were designed and synthesized. All the rhodium (III) complexes exhibited higher in vitro cytotoxicity for Hep G2, HeLa 229, MGC80-3, and NCI-H460 human tumor cell lines than their ligands and cisplatin, and among them complex 9 was found to be selectively cytotoxic to tumor cells. Further investigation revealed that complex 9 caused cell cycle arrest at the G2/M phase and induced apoptosis, and inhibited the proliferation of Hep G2 cells by impeding the phosphorylation of epidermal growth factor receptor (EGFR) and its downstream enzymes. Complex 9 also up-regulated the proapoptotic proteins Bak, Bax, and Bim, which altogether activated caspase-3/9 to initiate cell apoptosis. Notably, complex 9 effectively inhibited tumor growth in the NCI-H460 xenograft mouse model with less adverse effect than cisplatin. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Ligand-Enabled γ-C(sp3)–H Olefination of Amines: En Route to Pyrrolidines

Science.gov (United States)

Jiang, Heng; He, Jian; Liu, Tao

2016-01-01

Pd(II)-catalyzed olefination of γ-C(sp3)–H bonds of triflyl (Tf) and 4-nitrobenzenesulfonyl (Ns) protected amines is achieved. Subsequent aza-Wacker oxidative cyclization or conjugate addition of the olefinated intermediates provides a variety of C-2 alkylated pyrrolidines. Three pyridine- and quinoline-based ligands are developed to match different classes of amine substrates, demonstrating a rare example of ligand-enabled C(sp3)–H olefination reaction. The use of Ns protecting group to direct C(sp3)–H activation of alkyl amine is also a significant step towards practical C–H functionalizations of alkyl amines. PMID:26796676

pH-metric studies on the mixed ligand-chelates of oxovanadium(IV) with 2,2'-bipyridyl and dicarboxylic or hydroxy acids

Energy Technology Data Exchange (ETDEWEB)

Jain, A K; Kumari, V; Chaturvedi, G K [Agra Coll. (India)

1978-12-01

The interaction of vanadyl ion with 2,2'-bipyridyl and some dicarboxylic or hydroxy acids (where dicarboxylic acid = oxalic (OX), malonic (MALN), phthalic (PHA), maleic (MAL) acids; hydroxy acids salicylic (SA), 5-sulfosalicylic (5-SSA), mandelic (MAND) and glycollic (HG) acids was studied potentiometrically. pH-titrations of the reaction mixtures containing vanadyl sulphate, 2,2'-bipyridyl and one of the dicarboxylic or hydroxy acids (OX, MALN, PHA, MAL, SA, 5-SSA, MAND and HG acids) in equimolar ratio exhibited the formation of 1:1:1 mixed ligand chelates. The formation constants of the resulting biligand chelates were calculated, at 35/sup +/-1/sup 0/ and 45/sup +/-1/sup 0/ and also the thermodynamic functions viz. ..delta..F, ..delta..H and ..delta..S (..mu..=0.1M KNO/sub 3/) (auth.).

Ruthenium(II) carbonyl compounds with the 4'-chloro-2,2':6',2''-terpyridine ligand.

Science.gov (United States)

Tatikonda, Rajendhraprasad; Haukka, Matti

2017-04-01

Two ruthenium carbonyl complexes with the 4'-chloro-2,2':6',2''-terpyridine ligand (tpy-Cl, C 15 H 10 ClN 3 ), i.e. [RuCl(tpy-Cl)(CO) 2 ][RuCl 3 (CO) 3 ] (I) [systematic name: cis -di-carbonyl-chlorido(4'-chloro-2,2':6',2''-terpyridine-κ 3 N )ruthenium(II) fac -tricarbonyltri-chlorido-ruthenate(II)], and [RuCl 2 (tpy-Cl)(CO) 2 ] (II) [ cis -dicarbonyl- trans -di-chlorido(4'-chloro-2,2':6',2''-terpyridine-κ 2 N 1 , N 1' )ruthenium(II)], were synthesized and characterized by single-crystal X-ray diffraction. The Ru II atoms in both centrosymmetric structures (I) and (II) display similar, slightly distorted octa-hedral coordination spheres. The coordination sphere in the complex cation in compound (I) is defined by three N atoms of the tridentate tpy-Cl ligand, two carbonyl carbon atoms and one chlorido ligand; the charge is balanced by an octa-hedral [Ru(CO) 3 Cl 3 ] - counter-anion. In the neutral compound (II), the tpy-Cl ligand coordinates to the metal only through two of its N atoms. The coordination sphere of the Ru II atom is completed by two carbonyl and two chlorido ligands. In the crystal structures of both (I) and (II), weak C-H⋯Cl inter-actions are observed.

Effect of H-2 complex on the growth of embryo-derived teratomas in mice

International Nuclear Information System (INIS)

Taya, C.; Moriwaki, K.

1986-01-01

Seven-day-old embryos of several H-2 congenic strains were transplanted under the kidney capsules of syngeneic adult recipients to determine the genetic factors(s) governing the in vivo growth of embryo-derived teratomas. A.TH(H-2t2) and A.TL(H-2t1) strains showed significantly greater tumor weights than A.BY(H-2b) and A.SW(H-2s) strains. The A(H-2a) strain was intermediate in tumor size. A comparison of the genic constitution of the H-2 complex in each congenic strain suggested that the H-2D locus and/or its distal regions affected the growth of embryo-derived teratomas. The teratoma induced in the B10.A(H-2a) strain was smaller than that in the A(H-2a) strain, indicating that the genetic background of the A strain is favorable for teratoma growth. Histological observations demonstrated that the existence of embryonal carcinoma cells was necessary for the growth of teratomas. A radiation-sensitive immunological factor in the recipient probably plays a role in stimulating teratoma growth

A series of coordination polymers constructed from R-isophthalic acid (R=-SO3H, -NO2, and -OH) and N-donor ligands: Syntheses, structures and fluorescence properties

Science.gov (United States)

Zhou, Yong-Hong; Zhou, Xu-Wan; Zhou, Su-Rong; Tian, Yu-Peng; Wu, Jie-Ying

2017-01-01

Six novel Zn(II), Cd(II), and Cu(II) mixed-ligand coordination complexes, namely, [Zn2Na(sip)2(bpp)3(Hbpp)(H2O)2]·8H2O (1), [Cd3(sip)2(nbi)6(H2O)2]·7H2O (2), [Zn(sip)(nbi)2(H2O)]·Hnbi·3H2O (3), [Cd(hip)(nbi)2(H2O)]·nbi·5H2O (4), [Cd2(nip)2(nbi)2(H2O)2]·DMF (5), and [Cu(nip)(nbi)(H2O)2]·H2O (6) (H3sip=5-sulfoisophthalic acid, H2hip=5-hydroxylisophthalic acid, H2nip=5-nitroisophthalic acid, bpp=1,3-bis(4-pyridyl)propane, and nbi=6-nitrobenzimidazole) have been synthesized hydrothermally by the self-assembly of R-isophthalic acid (R=-SO3H, -NO2, and -OH) and N-donor ligands. Single crystal X-ray analyses reveal that two Zn(II) ions and one Na(I) ion of complex 1 are linked through O atoms to generate a 1D linear chain. Then the 2D supramolecular architectures are constructed via intermolecular interactions. In complex 2, the Cd1 ions are connected by bridging carboxyl groups from sip3- anions to form 1D double chain, which are further connected by Cd2 ions to afford 2D layer structure. The adjacent 2D layers are further linked via hydrogen-bonding interactions to give 3D supramolecular network. Compounds 3-5 show 1D chain structures, which are assembled into 2D or 3D supramolecular frameworks via weak interactions. In compound 6, the Cu(II) ions are bridged by the nip2- ligands to form 48-membered ring, which is assembled into 1Dchain via the π-π stacking interaction. In addition, the thermal stabilities and fluorescence properties of these compounds have also been studied.

Mutation of the His ligand in mitoNEET stabilizes the 2Fe–2S cluster despite conformational heterogeneity in the ligand environment

Energy Technology Data Exchange (ETDEWEB)

Conlan, Andrea R.; Paddock, Mark L.; Homer, Christina [University of California at San Diego, La Jolla, CA 92093 (United States); Axelrod, Herbert L.; Cohen, Aina E. [Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Abresch, Edward C.; Zuris, John A. [University of California at San Diego, La Jolla, CA 92093 (United States); Nechushtai, Rachel [Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904 (Israel); Jennings, Patricia A., E-mail: pajennin@ucsd.edu [University of California at San Diego, La Jolla, CA 92093 (United States)

2011-06-01

The spectroscopic and stability properties and X-ray crystal structure of the H87C mutant of the 2Fe–2S ligand mitoNEET are reported. Strikingly, the single point mutation leads to changes in its absorbance and CD spectra and an increase of around sixfold in the stability of the 2Fe–2S clusters over the pH range 5–7. However, the crystal structure of the H87C mutant displays heterogeneity in a few key residues, including the introduced cysteine ligand. Nonetheless, the cluster is highly stabilized from release. MitoNEET is the only identified Fe–S protein localized to the outer mitochondrial membrane and a 1.5 Å resolution X-ray analysis has revealed a unique structure [Paddock et al. (2007 ▶), Proc. Natl Acad. Sci. USA, 104, 14342–14347]. The 2Fe–2S cluster is bound with a 3Cys–1His coordination which defines a new class of 2Fe–2S proteins. The hallmark feature of this class is the single noncysteine ligand His87, which when replaced by Cys decreases the redox potential (E{sub m}) by ∼300 mV and increases the stability of the cluster by around sixfold. Unexpectedly, the pH dependence of the lifetime of the 2Fe–2S cluster remains the same as in the wild-type protein. Here, the crystal structure of H87C mitoNEET was determined to 1.7 Å resolution (R factor = 18%) to investigate the structural basis of the changes in the properties of the 2Fe–2S cluster. In comparison to the wild type, structural changes are localized to the immediate vicinity of the cluster-binding region. Despite the increased stability, Cys87 displays two distinct conformations, with distances of 2.3 and 3.2 Å between the S{sup γ} and the outer Fe of the 2Fe–2S cluster. In addition, Lys55 exhibits multiple conformations in the H87C mutant protein. The structure and distinct characteristics of the H87C mutant provide a framework for further studies investigating the effects of mutation on the properties of the 2Fe–2S cluster in this new class of proteins.

Arrested α-hydride migration activates a phosphido ligand for C–H insertion

Energy Technology Data Exchange (ETDEWEB)

Hickey, Anne K. [Indiana Univ., Bloomington, IN (United States); Muñoz, Salvador B. [Indiana Univ., Bloomington, IN (United States); Lutz, Sean A. [Indiana Univ., Bloomington, IN (United States); Pink, Maren [Indiana Univ., Bloomington, IN (United States); Chen, Chun-Hsing [Indiana Univ., Bloomington, IN (United States); Smith, Jeremy M. [Indiana Univ., Bloomington, IN (United States)

2016-12-05

Bulky tris(carbene)borate ligands provide access to high spin iron(II) phosphido complexes. The complex PhB(MesIm)₃FeP(H)Ph is thermally unstable, and we observed [PPh] group insertion into a C–H bond of the supporting ligand. An arrested α-hydride migration mechanism suggests increased nucleophilicity of the phosphorus atom facilitates [PPh] group transfer reactivity.

Benzannulated Tris(2-mercapto-1-imidazolyl)hydroborato Ligands: Tetradentate κ4–S3H Binding and Access to Monomeric Monovalent Thallium in an [S3] Coordination Environment

Science.gov (United States)

Rong, Yi; Palmer, Joshua H.; Parkin, Gerard

2013-01-01

The benzannulated tris(mercaptoimidazolyl)borohydride sodium complex, [TmButBenz]Na, has been synthesized via the reaction of NaBH4 with 1-tert-butyl-1,3-dihydro-2H-benzimidazole-2-thione, while [TmMeBenz]K has been synthesized via the reaction of KBH4 with 1-methyl-1,3-dihydro-2H-benzimidazole-2-thione. The molecular structures of the solvated adducts, {[TmButBenz]Na(THF)}2(μ-THF)2 and [TmMeBenz]K(OCMe2)3, have been determined by X-ray diffraction, which demonstrates that the [TmR] ligands in these complexes adopt different coordination modes to that in {[TmMeBenz]Na}2(μ-THF)3. Specifically, while the [TmMeBenz] ligand of the sodium complex {[TmMeBenz]Na}2(μ-THF)3 adopts a κ3-S3 coordination mode, the potassium complex [TmMeBenz]K(OCMe2)3 adopts a most uncommon inverted κ4-S3H coordination mode in which the potassium binds to all three sulfur donors and the hydrogen of the B–H group in a linear K•••H–B manner. Furthermore, the [TmButBenz] ligand of {[TmButBenz]Na(THF)}2(μ-THF)2 adopts a κ3-S2H coordination mode, thereby demonstrating the flexibility of this ligand system. The monovalent thallium compounds, [TmMeBenz]Tl and [TmButBenz]Tl, have been obtained via the corresponding reactions of [TmMeBenz]Na and [TmButBenz]Na with TlOAc. X-ray diffraction demonstrates that the three sulfur donors of the [TmRBenz] ligands of both [TmMeBenz]Tl and [TmButBenz]Tl chelate to thallium. This coordination mode is in marked contrast to that in other [TmR]Tl compounds, which exist as dinuclear molecules wherein two of the sulfur donors coordinate to different thallium centers. As such, this observation provides further evidence that benzannulation promotes κ3-S3 coordination in this system. PMID:24201311

Gaseous ligand selectivity of the H-NOX sensor protein from Shewanella oneidensis and comparison to those of other bacterial H-NOXs and soluble guanylyl cyclase.

Science.gov (United States)

Wu, Gang; Liu, Wen; Berka, Vladimir; Tsai, Ah-Lim

2017-09-01

To delineate the commonalities and differences in gaseous ligand discrimination among the heme-based sensors with Heme Nitric oxide/OXygen binding protein (H-NOX) scaffold, the binding kinetic parameters for gaseous ligands NO, CO, and O 2 , including K D , k on , and k off , of Shewanella oneidensis H-NOX (So H-NOX) were characterized in detail in this study and compared to those of previously characterized H-NOXs from Clostridium botulinum (Cb H-NOX), Nostoc sp. (Ns H-NOX), Thermoanaerobacter tengcongensis (Tt H-NOX), Vibrio cholera (Vc H-NOX), and human soluble guanylyl cyclase (sGC), an H-NOX analogue. The K D (NO) and K D (CO) of each bacterial H-NOX or sGC follow the "sliding scale rule"; the affinities of the bacterial H-NOXs for NO and CO vary in a small range but stronger than those of sGC by at least two orders of magnitude. On the other hand, each bacterial H-NOX exhibits different characters in the stability of its 6c NO complex, reactivity with secondary NO, stability of oxyferrous heme and autoxidation to ferric heme. A facile access channel for gaseous ligands is also identified, implying that ligand access has only minimal effect on gaseous ligand selectivity of H-NOXs or sGC. This comparative study of the binding parameters of the bacterial H-NOXs and sGC provides a basis to guide future new structural and functional studies of each specific heme sensor with the H-NOX protein fold. Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Ruthenium(II carbonyl compounds with the 4′-chloro-2,2′:6′,2′′-terpyridine ligand

Directory of Open Access Journals (Sweden)

Rajendhraprasad Tatikonda

2017-04-01

Full Text Available Two ruthenium carbonyl complexes with the 4′-chloro-2,2′:6′,2′′-terpyridine ligand (tpy-Cl, C15H10ClN3, i.e. [RuCl(tpy-Cl(CO2][RuCl3(CO3] (I [systematic name: cis-dicarbonylchlorido(4′-chloro-2,2′:6′,2′′-terpyridine-κ3Nruthenium(II fac-tricarbonyltrichloridoruthenate(II], and [RuCl2(tpy-Cl(CO2] (II [cis-dicarbonyl-trans-dichlorido(4′-chloro-2,2′:6′,2′′-terpyridine-κ2N1,N1′ruthenium(II], were synthesized and characterized by single-crystal X-ray diffraction. The RuII atoms in both centrosymmetric structures (I and (II display similar, slightly distorted octahedral coordination spheres. The coordination sphere in the complex cation in compound (I is defined by three N atoms of the tridentate tpy-Cl ligand, two carbonyl carbon atoms and one chlorido ligand; the charge is balanced by an octahedral [Ru(CO3Cl3]− counter-anion. In the neutral compound (II, the tpy-Cl ligand coordinates to the metal only through two of its N atoms. The coordination sphere of the RuII atom is completed by two carbonyl and two chlorido ligands. In the crystal structures of both (I and (II, weak C—H...Cl interactions are observed.

Manganese(I-Based CORMs with 5-Substituted 3-(2-PyridylPyrazole Ligands

Directory of Open Access Journals (Sweden)

Ralf Mede

2017-01-01

Full Text Available The reaction of [(OC5MnBr] with substituted 3-(2-pyridylpyrazoles 2-PyPzRH (1a-l in methanol or diethyl ether yields the yellow to orange manganese(I complexes [(OC3Mn(Br(2-PyPzRH] (2a-l, the substituents R being phenyl (a, 1-naphthyl (b, 2-anthracenyl (c, 1-pyrenyl (d, 4-bromophenyl (e, 3-bromophenyl (f, duryl (g, 2-pyridyl (h, 2-furanyl (i, 2-thienyl (j, ferrocenyl (k, and 1-adamantyl (l. The carbonyl ligands are arranged facially, leading to three chemically different CO ligands due to different trans-positioned Lewis donors. The diversity of the substituent R demonstrates that this photoCORM backbone can easily be varied with a negligible influence on the central (OC3MnBr fragment, because the structural parameters and the spectroscopic data of this unit are very similar for all these derivatives. Even the ferrocenyl complex 2k shows a redox potential for the ferrocenyl subunit which is identical to the value of the free 5-ferrocenyl-3-(2-pyridylpyrazole (1k. The ease of variation of the starting 5-substituted 3-(2-pyridylpyrazoles offers a modular system to attach diverse substituents at the periphery of the photoCORM complex.

5-Chloro-2-(2'-((dimethylamino)methyl)-4'-iodophenylthio)benzenamine: a new serotonin transporter ligand

Energy Technology Data Exchange (ETDEWEB)

Oya, Shunichi [Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104 (United States); Choi, Seok-Rye [Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104 (United States); Kung, Mei-Ping [Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104 (United States); Kung, Hank F. [Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104 (United States); Department of Pharmacology, University of Pennsylvania, Philadelphia, PA 19104 (United States)

2007-02-15

Two novel ligands with 4' substitution on the Phenyl Ring B of biphenylthiol, 5-chloro-2-(2'-((dimethylamino)methyl)-4'-iodophenylthio)benzenamine (7) and 2-(2'-((dimethylamino)methyl)-4'-methoxyphenylthio)-5-iodobenzenamine (8), were prepared and tested as potential serotonin transporter (SERT) imaging agents. The new ligands displayed extremely high binding affinities to SERT (K {sub i}=0.22{+-}0.09 and 0.11{+-}0.04 nM, respectively), with very low binding affinities to dopamine and norepinephrine transporters (K {sub i}>1000 nM). The corresponding [{sup 125}I]7 and [{sup 125}I]8 were successfully prepared from tri-n-butyltin derivatives. They showed good brain uptakes and prolonged retention after intravenous injection in rats (brain uptake was 1.77% and 0.98% dose/g for [{sup 125}I]7, and 0.92% and 0.29% dose/g for [{sup 125}I]8, at 2 and 120 min, respectively). Significantly, [{sup 125}I]7 showed excellent uptake and prolonged retention in the hypothalamus, where SERT concentration was highest. The hypothalamus/cerebellum (HY/CB) ratios (target/background ratios) were 4.24, 7.10, 8.24 and 12.6 at 2, 4, 6 and 12 h, respectively. The HY/CB ratios for [{sup 125}I]8 were 3.97, 5.57 and 5.06 at 1, 2 and 4 h, respectively. Adding the 4'-iodo group to the Phenyl Ring B of Compound (7) appeared to reduce the rate of clearance from the brain, and kinetics favored uptake and retention in the hypothalamus. The localization of [{sup 125}I]7 in the hypothalamus region in the rat brain could be blocked by pretreatment with (+)McN5652, escitalopram and ADAM (2), which are all selective SERT ligands (at 2 mg/kg iv, 5 min pretreatment). Ex vivo autoradiograms of rat brain sections (at 4 h after intravenous injection of [{sup 125}I]7) showed intense labeling in regions of the brain known to have high SERT density. The excellent selective uptake and retention in the hypothalamus region suggest that [{sup 123}I]7 is a potential lead compound for

Synthesis and Structural Characterization of [Ir4(m-CO(CO7{m4-h3-Ph2PC(HC(PhPCBut}(m-PPh2]: Alkyne-Phosphaalkyne Coupling and Formation of a Novel 2-phosphabutadienylphosphine Ligand

Directory of Open Access Journals (Sweden)

Araujo Maria Helena

1998-01-01

Full Text Available Reaction of [Ir4(mu-H(CO9(Ph2PCºCPh(mu-PPh2] 1 with PºCBu t in CH2Cl2, at 35 °C, for 4 h yields the novel compound [Ir4(mu-CO(CO7{mu4-eta³-Ph2PC(HC(PhPCBu t}(mu-PPh2] 2, which contains the 2-phosphabutadienylphosphine chain. Compound 2 is also formed upon thermolysis of [Ir4(CO10(Ph2PCºCPh(PPh2H] 3 in the presence of PºCBu t in thf, at 40 °C, for 48 h. Small amounts of [Ir4(mu-CO(CO7(mu3-eta²-HCCPh(mu-PPh22] 4 are always obtained from both reactions, because of the competing rates of the transformations of 1 and 3 into 4 and of their reactions with PºCBu t. Compound 2 was characterized by analytical and spectroscopic studies such as FAB ms, ¹H, 31P,13C, 2D31P-¹H HETCOR, nOe difference and DEPT NMR experiments, which led to its formulation and established the coupling between the coordinated Ph2PCºCPh and PºCBu t and the migration of the hydride to the Calpha of the Ph2PCºCPh ligand. However, it was impossible to establish unambiguously if cleavage of the P-Csp bond of the Ph2PCºCPh ligand had occurred and the mode of interaction of the organophosphorus chain. An X-ray diffraction study of compound 2 established a butterfly arrangement of iridium atoms with the new ligand interacting with the metal framework via four sigma bonds and the PPh2 phosphorus lone pair.

Formation, spectroscopic characterization, and solution stability of an [Fe4S4]2+ cluster derived from β-cyclodextrin dithiolate.

Science.gov (United States)

Lo, Wayne; Zhang, Ping; Ling, Chang-Chun; Huang, Shaw; Holm, R H

2012-09-17

The formation and solution properties, including stability in mixed aqueous-Me(2)SO media, have been investigated for an [Fe(4)S(4)](2+) cluster derived from β-cyclodextrin (CD) dithiolate. Clusters of the type [Fe(4)S(4)(SAr)(4)](2-) (Ar = Ph, C(6)H(4)-3-F) are generated in Me(2)SO by redox reactions of [Fe(4)S(4)(SEt)(4)](2-) with 2 equiv of ArSSAr. An analogous reaction with the intramolecular disulfide of 6(A),6(D)-(3-NHCOC(6)H(4)-1-SH)(2)-6(A),6(D)-dideoxy-β-cyclodextrin (14), whose synthesis is described, affords a completely substituted cluster formulated as [Fe(4)S(4){β-CD-(1,3-NHCOC(6)H(4)S)(2)}(2)](2-) (15). Ligand binding is indicated by a circular dichroism spectrum and also by UV-visible and isotropically shifted (1)H NMR spectra and redox behavior convincingly similar to [Fe(4)S(4)(SPh)(4)](2-). One formulation of 15 is a single cluster to which two dithiolates are bound, each in bidentate coordination. With there being no proven precedent for this binding mode, we show that the cluster [Fe(4)S(4)(S(2)-m-xyl)(2)](2-) is a single cubane whose m-xylyldithiolate ligands are bound in a bidentate arrangement. This same structure type was proposed for a cluster formulated as [Fe(4)S(4){β-CD-(1,3-SC(6)H(4)S)(2)}(2)](2-) (16; Kuroda et al. J. Am. Chem. Soc.1988, 110, 4049-4050) and reported to be water-stable. Clusters 15 and 16 are derived from similar ligands differing only in the spacer group between the thiolate binding site and the CD platform. In our search for clusters stable in aqueous or organic-aqueous mixed solvents that are potential candidates for the reconstitution of scaffold proteins implicated in cluster biogenesis, 15 is the most stable cluster that we have thus far encountered under anaerobic conditions in the absence of added ligand.

Synthesis and characterization of 6,6'-bis(2-hydroxyphenyl)-2,2'-bipyridine ligand and its interaction with ct-DNA

Science.gov (United States)

Selamat, Norhidayah; Heng, Lee Yook; Hassan, Nurul Izzaty; Karim, Nurul Huda Abd

2015-09-01

The tetradentate ligand with four donor atoms OONN was synthesized. Bis(phenoxy)bipyridine ligand was prepared by Suzuki coupling reaction between 6,6'-dibromo-2,2'-bipyridyl and 2-hydroxyphenylboronic acid with presence of palladium (II) acetate. Bis(phenoxy)bipyridine ligand was also synthesized by demethylating of 6,6'-bis(2-methoxyphenyl)-2,2'-bipyridyl ligand through solvent free reaction using pyridine hydrocloride. The formation of both phenoxy and methoxy ligands was confirmed by 1H, 2D cosy and 13C NMR spectroscopy, ESI-MS spectrometry, FTIR spectroscopy. The purity of the ligand was confirmed by melting point. Binding studies of small molecules with DNA are useful to understand the reaction mechanism and to provide guidance for the application and design of new and more efficient drugs targeted to DNA. In this study, the binding interaction between the synthesized ligand with calf thymus-DNA (ct-DNA) has been investigated by UV/Vis DNA titration study. From the UV/Vis DNA study, it shows that bis(phenoxy)bipyridine ligand bind with ct-DNA via outside binding with binding contant Kb = 1.19 × 103 ± 0.08 M-1.

Studies on some mixed ligand complexes of UO2(VI) in solution

International Nuclear Information System (INIS)

Katkar, V.S.; Munshi, K.N.

1987-01-01

Potentiometric studies on some mixed ligand complexes of UO 2 (VI) with ethylenediamine N,N' diacetic acid as primary ligand and succinic acid, malic acid, maleic acid, fumaric acid, malonic acid, adipic acid, itaconic acid, phthalic acid and mandelic acid as secondary ligands have been carried out employing modified form of Irving-Rossotti's pH titration technique. The study was carried out at three different temperatures, viz. 5deg, 25deg and 45degC and at fixed ionic strength of 0.2M KNO 3 . Thermodynamic parameters, e.g. ΔG, ΔH and ΔS have been evaluated and further ΔG and ΔH values have been separated into their electrostatic components, ΔGe and ΔHe and cratic components, ΔGsub(c) and ΔHsub(c). The effect of change in dielectric constant and change in ionic strength of the medium have also been investigated. The sequence of stability constants has been correlated with the properties of secondary ligands. (author). 21 refs., 5 tabs

What is the best bonding model of the (σ-H-BR) species bound to a transition metal? Bonding analysis in complexes [(H)2Cl(PMe3)2M(σ-H-BR)] (M = Fe, Ru, Os).

Science.gov (United States)

Pandey, Krishna K

2012-03-21

Density Functional Theory calculations have been performed for the σ-hydroboryl complexes of iron, ruthenium and osmium [(H)(2)Cl(PMe(3))(2)M(σ-H-BR)] (M = Fe, Ru, Os; R = OMe, NMe(2), Ph) at the BP86/TZ2P/ZORA level of theory in order to understand the interactions between metal and HBR ligands. The calculated geometries of the complexes [(H)(2)Cl(PMe(3))(2)Ru(HBNMe(2))], [(H)(2)Cl(PMe(3))(2)Os(HBR)] (R = OMe, NMe(2)) are in excellent agreement with structurally characterized complexes [(H)(2)Cl(P(i)Pr(3))(2)Os(σ-H-BNMe(2))], [(H)(2)Cl(P(i)Pr(3))(2)Os{σ-H-BOCH(2)CH(2)OB(O(2)CH(2)CH(2))}] and [(H)(2)Cl(P(i)Pr(3))(2)Os(σ-H-BNMe(2))]. The longer calculated M-B bond distance in complex [(H)(2)Cl(PMe(3))(2)M(σ-H-BNMe(2))] are due to greater B-N π bonding and as a result, a weaker M-B π-back-bonding. The B-H2 bond distances reveal that (i) iron complexes contain bis(σ-borane) ligand, (ii) ruthenium complexes contain (σ-H-BR) ligands with a stretched B-H2 bond, and (iii) osmium complexes contain hydride (H2) and (σ-H-BR) ligands. The H-BR ligands in osmium complexes are a better trans-directing ligand than the Cl ligand. Values of interaction energy, electrostatic interaction, orbital interaction, and bond dissociation energy for interactions between ionic fragments are very large and may not be consistent with M-(σ-H-BR) bonding. The EDA as well as NBO and AIM analysis suggest that the best bonding model for the M-σ-H-BR interactions in the complexes [(H)(2)Cl(PMe(3))(2)M(σ-H-BR)] is the interaction between neutral fragments [(H)(2)Cl(PMe(3))(2)M] and [σ-H-BR]. This becomes evident from the calculated values for the orbital interactions. The electron configuration of the fragments which is shown for C in Fig. 1 experiences the smallest change upon the M-σ-H-BR bond formation. Since model C also requires the least amount of electronic excitation and geometry changes of all models given by the ΔE(prep) values, it is clearly the most appropriate choice of

catena-Poly[[bromidocopper(I)]-?-?2,?1-3-(2-allyl-2H-tetra?zol-5-yl)pyridine

OpenAIRE

Wang, Wei

2008-01-01

The title compound, [CuBr(C9H9N5)] n , has been prepared by the solvothermal treatment of CuBr with 3-(2-allyl-2H-tetra?zol-5-yl)pyridine. It is a new homometallic CuI olefin coord?ination polymer in which the CuI atoms are linked by the 3-(2-allyl-2H-tetra?zol-5-yl)pyridine ligands and bonded to one terminal Br atom each. The organic ligand acts as a bidentate ligand connecting two neighboring Cu centers through the N atom of the pyridine ring and the double bond of the allyl group. A three-...

Designer ligands. Part 15. Synthesis and characterisation of novel Mn(lI), Ni(II) and Zn(II) complexes of 1,10-phenanthroline-derived ligands

CSIR Research Space (South Africa)

Wellington, Kevin W

2009-01-01

Full Text Available Series of manganese(II), nickel(II) and zinc(II) complexes have been prepared using 1,10-phenanthroline-derived ligands, and their coordination geometries have been assigned using infrared data. It is apparent that, depending on the ligand...

Identification of MHC class I H-2 Kb/Db-restricted immunogenic peptides derived from retinal proteins

DEFF Research Database (Denmark)

Wang, Mingjun; Bai, Fang; Pries, Mette

2006-01-01

PURPOSE: To identify H-2 Kb/Db-binding immunogenic peptides derived from retinal proteins. METHODS: Computer-based prediction was used to identify potentially H-2 Kb/Db-binding peptides derived from the interphotoreceptor retinol-binding protein (IRBP), soluble retinal antigen (S...... on day 21 after immunization with IRBP or IRBP and the immunogenic peptides. RESULTS: All the 21 predicted peptides were found to upregulate expression of H-2 Kb/Db on RMA-S cells. Five peptides, the two IRBP-derived peptides IRBP89-96 and IRBP(101-108), and the three PEDF-derived peptides, PEDF389....... The immunogenic peptides alone did not induce inflammation in the eyes, but they could enhance severity of uveitis induced by IRBP. CONCLUSIONS: Five of 21 H-2 Kb/Db-binding retinal protein-derived peptides were found to be immunogenic, suggesting that these peptides could function as autoantigenic epitopes...

Synthesis, characterization, DNA/protein interaction and cytotoxicity studies of Cu(II) and Co(II) complexes derived from dipyridyl triazole ligands

Science.gov (United States)

Zhang, Wei; Yao, Di; Wei, Yi; Tang, Jie; Bian, He-Dong; Huang, Fu-Ping; Liang, Hong

2016-06-01

Four different transition metal complexes containing dipyridyl triazole ligands, namely [Cu(abpt)2Cl2]·2H2O (1), [Cu(abpt)2(ClO4)2] (2), [Co2(abpt)2(H2O)2Cl2]·Cl2·4H2O (3) and [Co2(Hbpt)2(CH3OH)2(NO3)2] (4) have been designed, synthesized and further structurally characterized by X-ray crystallography, ESI-MS, elemental analysis, IR and Raman spectroscopy. In these complexes, the both ligands act as bidentate ligands with N, N donors. DNA binding interactions with calf thymus DNA (ct-DNA) of the ligand and its complexes 1 ~ 4 were investigated via electronic absorption, fluorescence quenching, circular dichroism and viscosity measurements as well as confocal Laser Raman spectroscopy. The results show these complexes are able to bind to DNA via the non-covalent mode i.e. intercalation and groove binding or electrostatic interactions. The interactions with bovine serum albumin (BSA) were also studied using UV-Vis and fluorescence spectroscopic methods which indicated that fluorescence quenching of BSA by these compounds was the presence of both static and dynamic quenching. Moreover, the in vitro cytotoxic effects of the complexes against four cell lines SK-OV-3, HL-7702, BEL7404 and NCI-H460 showed the necessity of the coordination action on the biological properties on the respective complex and that all four complexes exhibited substantial cytotoxic activity.

Anti-Inflammatory Oxicams as Multi-donor Ligand Systems: pH- and Solvent-Dependent Coordination Modes of Meloxicam and Piroxicam to Ru and Os.

Science.gov (United States)

Aman, Farhana; Hanif, Muhammad; Kubanik, Mario; Ashraf, Adnan; Söhnel, Tilo; Jamieson, Stephen M F; Siddiqui, Waseeq Ahmad; Hartinger, Christian G

2017-04-06

The nitrogen- and sulfur-containing 1,2-benzothiazines meloxicam and piroxicam are widely used as nonsteroidal anti-inflammatory drugs. Intrigued by the presence of multiple donor atoms and therefore potentially rich coordination chemistry, we prepared a series of organometallic Ru and Os compounds with meloxicam and piroxicam featuring either as mono- or bidentate ligand systems. The choice of the solvent and the pH value was identified as the critical parameter to achieve selectively mono- or bidentate coordination. The coordination modes were confirmed experimentally by NMR spectroscopy and single crystal X-ray diffraction analysis. Using DFT calculations, it was established that complexes in which meloxicam acts as a bidentate N,O donor are energetically more favorable than coordination as O,O and S,O donor systems. Since meloxicam and piroxicam derivatives have shown anticancer activity in the past, we aimed to compare the complexes with mono- and bidentate ligands on their in vitro anticancer activity. However, stability studies revealed that only the latter complexes were stable in [D 6 ]DMSO/D 2 O (5:95) and therefore no direct comparisons could be made. The meloxicam complexes 1 and 2 showed moderate cytotoxicity, whereas the piroxicam derivatives 5 and 6 were hardly active against the utilized cell lines. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Selective extraction of trivalent actinides with hard-soft mixed donor ligands: role of intra-ligand synergism

International Nuclear Information System (INIS)

Ghanty, Tapan K.

2016-01-01

In recent years, considerable attention has been given to understand the coordination chemistry of trivalent lanthanide (Ln) and actinide (An) with various ligands because of its close link with the nuclear waste management processes. It is well known that lanthanide-actinide separation is a challenging and difficult task because of very similar chemical properties of these two series of ions, which are associated with similar ionic radii and coordination numbers. Recently, we have introduced a new concept, 'intra-ligand synergism', where hard donor atom, such as, oxygen preferentially binds to trivalent actinides (An(III)) as compared to the valence iso-electronic trivalent lanthanides (Ln(III)) in presence of another soft donor centre. In the present work, the conventional concept of selective complexation of actinides with soft donor ligands (either S or N donor) has been modified through exploiting this concept, and thereby the higher selectivity of 1,10-phenanthroline-2,9-dicarboxylamide (PDAM) based ligands, namely PDAM and its isobutyl and decyl derivatives towards Am(III) ion has been predicted theoretically through density functional calculations. Subsequently, several such amide derivatives have been synthesized to optimize the solubility of the ligands in organic phase. Finally, solvent extraction experiments have been carried out to validate the theoretical prediction on the selectivity of oxygen donor ligands towards Am(III) as compared to Eu(III), and a maximum separation factor of about 51 has been achieved experimentally using 2,9-bis(N-decylaminocarbonyl)-1,10-phenanthroline ligand. The separation factor is increased with the decrease in pH, which is very interesting since extraction of the Am 3+ ion is considered to be important under highly acidic conditions from the nuclear waste management point of view. (author)

Triosmium cluster compounds containing isocyanide and hydride ligands. Crystal and molecular structure of (μ-H)(μ-eta1-C==N(H)(t-C4H9))Os3(CO)10

International Nuclear Information System (INIS)

Adams, R.D.; Golembeski, N.M.

1979-01-01

The crystal and molecular structure of the compound (μ-H)(μ-eta 1 -C==N(H)(t-C 4 H 9 ))Os 3 (CO) 10 has been determined by X-ray crystallographic methods. The compound crystallizes in the centrosymmetric monoclinic space group P2 1 /n[C/sub 2h/ 5 ]:a = 13.651 (4) A, b = 9.156 (4) A, c = 18.275 (5) A, β = 111.42 (2) 0 , V = 2126.3 (25) A 3 , Z = 4, rho/sub calcd/ = 2.92 g cm -3 . A uniform triangular cluster of three osmium atoms contains ten linear carbonyl groups and a μ-eta 1 -C==N(H)(t-C 4 H 9 ) iminyl ligand. The carbon atom of the iminyl ligand symmetrically bridges one osmium-osmium bond, as is shown by the internuclear separations Os(2)-C(11) = 2.066 (8) A and Os(3)-C(11) = 2.043 (8) A. The iminyl bond, C(11)-N, is double with the C-N distance being 1.298 (10) A

Synthesis, spectroscopic and catalytic properties of some new boron hybrid molecule derivatives by BF2 and BPh2 chelation

Science.gov (United States)

Kilic, Ahmet; Alcay, Ferhat; Aydemir, Murat; Durgun, Mustafa; Keles, Armagan; Baysal, Akın

2015-05-01

A new series of Schiff base ligands (L1-L3) and their corresponding fluorine/phenyl boron hybrid complexes [LnBF2] and [LnBPh2] (n = 1, 2 or 3) have been synthesized and well characterized by both analytical and spectroscopic methods. The Schiff base ligands and their corresponding fluorine/phenyl boron hybrid complexes have been characterized by NMR (1H, 13C and 19F), FT-IR, UV-Vis, LC-MS, and fluorescence spectroscopy as well as melting point and elemental analysis. The fluorescence efficiencies of phenyl chelate complexes are greatly red-shifted compared to those of the fluorine chelate analogs based on the same ligands, presumably due to the large steric hindrance and hard π → π∗ transition of the diphenyl boron chelation, which can effectively prevent molecular aggregation. The boron hybrid complexes were applied to the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of 2-propanol as the hydrogen source. The catalytic studies showed that boron hybrid complexes are good catalytic precursors for transfer hydrogenation of aromatic ketones in 0.1 M iso-PrOH solution. Also, we have found that both steric and electronic factors have a significant impact on the catalytic properties of this class of molecules.

(E)-6-Amino-1,3-dimethyl-5-[(pyridin-2-yl-methyl-idene)amino]-pyrimidine-2,4(1H,3H)-dione.

Science.gov (United States)

Booysen, Irvin; Hlela, Thulani; Ismail, Muhammed; Gerber, Thomas; Hosten, Eric; Betz, Richard

2011-09-01

In the title compound, C(12)H(13)N(5)O(2), a Schiff-base-derived chelate ligand, the non-aromatic heterocycle and its substituents essentially occupy one common plane (r.m.s. of fitted non-H atoms = 0.0503 Å). The N=C bond is E-configured. Intra-cyclic angles in the pyridine moiety cover the range 117.6 (2)-124.1 (2)°. Intra- and inter-molecular N-H⋯N and N-H⋯O hydrogen bonds are observed in the crystal structure, as are intra- and inter-molecular C-H⋯O contacts which, in total, connect the mol-ecules into a three-dimensional network. The shortest ring-centroid-to-ring-centroid distance of 3.5831 (14) Å is between the two different types of six-membered rings.

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.

Interaction between alkaline earth cations and oxo-ligands. DFT study of the affinity of the Ca2+ cation for carbonyl ligands.

Science.gov (United States)

da Costa, Leonardo Moreira; Carneiro, José Walkimar de Mesquita; Romeiro, Gilberto Alves; Paes, Lilian Weitzel Coelho

2011-02-01

The affinity of the Ca(2+) ion for a set of substituted carbonyl ligands was analyzed with both the DFT (B3LYP/6-31+G(d)) and semi-empirical (PM6) methods. Two types of ligands were studied: a set of monosubstituted [O=CH(R)] and a set of disubstituted ligands [O=C(R)(2)] (R=H, F, Cl, Br, OH, OCH(3), CH(3), CN, NH(2) and NO(2)), with R either directly bound to the carbonyl carbon atom or to the para position of a phenyl ring. The interaction energy was calculated to quantify the affinity of the Ca(2+) cation for the ligands. Geometric and electronic parameters were correlated with the intensity of the metal-ligand interaction. The electronic nature of the substituent is the main parameter that determines the interaction energy. Donor groups make the interaction energy more negative (stabilizing the complex formed), while acceptor groups make the interaction energy less negative (destabilizing the complex formed).

Formation of closo-rhodacarboranes with the η2,η3-(CH2=CHC5H6) ligand in the reaction of μ-dichloro-bis[(η4-norbornadiene)rhodium] with nido-dicarbaundecaborates [K][nido-7-R1-8-R2-7,8-C2B9H10

International Nuclear Information System (INIS)

Safronov, A.V.; Sokolova, M.N.; Vorontsov, E.V.; Petrovskij, P.V.; Barakovskaya, I.G.; Chizhevskij, I.T.

2004-01-01

New closo-(η 2 ,η 3 -(4-vinylcyclopentene-3-yl)rhodacarboranes were prepared by reaction of the complex [(η 4 -C 7 H 8 )RhCl] 2 (C 7 H 8 -norbornadiene) with salts of substituted nido-dicarbaundecaborates [K][nido-7-R 1 -8-R 2 -7,8-C 2 B 9 H 10 ] (R 1 =R 2 =H (a); R = R 2 =Me (b); R 1 , R 2 =1',2'-(CH 2 ) 2 C 6 H 4 (c); R 1 =Me, R 2 =Ph (d) in CH 2 Cl 2 . The structure of the compounds prepared in solution was studied by the method of multinuclear NMR spectroscopy. A probable mechanism of the norbornadiene ligand regrouping was suggested [ru

CdBr2 complexes of 1,2-bis-[2-(5-H/methyl/chloro/nitro)-1H-benzimidazolyl]-1,2-ethanediols

International Nuclear Information System (INIS)

Aydin Tavman

2005-01-01

The complexes of 1,2-bis-[2-(5-H/methyl/chloro/nitro)-1H-benzimidazolyl]-1,2-ethanediols with CdBr 2 were synthesized and characterized by elemental analysis, molar conductivity, IR and NMR spectra. The ligands act as a bidentate only through both oxygen atoms of hydroxyl groups in complexes with ratio M:L=1:1 [ru

Iridium/Bipyridine-Catalyzed ortho-Selective C-H Borylation of Phenol and Aniline Derivatives.

Science.gov (United States)

Li, Hong-Liang; Kanai, Motomu; Kuninobu, Yoichiro

2017-11-03

An iridium-catalyzed ortho-selective C-H borylation of phenol and aniline derivatives has been successfully developed. Iridium/bipyridine-catalyzed C-H borylation generally occurred at the meta- and para-positions of aromatic substrates. Introduction of an electron-withdrawing substituent on the bipyridine-type ligand and a methylthiomethyl group on the hydroxy and amino groups of the phenol and aniline substrates, however, dramatically altered the regioselectivity, affording exclusively ortho-borylated products. The reaction proceeded in good to excellent yields with good functional group tolerance. C-H borylation was applied to the synthesis of a calcium receptor modulator.

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

Cysteine as a ligand platform in the biosynthesis of the FeFe hydrogenase H cluster.

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Suess, Daniel L M; Bürstel, Ingmar; De La Paz, Liliana; Kuchenreuther, Jon M; Pham, Cindy C; Cramer, Stephen P; Swartz, James R; Britt, R David

2015-09-15

Hydrogenases catalyze the redox interconversion of protons and H2, an important reaction for a number of metabolic processes and for solar fuel production. In FeFe hydrogenases, catalysis occurs at the H cluster, a metallocofactor comprising a [4Fe-4S]H subcluster coupled to a [2Fe]H subcluster bound by CO, CN(-), and azadithiolate ligands. The [2Fe]H subcluster is assembled by the maturases HydE, HydF, and HydG. HydG is a member of the radical S-adenosyl-L-methionine family of enzymes that transforms Fe and L-tyrosine into an [Fe(CO)2(CN)] synthon that is incorporated into the H cluster. Although it is thought that the site of synthon formation in HydG is the "dangler" Fe of a [5Fe] cluster, many mechanistic aspects of this chemistry remain unresolved including the full ligand set of the synthon, how the dangler Fe initially binds to HydG, and how the synthon is released at the end of the reaction. To address these questions, we herein show that L-cysteine (Cys) binds the auxiliary [4Fe-4S] cluster of HydG and further chelates the dangler Fe. We also demonstrate that a [4Fe-4S]aux[CN] species is generated during HydG catalysis, a process that entails the loss of Cys and the [Fe(CO)2(CN)] fragment; on this basis, we suggest that Cys likely completes the coordination sphere of the synthon. Thus, through spectroscopic analysis of HydG before and after the synthon is formed, we conclude that Cys serves as the ligand platform on which the synthon is built and plays a role in both Fe(2+) binding and synthon release.

Thermodynamic Studies of (H2Rh(diphosphine)2)+ and (HRh(diphosphine)2(CH3CN))2+ Complexes in Acetonitrile

International Nuclear Information System (INIS)

Wilson, Aaron D.; Miller, Alexander J.M.; DuBois, Daniel L.; Labinger, Jay A.; Bercaw, John E.

2011-01-01

Thermodynamic studies of a series of (H2Rh(PP)2)+ and (HRh(PP)2(CH3CN))2+ complexes have been carried out in acetonitrile. Seven different diphosphine (PP) ligands were selected to allow variation of the electronic properties of the ligand substituents, the cone angles, and the natural bite angles (NBAs). Oxidative addition of H2 to (Rh(PP)2)+ complexes is favored by diphosphine ligands with large NBAs, small cone angles, and electron donating substituents, with the NBA being the dominant factor. Large pKa values for (HRh(PP)2(CH3CN))2+ complexes are favored by small ligand cone angles, small NBAs, and electron donating substituents with the cone angles playing a major role. The hydride donor abilities of (H2Rh(PP)2)+ complexes increase as the NBAs decrease, the cone angles decrease, and the electron donor abilities of the substituents increase. These results indicate that if solvent coordination is involved in hydride transfer or proton transfer reactions, the observed trends can be understood in terms of a combination of two different steric effects, NBAs and cone angles, and electron-donor effects of the ligand substituents.

Synthesis of Some O-Substituted Derivatives of Natural 6-hydroxymethyl-4-methoxy-2H-pyran-2-one (opuntiol)

International Nuclear Information System (INIS)

Shahzadi, T.; Akhtar, M.; Rehman, A.; Riaz, T.; Ashraf, M.

2013-01-01

This manuscript reports the synthesis of a series of new O-substituted derivatives of opuntiol (1) which is a naturally occurring compound isolated from a plant Opuntia dillenii Haw belonging to family Cactaceae. These derivatives 3a-t, were characterized by FAB-MS, IR, and 1H-NMR and then screened against acetylcholinesterase, butyrylcholinesterase, lipoxygenase and H-chymotrypsin enzymes. The screening results revealed that 6-(acetyloxy) methyl- 4-methoxy-2H-pyran-2-one (3b) and N-(2,5-dimethylphenyl)-2-((4-methoxy-6-oxo-2H-pyran-2-yl) methoxy)acetamide (3p) were found to be the inhibitor of butyrylcholinesterase while 6-(acetyloxy) methyl- 4-methoxy-2H-pyran-2-one (3b), 6-(ethoxymethyl)-4-methoxy-2H-pyran-2-one (3c), 4-methoxy-6-((phenylmethoxy)methyl)-2H-pyran-2-one (3g), 6-((2-bromoethyloxy)methyl)-4-methoxy-2H-pyran-2-one (3j), N-(5-chloro-2-ethoxyphenyl)-2-((4-methoxy-6-oxo-2H-pyran-2-yl)methoxy) acetamide (3r), N-(3,4-dimethylphenyl)-2-((4-methoxy-6-oxo-2H-pyran-2-yl)methoxy)acetamide (3s) N-(3,5-dimethylphenyl)-2-((4-methoxy-6-oxo-2H-pyran-2-yl)methoxy)acetamide (3t) were found to be active against H-chymotrypsin and among these 3s was the good inhibitor of this enzyme having IC50 value of 142.71 +- 0.22 micro moles/L. (author)

[KDy(Hptc3(H3ptc]n·2n(Hbipy·5n(H2O, a Layered Coordination Polymer Containing DyO6N3 Tri-Capped Trigonal Prisms (H3ptc = Pyridine 2,4,6-Tricarboxylic Acid, C8H5NO6; Bipy = 2,2'-Bipyridine, C10H8N2

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Shoaib Anwar

2012-08-01

Full Text Available The synthesis, structure and properties of the bimetallic layered coordination polymer, [KDy(C8H3NO63(C8H5NO6]n·2n(C10H9N2·5n(H2O = [KDy(Hptc3(H3ptc]n·2n(Hbipy·5n(H2O, are described. The Dy3+ ion is coordinated by three O,N,O-tridentate doubly-deprotonated pyridine tri-carboxylate (Hptc ligands to generate a fairly regular DyO6N3 tri-capped trigonal prism, with the N atoms acting as the caps. The potassium ion is coordinated by an O,N,O-tridentate H3ptc molecule as well as monodentate and bidentate Hptc ligands to result in an irregular KNO9 coordination geometry. The ligands bridge the metal-atom nodes into a bimetallic, layered, coordination polymer, which extends as corrugated layers in the (010 plane, with the mono-protonated bipyridine cations and water molecules occupying the inter-layer regions: Unlike related structures, there are no dysprosium–water bonds. Many O–HLO and N–HLO hydrogen bonds consolidate the structure. Characterization and bioactivity data are described. Crystal data: C52H42DyKN8O29, Mr = 1444.54, triclinic,  (No. 2, Z = 2, a = 9.188(2 Å, b = 15.7332(17 Å, c = 19.1664(19 Å, α = 92.797(6°, β = 92.319(7°, γ = 91.273(9°, V = 2764.3(7 Å3, R(F = 0.029, wR(F2 = 0.084.

Identification of naturally processed hepatitis C virus-derived major histocompatibility complex class I ligands.

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Benno Wölk

Full Text Available Fine mapping of human cytotoxic T lymphocyte (CTL responses against hepatitis C virus (HCV is based on external loading of target cells with synthetic peptides which are either derived from prediction algorithms or from overlapping peptide libraries. These strategies do not address putative host and viral mechanisms which may alter processing as well as presentation of CTL epitopes. Therefore, the aim of this proof-of-concept study was to identify naturally processed HCV-derived major histocompatibility complex (MHC class I ligands. To this end, continuous human cell lines were engineered to inducibly express HCV proteins and to constitutively express high levels of functional HLA-A2. These cell lines were recognized in an HLA-A2-restricted manner by HCV-specific CTLs. Ligands eluted from HLA-A2 molecules isolated from large-scale cultures of these cell lines were separated by high performance liquid chromatography and further analyzed by electrospray ionization quadrupole time of flight mass spectrometry (MS/tandem MS. These analyses allowed the identification of two HLA-A2-restricted epitopes derived from HCV nonstructural proteins (NS 3 and 5B (NS3₁₄₀₆₋₁₄₁₅ and NS5B₂₅₉₄₋₂₆₀₂. In conclusion, we describe a general strategy that may be useful to investigate HCV pathogenesis and may contribute to the development of preventive and therapeutic vaccines in the future.

A new class of pyrazolo[5,1-c][1,2,4]triazines as γ-aminobutyric type A (GABAA) receptor subtype ligand: synthesis and pharmacological evaluation.

Science.gov (United States)

Guerrini, Gabriella; Ciciani, Giovanna; Daniele, Simona; Martini, Claudia; Costagli, Camilla; Guarino, Chiara; Selleri, Silvia

2018-05-15

A comparison between compounds with pyrazolo[1,5-a]pyrimidine structure (series 4-6) and pyrazolo[5,1-c][1,2,4]triazine core (series 9) as ligands at GABA A -receptor subtype, was evaluated. Moreover, for pyrazolotriazine derivatives having binding recognition, the interaction on recombinant rat α(1-3,5) GABA A receptor subtypes, was performed. Among these latter, emerge compounds 9c, 9k, 9l, 9m and 9n as α1-selective and 9h as α2-selective ligands. Copyright © 2018 Elsevier Ltd. All rights reserved.

AOI [3] High-Temperature Nano-Derived Micro-H₂ and - H₂S Sensors

Energy Technology Data Exchange (ETDEWEB)

Sabolsky, Edward M. [West Virginia Univ., Morgantown, WV (United States)

2014-08-01

The emissions from coal-fired power plants remain a significant concern for air quality. This environmental challenge must be overcome by controlling the emission of sulfur dioxide (SO₂) and hydrogen sulfide (H₂S) throughout the entire coal combustion process. One of the processes which could specifically benefit from robust, low cost, and high temperature compatible gas sensors is the coal gasification process which converts coal and/or biomass into syngas. Hydrogen (H₂), carbon monoxide (CO) and sulfur compounds make up 33%, 43% and 2% of syngas, respectively. Therefore, development of a high temperature (>500°C) chemical sensor for in-situ monitoring of H₂, H₂S and SO2₂ levels during coal gasification is strongly desired. The selective detection of SO₂/H₂S in the presence of H₂, is a formidable task for a sensor designer. In order to ensure effective operation of these chemical sensors, the sensor system must inexpensively function within harsh temperature and chemical environment. Currently available sensing approaches, which are based on gas chromatography, electrochemistry, and IR-spectroscopy, do not satisfy the required cost and performance targets. This work focused on the development microsensors that can be applied to this application. In order to develop the high- temperature compatible microsensor, this work addressed various issues related to sensor stability, selectivity, and miniaturization. In the research project entitled “High-Temperature Nano-Derived Micro-H₂ and -H₂S Sensors”, the team worked to develop micro-scale, chemical sensors and sensor arrays composed of nano-derived, metal-oxide composite materials to detect gases like H₂, SO₂, and H₂S within high-temperature environments (>500°C). The research was completed in collaboration with NexTech Materials, Ltd. (Lewis Center, Ohio). Nex

Homochiral coordination polymers constructed from aminocarboxylate derivates: Effect of bipyridine on the amidation reaction

International Nuclear Information System (INIS)

Chen Jianshan; Sheng Tianlu; Hu Shengmin; Xiang Shengchang; Fu Ruibiao; Zhu Qilong; Wu Xintao

2012-01-01

Using aminocarboxylate derivates (S)-N-(4-cyanobenzoic)-glutamic acid (denoted as cbg, 1a) and (S)-N-(4-nitrobenzoic)-glutamic acid (denoted as nbg, 1b) as chiral ligands, five new homochiral coordination polymers formulated as [Cu(cbg)(H 2 O) 2 ] n (3), [Cu(cbop) 2 (4,4′-bipy)(H 2 O)] n (4) (cbop=(S)-N-(4-cyanobenzoic)-5-oxoproline, 4,4′-bipy=4,4′-bipyridine), {[Cu(nbop) 2 (4,4′-bipy)]·4H 2 O} n (5) (nbop=(S)-N-(4-nitrobenzoic)-5-oxoproline), {[Cd(nbop) 2 (4,4′-bipy)]·2H 2 O} n (6), and [Ni(nbop) 2 (4,4′-bipy)(H 2 O) 2 ] n (7) have been hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction study reveals that the original chirality of aminocarboxylate derivates is maintained in all these complexes. Complexes 3, 4, and 7 are one-dimensional infinite chain coordination polymers, while complexes 5 and 6 possess two-dimensional network structures. In situ cyclization of 1a and 1b was taken place in the formation of complexes 4–7, which may be due to the competition of 4,4′-bipyridine with chiral ligands during the coordination process. Preliminary optical behavior investigation indicates that ligands 1a, 1b, and complexes 6, 7 are nonlinear optical active. - Graphical abstract: Using aminocarboxylate derivates as chiral ligands, five new homochiral coordination polymers possessing second harmonic generation activities have been hydrothermally synthesized. Highlights: ► Two new chiral aminocarboxylate derivates were firstly synthesized. ► Five new homochiral metal organic complexes were obtained hydrothermally based on these ligands. ► Intramolecular amidation was taken place on the aminocarboxylate derivates during the formation of these complexes. ► In situ amidation may be due to the impact of 4,4′-bipyridine. ► The homochiral complexes are nonlinear optical active.

Synthesis, characterization, spectroscopic and catalytic oxidation studies of Fe(III), Ni(II), Co(III), V(IV) and U(VI) Schiff base complexes with N, O donor ligands derived from 2,3-diaminopyridine

Energy Technology Data Exchange (ETDEWEB)

Zabardasti, Abedien; Shangaie, Sayed Asad [Lorestan Univ., Khorramabad (Iran, Islamic Republic of). Dept. of Chemistry

2016-10-15

Fifteen new complexes of transition metals were designed using three Schiff base ligands and aldol condensation of 2,3-diaminopyridine with 5-R-2-hydroxybenzaldehyde (R = F, Cl, Br) in the 1:2 molar ratio. The tetradentate ligands N,N{sup '}-bis(5-R-2-hydroxybenzaldehyde) pyridine were acquired with the common formula H{sub 2}[(5-R-sal){sub 2}py] and characterized by IR, UV-Vis spectra, {sup 1}H-NMR and elemental analysis. These ligands produce 1:1 complexes M[(5-R-sal){sub 2}py] with Fe(III), Ni(II), Co(III), V(IV) and U(VI) metal ions. The electronic property and nature of complexes were identified by IR, UV-Vis spectra, elemental analysis, X-ray crystallography and cyclic voltammetric methods. The catalytic activity of complexes for epoxidation of styrene with UHP as primary oxidant at minimal temperature (10 C) has been planned. The spectral data of the ligands and their complexes are deliberate in connection with the structural changes which happen due to complex preparation. The electrochemical outcome has good conformability with what suggested for electronic interaction among metal center and ligand by the UV-Vis and IR measurements.

A meta-selective C-H borylation directed by a secondary interaction between ligand and substrate

Science.gov (United States)

Kuninobu, Yoichiro; Ida, Haruka; Nishi, Mitsumi; Kanai, Motomu

2015-09-01

Regioselective C-H bond transformations are potentially the most efficient method for the synthesis of organic molecules. However, the presence of many C-H bonds in organic molecules and the high activation barrier for these reactions make these transformations difficult. Directing groups in the reaction substrate are often used to control regioselectivity, which has been especially successful for the ortho-selective functionalization of aromatic substrates. Here, we describe an iridium-catalysed meta-selective C-H borylation of aromatic compounds using a newly designed catalytic system. The bipyridine-derived ligand that binds iridium contains a pendant urea moiety. A secondary interaction between this urea and a hydrogen-bond acceptor in the substrate places the iridium in close proximity to the meta-C-H bond and thus controls the regioselectivity. 1H NMR studies and control experiments support the participation of hydrogen bonds in inducing regioselectivity. Reversible direction of the catalyst through hydrogen bonds is a versatile concept for regioselective C-H transformations.

Impact of protein and ligand impurities on ITC-derived protein-ligand thermodynamics.

Science.gov (United States)

Grüner, Stefan; Neeb, Manuel; Barandun, Luzi Jakob; Sielaff, Frank; Hohn, Christoph; Kojima, Shun; Steinmetzer, Torsten; Diederich, François; Klebe, Gerhard

2014-09-01

The thermodynamic characterization of protein-ligand interactions by isothermal titration calorimetry (ITC) is a powerful tool in drug design, giving valuable insight into the interaction driving forces. ITC is thought to require protein and ligand solutions of high quality, meaning both the absence of contaminants as well as accurately determined concentrations. Ligands synthesized to deviating purity and protein of different pureness were titrated by ITC. Data curation was attempted also considering information from analytical techniques to correct stoichiometry. We used trypsin and tRNA-guanine transglycosylase (TGT), together with high affinity ligands to investigate the effect of errors in protein concentration as well as the impact of ligand impurities on the apparent thermodynamics. We found that errors in protein concentration did not change the thermodynamic properties obtained significantly. However, most ligand impurities led to pronounced changes in binding enthalpy. If protein binding of the respective impurity is not expected, the actual ligand concentration was corrected for and the thus revised data compared to thermodynamic properties obtained with the respective pure ligand. Even in these cases, we observed differences in binding enthalpy of about 4kJ⋅mol(-1), which is considered significant. Our results indicate that ligand purity is the critical parameter to monitor if accurate thermodynamic data of a protein-ligand complex are to be recorded. Furthermore, artificially changing fitting parameters to obtain a sound interaction stoichiometry in the presence of uncharacterized ligand impurities may lead to thermodynamic parameters significantly deviating from the accurate thermodynamic signature. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis, crystal structure and magnetic properties of [Cu(mal(abpt(H2O].3/2H2O and [Cu2(sq(abpt 2].2H2O (mal = malonate, sq = squarate, abpt = 4-amino-3,5-di-2-pyridyl-4H-1,2,4 triazole

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Eno A. Ededet

2011-04-01

Full Text Available Two new mixed-ligand complexes of formula [Cu(mal(abpt(H2O].3/2H2O (1 and [Cu2(sq(abpt2].2H2O (2 [mal = malonate, abpt = 4-amino-3,5-di-2-pyridyl-4H-1,2,4 triazole and sq = squarate], have been prepared and characterized by X-ray crystal structure determination and magnetic studies. Complex 1 crystallizes in the monoclinic system, space group C2/c, with a = 14.0086(2 Å, b = 10.0980(2 Å, c = 25.630(4 Å; β = 97.5900(10 o, and Z = 8. Complex 2 crystallizes in the triclinic system, space group P-1 with a = 7.5696(15 Å, b = 8.4697(17 Å, c = 11.049(2 Å; β = 93.00(3o, α = 96.98(3, γ = 90.111(3 and Z = 1. Complex 1 consist of a neutral mononuclear [Cu(mal(abpt(H2O] unit and water molecule of crystallization in a distorted square pyramidal coordination sphere, while complex 2 is viewed as being made up of [Cu(sq(abpt2] units with the squarato ligand bridging the two copper(II cations. Variable temperature magnetic behaviour of the complexes reveals the existence of weak antiferromagnetic interaction for complex 1 and weak ferromagnetic intrachain interaction for complex 2.

Ammonia formation by metal-ligand cooperative hydrogenolysis of a nitrido ligand

Science.gov (United States)

Askevold, Bjorn; Nieto, Jorge Torres; Tussupbayev, Samat; Diefenbach, Martin; Herdtweck, Eberhardt; Holthausen, Max C.; Schneider, Sven

2011-07-01

Bioinspired hydrogenation of N2 to ammonia at ambient conditions by stepwise nitrogen protonation/reduction with metal complexes in solution has experienced remarkable progress. In contrast, the highly desirable direct hydrogenation with H2 remains difficult. In analogy to the heterogeneously catalysed Haber-Bosch process, such a reaction is conceivable via metal-centred N2 splitting and unprecedented hydrogenolysis of the nitrido ligands to ammonia. We report the synthesis of a ruthenium(IV) nitrido complex. The high nucleophilicity of the nitrido ligand is demonstrated by unusual N-C coupling with π-acidic CO. Furthermore, the terminal nitrido ligand undergoes facile hydrogenolysis with H2 at ambient conditions to produce ammonia in high yield. Kinetic and quantum chemical examinations of this reaction suggest cooperative behaviour of a phosphorus-nitrogen-phosphorus pincer ligand in rate-determining heterolytic hydrogen splitting.

Understanding Am3+/Cm3+ separation with H4TPAEN and its hydrophilic derivatives: a quantum chemical study.

Science.gov (United States)

Huang, Pin-Wen; Wang, Cong-Zhi; Wu, Qun-Yan; Lan, Jian-Hui; Song, Gang; Chai, Zhi-Fang; Shi, Wei-Qun

2018-05-10

Am3+/Cm3+ separation is an extremely hard but important task in nuclear waste treatment. In this study, Am and Cm complexes formed with a back-extraction agent N,N,N',N'-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylene-diamine (H4TPAEN) and its two derivatives with hydrophilic substituents (methoxy and morpholine groups) were investigated using the density functional theory (DFT). The optimized geometrical structures indicated that the Am3+ cation matched better with the cavities of the three studied ligands than Cm3+, and the Am3+ cations were located deeper in the cavities of the ligands. The bond order and quantum theory of atoms in molecules (QTAIM) analyses suggested that ionic interactions dominated An-N and An-O (An = Cm and Am) bonds. However, weak and different extents of partial covalency could also be found in the Am-N and Cm-N bonds. The O donor atoms in the carboxylate groups preferably coordinated with Cm3+ rather than Am3+, whereas the N atoms preferred Am3+. Therefore, the Am3+/Cm3+ selectivity of H4TPAEN and its two hydrophilic derivatives may be ascribed to the competition between the An-N and An-O interactions and the few dissimilarities in their geometrical structures. Based on our calculations, the methoxy and morpholine groups in the two derivatives can serve as electron-donating groups and enhance the strength of the An-NPY bonds (NPY denotes the nitrogen atom of pyridine ring). When compared with the Am-complex, the Cm-complex exhibited significant strength effect, resulting in the relatively lower Am3+/Cm3+ separation ability of the H4TPAEN's hydrophilic derivatives.

Construction of three metal-organic frameworks based on multifunctional T-shaped tripodal ligands, H3PyImDC

KAUST Repository

Jing, Xuemin; Meng, He; Li, Guanghua; Yü , Yang; Huo, Qisheng; Eddaoudi, Mohamed; Liu, Yunling

2010-01-01

Three novel metal-organic frameworks (MOFs), |(C3H 7NO)2(H2O)|[Zn3(C10H 5N3O4)3(C3H 7NO)2] (1), |(H2O)5(H 3O)(NO3)|[Nd2(C10H5N 3O4)3(H2O)4] (2), and |(H2O)2|[Nd3(C10H5N 3O4)3(C10H4N 3O4)] (3), based on the T-shaped tripodal ligands 2-(pyridine-4-yl

Synthesis and characterization of 6,6’-bis(2-hydroxyphenyl)-2,2’-bipyridine ligand and its interaction with ct-DNA

International Nuclear Information System (INIS)

Selamat, Norhidayah; Heng, Lee Yook; Hassan, Nurul Izzaty; Karim, Nurul Huda Abd

2015-01-01

The tetradentate ligand with four donor atoms OONN was synthesized. Bis(phenoxy)bipyridine ligand was prepared by Suzuki coupling reaction between 6,6’-dibromo-2,2’-bipyridyl and 2-hydroxyphenylboronic acid with presence of palladium (II) acetate. Bis(phenoxy)bipyridine ligand was also synthesized by demethylating of 6,6’-bis(2-methoxyphenyl)-2,2’-bipyridyl ligand through solvent free reaction using pyridine hydrocloride. The formation of both phenoxy and methoxy ligands was confirmed by 1 H, 2D cosy and 13 C NMR spectroscopy, ESI-MS spectrometry, FTIR spectroscopy. The purity of the ligand was confirmed by melting point. Binding studies of small molecules with DNA are useful to understand the reaction mechanism and to provide guidance for the application and design of new and more efficient drugs targeted to DNA. In this study, the binding interaction between the synthesized ligand with calf thymus-DNA (ct-DNA) has been investigated by UV/Vis DNA titration study. From the UV/Vis DNA study, it shows that bis(phenoxy)bipyridine ligand bind with ct-DNA via outside binding with binding contant K b = 1.19 × 10 3 ± 0.08 M −1

Retinal astrocytes pretreated with NOD2 and TLR2 ligands activate uveitogenic T cells.

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Guomin Jiang

Full Text Available On entering the tissues, infiltrating autoreactive T cells must be reactivated locally to gain pathogenic activity. We have previously reported that, when activated by Toll-like receptor 3 (TLR3 and TLR4 ligands, retinal astrocytes (RACs are able to function as antigen-presenting cells to re-activate uveitogenic T cells and allow responder T cells to induce uveitis in mice. In the present study, we found that, although the triggering of TLR2 or nucleotide-binding oligomerization domain receptor 2 (NOD2 alone did not activate RACs, their combined triggering induced RACs with the phenotypes required to efficiently re-activate interphotoreceptor retinoid-binding protein (IRBP-specific T cells. The synergistic effect of TLR2 and NOD2 ligands on RAC activation might be explained by the observations that bacterial lipoprotein (BLP, a TLR2 ligand was able to upregulate NOD2 expression and the combination of BLP and muramyldipeptide (MDP, a NOD2 ligand enhanced the expression of RICK (Rip2, the signaling molecule of NOD2. Moreover, the synergistic effect of MDP and BLP on RACs was lost when the RACs were derived from NOD2 knockout mice or were pre-treated with Rip2 antagonist. Thus, our data suggest that exogenous or endogenous molecules acting on both TLR2 and NOD2 on RACs might have an enhancing effect on susceptibility to autoimmune uveitis.

Preparations and crystal structures of 8 coordinate uranyl(VI) complexes having macrocyclic ligands derived from pyrroledicarboxialdehydes and diamines

International Nuclear Information System (INIS)

Komagine, J.; Takeda, M.; Takahashi, M.

2006-01-01

Six 8-coordinate uranyl(VI) complexes with macrocyclic Schiff base ligands derived from 2,6-pyrroledicarboxialdehyde and diamines are prepared and the crystal structures for two of them are determined focusing on the relation between the size of the ligands and U-N bond distances. No difference in average uranyl bond distances and bond angles are observed between [UO 2 (bipytn)](a) and [UO 2 (bipydmtn)](b). U-N bonds of these complexes are, however, not equal; the U-N(pyrrole) bonds [2.45(a), 2.44(b) A] are much shorter than the U-N(imine) bonds [2.67(a), 2.67(b) A]. (author)

Synthesis and biological evaluation of bivalent cannabinoid receptor ligands based on hCB₂R selective benzimidazoles reveal unexpected intrinsic properties.

Science.gov (United States)

Nimczick, Martin; Pemp, Daniela; Darras, Fouad H; Chen, Xinyu; Heilmann, Jörg; Decker, Michael

2014-08-01

The design of bivalent ligands targeting G protein-coupled receptors (GPCRs) often leads to the development of new, highly selective and potent compounds. To date, no bivalent ligands for the human cannabinoid receptor type 2 (hCB₂R) of the endocannabinoid system (ECS) are described. Therefore, two sets of homobivalent ligands containing as parent structure the hCB2R selective agonist 13a and coupled at different attachment positions were synthesized. Changes of the parent structure at these positions have a crucial effect on the potency and efficacy of the ligands. However, we discovered that bivalency has an influence on the effect at both cannabinoid receptors. Moreover, we found out that the spacer length and the attachment position altered the efficacy of the bivalent ligands at the receptors by turning agonists into antagonists and inverse agonists. Copyright © 2014 Elsevier Ltd. All rights reserved.

A series of coordination polymers constructed from R-isophthalic acid (R=–SO{sub 3}H, –NO{sub 2}, and –OH) and N-donor ligands: Syntheses, structures and fluorescence properties

Energy Technology Data Exchange (ETDEWEB)

Zhou, Yong-Hong, E-mail: zhou21921@sina.com [School of Chemistry and Material Science, Huaibei Normal University, Huaibei 235000 (China); Zhou, Xu-Wan; Zhou, Su-Rong [School of Chemistry and Material Science, Huaibei Normal University, Huaibei 235000 (China); Tian, Yu-Peng; Wu, Jie-Ying [Department of Chemistry and Chemical Technology, Anhui University, Hefei 230039 (China)

2017-01-15

Six novel Zn(II), Cd(II), and Cu(II) mixed-ligand coordination complexes, namely, [Zn{sub 2}Na(sip){sub 2}(bpp){sub 3}(Hbpp)(H{sub 2}O){sub 2}]·8H{sub 2}O (1), [Cd{sub 3}(sip){sub 2}(nbi){sub 6}(H{sub 2}O){sub 2}]·7H{sub 2}O (2), [Zn(sip)(nbi){sub 2}(H{sub 2}O)]·Hnbi·3H{sub 2}O (3), [Cd(hip)(nbi){sub 2}(H{sub 2}O)]·nbi·5H{sub 2}O (4), [Cd{sub 2}(nip){sub 2}(nbi){sub 2}(H{sub 2}O){sub 2}]·DMF (5), and [Cu(nip)(nbi)(H{sub 2}O){sub 2}]·H{sub 2}O (6) (H{sub 3}sip=5-sulfoisophthalic acid, H{sub 2}hip=5-hydroxylisophthalic acid, H{sub 2}nip=5-nitroisophthalic acid, bpp=1,3-bis(4-pyridyl)propane, and nbi=6-nitrobenzimidazole) have been synthesized hydrothermally by the self-assembly of R-isophthalic acid (R=–SO{sub 3}H, –NO{sub 2}, and –OH) and N-donor ligands. Single crystal X-ray analyses reveal that two Zn(II) ions and one Na(I) ion of complex 1 are linked through O atoms to generate a 1D linear chain. Then the 2D supramolecular architectures are constructed via intermolecular interactions. In complex 2, the Cd1 ions are connected by bridging carboxyl groups from sip{sup 3−} anions to form 1D double chain, which are further connected by Cd2 ions to afford 2D layer structure. The adjacent 2D layers are further linked via hydrogen-bonding interactions to give 3D supramolecular network. Compounds 3–5 show 1D chain structures, which are assembled into 2D or 3D supramolecular frameworks via weak interactions. In compound 6, the Cu(II) ions are bridged by the nip{sup 2−} ligands to form 48-membered ring, which is assembled into 1Dchain via the π-π stacking interaction. In addition, the thermal stabilities and fluorescence properties of these compounds have also been studied. - Graphical abstract: A series of Cd(II)/Zn(II)/ Cu(II) coordination polymers based on R-isophthalic acid (R=–SO{sub 3}H, –NO{sub 2}, and –OH) and N-donor ligands have been synthesized under hydrothermal conditions and structurally characterized. Photoluminescent properties

Photooxidative cleavage of 4(1H)-quinolinones to 2-acylaminobenzoic acids and derivatives

Energy Technology Data Exchange (ETDEWEB)

Staskun, B. (University of the Witwatersrand, Johannesburg (South Africa). Dept. of Chemistry); Foote, C.S. (California Univ., Los Angeles (USA). Dept. of Chemistry)

1984-12-01

4(1H)-Quinolinones undergo oxidative cleavage to afford the corresponding 2-acylaminobenzoic acids when subjected to dye-sensitized photooxygenation in methanol-aqueous sodium hydroxide solution. The derived 2-aminobenzoic acid was the predominant product in certain instances. The reaction, with singlet oxygen suggested as the active species, provides an alternative methodology for access to nuclear- substituted anthranilic acids and derivatives.

Synthesis, spectral, thermal and biological studies of transition metal complexes of 4-hydroxy-3-[3-(4-hydroxyphenyl-acryloyl]-6-methyl-2H-pyran-2-one

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BALASAHEB R. ARBAD

2011-09-01

Full Text Available The solid complexes of Mn(II, Fe(III, Co(II, Ni(II, and Cu(II with 4-hydroxy-3-[(2E-3-(4-hydroxyphenylprop-2-enoyl]-6-methyl-2H-pyran-2-one, derived from 3-acetyl-6-methyl-2H-pyran-2,4(3H-dione (dehydroacetic acid and 4-hydroxybenzaldehyde, were synthesized and characterized by elemental analysis, conductometry, thermal analysis, magnetic measurements, IR, 1H-NMR and UV–Vis spectroscopy and a biological study. From the analytical and spectral data, the stoichiometry of the complexes was found to be 1:2 (metal:ligand. The physico–chemical data suggest a distorted octahedral geometry for the Cu(II complexes and an octahedral geometry for all the other complexes. The thermal decomposition of all the complexes was studied by the TG–DTA method. The synthesized ligand and its metal complexes were screened for their in vitro antibacterial activity against Gram-negative (Escherichia coli and Gram-positive (Staphylococcus aureus bacterial strains and for in vitro antifungal activity against Aspergillus flavus, Curvularia lunata and Penicillium notatum. The results of these studies showed the metal complexes to be more antibacterial/antifungal against one or more species as compared with the non-complexed ligand.

Gas-phase behaviour of Ru(II) cyclopentadienyl-derived complexes with N-coordinated ligands by electrospray ionization mass spectrometry: fragmentation pathways and energetics.

Science.gov (United States)

Madeira, Paulo J Amorim; Morais, Tânia S; Silva, Tiago J L; Florindo, Pedro; Garcia, M Helena

2012-08-15

The gas-phase behaviour of six Ru(II) cyclopentadienyl-derived complexes with N-coordinated ligands, compounds with antitumor activities against several cancer lines, was studied. This was performed with the intent of establishing fragmentation pathways and to determine the Ru-L(N) and Ru-L(P) ligand bond dissociation energies. Such knowledge can be an important tool for the postulation of the mechanisms of action of these anticancer drugs. Two types of instruments equipped with electrospray ionisation were used (ion trap and a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer). The dissociation energies were determined using energy-variable collision-induced dissociation measurements in the ion trap. The FTICR instrument was used to perform MS(n) experiments on one of the compounds and to obtain accurate mass measurements. Theoretical calculations were performed at the density functional theory (DFT) level using two different functionals (B3LYP and M06L) to estimate the dissociation energies of the complexes under study. The influence of the L(N) on the bond dissociation energy (D) of RuCp compounds with different nitrogen ligands was studied. The lability order of L(N) was: imidazole<1-butylimidazole<5-phenyl-1H-tetrazole<1-benzylimidazole. Both the functionals used gave the following ligand lability order: imidazole<1-benzylimidazole<5-phenyl-1H-tetrazole<1-butylimidazole. It is clear that there is an inversion between 1-benzylimidazole and 1-butylimidazole for the experimental and theoretical lability orders. The M06L functional afforded values of D closer to the experimental values. The type of phosphane (L(P) ) influenced the dissociation energies, with values of D being higher for Ru-L(N) with 1-butylimidazole when the phosphane was 1,2-bis(diphenylphosphino)ethane. The Ru-L(P) bond dissociation energy for triphenylphosphane was independent of the type of complex. The D values of Ru-L(N) and Ru-L(P) were determined for all six compounds and

Synthesis, structural characterization, electrochemical and biological studies on divalent metal chelates of a new ligand derived from pharmaceutical preservative, dehydroacetic acid, with 1,4-diaminobenzene

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Sanaa M. Emam

2017-05-01

Full Text Available Cobalt(II, nickel(II, copper(II, zinc(II and cadmium(II complexes of new 3-acetyl-4-[(4-aminophenylamino]-6-methyl-2H-pyran-2-one (HL1 derived from dehydroacetic acid and 1,4-diaminobenzene were prepared and characterized. The structural features were determined from their elemental analyses, 1H, and 13C-NMR spectra, molar conductivities, magnetic moments, IR, UVvis. spectra, thermal analyses (D.T.A. and T.G.A. and E.S.R. measurements. Their magnetic susceptibility measurements and low conductance data provide evidence for the mono- or dimeric and non-electrolytic nature of the solid complexes. The E.S.R. spectra of copper(II complexes show axial type symmetry with covalent or ionic bond character. The electrochemical behavior of the complexes in DMF (dimethylformamide solvent at 298 K was studied. The biological activity of the ligand and its metal(II complexes was also studied. The obtained complexes showed higher activities than the free ligand in protecting the Egyptian cotton fields from Spodoptera littoralis larvae.

Structure of Chloro bis(1,10-phenanthroline)Cobalt(II) Complex, [Co(phen)2(Cl)(H2O)]Cl · 2H2O

International Nuclear Information System (INIS)

Zhao, Pu Su; Lu, Lu De; Jian, Fang Fang

2003-01-01

The crystal structure of [Co(phen) 2 (Cl)(H 2 O)] Cl · 2H 2 O(phen=1,10-phenanthroline) has been determined by X-ray crystallography. It crystallizes in the triclinic system, space group P 1 , with lattice parameters a=9.662(2), b=11.445(1), c=13.037(2)A, α=64.02(1), β=86.364(9), γ=78.58(2) .deg., and Z=2. The coordinated cations contain a six-coordinated cobalt atom chelated by two phen ligands and one chloride anion and one water ligand in cis arrangement. In addition to the chloride coordinated to the cobalt, there are one chloride ion and four water molecules which complete the crystal structure. In the solid state, the title compound forms three dimensional network structure through hydrogen bonds, within which exists the strongest hydrogen bond (O(3)-O(4)=2.33A). The intermolecular hydrogen bonds connect the [Co(phen) 2 (Cl)(H 2 O)] 1+ , H 2 O moieties and chloride ion

Bioactive 2(1H-Pyrazinones and Diketopiperazine Alkaloids from a Tunicate-Derived Actinomycete Streptomyces sp.

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Lamiaa A. Shaala

2016-08-01

Full Text Available As a part of our ongoing effort to allocate marine microbial bioactive leads, a tunicate-derived actinomycete, Streptomyces sp. Did-27, was investigated. Three new 2(1H-pyrazinones derivatives, (S-6-(sec-butyl-3-isopropylpyrazin-2(1H-one (1, (S-3-(sec-butyl-6-isopropylpyrazin-2(1H-one (2 and (S-6-(sec-butyl-3-isobutylpyrazin-2(1H-one (3, together with the known (1H-pyrazinones analogues deoxymutaaspergillic acid (4, 3,6-diisobutyl-2(1H-pyrazinone (5 and 3,6-di-sec-butyl-2(1H-pyrazinone (6, and the diketopiperazine alkaloids cyclo(6-OH-d-Pro-l-Phe (7, bacillusamide B (8, cyclo(l-Pro-l-Leu and cyclo(l-Pro-l-Ile (10 were isolated from this strain. The structures of the compounds were determined by study of their one- and two-dimensional NMR spectra as well as high-resolution mass spectral determinations. Compound 4 was reported previously as a synthetic product, while compound 6 was reported as 2-hydroxy-3,6-di-sec-butylpyrazine. Herein, we report the complete NMR data for compounds 4 and 6. The compounds were evaluated for their cytotoxic activities against three cell lines. Compound 5 showed potent and selective activity against HCT-116 cell line with IC50 of 1.5 μg/mL, while 1–10 showed variable cytotoxic activities against these cancer cell lines. These results provide further understanding about the chemistry and bioactivities of the alkylated 2(1H-pyrazinone derivatives.

Sequential application of ligand and structure based modeling approaches to index chemicals for their hH4R antagonism.

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Matteo Pappalardo

Full Text Available The human histamine H4 receptor (hH4R, a member of the G-protein coupled receptors (GPCR family, is an increasingly attractive drug target. It plays a key role in many cell pathways and many hH4R ligands are studied for the treatment of several inflammatory, allergic and autoimmune disorders, as well as for analgesic activity. Due to the challenging difficulties in the experimental elucidation of hH4R structure, virtual screening campaigns are normally run on homology based models. However, a wealth of information about the chemical properties of GPCR ligands has also accumulated over the last few years and an appropriate combination of these ligand-based knowledge with structure-based molecular modeling studies emerges as a promising strategy for computer-assisted drug design. Here, two chemoinformatics techniques, the Intelligent Learning Engine (ILE and Iterative Stochastic Elimination (ISE approach, were used to index chemicals for their hH4R bioactivity. An application of the prediction model on external test set composed of more than 160 hH4R antagonists picked from the chEMBL database gave enrichment factor of 16.4. A virtual high throughput screening on ZINC database was carried out, picking ∼ 4000 chemicals highly indexed as H4R antagonists' candidates. Next, a series of 3D models of hH4R were generated by molecular modeling and molecular dynamics simulations performed in fully atomistic lipid membranes. The efficacy of the hH4R 3D models in discrimination between actives and non-actives were checked and the 3D model with the best performance was chosen for further docking studies performed on the focused library. The output of these docking studies was a consensus library of 11 highly active scored drug candidates. Our findings suggest that a sequential combination of ligand-based chemoinformatics approaches with structure-based ones has the potential to improve the success rate in discovering new biologically active GPCR drugs and

Sequential application of ligand and structure based modeling approaches to index chemicals for their hH4R antagonism.

Science.gov (United States)

Pappalardo, Matteo; Shachaf, Nir; Basile, Livia; Milardi, Danilo; Zeidan, Mouhammed; Raiyn, Jamal; Guccione, Salvatore; Rayan, Anwar

2014-01-01

The human histamine H4 receptor (hH4R), a member of the G-protein coupled receptors (GPCR) family, is an increasingly attractive drug target. It plays a key role in many cell pathways and many hH4R ligands are studied for the treatment of several inflammatory, allergic and autoimmune disorders, as well as for analgesic activity. Due to the challenging difficulties in the experimental elucidation of hH4R structure, virtual screening campaigns are normally run on homology based models. However, a wealth of information about the chemical properties of GPCR ligands has also accumulated over the last few years and an appropriate combination of these ligand-based knowledge with structure-based molecular modeling studies emerges as a promising strategy for computer-assisted drug design. Here, two chemoinformatics techniques, the Intelligent Learning Engine (ILE) and Iterative Stochastic Elimination (ISE) approach, were used to index chemicals for their hH4R bioactivity. An application of the prediction model on external test set composed of more than 160 hH4R antagonists picked from the chEMBL database gave enrichment factor of 16.4. A virtual high throughput screening on ZINC database was carried out, picking ∼ 4000 chemicals highly indexed as H4R antagonists' candidates. Next, a series of 3D models of hH4R were generated by molecular modeling and molecular dynamics simulations performed in fully atomistic lipid membranes. The efficacy of the hH4R 3D models in discrimination between actives and non-actives were checked and the 3D model with the best performance was chosen for further docking studies performed on the focused library. The output of these docking studies was a consensus library of 11 highly active scored drug candidates. Our findings suggest that a sequential combination of ligand-based chemoinformatics approaches with structure-based ones has the potential to improve the success rate in discovering new biologically active GPCR drugs and increase the

Crystal structure of cis-1-phenyl-8-(pyridin-2-ylmethyldibenzo[1,2-c:2,1-h]-2,14-dioxa-8-aza-1-borabicyclo[4.4.0]deca-3,8-diene

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Gabriela Ledesma

2017-12-01

Full Text Available The title compound, C26H23BN2O2, was obtained as by product during synthetic attempts of a complexation reaction between the tripodal ligand H2L [N,N-bis(2-hydroxybenzyl(pyridin-2-ylmethylamine] and manganese(III acetate in the presence of NaBPh4. The isolated B-phenyl dioxazaborocine contains an N→B dative bond with a cis conformation. In the crystal, C—H...O hydrogen bonds define chains parallel to the b-axis direction. A comparative analysis with other structurally related derivatives is also included, together with a rationalization of the unexpected production of this zwitterionic heterocycle.

Synthesis, characterisation and antimicrobial activities of cobalt(II, copper(II and zinc(II mixed-ligand complexes containing 1,10-phenanthroline and 2,2’-bipyridine

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A. Mohamadou

2010-06-01

Full Text Available Three new 1,10-phenanthroline and 2,2’-bipyridine mixed-ligand complexes of [Co(bpy(phen2](NO32.2H2O, [Cu(bpy(phen H2O 2]Cl2.2H2O, and [Zn(bpy2(phen]Cl2.6H2O were synthesized. The complexes were characterized by elemental, IR and visible spectroscopic analyses and the results indicate that both ligands are coordinated to the respective metal ions giving octahedral complexes. Antimicrobial studies showed that there is increased antimicrobial activity of the metal ions on coordination to the ligands. The water soluble complexes showed antimicrobial activities that are higher than those of the metal salts and 2,2’-bipyridine but lower than those of 1,10-phenanthroline. The copper complex [Cu(bpy(phen(H2O 2]Cl2.2H2O shows the highest activity.

Development of [3H]2-Carboxy-4,6-dichloro-1H-indole-3-propionic Acid ([3H]PSB-12150): A Useful Tool for Studying GPR17

Science.gov (United States)

2014-01-01

The recently described synthetic GPR17 agonist 2-carboxy-4,6-dichloro-1H-indole-3-propionic acid (1) was prepared in tritium-labeled form by catalytic hydrogenation of the corresponding propenoic acid derivative 8 with tritium gas. The radioligand [3H]PSB-12150 (9) was obtained with a specific activity of 17 Ci/mmol (629 GBq/mmol). It showed specific and saturable binding to a single binding site in membrane preparations from Chinese hamster ovary cells recombinantly expressing the human GPR17. A competition assay procedure was established, which allows the determination of ligand binding affinities. PMID:24900835

Development of [(3)H]2-Carboxy-4,6-dichloro-1H-indole-3-propionic Acid ([(3)H]PSB-12150): A Useful Tool for Studying GPR17.

Science.gov (United States)

Köse, Meryem; Ritter, Kirsten; Thiemke, Katharina; Gillard, Michel; Kostenis, Evi; Müller, Christa E

2014-04-10

The recently described synthetic GPR17 agonist 2-carboxy-4,6-dichloro-1H-indole-3-propionic acid (1) was prepared in tritium-labeled form by catalytic hydrogenation of the corresponding propenoic acid derivative 8 with tritium gas. The radioligand [(3)H]PSB-12150 (9) was obtained with a specific activity of 17 Ci/mmol (629 GBq/mmol). It showed specific and saturable binding to a single binding site in membrane preparations from Chinese hamster ovary cells recombinantly expressing the human GPR17. A competition assay procedure was established, which allows the determination of ligand binding affinities.

Modeling the Syn-Disposition of Nitrogen Donors in Non-Heme Diiron Enzymes. Synthesis, Characterization, and Hydrogen Peroxide Reactivity of Diiron(III) Complexes with the Syn N-Donor Ligand H2BPG2DEV

Science.gov (United States)

Friedle, Simone; Kodanko, Jeremy J.; Morys, Anna J.; Hayashi, Takahiro; Moënne-Loccoz, Pierre; Lippard, Stephen J.

2009-01-01

In order to model the syn disposition of histidine residues in carboxylate-bridged non-heme diiron enzymes, we prepared a new dinucleating ligand, H2BPG2DEV, that provides this geometric feature. The ligand incorporates biologically relevant carboxylate functionalities, which have not been explored as extensively as nitrogen-only analogs. Three novel oxo-bridged diiron(III) complexes [Fe2(μ-O)(H2O)2-(BPG2DEV)](ClO4)2 (6), [Fe2(μ-O)(μ-O CAriPrO)(BPG2DEV)](ClO4) (7), and [Fe2(μ-O)(μ-CO3)(BPG2DEV)] (8) were prepared. Single crystal X-ray structural characterization confirms that two pyridines are bound syn with respect to the Fe–Fe vector in these compounds. The carbonato-bridged complex 8 forms quantitatively from 6 in a rapid reaction with gaseous CO2 in organic solvents. A common maroon-colored intermediate (λmax = 490 nm; ε = 1500 M−1 cm−1) forms in reactions of 6, 7, or 8 with H2O2 and NEt3 in CH3CN/H2O solutions. Mass spectrometric analyses of this species, formed using 18O-labeled H2O2, indicate the presence of a peroxide ligand bound to the oxo-bridged diiron(III) center. The Mössbauer spectrum at 90 K of the EPR-silent intermediate exhibits a quadrupole doublet with δ. = 0.58 mm/s and ΔEQ = 0.58 mm/s. The isomer shift is typical for a peroxodiiron(III) species, but the quadrupole splitting parameter is unusually small compared to related complexes. These Mössbauer parameters are comparable to those observed for a peroxo intermediate formed in the reaction of reduced toluene/o-xylene monooxygenase hydroxylase (ToMOH) with dioxygen. Resonance Raman studies reveal an unusually low-energy O–O stretching mode in the peroxo intermediate that is consistent with a short diiron distance. Although peroxodiiron(III) intermediates generated from 6, 7, and 8 are poor O-atom transfer catalysts, they display highly efficient catalase activity, with turnover numbers up to 10,000. In contrast to hydrogen peroxide reactions of diiron(III) complexes that lack

Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1,10-phenanthroline)2 building blocks

International Nuclear Information System (INIS)

Yu Yunfang; Wei Yongqin; Broer, Ria; Sa Rongjian; Wu Kechen

2008-01-01

Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen) 2 (H 2 O)(HTST)].2H 2 O (1), [Co 3 (phen) 6 (H 2 O) 2 (TST) 2 ].7H 2 O (2), and [Co 2 Cu(phen) 6 (H 2 O) 2 (TST) 2 ].10H 2 O (3), have been synthesized by the reactions of a new tri-sulfonate ligand (2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, H 3 TST) with the M 2+ (M=Co, Cu) and the second ligand 1,10-phenanthroline (phen). Complex 1 contains a cis-Co(II)(phen) 2 building block and an HTST as monodentate ligand; complex 2 consists of two TST as bidentate ligands connecting one trans- and two cis-Co(II)(phen) 2 building blocks; complex 3 is formed by replacing the trans-Co(II)(phen) 2 in 2 with a trans-Cu(II)(phen) 2 , which is the first reported hetero-trinuclear supramolecular complex containing both the Co(II)(phen) 2 and Cu(II)(phen) 2 as building blocks. The study shows the flexible multifunctional self-assembly capability of the H 3 TST ligands presenting in these supramolecular complexes through coordinative, H-bonding and even π-π stacking interactions. The photoluminescent optical properties of these complexes are also investigated and discussed as well as the second-order nonlinear optical properties of 1. - Graphical abstract: Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen) 2 (H 2 O)(HTST)].2H 2 O (1), [Co 3 (phen) 6 (H 2 O) 2 (TST) 2 ].7H 2 O (2), and [Co 2 Cu(phen) 6 (H 2 O) 2 (TST) 2 ].10H 2 O (3), have been synthesized by the reactions of a new tri-sulfonate ligand (2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, H 3 TST) with the M 2+ (M=Co, Cu) and the second ligand 1,10-phenanthroline (phen). The study shows the flexible multifunctional self-assembly capability of H 3 TST ligand presenting in these supramolecular complexes

Isotopic studies on ligand exchange between complex and simple cyanides in water medium and in liquid hydrogen cyanide. Part 2. Radiocyanide ligand exchange study between hydrogen cyanide and octacyanotungstate(4) in water solutions of mineral acids

International Nuclear Information System (INIS)

Zielinski, M.

1979-01-01

Radiocyanide ligand exchange between potassium octacyanotungstate(4) and hydrogen cyanide in aqueous solutions of sulfuric acid and between octacyanotungstic(4) acid and hydrogen cyanide in aqueous solutions have been investigated experimentally. The observed enhancement of the rate of ligand exchange in acidic medium has been rationalized in terms of the proposed new general reaction scheme taking into account the reversible decomposition of complex cyanide at low pH, and irreversible one at high pH. The discussion on the results obtained has been carried out within the framework of derived formal kinetic equations. (author)

New Hybrid Properties of TiO2 Nanoparticles Surface Modified With Catecholate Type Ligands

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Džunuzović Enis

2009-01-01

Full Text Available Abstract Surface modification of nanocrystalline TiO2 particles (45 Å with bidentate benzene derivatives (catechol, pyrogallol, and gallic acid was found to alter optical properties of nanoparticles. The formation of the inner-sphere charge–transfer complexes results in a red shift of the semiconductor absorption compared to unmodified nanocrystallites. The binding structures were investigated by using FTIR spectroscopy. The investigated ligands have the optimal geometry for chelating surface Ti atoms, resulting in ring coordination complexes (catecholate type of binuclear bidentate binding–bridging thus restoring in six-coordinated octahedral geometry of surface Ti atoms. From the Benesi–Hildebrand plot, the stability constants at pH 2 of the order 103 M−1 have been determined.

Synthesis and characterization of a pentadentate Schiff base N3O2 ligand and its neutral technetium(V) complex. X-ray structure of (N,N'-3-azapentane-1,5-diylbis(3-(1-iminoethyl)-6-methyl-2H-pyran-2,4(3H)-dionato)(3-)-O,O',N,N',N double-prime)oxotechnetium(V)

International Nuclear Information System (INIS)

Shuang Liu; Rettig, S.J.; Orvig, C.

1991-01-01

Preparations of a potentially pentadentate ligand, N,N'-3-azapentane-1,5-diylbis(3-(1-iminoethyl)-6-methyl-2H-pyran-2,4-(3H)-dione) (H 3 apa), and its neutral technetium(V) complex, [TcO(apa)], are described. The 13 C and 1 H NMR, infrared, optical, and mass spectra of the pentadentate ligand and its technetium(V) complex are reported. The X-ray structure of [TcO(apa)] has been determined. Crystals are orthorhombic, space group Pbca, with a = 12.833 (2) angstrom, b = 33.320 (5) angstrom, c = 9.942(4) angstrom, V = 4251 (2) angstrom, and Z = 8. The structure was solved by Patterson and Fourier methods and was refined by full-matrix least-squares procedures to R = 0.028 and R W = 0.032 for 4054 reflections with I ≥ 3σ(I). The technetium(V) complex has a highly distorted octahedral coordination geometry comprising a [TcO] 3+ core and the triply deprotonated pentadentate ligand wrapping around the metal center. One of the two oxygen donor atoms of the pentadentate ligand is located trans to the Tc double-bond O bond while the remaining four donor atoms, N 3 O, occupy the equatorial sites. The distance between the deprotonated N(1) atom to the Tc center is significantly shorter than a normal Tc-N single bond length of 2.10 angstroms, but longer than that for a Tc-N triple bond. 1 H NMR spectral data reveal a rigid solution structure for the complex, which undergoes no conformational and configurational exchange at temperatures up to 50C

Synthesis and characterization of 6,6’-bis(2-hydroxyphenyl)-2,2’-bipyridine ligand and its interaction with ct-DNA

Energy Technology Data Exchange (ETDEWEB)

Selamat, Norhidayah; Heng, Lee Yook; Hassan, Nurul Izzaty; Karim, Nurul Huda Abd [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43650 Bangi, Selangor (Malaysia)

2015-09-25

The tetradentate ligand with four donor atoms OONN was synthesized. Bis(phenoxy)bipyridine ligand was prepared by Suzuki coupling reaction between 6,6’-dibromo-2,2’-bipyridyl and 2-hydroxyphenylboronic acid with presence of palladium (II) acetate. Bis(phenoxy)bipyridine ligand was also synthesized by demethylating of 6,6’-bis(2-methoxyphenyl)-2,2’-bipyridyl ligand through solvent free reaction using pyridine hydrocloride. The formation of both phenoxy and methoxy ligands was confirmed by {sup 1}H, 2D cosy and {sup 13}C NMR spectroscopy, ESI-MS spectrometry, FTIR spectroscopy. The purity of the ligand was confirmed by melting point. Binding studies of small molecules with DNA are useful to understand the reaction mechanism and to provide guidance for the application and design of new and more efficient drugs targeted to DNA. In this study, the binding interaction between the synthesized ligand with calf thymus-DNA (ct-DNA) has been investigated by UV/Vis DNA titration study. From the UV/Vis DNA study, it shows that bis(phenoxy)bipyridine ligand bind with ct-DNA via outside binding with binding contant K{sub b} = 1.19 × 10{sup 3} ± 0.08 M{sup −1}.

Comparative assessment of a 99mTc labeled H1299.2-HYNIC peptide bearing two different co-ligands for tumor-targeted imaging.

Science.gov (United States)

Torabizadeh, Seyedeh Atekeh; Abedi, Seyed Mohammad; Noaparast, Zohreh; Hosseinimehr, Seyed Jalal

2017-05-01

Peptides are a class of targeting agents that bind to cancer-specific cell surfaces. Since they specifically target cancer cells, they could be used as molecular imaging tools. In this study, the 15-mer peptide Ac-H1299.2 (YAAWPASGAWTGTAP) was conjugated with HYNIC via lysine amino acid on C-terminus and labeled with 99m Tc using tricine and EDDA/tricine as the co-ligands. These radiotracers were evaluated for potential utilization in diagnostic imaging of ovarian cancer cells (SKOV-3). The cell-specificity of these radiolabeled peptides was determined based on their binding on an ovarian cancer cell line (SKOV-3), and displaying a low affinity for lung adenocarcinoma cell line (A549) and breast cancer cell line (MCF7). Biodistribution studies were conducted in normal mice as well as in nude mice bearing SKOV-3 ovarian cancer xenografts. HYNIC-peptide was labeled with 99m Tc with more than 99% efficiency and showed high stability in buffer and serum. We observed nanomolar binding affinities for both radiolabeled peptides. The tumor uptakes were 3.27%±0.46% and 1.55%±0.20% for tricine and 2.34±1.1% and 1.09%±0.18% for EDDA/tricine at 1 and 4h after injection, respectively. A higher tumor to background ratio and lower radioactivity in the blood were observed for EDDA/tricine co-ligands, leading to clear tumor visualization in imaging with injection of this peptide. This new 99m Tc-labeled peptide selectively targeted ovarian cancer and introduction of a (EDDA/tricine) as a co-ligand improved the pharmacokinetics of 99m Tc-labeled H1299.2 for tumor imaging in animals. Copyright © 2017 Elsevier Ltd. All rights reserved.

New transition metal complexes of 2,4-dihydroxybenzaldehyde benzoylhydrazone Schiff base (H2dhbh): Synthesis, spectroscopic characterization, DNA binding/cleavage and antioxidant activity

Science.gov (United States)

Aboafia, Seyada A.; Elsayed, Shadia A.; El-Sayed, Ahmed K. A.; El-Hendawy, Ahmed M.

2018-04-01

New complexes [VO2(Hdhbh)] (1), [VO(phen)(dhbh)].1.5H2O (2), [Zn(Hdhbh)2] (3), [MoO2(dhbh)(D)] (D = H2O (4) or MeOH (5)), [Ru(PPh3)(dhbh)Cl(H2O)] (6), and [Pd(Hdhbh)Cl]·H2O (7) (H2dhbh = Schiff base derived from 2,4-dihydroxybenzaldehyde and benzoylhydrazone) have been isolated and characterized by IR, 1H NMR, Mass, UV-Visible and ESR spectroscopy. They were also investigated by cyclic voltammetry, thermal and magnetic measurements and the structure of complex cis-[MoO2(dhbh)(H2O)] (4) was solved by X-ray crystallography. Analytical data showed that H2dhbh behaves as monobasic/or dibasic tridentate ligand via phenolate O, azomethine N and amide O/or deprotonated amide O atoms. Antioxidant activity of the complexes has been evaluated against DPPH (2,2-diphenyl-1-picrylhydrazyl) radical and it has been found that oxovandium (IV) complex (2) displays the highest radical scavenging potency comparable to ascorbic acid as a standard antioxidant. The DNA binding properties of the ligand and its complexes have been investigated by electronic spectroscopy together with DNA cleavage by gel electrophoresis whose results showed also that vanadium (IV) complex (2) has a significant oxidative cleavage among other complexes.

Crystal structures of bis[2-(pyridin-2-ylphenyl-κ2N,C1]rhodium(III complexes containing an acetonitrile or monodentate thyminate(1− ligand

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Mika Sakate

2016-04-01

Full Text Available The crystal structures of bis[2-(pyridin-2-ylphenyl]rhodium(III complexes with the metal in an octahedral coordination containing chloride and acetonitrile ligands, namely (OC-6-42-acetonitrilechloridobis[2-(pyridin-2-ylphenyl-κ2N,C1]rhodium(III, [RhCl(C11H8N2(CH3CN] (1, thyminate(1− and methanol, namely (OC-6-42-methanol(5-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-ido-κN1bis[2-(pyridin-2-ylphenyl-κ2N,C1]rhodium(III, [Rh(C11H8N2(C5H5N2O2(CH3OH]·CH3OH·0.5H2O (2, and thyminate(1− and ethanol, namely (OC-6-42-ethanol(5-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-ido-κN1bis[2-(pyridin-2-ylphenyl-κ2N,C1]rhodium(III, [Rh(C11H8N2(C5H5N2O2(C2H5OH]·C2H5OH (3, are reported. The acetonitrile complex, 1, is isostructural with the IrIII analog. In complexes 2 and 3, the monodeprotonated thyminate (Hthym− ligand coordinates to the RhIII atom through the N atom, and the resulting Rh—N(Hthym bond lengths are relatively long [2.261 (2 and 2.252 (2 Å for 2 and 3, respectively] as compared to the Rh—N bonds in the related thyminate complexes. In each of the crystals of 2 and 3, the complexes are linked via a pair of intermolecular N—H...O hydrogen bonds between neighbouring Hthym− ligands, forming an inversion dimer. A strong intramolecular O—H...O hydrogen bond between the thyminate(1− and alcohol ligands in mutually cis positions to each other is also observed.

B7H6-derived peptides trigger TNF-α-dependent immunostimulatory activity of lymphocytic NK92-MI cells.

Science.gov (United States)

Phillips, Mariana; Romeo, Francesca; Bitsaktsis, Constantine; Sabatino, David

2016-09-01

The rise of biologics that can stimulate immune responses towards the eradication of tumors has led to the evolution of cancer-based immunotherapy. Representatively, B7H6 has been recently identified as a protein ligand on tumor cells that binds specifically to the NKp30 receptor and triggers NK cell-derived cytokine production, which ultimately leads to tumor cell lysis and death. In an effort to develop effective immunotherapy approaches, the rational design of a novel class of immunostimulatory peptides (IPs) derived from the binding interface of B7H6:NKp30 is described in this study. The IPs comprised the B7H6 active site sequence for NKp30 binding and immunostimulatory activity. An aminohexanoic acid linker was also introduced at the N-terminus of the peptides for FITC-labeling by Fmoc-solid phase peptide synthesis. The peptides were characterized by LCMS to confirm identities and purities >95%. The secondary structures of the peptides were examined by CD spectroscopy in H2 O, PBS and a H2 O:TFE mixture which demonstrated versatile peptide structures which transitioned from random coil (H2 O) to α-helical (PBS) and turn-type (H2 O:TFE) conformations. Their biological properties were then evaluated by flow cytometry, enzyme-linked immunosorbent assays (ELISAs), and cell death assays. The occupancy of the synthetic peptides to a human NK cell line demonstrated comparable binding relative to the natural NKp30 ligand, B7H6, and the human anti-NKp30 monoclonal antibody (mAb), in a concentration dependent manner. A competitive binding assay between the human anti-NKp30 mAb or B7H6, and the synthetic peptides, demonstrated partial displacement of the ligands upon anti-NKp30 mAb treatment, suggesting NKp30 receptor specificities by the synthetic peptides. Moreover, the immunostimulatory activity of B7H6 was demonstrated by the secretion of the pro-inflammatory cytokines tumor necrosis factor-alfa (TNF-α) and interferon gamma (IFN-γ) by the human NK cell line. The

Synthesis, biological evaluation and docking studies of 2,3-dihydroquinazolin-4(1H)-one derivatives as inhibitors of cholinesterases.

Science.gov (United States)

Sarfraz, Muhammad; Sultana, Nargis; Rashid, Umer; Akram, Muhammad Safwan; Sadiq, Abdul; Tariq, Muhammad Ilyas

2017-02-01

In search of potent inhibitors of cholinesterases, we have synthesized and evaluate a number of 2,3-dihydroquinazolin-4(1H)-one derivatives. The synthetic approach provided an efficient synthesis of the target molecules with excellent yield. All the tested compounds showed activity against both the enzymes in micromolar range. In many case, the inhibition of both enzymes are higher than or comparable to the standard drug galatamine. With the selectivity index of 2.3 for AChE, compound 5f can be considered as a potential lead compound with a feature of dual AChE/BChE inhibition with IC 50 =1.6±0.10μM (AChE) and 3.7±0.18μM (BChE). Binding modes of the synthesized compounds were explored by using GOLD (Genetic Optimization for Ligand Docking) suit v5.4.1. The computed binding modes of these compounds in the active site of AChE and BChE provide an insight into the mechanism of inhibition of these two enzyme. Copyright © 2017 Elsevier Inc. All rights reserved.

Structural modulation and luminescent properties of four Cd{sup II} coordination architectures based on 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole and flexible/rigid dicarboxylate ligands

Energy Technology Data Exchange (ETDEWEB)

Xia, Liang; Dong, Wen-Wen, E-mail: dongww1@126.com; Ye, Xiao; Zhao, Jun; Li, Dong-Sheng, E-mail: lidongsheng1@126.com

2016-10-15

To systematically investigate the influence of the flexible or rigid auxiliary ligands on the structures and properties of transition metal compounds, we synthesized four new d{sup 10} coordination polymers (CPs) from 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole (4-Hpzpt) and flexible/rigid dicarboxylate ligands, [Cd(4-pzpt){sub 2}]{sub n} (1), [Cd{sub 3}(4-pzpt){sub 2}(suc){sub 2}]{sub n} (2), [Cd{sub 2}(4-Hpzpt)(nbc){sub 2}(H{sub 2}O)]{sub n} (3) and ([Cd{sub 2}(4-pzpt){sub 2}(tfbdc)(H{sub 2}O){sub 4}]·H{sub 2}O){sub n} (4) (H{sub 2}suc=1,2-ethanedicarboxylic acid, H{sub 2}nbc=hthalene-1,4-dicarboxylic acid, H{sub 2}tfbdc =2,3,5,6-tetrafluoroterephthalic acid). Single crystal X-ray analysis indicates that compound 1 shows a 4{sup 4}-sql layer, which is extended to a 3D network via nonclassical C–H{sup …}N hydrogen bonds. Compound 2 possesses a 6-connected pcu-4{sup 12}0.6{sup 3} net composed of trinuclear Cd{sup II}-clusters. Compound 3 represents a rare 3D (3,4,4,5)-connected topology with a Schläfli symbol of (4·6·7)(4·5{sup 3}·7{sup 2})(5{sup 3}·6·7·9)(4{sup 2}·5{sup 5}·6·7{sup 2}). Compound 4 exhibits a 2D+2D→2D parallel interpenetrated 6{sup 3}-hcb network. The adjacent 2D networks are interdigitated with each other to form the resulting 3D supramolecular architecture through classical O–H{sup …}N and O–H{sup …}O hydrogen bonds. Structural diversities indicate that the nature of flexible/rigid-dicarboxlates plays crucial roles in modulating structures of these compounds. Moreover, the luminescent properties of them have been briefly investigated. - Graphical abstract: Four new Cd{sup II} coordination architectures constructed from the primary ligand 4-Hpzpt and flexible/rigid dicarboxylate coligands. Structural diversities indicate that the nature of flexible/rigid-dicarboxlates plays crucial roles in modulating structures of these compounds. And more, the thermal stability and luminescence are discussed. - Highlights: �

Synthesis, fluorescence properties of Tb(Ⅲ) complexes with novel mono-substituted β-diketone ligands

Institute of Scientific and Technical Information of China (English)

罗一鸣; 李石凤; 李军; 陈学娟; 唐瑞仁

2010-01-01

Two novel pyridine-2,6-dicarboxylic acid derivatives of mono-β-diketone named methyl 6-biphenylacetyl-2-pyridinecarboxylate (MBP) and 6-biphenylacetyl-2-pyridinecarboxylic acid (BAA) and their corresponding binary complexes Tb(MBP)3.6H2O and Tb(BAA)3·6H2O were synthesized. The ligands were characterized by elemental analysis, FT-IR and 1H-NMR, and the complexes were characterized with elemental analysis, FT-IR, 1H-NMR and thermogravimetric and differential thermal analysis(TG-DTA). The investigation of fluo...

Quinoline-2-thiol Derivatives as Fluorescent Sensors for Metals, pH and HNO

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Naphtali A. O’Connor

2014-06-01

Full Text Available A tautomeric equilibrium exists for quinoline-2-thiol and quinoline-2(1H-thione. Quantum mechanical calculations predict the thione is the major tautomer and this is confirmed by the absorption spectra. The utility of quinolone-2-thiol/quinoline-2(1H-thione as a chromophore for developing fluorescent sensors is explored. No fluorescence is observed when excited at absorption maxima, however a fluorescence increase is observed when exposed to HNO, a molecule of import as a cardiovascular therapeutic. Alkylated quinoline-2-thiol derivatives are found to be fluorescent and show a reduction in fluorescence when exposed to metals and changes in pH.

Nido-Carborane building-block reagents. 2. Bulky-substituent (alkyl)2C2B4H6 derivatives and (C6H5)2C2B4H6: synthesis and properties

International Nuclear Information System (INIS)

Boyter, H.A. Jr.; Grimes, R.N.

1988-01-01

The preparation and chemistry of nido-2,3-R 2 C 2 C 2 B 4 H 6 carboranes in which R is n-butyl, isopentyl, n-hexyl, and phenyl was investigated in order to further assess the steric and electronic influence of the R groups on the properties of the nido-C 2 B 4 cage, especially with respect to metal complexation at the C 2 B 3 face and metal-promoted oxidative fusion. The three dialkyl derivatives were prepared from the corresponding dialkylacetylenes via reaction with B 5 H 9 and triethylamine, but the diphenyl compound could not be prepared in this manner and was obtained instead in a thermal reaction of B 5 H 9 with diphenylacetylene in the absence of amine. All four carboranes are readily bridge-deprotonated by NaH in THF, and the anions of the dialkyl species, on treatment with FeCl 2 and air oxidation, generate the respective R 4 C 4 B 8 H 8 carborane fusion products were R = n-C 4 H 9 , i-C 5 H 11 or n-C 6 H 13 . The diphenylcarborane anion Ph 2 C 2 B 4 H 5 - did not form detectable metal complexes with Fe 2+ , Co 2+ , or Ni 2+ , and no evidence of a Ph 4 C 4 B 8 H 8 fusion product has been found. Treatment of Ph 2 C 2 B 4 H 6 with Cr(CO) 6 did not lead to metal coordination of the phenyl rings, unlike (PhCH 2 ) 2 C 2 B 4 H 6 , which had previously been shown to form mono- and bis(tricarbonylchromium) complexes. However, the reaction of Ph 2 C 2 B 4 H 5 - , CoCl 2 , and (PhPCH 2 ) 2 did give 1,1-(Ph 2 PCH 2 ) 2 -1-Cl-1,2,3-Co(Ph 2 C 2 B 4 H 4 ), the only case in which metal complexation of the diphenylcarborane was observed. 14 references, 3 figures, 3 tables

A series of Cd(II) complexes with π-π stacking and hydrogen bonding interactions: Structural diversities by varying the ligands

International Nuclear Information System (INIS)

Wang Xiuli; Zhang Jinxia; Liu Guocheng; Lin Hongyan

2011-01-01

Seven new Cd(II) complexes consisting of different phenanthroline derivatives and organic acid ligands, formulated as [Cd(PIP) 2 (dnba) 2 ] (1), [Cd(PIP)(ox)].H 2 O (2), [Cd(PIP)(1,4-bdc)(H 2 O)].4H 2 O (3), [Cd(3-PIP) 2 (H 2 O) 2 ].4H 2 O (4), [Cd 2 (3-PIP) 4 (4,4'-bpdc)(H 2 O) 2 ].5H 2 O (5), [Cd(3-PIP)(nip)(H 2 O)].H 2 O (6), [Cd 2 (TIP) 4 (4,4'-bpdc)(H 2 O) 2 ].3H 2 O (7) (PIP=2-phenylimidazo[4,5-f]1,10-phenanthroline, 3-PIP=2-(3-pyridyl)imidazo[4,5-f]1,10-phenanthroline, TIP=2-(2-thienyl)imidazo[4,5-f]1,10-phenanthroline, Hdnba=3,5-dinitrobenzoic acid, H 2 ox=oxalic acid, 1,4-H 2 bdc=benzene-1,4-dicarboxylic acid, 4,4'-H 2 bpdc=biphenyl-4,4'-dicarboxylic acid, H 2 nip=5-nitroisophthalic acid) have been synthesized under hydrothermal conditions. Complexes 1 and 4 possess mononuclear structures; complexes 5 and 7 are isostructural and have dinuclear structures; complexes 2 and 3 feature 1D chain structures; complex 6 contains 1D double chain, which are further extended to a 3D supramolecular structure by π-π stacking and hydrogen bonding interactions. The N-donor ligands with extended π-system and organic acid ligands play a crucial role in the formation of the final supramolecular frameworks. Moreover, thermal properties and fluorescence of 1-7 are also investigated. -- Graphical abstract: Seven new supramolecular architectures have been successfully isolated under hydrothermal conditions by reactions of different phen derivatives and Cd(II) salts together with organic carboxylate anions auxiliary ligands. Display Omitted Research highlights: → Complexes 1-7 are 0D or 1D polymeric structure, the π-π stacking and H-bonding interactions extend the complexes into 3D supramolecular network. To our knowledge, systematic study on π-π stacking and H-bonding interactions in cadmium(II) complexes are still limited. → The structural differences among the title complexes indicate the importance of N-donor chelating ligands for the creation of molecular

Coordination of N,O-donor appended Schiff base ligand (H2L1) towards Zinc(II) in presence of pseudohalides: Syntheses, crystal structures, photoluminescence, antimicrobial activities and Hirshfeld surfaces

Science.gov (United States)

Majumdar, Dhrubajyoti; Biswas, Jayanta Kumar; Mondal, Monojit; Surendra Babu, M. S.; Metre, Ramesh K.; Das, Sourav; Bankura, Kalipada; Mishra, Dipankar

2018-03-01

A series of dinuclear Zn(II) complexes [Zn2 (L1) (CH3OH)2(SCN) (OAc)](1), [Zn2 (L1) (CH3OH)2(N3)2](2) and [Zn2 (L1) (Cl)2(CH3OH)]·CH3OH (3) have been synthesized by the reaction of compartmental Schiff base ligand (H2L1) [N,N‧-Bis(3-ethoxysalicylidenimino)-1,3-diaminopropane] with Zn(OAc)2·2H2O in presence of coligand like KSCN, NaN3 and NaCl respectively. X-ray diffraction analysis revealed that all the complexes are neutral and possess a 4-membered Zn2 (μ2-O)2 ring fastened by the unified coordination action of a doubly deprotonated ligand. In addition, solid state structure of the complexes display extensive intermolecular interaction which has been supported theoretically by Hirshfeld surface analysis with 2D Fingerprint plots. The synthesized Zn(II) metal complexes observed enhancement of luminescence emission compared to the parent Schiff base due to emanating ligand based intraligand (π→π∗) fluorescence. Additionally, Zn(II) metal complexes exhibited considerable antimicrobial potency against some important Gram +ve and Gram -ve bacteria.

Binuclear trivalent and tetravalent uranium halides and cyanides supported by cyclooctatetraene ligands

International Nuclear Information System (INIS)

Wang, Cong-Zhi; Wu, Qun-Yan; Lan, Jian-Hui; Shi, Wei-Qun; Gibson, John K.

2017-01-01

Although the first organoactinide chloride Cp_3UCl (Cp = η"5-C_5H_5) was synthesized more than 50 years ago, binuclear uranium halides remain very rare in organoactinide chemistry. Herein, a series of binuclear trivalent and tetravalent uranium halides and cyanides with cyclooctatetraene ligands, (COT)_2U_2X_n (COT = η"8-C_8H_8; X=F, Cl, CN; n=2, 4), have been systematically studied using scalar-relativistic density functional theory (DFT). The structures with bridging halide or cyanide ligands were predicted to be the most stable complexes of (COT)_2U_2X_n, and all the complexes show weak antiferromagnetic interactions between the uranium centers. However, for each species, there is no significant uranium-uranium bonding interaction. The bonding between the metal and the ligands shows some degree of covalent character, especially between the metal and terminal halide or cyanide ligands. The U-5f and 6d orbitals are predominantly involved in the metal-ligand bonding. All the (COT)_2U_2X_n species were predicted to be more stable compared to the mononuclear half-sandwich complexes at room temperature in the gas phase such that (COT)_2U_2X_4 might be accessible through the known (COT)_2U complex. The tetravalent derivatives (COT)_2U_2X_4 are more energetically favorable than the trivalent (COT)_2U_2X_2 analogs, which may be attributed to the greater number of strong metal-ligand bonds in the former complexes.

Synthetic, spectroscopic and structural studies on 4-aminobenzoate complexes of divalent alkaline earth metals: x-ray crystal structures of [[Mg(H2O)6] (4-aba)2].2H2O and [Ca(H2O)2(4-aba)2] (4-aba=4-aminobenzoate)

International Nuclear Information System (INIS)

Murugavel, Ramaswamy; Karambelkar, Vivek V.; Anantharaman, Ganapathi

2000-01-01

Reactions between MCl 2 .nH 2 O (M = Mg, Ca, Sr, and Ba) and 4-aminobenzoic acid (4-abaH) result in the formation of complexes [(Mg(H 2 O) 6 )(4-aba) 2 ) .2H 2 O (I), [Ca(4-aba) 2 (H2 O ) 2 ] (2), [Sr(4-aba) 2 (H2 O ) 2 ] (3), and [Ba(4-aba) 2 Cl] (4), respectively. The new compounds 1 and 2, as well as the previously reported 3 and 4 form an extended intra- and intermolecular hydrogen bonded network in the solid-state. The compounds have been characterized by elemental analysis, pH measurements, thermogravimetric studies, and IR, NMR, and UV-Vis spectroscopy. The solid state structures of the molecules 1 and 2 have been determined by single crystal x-ray diffraction studies. In the case of magnesium complex 1, the dipositively charged Mg cation is surrounded by six water molecules and the two 4-aminobenzoate ligands show no direct bonding to the metal ion. The calcium ion in 2 is octa-coordinated with direct coordination of the 4-aminobenzoate ligands to the metal ion. The Ca-Ca separation in the polymeric chain of 2 is 3.9047(5) A. (author)

Group 13 β-ketoiminate compounds: gallium hydride derivatives as molecular precursors to thin films of Ga2O3.

Science.gov (United States)

Pugh, David; Marchand, Peter; Parkin, Ivan P; Carmalt, Claire J

2012-06-04

Bis(β-ketoimine) ligands, [R{N(H)C(Me)-CHC(Me)═O}(2)] (L(1)H(2), R = (CH(2))(2); L(2)H(2), R = (CH(2))(3)), linked by ethylene (L(1)) and propylene (L(2)) bridges have been used to form aluminum, gallium, and indium chloride complexes [Al(L(1))Cl] (3), [Ga(L(n))Cl] (4, n = 1; 6, n = 2) and [In(L(n))Cl] (5, n = 1; 7, n = 2). Ligand L(1) has also been used to form a gallium hydride derivative [Ga(L(1))H] (8), but indium analogues could not be made. β-ketoimine ligands, [Me(2)N(CH(2))(3)N(H)C(R')-CHC(R')═O] (L(3)H, R' = Me; L(4)H, R' = Ph), with a donor-functionalized Lewis base have also been synthesized and used to form gallium and indium alkyl complexes, [Ga(L(3))Me(2)] (9) and [In(L(3))Me(2)] (10), which were isolated as oils. The related gallium hydride complexes, [Ga(L(n))H(2)] (11, n = 3; 12, n = 4), were also prepared, but again no indium hydride species could be made. The complexes were characterized mainly by NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction. The β-ketoiminate gallium hydride compounds (8 and 11) have been used as single-source precursors for the deposition of Ga(2)O(3) by aerosol-assisted (AA)CVD with toluene as the solvent. The quality of the films varied according to the precursor used, with the complex [Ga(L(1))H] (8) giving by far the best quality films. Although the films were amorphous as deposited, they could be annealed at 1000 °C to form crystalline Ga(2)O(3). The films were analyzed by powder XRD, SEM, and EDX.

Screening the efficient biological prospects of triazole allied mixed ligand metal complexes

Science.gov (United States)

Utthra, Ponnukalai Ponya; Kumaravel, Ganesan; Raman, Natarajan

2017-12-01

Triazole appended mixed ligand complexes (1-8) of the general formula [ML (bpy/phen)2]Cl2, where M = Cu(II), Co(II), Ni(II) and Zn(II), L = triazole appended Schiff base (E)sbnd N-(4-nitrobenzylidene)-1H-1,2,4-triazol-3-amine and bpy/phen = 2,2‧-bipyridine/1,10-phenanthroline, have been synthesized. The design and synthesis of this elaborate ligand has been performed with the aim of increasing stability and conjugation of 1,2,4 triazole, whose Schiff base derivatives are known as biologically active compounds thereby exploring their DNA binding affinity and other biological applications. The compounds have been comprehensively characterized by elemental analysis, spectroscopic methods (IR, UV-Vis, EPR, 1H and 13C NMR spectroscopy), ESI mass spectrometry and magnetic susceptibility measurements. The complexes were found to exhibit octahedral geometry. The complexes 1-8 were subjected to DNA binding techniques evaluated using UV-Vis absorption, CV, CD, Fluorescence spectroscopy and hydrodynamic measurements. Complex 5 showed a Kb value of 3.9 × 105 M-1. The DNA damaging efficacy for the complexes was observed to be high compared to the ligand. The antimicrobial screening of the compounds against bacterial and fungal strains indicates that the complexes possess excellent antimicrobial activity than the ligand. The overall biological activity of the complexes with phen as a co-ligand possessed superior potential than the ligand.

Bis[2-(2H-benzotriazol-2-yl-4-methylphenolato]palladium(II

Directory of Open Access Journals (Sweden)

Chen-Yen Tsai

2009-06-01

Full Text Available In the title complex, [Pd(C13H10N3O2], the PdII atom is tetracoordinated by two N atoms and two O atoms from two bidentate 2-(2H-benzotriazol-2-yl-4-methylphenolate ligands, forming a square-planar environment. The asymmetric unit contains one half molecule in which the Pd atom lies on a centre of symmetry.

Magnetocaloric effect in gadolinium-oxalate framework Gd2(C2O4)3(H2O)6⋅(0⋅6H2O)

International Nuclear Information System (INIS)

Sibille, Romain; Didelot, Emilie; Mazet, Thomas; Malaman, Bernard; François, Michel

2014-01-01

Magnetic refrigerants incorporating Gd 3+ ions and light organic ligands offer a good balance between isolation of the magnetic centers and their density. We synthesized the framework material Gd 2 (C 2 O 4 ) 3 (H 2 O) 6 ⋅0.6H 2 O by a hydrothermal route and characterized its structure. The honeycomb lattice of Gd 3+ ions interlinked by oxalate ligands in the (a,c) plane ensures their decoupling in terms of magnetic exchange interactions. This is corroborated by magnetic measurements indicating negligible interactions between the Gd 3+ ions in this material. The magnetocaloric effect was evaluated from isothermal magnetization measurements. The maximum entropy change −ΔS M max reaches 75.9 mJ cm −3 K −1 (around 2 K) for a moderate field change (2 T)

Entangled zinc-ditetrazolate frameworks involving in situ ligand synthesis and topological modulation by various secondary N-donor ligands

International Nuclear Information System (INIS)

Li Yunwu; Chen Weilin; Wang Yonghui; Li Yangguang; Wang Enbo

2009-01-01

The introduction of various secondary N-donor ligands into an in situ ditetrazolate-ligand synthesis system of terephthalonitrile, NaN 3 and ZnCl 2 led to the formation of three new entangled frameworks Zn(pdtz)(4,4'-bipy).3H 2 O (1), [Zn(pdtz)(bpp)] 2 .3H 2 O (2) and Zn(pdtz) 0.5 (N 3 )(2,2'-bipy) (3) (4,4'-bipy=4,4'-bipyridine; bpp=1,3-bis(4-pyridyl)propane; 2,2'-bipy=2,2'-bipyridine; H 2 pdtz=5,5'-1,4-phenylene-ditetrazole). The formation of pdtz 2- ligand involves the Sharpless [2+3] cycloaddition reaction between terephthalonitrile and NaN 3 in the presence of Zn 2+ ion as a Lewis-acid catalyst under hydrothermal conditions. Compound 1 exhibits a fivefold interpenetrating 3D framework based on the diamondoid topology. Compound 2 displays a twofold parallel interpenetrating framework based on the wavelike individual network. Compound 3 possesses a 2D puckered network. These new Zn-ditetrazolate frameworks are highly dependent on the modulation of different secondary N-donor ligands. Their luminescent properties were investigated. - Graphical abstract: Three new entangled frameworks were prepared by an in situ ditetrazolate-ligand synthesis system assisted with various auxiliary N-donor ligands. The entangled structures can be modulated by different secondary ligands.

EXAFS Characterization of Dendrimer-Derived Pt/γ-Al2O3

International Nuclear Information System (INIS)

Siani, A.; Alexeev, O. S.; Williams, C. T.; Ploehn, H. J.; Amiridis, M. D.

2007-01-01

The various steps involved in the preparation of a Pt/γ-Al2O3 material using hydroxyl-terminated generation four (G4OH) PAMAM dendrimers as templates were monitored by EXAFS. The results indicate that Cl ligands in the Pt precursors (H2PtCl6 and K2PtCl4) were partially replaced by aquo ligands upon hydrolysis to form [PtCl3(H2O)3]+ and [PtCl2(H2O)2] species. After interaction of such species with G4OH, Cl ligands from the first coordination shell of Pt were further replaced by nitrogen atoms from the dendrimer interior, indicating the complexation of Pt with the dendrimer. This process was accompanied by a transfer of the electron density from the dendrimer to Pt, indicating that the former plays the role of a ligand. Following treatment of the H2PtCl6/G4OH and K2PtCl4/G4OH composites with NaBH4, no substantial changes were detecteded in the electronic or coordination environment of Pt, and no formation of metal nanoparticles was observed. However, when the reduction treatment was performed with H2, the formation of extremely small Pt clusters incorporating no more than 4 Pt atoms was observed. These Pt species remained strongly bonded to the dendrimer and their nuclearity depends on the length of the H2 treatment. Formation of Pt nanoparticles with an average diameter of approximately 10 A was finally observed after the deposition of H2PtCl6/G4OH on γ-Al2O3 and drying, suggesting that their formation may be related to the collapse of the dendrimer structure. The Pt nanoparticles formed appear to have high mobility, since subsequent thermal treatment in O2/H2 led to further sintering

Synthesis, structural studies and antituberculosis evaluation of new hydrazone derivatives of quinoline and their Zn(II complexes

Directory of Open Access Journals (Sweden)

Mustapha C. Mandewale

2018-02-01

Full Text Available The quinoline hydrazone ligands were synthesized through multi-step reactions. The 2-hydroxy-3-formylquinoline derivatives (1a–1c were prepared from acetanilide derivatives as starting materials using Vilsmeier–Haack reaction. Then the condensation of 2-hydroxy-3-formylquinoline derivatives with hydrazide derivatives (2a–2c yielded quinoline hydrazone ligands (3a–3i. The synthesis of a new series of Zn(II complexes carried out by refluxing with these quinoline hydrazone ligands (3a–3i is reported. The molecular structures of the ligands (3a–3i and the Zn complexes were characterized by elemental analysis and spectral studies like FT-IR, 1H and 13C NMR, MS, UV–Visible and fluorescence. The preliminary results of antituberculosis study showed that most of the Zn(II complexes 4a–4i demonstrated very good antituberculosis activity while the ligands 3a–3i showed moderate activity. Among the tested compounds 4e and 4g were found to be most active with minimum inhibitory concentration (MIC of 8.00μM and 7.42 μM respectively against Mycobacterium tuberculosis (H37 RV strain ATCC No-27294 which is comparable to “first and second line” drugs used to treat tuberculosis.

CYP epoxygenase-derived H2O2 is involved in the endothelium-derived hyperpolarization (EDH) and relaxation of intrarenal arteries.

Science.gov (United States)

Muñoz, Mercedes; López-Oliva, Maria Elvira; Pinilla, Estéfano; Martínez, María Pilar; Sánchez, Ana; Rodríguez, Claudia; García-Sacristán, Albino; Hernández, Medardo; Rivera, Luis; Prieto, Dolores

2017-05-01

Reactive oxygen species (ROS) like hydrogen peroxide (H 2 O 2 ) are involved in the in endothelium-derived hyperpolarization (EDH)-type relaxant responses of coronary and mesenteric arterioles. The role of ROS in kidney vascular function has mainly been investigated in the context of harmful ROS generation associated to kidney disease. The present study was sought to investigate whether H 2 O 2 is involved in the endothelium-dependent relaxations of intrarenal arteries as well the possible endothelial sources of ROS generation involved in these responses. Under conditions of cyclooxygenase (COX) and nitric oxide (NO) synthase inhibition, acetylcholine (ACh) induced relaxations and stimulated H 2 O 2 release that were reduced by catalase and by the glutathione peroxidase (GPx) mimetic ebselen in rat renal interlobar arteries, suggesting the involvement of H 2 O 2 in the endothelium-dependent responses. ACh relaxations were also blunted by the CYP2C inhibitor sulfaphenazole and by the NADPH oxidase inhibitor apocynin. Acetylcholine stimulated both superoxide (O 2 •- ) and H 2 O 2 production that were reduced by sulfaphenazole and apocynin. Expression of the antioxidant enzyme CuZnSOD and of the H 2 O 2 reducing enzymes catalase and GPx-1 was found in both intrarenal arteries and renal cortex. On the other hand, exogenous H 2 O 2 relaxed renal arteries by decreasing vascular smooth muscle (VSM) intracellular calcium concentration [Ca 2+ ] i and markedly enhanced endothelial K Ca currents in freshly isolated renal endothelial cells. CYP2C11 and CYP2C23 epoxygenases were highly expressed in interlobar renal arteries and renal cortex, respectively, and were co-localized with eNOS in renal endothelial cells. These results demonstrate that H 2 O 2 is involved in the EDH-type relaxant responses of renal arteries and that CYP 2C epoxygenases are physiologically relevant endothelial sources of vasodilator H 2 O 2 in the kidney. Copyright © 2017 Elsevier Inc. All rights

Labeling by [3H]1,3-di(2-tolyl)guanidine of two high affinity binding sites in guinea pig brain: Evidence for allosteric regulation by calcium channel antagonists and pseudoallosteric modulation by sigma ligands

International Nuclear Information System (INIS)

Rothman, R.B.; Reid, A.; Mahboubi, A.; Kim, C.H.; De Costa, B.R.; Jacobson, A.E.; Rice, K.C.

1991-01-01

Equilibrium binding studies with the sigma receptor ligand [ 3 H]1,3-di(2-tolyl)guanidine ([ 3 H]DTG) demonstrated two high affinity binding sites in membranes prepared from guinea pig brain. The apparent Kd values of DTG for sites 1 and 2 were 11.9 and 37.6 nM, respectively. The corresponding Bmax values were 1045 and 1423 fmol/mg of protein. Site 1 had high affinity for (+)-pentazocine, haloperidol, (R)-(+)-PPP, carbepentane, and other sigma ligands, suggesting a similarity with the dextromethorphan/sigma 1 binding site described by Musacchio et al. [Life Sci. 45:1721-1732 (1989)]. Site 2 had high affinity for DTG and haloperidol (Ki = 36.1 nM) and low affinity for most other sigma ligands. Kinetic experiments demonstrated that [ 3 H]DTG dissociated in a biphasic manner from both site 1 and site 2. DTG and haloperidol increased the dissociation rate of [ 3 H]DTG from site 1 and site 2, demonstrating the presence of pseudoallosteric interactions. Inorganic calcium channel blockers such as Cd2+ selectively increased the dissociation rate of [ 3 H]DTG from site 2, suggesting an association of this binding site with calcium channels

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.

Nuclear receptor ligand-binding domains: reduction of helix H12 dynamics to favour crystallization

Energy Technology Data Exchange (ETDEWEB)

Nahoum, Virginie; Lipski, Alexandra; Quillard, Fabien; Guichou, Jean-François [INSERM, U554, 34090 Montpellier (France); Université de Montpellier, CNRS, UMR5048, Centre de Biochimie Structurale (CBS), 34090 Montpellier (France); Boublik, Yvan [CNRS, UMR5237, Centre de Recherche de Biochimie Macromoléculaire (CRBM), 34293 Montpellier (France); Pérez, Efrèn [Universidade de Vigo, Departamento de Quimica Organica, Facultad de Química, 36310 Vigo (Spain); Germain, Pierre [Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), BP 10142, 67404 Illkirch CEDEX (France); Lera, Angel R. de [Universidade de Vigo, Departamento de Quimica Organica, Facultad de Química, 36310 Vigo (Spain); Bourguet, William, E-mail: bourguet@cbs.cnrs.fr [INSERM, U554, 34090 Montpellier (France); Université de Montpellier, CNRS, UMR5048, Centre de Biochimie Structurale (CBS), 34090 Montpellier (France)

2008-07-01

Attempts have been made to crystallize the ligand-binding domain of the human retinoid X receptor in complex with a variety of newly synthesized ligands. An inverse correlation was observed between the ‘crystallizability’ and the structural dynamics of the various receptor–ligand complexes. Crystallization trials of the human retinoid X receptor α ligand-binding domain (RXRα LBD) in complex with various ligands have been carried out. Using fluorescence anisotropy, it has been found that when compared with agonists these small-molecule effectors enhance the dynamics of the RXRα LBD C-terminal helix H12. In some cases, the mobility of this helix could be dramatically reduced by the addition of a 13-residue co-activator fragment (CoA). In keeping with these observations, crystals have been obtained of the corresponding ternary RXRα LBD–ligand–CoA complexes. In contrast, attempts to crystallize complexes with a highly mobile H12 remained unsuccessful. These experimental observations substantiate the previously recognized role of co-regulator fragments in facilitating the crystallization of nuclear receptor LBDs.

[Study on the ultraviolet spectrum in a series of 2 (1H)-quinoxalin-2-one derivatives].

Science.gov (United States)

Yang, Xiao-bing; Ding, Song-tao; Wang, An-bang; Yang, Yu-sheng

2003-02-01

A series of 2 (1H)-quinoxalin-2-one derivatives: 1-alkyl-3-methyl-2 (1H)-quinoxalin-2-one (AMQ, alkyl = H, CH3, C2H5, n-C3H7, n-C5H11, n-C16H33) have been studied by ultraviolet spectrometry. They may be used as highly active fungicides, compounds inhibiting the growth of plants, neuroprotectant for cerebral ischemia, new fluorescent probes, selective antagonists to alpha-amino-3-hydroxy-5-methly-4-isoxazole propionic acid (AMPA) et al. Results show that as the length of the alky1 chain at the nitrogen on the 1-position increases, little changes have been found in the ultraviolet absorption spectra. All spectra have similar peak shape, a strong shoulder peak appears around 327 and 340 nm with a weaker peak around 280 nm. The peak about 340 nm in the UV spectrum is mainly due to the transition of n-->pi* and pi-->pi*, the intense absorption peak about 327 and 280 nm is as the result of the transition of pi-->pi*.

Hydrogenation of imines catalysed by ruthenium(II) complexes based on lutidine-derived CNC pincer ligands.

Science.gov (United States)

Hernández-Juárez, Martín; Vaquero, Mónica; Álvarez, Eleuterio; Salazar, Verónica; Suárez, Andrés

2013-01-14

The preparation of new Ru(II) complexes incorporating fac-coordinated lutidine-derived CNC ligands is reported. These derivatives are selectively deprotonated by (t)BuOK at one of the methylene arms of the pincer, leading to catalytically active species in the hydrogenation of imines.

Interaction between diethylenetrithiodiacetic acid (H2T) derivatives and trivalent lanthanide ions

International Nuclear Information System (INIS)

Matos, J.E.X.; Melo, S.M.; Fontenele, E.M.G.

1984-01-01

Thiopolycarboxylic acids are a class of ligands which contain, besides carboxi-groups, sulfur atoms showing a distinct affinity towards certain solft metals. Stability constant measurements were made for metaldithiocarboxylic acid systems and performed by several authors. Some soLid complexes with 1:1 and 1:2 metal-ligand ratios were isolated and their structures determined by spectroscopic and magnetic methods. Solid complexes between some lanthanides and ethylenedithiodiacetic acid were prepared and characterized by Holanda and Giesbrecht. Investigations of the crystal structure of Zn (II), Cd (II), and Nd (III) complexes with thiodiacetic acid showed, besides coordination to carboxylic groups, the ligand being linked to the metal through the sulfur atom. (Author) [pt

SKF 525-A and cytochrome P-450 ligands inhibit with high affinity the binding of [3H]dextromethorphan and σligands to guinea pig brain

International Nuclear Information System (INIS)

Klein, M.; Canoll, P.D.; Musacchio, J.M.

1991-01-01

The DM 1 /σ 1 site binds dextromethorphan (DM) and σ receptor ligands. The broad binding specificity of this site and its peculiar subcellular distribution prompted us to explore the possibility that this site is a member of the cytochrome P-450 superfamily of enzymes. We tested the effects of the liver microsomal monooxygenase inhibitor SKF 525-A (Proadifen), and other P-450 substrates on the binding of [ 3 H]dextromethorphan, [ 3 H]3-(3-Hydroxyphenyl)-N-(1-propyl)piperidine and (+)-[ 3 H]1,3-Di-o-tolyl-guanidine ([ 3 H]DTG) to the guinea pig brain. SKF 525-A, l-lobeline and GBR-12909 inhibited the binding of the three labeled ligands with nM affinity. Each drug has identical nM K i values for the high-affinity site labeled by the three ligands. This indicated that they displaced the labeled ligands from the common DM 1 σ 1 site. Debrisoquine and sparteine, prototypical substrates for liver debrisoquine 4-hydroxylase, displayed K i values of 9-13 and 3-4 μM respectively against the three labeled ligands. These results, the broad specificity of the DM 1 /σ 1 binding site, and its peculiar subcellular distribution, raises the possibility that this binding site is a member of the cytochrome P-450 superfamily of isozymes, rather than a neurotransmitter receptor

Synthesis and Characterization of a Triphos Ligand Derivative and the Corresponding Pd ^II Complexes: Triphos Ligand Derivative and Corresponding Pd ^II Complexes

Energy Technology Data Exchange (ETDEWEB)

Miller, Deanna L.; Boro, Brian J.; Grubel, Katarzyna; Helm, Monte L.; Appel, Aaron M.

2015-11-16

The synthesis of the new bis(2-(diphenylphosphino)ethyl)methylhydroxyphosphine tridentate phosphine ligand, LCH2OH/Ph, is reported. The ligand reacts with [Pd(Cl)2(PhCN)2 to form [Pd(LCH2OH/Ph)Cl]Cl. Exchange of the chloride ions for triflate (OTf–) using AgOTf yielded pure [Pd(LCH2OH/Ph)OTf]OTf. In addition to spectral characterization the free ligand, LCH2OH/Ph, and Pd(II) complex, [Pd(LCH2OH/Ph)OTf]OTf, are structurally characterized. This research was supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences, and Geosciences. Pacific Northwest National Laboratory is a multiprogram national laboratory operated by Battelle for DOE.

Statistical removal of background signals from high-throughput 1H NMR line-broadening ligand-affinity screens

International Nuclear Information System (INIS)

Worley, Bradley; Sisco, Nicholas J.; Powers, Robert

2015-01-01

NMR ligand-affinity screens are vital to drug discovery, are routinely used to screen fragment-based libraries, and used to verify chemical leads from high-throughput assays and virtual screens. NMR ligand-affinity screens are also a highly informative first step towards identifying functional epitopes of unknown proteins, as well as elucidating the biochemical functions of protein–ligand interaction at their binding interfaces. While simple one-dimensional 1 H NMR experiments are capable of indicating binding through a change in ligand line shape, they are plagued by broad, ill-defined background signals from protein 1 H resonances. We present an uncomplicated method for subtraction of protein background in high-throughput ligand-based affinity screens, and show that its performance is maximized when phase-scatter correction is applied prior to subtraction

[Pr2(pdc3(Hpdc(H2O4]n·n(H3hp·8n(H2O, a One-Dimensional Coordination Polymer Containing PrO6N3 Tri-Capped Trigonal Prisms and PrO8N Mono-Capped Square Anti-Prisms (H2pdc = Pyridine 2,6-Dicarboxylic Acid, C7H5NO4; 3hp = 3-Hydroxy Pyridine, C5H5NO

Directory of Open Access Journals (Sweden)

Shahzad Sharif

2012-08-01

Full Text Available The synthesis, structure and some properties of the one-dimensional coordination polymer, [Pr2(pdc3(Hpdc]n·n(H3hp·8n(H2O, (H2pdc = pyridine 2,6-dicarboxylic acid, C7H5NO4; 3hp = 3-hydroxypyridine, C5H5NO are described. One of the Pr3+ ions is coordinated by two O,N,O-tridentate pdc2− ligands and one tridentate Hpdc− anion to generate a fairly regular PrO6N3 tri-capped trigonal prism, with the N atoms acting as the caps. The second Pr3+ ion is coordinated by one tridentate pdc2− dianion, four water molecules and two monodentate bridging pdc2− ligands to result in a PrO8N coordination polyhedron that approximates to a mono-capped square-anti-prism. The ligands bridge the metal-atom nodes into a chain, which extends in the [100] direction. The H3hp+ cation and uncoordinated water molecules occupy the inter-chain regions and an N–HLO and numerous O–HLO hydrogen bonds consolidate the structure. The H3hp+ species appears to intercalate between pendant pdc rings to consolidate the polymeric structure. Crystal data: 1 (C33H43N5O29Pr2, Mr = 1255.54, triclinic,  (No. 2, Z = 2, a = 13.2567(1 Å, b = 13.6304(2 Å, c = 13.6409(2 Å, α = 89.695(1°, β = 63.049(1°, γ = 86.105(1°, V = 2191.16(5 Å3, R(F = 0.033, wR(F2 = 0.084.

Structural analysis and antimicrobial activity of 2[1H]-pyrimidinethione/selenone derivatives

Science.gov (United States)

Żesławska, Ewa; Korona-Głowniak, Izabela; Szczesio, Małgorzata; Olczak, Andrzej; Żylewska, Alicja; Tejchman, Waldemar; Malm, Anna

2017-08-01

Four new crystal structures of sulfur and selenium analogues of 2[1H]-pyrimidinone derivatives were determined with the use of X-ray diffraction method. The molecular geometry and intermolecular interactions of the investigated molecules were analyzed in order to find the structural features and geometrical parameters, which can be responsible for antimicrobial activities. The influence of chalcogen substituents (sulfur and selenium) on the crystal packing was also studied. The main differences in the molecular structures exist in mutual arrangement of two aromatic rings. The intermolecular interactions in all investigated compounds are similar. Furthermore, the in vitro antibacterial and antifungal activities for these compounds were evaluated. Preliminary investigations have identified two highly potent antibacterial compounds containing selenium atom, which display selectivity towards staphylococci and micrococci. This selectivity was not observed for a control compound used as a drug, namely vancomycin. These compounds possess also good antifungal activity. This is the first report of biological activities of 2[1H]-pyrimidineselenone derivatives.

Synthesis of an S T = 7 [Mn 3 ] Mixed-Valence Complex Based on 1,3-Propanediol Ligand Derivatives and Its One-Dimensional Assemblies

KAUST Repository

Huang, Jian

2013-10-07

Controlled organization of high-spin complexes and single-molecule magnets is a great challenge in molecular magnetism in order to study the effect of the intercomplex magnetic interactions on the intrinsic properties of a given magnetic object. In this work, a new ST = 7 trinuclear mixed-valence Mn complex, [MnIIIMnII 2(LA) 2(Br)4(CH3OH)6] ·Br· (CH3OH)1.5·(H2O)0.5 (1), is reported using a pyridinium-functionalized 1,3-propanediol ligand (H 2LABr = 1-(3-bromo-2,2-bis(hydroxymethyl)propyl)pyridinium bromide). Using azido anions as bridging ligands and different pyridinium-functionalized 1,3-propanediol ligands (H2LBBr = 1-(3-bromo-2,2-bis(hydroxymethyl)propyl)-4-picolinium bromide; H 2LCBr = 1-(3-bromo-2,2-bis(hydroxymethyl)propyl)-3,5- lutidinium bromide), the linear [MnIIIMnII 2L2X4]+ building block has been assembled into one-dimensional coordination networks: [MnIIIMn II 2(LA)2(Br)4(CH 3OH)4(N3)]·((C2H 5)2O)1.25 (2∞), [MnIIIMn II 2(LB)2(Br)4(C 2H5OH)(CH3OH)(H2O) 2(N3)]·(H2O)0.25 (3∞), and [MnIIIMnII 2(LC) 2(Cl)3.8(Br)0.2(C2H 5OH)3(CH3OH)(N3)] (4∞). The syntheses, characterization, crystal structures, and magnetic properties of these new [Mn3]-based materials are reported. © 2013 American Chemical Society.

Strong Ligand-Protein Interactions Derived from Diffuse Ligand Interactions with Loose Binding Sites.

Science.gov (United States)

Marsh, Lorraine

2015-01-01

Many systems in biology rely on binding of ligands to target proteins in a single high-affinity conformation with a favorable ΔG. Alternatively, interactions of ligands with protein regions that allow diffuse binding, distributed over multiple sites and conformations, can exhibit favorable ΔG because of their higher entropy. Diffuse binding may be biologically important for multidrug transporters and carrier proteins. A fine-grained computational method for numerical integration of total binding ΔG arising from diffuse regional interaction of a ligand in multiple conformations using a Markov Chain Monte Carlo (MCMC) approach is presented. This method yields a metric that quantifies the influence on overall ligand affinity of ligand binding to multiple, distinct sites within a protein binding region. This metric is essentially a measure of dispersion in equilibrium ligand binding and depends on both the number of potential sites of interaction and the distribution of their individual predicted affinities. Analysis of test cases indicates that, for some ligand/protein pairs involving transporters and carrier proteins, diffuse binding contributes greatly to total affinity, whereas in other cases the influence is modest. This approach may be useful for studying situations where "nonspecific" interactions contribute to biological function.

Successive ligand substitutions in the Fe(CO)n+/H2O systems (n = 1-5) observed in a triple cell FT-ICR mass spectrometer

International Nuclear Information System (INIS)

Le Caer, S.; Heninger, M.; Mestdagh, H.

2002-01-01

The reactivity of the Fe(CO) n + ions on H 2 O to obtain accurate information on the different ligand substitutions was studied. The energy dependence of rate constants was also investigated; various Fe(CO) n + /L(methanol, dimethylene) systems studied were found to be strongly dependent of the reacting ions. The experimental set-up consisted in three ICR cells which are differentially pumped. The first is used as an ion source: the ions are generated by electron impact ionization upon Fe(CO) 5 , and are mass selected; then they are transferred into the second cell, in which they can relaxed either radiatively or collisionally with Ar atoms, before going to the third cell where they react with water molecules during various times at constant pressure. Then they are drifted back to the second cell in order to be mass detected. In all the Fe(CO) n + ions / H 2 O systems (n=1-4), ligand substitutions were the only reactions observed. No reaction was observed in the Fe(CO) 5 + ions / H 2 O system. The different reactions along with the rate constants as well as the experimental dependence of the rate constant k as a function of the number of collisions with Ar atoms in the third cell are presented. (nevyjel)

Homochiral coordination polymers with helixes and metal clusters based on lactate derivatives

Energy Technology Data Exchange (ETDEWEB)

Xu, Zhong-Xuan, E-mail: xuzhongxuan4201@163.com [Department of Chemistry, Zunyi Normal College, Zunyi, Guizhou 563002 (China); Ma, Yu-Lu [School of Chemical Science and Technology, Yunnan University, Kunming 650091 (China); Lv, Guo-ling [Department of Chemistry, Zunyi Normal College, Zunyi, Guizhou 563002 (China)

2017-05-15

Utilizing the lactic acid derivatives (R)-4-(1-carboxyethoxy)benzoic acid (denoted: (R)-H{sub 2}CBA) and (S)-4-(1-carboxyethoxy)benzoic acid (denoted: (S)-H{sub 2}CBA)as chiral linkers to self-assemble with 4, 4′-bipyridine (denoted: BIP) and Cd(II) ions, a couple of three-dimensional homochiral coordination polymers, namely [Cd{sub 3}((R)-CBA){sub 3} (BIP){sub 2}(H{sub 2}O)]·xGuest (1-D) and [Cd{sub 3}((S)-CBA){sub 3}(BIP){sub 2}(H{sub 2}O)]·xGuest (1-L), have been synthesized under solvothermal reaction condition. Single crystal X-ray diffraction analysis reveals the two complexes contain single helical chains based on enantiopure ligands and cadmium clusters. Moreover, some physical characteristics such as PXRD, thermal stability, solid-state circular dichroism (CD) and luminescent were also investigated. - Graphical abstract: Utilizing enantiomeric lactic acid derivatives (R)-H{sub 2}CBA and (S)-H{sub 2}CBA to assemble with Cd{sup 2+} ions and ancillary BIP ligands, a couple of 3D homochiral coordination polymers with metal clusters and helical chains have been prepared by hydrothermal reaction. - Highlights: • Chiral lactic acid derivative. • Enantiomeric coordination polymer. • Helical chain. • Trinuclear cadmium cluster.

Complexes of technetium, rhenium, and rhodium with sexidentate Schiff-base ligands

International Nuclear Information System (INIS)

Hunter, G.; Kilcullen, N.

1989-01-01

The monocationic technetium (IV) and rhenium (IV) complexes with the sexidentate Schiff-base ligands tris[2-(2'-hydroxybenzylideneethyl)]amine and its substituted derivatives have been prepared and their electrochemical properties studied. The variable-temperature 90.6 MHz 13 C-{ 1 H} n.m.r. spectrum of the rhodium (III) complex of tris[2-(2-hydroxy-5'-isopropylbenzylideneethyl)-amine] has been observed, indicating fluxionality at temperatures above 218 K. (author)

Transition metal complexes with oxygen donor ligands: a synthesis, spectral, thermal and antimicrobial study

Directory of Open Access Journals (Sweden)

VAIBHAV N. PATANGE

2008-10-01

Full Text Available Transition metal complexes of chalcones derived from the conden¬sation of 3-acetyl-6-methyl-2H-pyran-2,4(3H-dione (dehydroacetic acid and p-methoxybenzaldehyde (HL1 or p-nitrobenzaldehyde (HL2 were synthesized and characterized by elemental analysis, conductometry, thermal analysis, magnetic measurements, IR, 1H-NMR, UV–Vis spectroscopy and a microbial study. From the analytical and thermal data, the stoichiometry of the complexes was found to be 1:2 (metal:ligand. The molar conductance data revealed that all the metal chelates were non-electrolytes. The thermal stability of the complexes was studied by thermogravimetry and the decomposition schemes of the complexes are given. The ligands and their metal complexes were screened for antibacterial activity against Staphylococcus aureus and Escherichia coli, and fungicidal activity against Aspergillus flavus, Curvularia lunata and Penicillium notatum.

Crystal structure of {(R-N2-[(benzo[h]quinolin-2-ylmethyl]-N2′-[(benzo[h]quinolin-2-ylmethylidene]-1,1′-binaphthyl-2,2′-diamine-κ4N,N′,N′′,N′′′}(trifluoromethanesulfonato-κOzinc(II} trifluoromethanesulfonate dichloromethane 1.5-solvate

Directory of Open Access Journals (Sweden)

Shayna R. Skokan

2017-07-01

Full Text Available The zinc(II atom in the title compound, [Zn(C48H31N4(CF3SO3](CF3SO3·1.5CH2Cl2, adopts a distorted five-coordinate square-pyramidal geometry. It is coordinated by one trifluoromethanesulfonate ligand and four N atoms of the N2-[(benzo[h]quinolin-2-ylmethyl]-N2′-[(benzo[h]quinolin-2-ylmethylidene]-1,1′-binaphthyl-2,2′-diamine ligand. The complex is present as a single-stranded P-helimer monohelical structure incorporating π–π and/or σ–π interactions. One of the imine bonds present in the original ligand framework is reduced, leading to variations in bond lengths and torsion angles for each side of the ligand motif. The imine-bond reduction also affects the bond lengths involving the metal atom with the N-donor atoms located on the imine bond. There are two molecules of the complex in the asymmetric unit. One of the molecules exhibits positional disorder within the coordinating trifluoromethanesulfonate ion making the molecules symmetrically non-equivalent.

Structural modulation and luminescent properties of four CdII coordination architectures based on 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole and flexible/rigid dicarboxylate ligands

Science.gov (United States)

Xia, Liang; Dong, Wen-Wen; Ye, Xiao; Zhao, Jun; Li, Dong-Sheng

2016-10-01

To systematically investigate the influence of the flexible or rigid auxiliary ligands on the structures and properties of transition metal compounds, we synthesized four new d10 coordination polymers (CPs) from 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole (4-Hpzpt) and flexible/rigid dicarboxylate ligands, [Cd(4-pzpt)2]n (1), [Cd3(4-pzpt)2(suc)2]n (2), [Cd2(4-Hpzpt)(nbc)2(H2O)]n (3) and {[Cd2(4-pzpt)2(tfbdc)(H2O)4]·H2O}n (4) (H2suc=1,2-ethanedicarboxylic acid, H2nbc=hthalene-1,4-dicarboxylic acid, H2tfbdc =2,3,5,6-tetrafluoroterephthalic acid). Single crystal X-ray analysis indicates that compound 1 shows a 44-sql layer, which is extended to a 3D network via nonclassical C-H…N hydrogen bonds. Compound 2 possesses a 6-connected pcu-4120.63 net composed of trinuclear CdII-clusters. Compound 3 represents a rare 3D (3,4,4,5)-connected topology with a Schläfli symbol of (4·6·7)(4·53·72)(53·6·7·9)(42·55·6·72). Compound 4 exhibits a 2D+2D→2D parallel interpenetrated 63-hcb network. The adjacent 2D networks are interdigitated with each other to form the resulting 3D supramolecular architecture through classical O-H…N and O-H…O hydrogen bonds. Structural diversities indicate that the nature of flexible/rigid-dicarboxlates plays crucial roles in modulating structures of these compounds. Moreover, the luminescent properties of them have been briefly investigated.

The proton-coupled amino acid transporter hPAT1 is the main transporter involved in vigabatrin uptake in intestinal Caco-2 cells

DEFF Research Database (Denmark)

Nøhr, Martha Kampp; Hansen, Steen Honore'; Brodin, Birger

2012-01-01

transporter hPAT1. The aim of the project was to identify if transporters are involved in cellular uptake of vigabatrin in Caco-2 cells. Methods: The uptake rate of vigabatrin was measured in Caco-2 cells at pH 6.0 or 7.4 for 15 min after application of 0.1 – 25.0 mM vigabatrin. The inhibitory effect...... of selected amino acids and -derivatives on the apical vigabatrin uptake in Caco-2 cells was investigated. Vigabatrin samples were analyzed using liquid chromatography (LC) coupled to a mass selective detector (MSD). Results: The uptake rate of vigabatrin in Caco-2 cells was pH-dependent. The uptake...... of vigabatrin was saturable at pH 6.0 with a Michaelis constant, Km of 12.7 ± 3.7 mM and a maximal flux, Jmax of 3.7 ± 0.5 nmol•min-1•cm-2. The presences of hPAT1 ligands significantly inhibited the uptake of vigabatrin in Caco-2 cells at pH 6.0, whereas hPAT1 non-ligands did not. Discussion: The saturability...

Labeling by ( sup 3 H)1,3-di(2-tolyl)guanidine of two high affinity binding sites in guinea pig brain: Evidence for allosteric regulation by calcium channel antagonists and pseudoallosteric modulation by sigma ligands

Energy Technology Data Exchange (ETDEWEB)

Rothman, R.B.; Reid, A.; Mahboubi, A.; Kim, C.H.; De Costa, B.R.; Jacobson, A.E.; Rice, K.C. (National Institute of Mental Health, Bethesda, MD (USA))

1991-02-01

Equilibrium binding studies with the sigma receptor ligand ({sup 3}H)1,3-di(2-tolyl)guanidine (({sup 3}H)DTG) demonstrated two high affinity binding sites in membranes prepared from guinea pig brain. The apparent Kd values of DTG for sites 1 and 2 were 11.9 and 37.6 nM, respectively. The corresponding Bmax values were 1045 and 1423 fmol/mg of protein. Site 1 had high affinity for (+)-pentazocine, haloperidol, (R)-(+)-PPP, carbepentane, and other sigma ligands, suggesting a similarity with the dextromethorphan/sigma 1 binding site described by Musacchio et al. (Life Sci. 45:1721-1732 (1989)). Site 2 had high affinity for DTG and haloperidol (Ki = 36.1 nM) and low affinity for most other sigma ligands. Kinetic experiments demonstrated that ({sup 3}H)DTG dissociated in a biphasic manner from both site 1 and site 2. DTG and haloperidol increased the dissociation rate of ({sup 3}H)DTG from site 1 and site 2, demonstrating the presence of pseudoallosteric interactions. Inorganic calcium channel blockers such as Cd2+ selectively increased the dissociation rate of ({sup 3}H)DTG from site 2, suggesting an association of this binding site with calcium channels.

Binuclear trivalent and tetravalent uranium halides and cyanides supported by cyclooctatetraene ligands

Energy Technology Data Exchange (ETDEWEB)

Wang, Cong-Zhi; Wu, Qun-Yan; Lan, Jian-Hui; Shi, Wei-Qun [Chinese Academy of Sciences, Beijing (China). Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety; Chai, Zhi-Fang [Chinese Academy of Sciences, Beijing (China). Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety; Soochow Univ., Suzhou (China). School of Radiological and Interdisciplinary Sciences (RAD-X); Gibson, John K. [Lawrence Berkeley National Laboratory, CA (United States). Chemical Sciences Division

2017-03-01

Although the first organoactinide chloride Cp{sub 3}UCl (Cp = η{sup 5}-C{sub 5}H{sub 5}) was synthesized more than 50 years ago, binuclear uranium halides remain very rare in organoactinide chemistry. Herein, a series of binuclear trivalent and tetravalent uranium halides and cyanides with cyclooctatetraene ligands, (COT){sub 2}U{sub 2}X{sub n} (COT = η{sup 8}-C{sub 8}H{sub 8}; X=F, Cl, CN; n=2, 4), have been systematically studied using scalar-relativistic density functional theory (DFT). The structures with bridging halide or cyanide ligands were predicted to be the most stable complexes of (COT){sub 2}U{sub 2}X{sub n}, and all the complexes show weak antiferromagnetic interactions between the uranium centers. However, for each species, there is no significant uranium-uranium bonding interaction. The bonding between the metal and the ligands shows some degree of covalent character, especially between the metal and terminal halide or cyanide ligands. The U-5f and 6d orbitals are predominantly involved in the metal-ligand bonding. All the (COT){sub 2}U{sub 2}X{sub n} species were predicted to be more stable compared to the mononuclear half-sandwich complexes at room temperature in the gas phase such that (COT){sub 2}U{sub 2}X{sub 4} might be accessible through the known (COT){sub 2}U complex. The tetravalent derivatives (COT){sub 2}U{sub 2}X{sub 4} are more energetically favorable than the trivalent (COT){sub 2}U{sub 2}X{sub 2} analogs, which may be attributed to the greater number of strong metal-ligand bonds in the former complexes.

Stabilization and reactivity of a terminal phosphidounit on Pt(II). Synthesis and X-ray structure of cationic diphelylphosphine [Pt{C6H3(CH2NMe2)2-2,6}(PHPh2)][CF3SO3] and Diphenyl-phosphido Bridged Pt(II)-Pd(II) Complex [Pt{C6H3(CH2NMe2)2-2,6} (µ-PPh2) Pd(C6H4CH2NMe2-2)(H2O)][BF4] CH2Cl2

NARCIS (Netherlands)

Koten, G. van; Maassarani, F.; Davidson, M.F.; Wehman-Ooyevaar, ICM; Grove, D.M.; Koten, M.A. van; Smeets, W.J.J.; Spek, A.L.

1995-01-01

Reaction of diphenylphosphine with the complexes [Pt(NCN)(H{2}O)]X (NCN = C{6}H{3}(CH{2}NMe{2}){2}-2, 6; X = BF{4} (1a), OSO{2}CF{3} (1b)) leads to substitution of the H{2}O ligand to afford the ionic Pt(II) complexes [Pt(NCN)(PHPh{2})]X (X = BF{4} (2a), OSO{2}CF{3} (2b)). The X-ray structure of the

Polymerization of 1,3-butadiene catalyzed by pincer cobalt(II) complexes derived from 2-(1-arylimino)-6-(pyrazol-1-yl)pyridine ligands

KAUST Repository

Gong, Dirong

2013-08-01

A new class of air stable and structurally well-defined cobalt complexes with unsymmetrical pincer type ligands ([2-(ArNCMe)-6-(Py)C5H 3N]CoCl2) (Ar = C6H5, Py = pyrazol-1-yl, 5a; Ar = 2,4,6-Me3C6H2, Py = pyrazol-1-yl, 5b; Ar = 2,6-iPr2C6H3, Py = pyrazol-1-yl, 5c; Ar = C6H5, Py = 3,5-Me 2pyrazol-1-yl, 5d; Ar = 2,4,6-Me3C6H 2, Py = 3,5-Me2pyrazol-1-yl, 5e; Ar = 2,6- iPr2C6H3, Py = 3,5-Me 2pyrazol-1-yl, 5f; Ar = 2,6-iPr2C 6H3, Py = 3,5-iPr2pyrazol-1-yl, 5g and [2-(OCMe)-6-(3,5-diphenylpyrazol-1-yl)C5H3N]CoCl 2 5h) were prepared and the molecular structures of 5a, 5c and 5f were determined by single crystal X-ray crystallography. Upon activation by methylaluminoxane (MAO) in toluene at room temperature, all complexes initiate polymerization of 1,3-butadiene (polymer yields: 65-99%), affording polybutadiene with excellent cis-1,4 regularity (97.5-98.7%). The polymer yields and properties in terms of molecular weight and distribution are well controlled by the substituents on iminoaryl rings and pyrazole rings. Selectivity switch from cis-1,4 to syndio-1,2 was also achievable by adding phosphine as microstructure regulator. © 2013 Elsevier B.V. All rights reserved.

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.

Dentritic Carbosilanes Containing Silicon-Bonded 1-[C6H2(CH2NMe2)2-3,5-Li-4] or 1-[C6H3(CH2NMe2)-4-Li-3] Mono-and Bis(amino)aryllithium End Groups: Structure of {[CH2SiMe2C6H3(CH2NMe2)-4-Li-3]2}2

NARCIS (Netherlands)

Koten, G. van; Kleij, A.W.; Kleijn, H.; Jastrzebski, J.T.B.H.; Smeets, W.J.J.; Spek, A.L.

1999-01-01

A useful synthetic procedure for the incorporation of the potentially multidentate monoanionic 1-[C6H2(CH2NMe2)2-3,5]- (=NCN) and 1-[C6H3(CH2NMe2)-4]- (=CN) ligands via the para-position on the periphery of carbosilane (CS) dendrimers has been developed. Lithiation of suitable brominated precursors

[Zn(phen)(O,N,O)(H2O)] and [Zn(phen)(O,N)(H2O)] with O,N,O is 2,6-dipicolinate and N,O is L-threoninate: synthesis, characterization, and biomedical properties.

Science.gov (United States)

Chin, Lee-Fang; Kong, Siew-Ming; Seng, Hoi-Ling; Tiong, Yee-Lian; Neo, Kian-Eang; Maah, Mohd Jamil; Khoo, Alan Soo-Beng; Ahmad, Munirah; Hor, Tzi-Sum Andy; Lee, Hong-Boon; San, Swee-Lan; Chye, Soi-Moi; Ng, Chew-Hee

2012-10-01

Two ternary Zn(II) complexes, with 1,10-phenanthroline (phen) as the main ligand and a carboxylate-containing ligand [dipicolinate (dipico) or L-threoninate (L-Thr)] as the subsidiary ligand, were prepared and characterized by elemental analysis, Fourier transform IR, UV, and fluorescence spectroscopy, X-ray diffraction, molar conductivity, and electrospray ionization mass spectrometry. X-ray structure analysis shows that both [Zn(phen)(dipico)(H(2)O)]·H(2)O (1) and [Zn(phen)(L-Thr)(H(2)O)Cl]·2H(2)O (2) have octahedral geometry about the Zn(II) atom. Both complexes can inhibit topoisomerase I, and have better anticancer activity than cisplatin against nasopharyngeal cancer cell lines, HK1 and HONE-1, with concentrations causing 50 % inhibition of cell proliferation (IC(50)) in the low micromolar range. Complex 2 has the highest therapeutic index for HK1. Both Zn(II) complexes can induce cell death by apoptosis. Changing the subsidiary ligand in the Zn(II) complexes affects the UV-fluorescence spectral properties of the coordinated phen ligand, the binding affinity for some DNA sequences, nucleobase sequence-selective binding, the phase at which cell cycle progression was arrested for treated cancer cells, and their therapeutic index.

1,2- and 1,3-dihydroxylated and hydroxynitrogenated monoterpenes as chiral ligands in the asymmetric reformatsky reaction

International Nuclear Information System (INIS)

Ribeiro, Carlos Magno R.; Morita, Cristina M.; Maia, Monica P.

2008-01-01

This study describes the use of three (-)-α-pinene derivatives, one diol-1,2 [(-)- (1R, 2R, 3S, 5R)-2,6,6-trimethylbicyclo[3.1.1]heptane-2,3-diol 4] and two pyridine-hydroxy derivatives [(+)-(1R,2S,3R,5S)-2,6,6- trimethyl-3-(2-pyridinylmethyl)bicyclo[3.1.1]heptane-3-ol 7 and (-)-(1R,2S,3R,5S)-2,6,6-trimethyl-3-[2-(2-pyridinyl) ethyl]bicyclo[3.1.1]heptane-3-ol 8]; one diol-1,3 [(-)-(1S,2R,5S)-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanol 5] derived from (+)-isopulegol 2 and one diol-1,3 [(+)-(1R,2R,5R)-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanol 6] derived from (+)-neoisopulegol 3, as ligands in the asymmetric Reformatsky reaction. The best enantiomeric excess of β-hydroxy ester obtained in the Reformatsky asymmetric reaction was 18% using ligand 6, and the chemical yield of the reactions was 65% on average. (author)

Synthesis, spectroscopic and DNA binding ability of Co{sup II}, Ni{sup II}, Cu{sup II} and Zn{sup II} complexes of Schiff base ligand (E)-1-(((1H-benzo[d]imidazol-2-yl)methylimino)methyl)naphthalen-2-ol. X-ray crystal structure determination of cobalt (II) complex

Energy Technology Data Exchange (ETDEWEB)

Yarkandi, Naeema H. [Chemistry Department, Faculty of Applied Science, Umm Al–Qura University, Makkah (Saudi Arabia); El-Ghamry, Hoda A., E-mail: helghamrymo@yahoo.com [Chemistry Department, Faculty of Applied Science, Umm Al–Qura University, Makkah (Saudi Arabia); Chemistry Department, Faculty of Science, Tanta University, Tanta (Egypt); Gaber, Mohamed [Chemistry Department, Faculty of Science, Tanta University, Tanta (Egypt)

2017-06-01

A novel Schiff base ligand, (E)-1-(((1H-benzo[d]imidazol-2-yl)methylimino)methyl)naphthalen-2-ol (HL), has been designed and synthesized in addition to its metal chelates [Co(L){sub 2}]·l2H{sub 2}O, [Ni(L)Cl·(H{sub 2}O){sub 2}].5H{sub 2}O, [Cu(L)Cl] and [Zn(L)(CH{sub 3}COO)]. The structures of the isolated compounds have been confirmed and identified by means of different spectral and physicochemical techniques including CHN analysis, {sup 1}H &{sup 13}C NMR, mass spectral analysis, molar conductivity measurement, UV–Vis, infrared, magnetic moment in addition to TGA technique. The infrared spectral results ascertained that the ligand acts as monobasic tridentate binding to the metal centers via deprotonated hydroxyl oxygen, azomethine and imidazole nitrogen atoms. The UV–Vis, magnetic susceptibility and molar conductivity data implied octahedral geometry for Co(II) & Ni(II) complexes, tetrahedral for Zn(II) complex and square planar for Cu(II) complex. X-ray structural analysis of Co(II) complex 1 has been reported and discussed. Moreover, the type of interaction between the ligand & its complexes towards salmon sperm DNA (SS-DNA) has been examined by the measurement of absorption spectra and viscosity which confirmed that the ligand and its complexes interact with DNA via intercalation interaction as concluded from the values of binding constants (K{sub b}). - Highlights: • Synthesis of Co{sup II}, Ni{sup II}, Cu{sup II} and Zn{sup II} complexes of the Schiff base ligand based on 2-(aminomethyl)benzimidazole moiety. • The constitutions and structures of the ligand and complexes were elucidated. • Molecular structure of Co{sup II} complex was confirmed by single crystal X-ray diffraction method. • The ligand and its complexes interact with SS-DNA via intercalation mods.

Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1,10-phenanthroline) 2 building blocks

Science.gov (United States)

Yu, Yunfang; Wei, Yongqin; Broer, Ria; Sa, Rongjian; Wu, Kechen

2008-03-01

Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen) 2(H 2O)(HTST)]·2H 2O ( 1), [Co 3(phen) 6(H 2O) 2(TST) 2]·7H 2O ( 2), and [Co 2Cu(phen) 6(H 2O) 2(TST) 2]·10H 2O ( 3), have been synthesized by the reactions of a new tri-sulfonate ligand (2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, H 3TST) with the M2+ ( M=Co, Cu) and the second ligand 1,10-phenanthroline (phen). Complex 1 contains a cis-Co(II)(phen) 2 building block and an HTST as monodentate ligand; complex 2 consists of two TST as bidentate ligands connecting one trans- and two cis-Co(II)(phen) 2 building blocks; complex 3 is formed by replacing the trans-Co(II)(phen) 2 in 2 with a trans-Cu(II)(phen) 2, which is the first reported hetero-trinuclear supramolecular complex containing both the Co(II)(phen) 2 and Cu(II)(phen) 2 as building blocks. The study shows the flexible multifunctional self-assembly capability of the H 3TST ligands presenting in these supramolecular complexes through coordinative, H-bonding and even π- π stacking interactions. The photoluminescent optical properties of these complexes are also investigated and discussed as well as the second-order nonlinear optical properties of 1.

Synthesis and crystal structures of 2-methyl-4-aryl-5-oxo-5H-indeno [1,2-b] pyridine carboxylate derivatives

DEFF Research Database (Denmark)

Pandian, Ramesh; Naushad, Edayadulla; Vijayakumar, Vinodhkumar

2014-01-01

pyridine derivatives through oxidation. Consequently, the interest in this aromatization reaction, investigation of a wide range of 1, 4-DHPs continues to attract the attention of researchers. Herein, we report the preparation of pyridine derivatives and the crystal structures determined by X......-ray crystallographic methods.Results: The crystal structures and conformational studies of two organic compounds, namely ethyl 2-methyl-4-phenyl-5-oxo-5H-indeno [1,2-b] pyridine-3-carboxylate (I) and ethyl 2-methyl-4-(4 chlorophenyl)-5-oxo-5H-indeno [1,2-b] pyridine-3-carboxylate (II) are reported. The terminal ethyl......) dimer running along 011 direction.Conclusion: The crystal structures ethyl 2-methyl-4-phenyl-5-oxo-5H-indeno [1,2-b] pyridine-3-carboxylate and ethyl 2-methyl-4-(4 chlorophenyl)-5-oxo-5H-indeno [1,2-b] pyridine-3-carboxylate have been investigated in detail. The terminal ethyl group of compound I...

Synthesis, structure and luminescence properties of zinc (II) complexes with terpyridine derivatives as ligands

International Nuclear Information System (INIS)

Chen Xuegang; Zhou Quanguo; Cheng Yanxiang; Geng Yanhou; Ma Dongge; Xie Zhiyuan; Wang Lixiang

2007-01-01

Five zinc (II) complexes (1-5) with 4'-phenyl-2,2':6',2''-terpyridine (ptpy) derivatives as ligands have been synthesized and fully characterized. The para-position of phenyl in ptpy is substituted by the group (R), i.e. tert-butyl (t-Bu), hexyloxy (OHex), carbazole-9-yl (Cz), naphthalen-1-yl-phenyl-amine-N-yl (NPA) and diphenyl amine-N-yl (DPA), with different electron-donating ability. With increasing donor ability of the R, the emission color of the complexes in film was modulated from violet (392 nm) to reddish orange (604 nm). The photoexcited luminescence exhibits significant solvatochromism because the emission of the complexes involves the intra-ligand charge transfer (ILCT) excited state. The electrochemical investigations show that the complexes with stronger electro-donating substituent have lower oxidation potential and then higher HOMO level. The electroluminescence (EL) properties of these zinc (II) complexes were studied with the device structure of ITO/PEDOT/Zn (II) complex: PBD:PMMA/BCP/AlQ/LiF/Al. Complexes 3, 4 and 5 exhibit EL wavelength at 552, 600 and 609 nm with maximum current efficiency of 5.28, 2.83 and 2.00 cd/A, respectively

PLASS: Protein-ligand affinity statistical score a knowledge-based force-field model of interaction derived from the PDB

Science.gov (United States)

Ozrin, V. D.; Subbotin, M. V.; Nikitin, S. M.

2004-04-01

We have developed PLASS (Protein-Ligand Affinity Statistical Score), a pair-wise potential of mean-force for rapid estimation of the binding affinity of a ligand molecule to a protein active site. This scoring function is derived from the frequency of occurrence of atom-type pairs in crystallographic complexes taken from the Protein Data Bank (PDB). Statistical distributions are converted into distance-dependent contributions to the Gibbs free interaction energy for 10 atomic types using the Boltzmann hypothesis, with only one adjustable parameter. For a representative set of 72 protein-ligand structures, PLASS scores correlate well with the experimentally measured dissociation constants: a correlation coefficient R of 0.82 and RMS error of 2.0 kcal/mol. Such high accuracy results from our novel treatment of the volume correction term, which takes into account the inhomogeneous properties of the protein-ligand complexes. PLASS is able to rank reliably the affinity of complexes which have as much diversity as in the PDB.

Hepatic Stellate Cell-Derived Microvesicles Prevent Hepatocytes from Injury Induced by APAP/H2O2

Directory of Open Access Journals (Sweden)

Renwei Huang

2016-01-01

Full Text Available Hepatic stellate cells (HSCs, previously described for liver-specific mesenchymal stem cells (MSCs, appear to contribute to liver regeneration. Microvesicles (MVs are nanoscale membrane fragments, which can regulate target cell function by transferring contents from their parent cells. The aim of this study was to investigate the effect of HSC-derived MVs on xenobiotic-induced liver injury. Rat and human hepatocytes, BRL-3A and HL-7702, were used to build hepatocytes injury models by n-acetyl-p-aminophenol n-(APAP or H2O2 treatment. MVs were prepared from human and rat HSCs, LX-2, and HST-T6 and, respectively, added to injured BRL-3A and HL-7702 hepatocytes. MTT assay was utilized to determine cell proliferation. Cell apoptosis was analyzed by flow cytometry and hoechst33258 staining. Western blot was used for analyzing the expression of activated caspase-3. Liver injury indicators, alanine aminotransferase (ALT, aspartate aminotransferase (AST, and lactate dehydrogenase (LDH in culture medium were also assessed. Results showed that (1 HSC-MVs derived from LX-2 and HST-T6 were positive to CD90 and annexin V surface markers; (2 HSC-MVs dose-dependently improved the viability of hepatocytes in both injury models; (3 HSC-MVs dose-dependently inhibited the APAP/H2O2 induced hepatocytes apoptosis and activated caspase-3 expression and leakage of LDH, ALT, and AST. Our results demonstrate that HSC-derived MVs protect hepatocytes from toxicant-induced injury.

A three-dimensional coordination polymer based on 1,2,3-triazole-4,5-dicarboxylic acid (H{sub 3}tda): ([Cd{sub 12}(tda){sub 8}(H{sub 2}O){sub 11}] · (H{sub 2}O)6.25){sub n}

Energy Technology Data Exchange (ETDEWEB)

Zhou, Xin-Hui, E-mail: iamxhzhou@njupt.edu.cn; Chen, Qiang [Nanjing University of Posts and Telecommunications, Key Laboratory for Organic Electronics and Information Displays and Institute of Advanced Materials, National Jiangsu Syngerstic Innovation Center for Advanced Materials (SICAM) (China)

2017-03-15

The title coordination polymer ([Cd{sub 12}(tda){sub 8}(H{sub 2}O){sub 11}] · (H{sub 2}O){sub 6.25}){sub n} (H{sub 3}tda = 1,2,3-triazole-4,5-dicarboxylic acid), has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complex crystallizes in orthorhombic sp. gr. Pmn2{sub 1} with Z = 4. The Cd{sub 2} unit doublebridged by one carboxylate oxygen atom and two neighboring nitrogen atoms from the tda{sup 3–} ligands are linked by the tda{sup 3–}ligands to lead to the 2D (4,4) network in the ac plane. The almost coplanar Cd{sub 2}(μ{sub 5}-tda){sub 2} unit comprised of two Cd ions double-bridged by two tda{sup 3–} ligands through the neighboring nitrogen atoms is connected with the other four Cd{sub 2}(μ{sub 5}-tda){sub 2} units form the undulating 2D network in the ac plane. The (4,4) networks and undulating 2D networks are alternatively connected along the b axis by the tda{sup 3–} ligands coordinating to the Cd ions to form the 3D framework.

Dinuclear hexamethylbenzene ruthenium cations containing eta(1):eta(2)-2-(ferrocenyl)ethen-1-yl ligands: Synthesis, structure, electrochemistry

Czech Academy of Sciences Publication Activity Database

Tschan, M. J.-L.; Therrien, B.; Ludvík, Jiří; Štěpnička, P.; Süss-Fink, G.

2006-01-01

Roč. 691, č. 20 (2006), s. 4304-4311 ISSN 0022-328X Institutional research plan: CEZ:AV0Z40400503 Keywords : arene ligands * electrochemistry * ferrocene derivatives Subject RIV: CG - Electrochemistry Impact factor: 2.332, year: 2006

A Spectroscopic Study of the effect of Ligand Complexation on the Reduction of Uranium(VI) by Anthraquinone-2,6-disulfonate (AH2DS)

International Nuclear Information System (INIS)

Wang, Zheming; Wagnon, Ken B.; Ainsworth, Calvin C.; Liu, Chongxuan; Rosso, Kevin M.; Fredrickson, Jim K.

2008-01-01

In this project, the reduction rate of uranyl complexes with hydroxide, carbonate, EDTA, and Desferriferrioxamine B (DFB) by anthraquinone-2,6-disulfonate (AH2DS), a potential electron shuttle for microbial reduction of metal ions (Newman and Kolter 2000), is studied by stopped-flow kinetics techniques under anoxic atmosphere. The apparent reaction rates varied with ligand type, solution pH, and U(VI) concentration. For each ligand, a single largest kobs within the studied pH range was observed, suggesting the influence of pH-dependent speciation on the U(VI) reduction rate. The maximum reaction rate found in each case followed the order of OH- > CO32- > EDTA > DFB, consistent with the same trend of the thermodynamic stability of the uranyl complexes and ionic sizes of the ligands. Increasing the stability of uranyl complexes and ligand size decreased the maximum reduction rate. The pH-dependent rates were modeled using a second-order rate expression that was assumed to be dependent on a single U(VI) complex and AH2DS species. By quantitatively comparing the calculated and measured apparent rate constants as a function of pH, species AHDS3- was suggested as the primary reductant in all cases examined. Species UO2CO3(aq) , UO2HEDTA-, and (UO2)2(OH)22+ were suggested as the principal electron acceptors among the U(VI) species mixture in carbonate, EDTA, and hydroxyl systems, respectively

The selenium metabolite methylselenol regulates the expression of ligands that trigger immune activation through the lymphocyte receptor NKG2D

DEFF Research Database (Denmark)

Hagemann-Jensen, Michael Henrik; Uhlenbrock, Franziska Katharina; Kehlet, Stephanie

2014-01-01

For decades Selenium (Se) research has been focused on the identification of active metabolites, which are crucial for Se chemoprevention of cancer. In this context, the metabolite methylselenol (CH3SeH) is known for its action to selectively kill transformed cells through mechanisms that include...... ligands. A balanced cell-surface expression of NKG2D ligands is considered as an innate barrier against tumor development. Our work therefore indicates that the application of selenium compounds, which are metabolized to CH3SeH, could improve NKG2D-based immune therapy.......: Increased formation of reactive oxygen species (ROS), induction of DNA damage, triggering of apoptosis and the inhibition of angiogenesis. Here, we revealed that CH3SeH modulates cell surface expression of NKG2D ligands. The expression of NKG2D ligands is induced by stress-associated pathways, which occur...

A 12-Fold ThSi2 Interpenetrated Network Utilizing a Glycine-Based Pseudopeptidic Ligand

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Edward Loukopoulos

2018-01-01

Full Text Available We report the synthesis and characterization of a 3D Cu(II coordination polymer, [Cu3(L12(H2O8]·8H2O (1, with the use of a glycine-based tripodal pseudopeptidic ligand (H3L1 = N,N′,N″-tris(carboxymethyl-1,3,5-benzenetricarboxamide or trimesoyl-tris-glycine. This compound presents the first example of a 12-fold interpenetrated ThSi2 (ths net. We attempt to justify the unique topology of 1 through a systematic comparison of the synthetic parameters in all reported structures with H3L1 and similar tripodal pseudopeptidic ligands. We additionally explore the catalytic potential of 1 in the A3 coupling reaction for the synthesis of propargylamines. The compound acts as a very good heterogeneous catalyst with yields up to 99% and loadings as low as 3 mol %.

Synthesis, characterization and biological activity of some transition metals with Schiff base derived from 2-thiophene carboxaldehyde and aminobenzoic acid

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Mohamed, Gehad G.; Omar, M. M.; Hindy, Ahmed M. M.

2005-12-01

Metal complexes of Schiff base derived from 2-thiophene carboxaldehyde and 2-aminobenzoic acid (HL) are reported and characterized based on elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance and thermal analysis (TGA). The ligand dissociation as well as the metal-ligand stability constants were calculated pH metrically at 25 °C and ionic strength μ = 0.1 (1 M NaCl). The complexes are found to have the formulae [M(HL) 2](X) n· yH 2O (where M = Fe(III) (X = Cl, n = 3, y = 3), Co(II) (X = Cl, n = 2, y = 1.5), Ni(II) (X = Cl, n = 2, y = 1) and UO 2(II) (X = NO 3, n = 2, y = 0)) and [M(L) 2] (where M = Cu(II) (X = Cl) and Zn(II) (X = AcO)). The molar conductance data reveal that Fe(III) and Co(II), Ni(II) and UO 2(II) chelates are ionic in nature and are of the type 3:1 and 2:1 electrolytes, respectively, while Cu(II) and Zn(II) complexes are non-electrolytes. IR spectra show that HL is coordinated to the metal ions in a terdentate manner with ONS donor sites of the carboxylate O, azomethine N and thiophene S. From the magnetic and solid reflectance spectra, it is found that the geometrical structure of these complexes are octahedral. The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, Δ H*, Δ S* and Δ G* are calculated from the DrTG curves using Coats-Redfern method. The synthesized ligands, in comparison to their metal complexes also were screened for their antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pyogones and Fungi (Candida). The activity data show that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species.

Regioselective synthesis of 7,8-dihydroimidazo[5,1-c][1,2,4]triazine-3,6(2H,4H-dione derivatives: A new drug-like heterocyclic scaffold

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Nikolay T. Tzvetkov

2012-09-01

Full Text Available Dihydroimidazo[5,1-c][1,2,4]triazine-3,6(2H,4H-dione derivatives were prepared by successive N3- and N1-alkylation of hydantoins, followed by regioselective thionation and subsequent cyclization under mild conditions. In a final alkylation step a further substituent may be introduced. The synthetic strategy allows broad structural variation of this new drug-like heterobicyclic scaffold. In addition to extensive NMR and MS analyses, the structure of one derivative was confirmed by X-ray crystallography.

Generation of an alpaca-derived nanobody recognizing γ-H2AX

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Rajan, Malini; Mortusewicz, Oliver; Rothbauer, Ulrich; Hastert, Florian D.; Schmidthals, Katrin; Rapp, Alexander; Leonhardt, Heinrich; Cardoso, M. Cristina

2015-01-01

Post-translational modifications are difficult to visualize in living cells and are conveniently analyzed using antibodies. Single-chain antibody fragments derived from alpacas and called nanobodies can be expressed and bind to the target antigenic sites in living cells. As a proof of concept, we generated and characterized nanobodies against the commonly used biomarker for DNA double strand breaks γ-H2AX. In vitro and in vivo characterization showed the specificity of the γ-H2AX nanobody. Mammalian cells were transfected with fluorescent fusions called chromobodies and DNA breaks induced by laser microirradiation. We found that alternative epitope recognition and masking of the epitope in living cells compromised the chromobody function. These pitfalls should be considered in the future development and screening of intracellular antibody biomarkers. PMID:26500838

Synthesis, spectroscopic and DNA binding ability of CoII, NiII, CuII and ZnII complexes of Schiff base ligand (E)-1-(((1H-benzo[d]imidazol-2-yl)methylimino)methyl)naphthalen-2-ol. X-ray crystal structure determination of cobalt (II) complex.

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Yarkandi, Naeema H; El-Ghamry, Hoda A; Gaber, Mohamed

2017-06-01

A novel Schiff base ligand, (E)-1-(((1H-benzo[d]imidazol-2-yl)methylimino)methyl)naphthalen-2-ol (HL), has been designed and synthesized in addition to its metal chelates [Co(L) 2 ]·l2H 2 O, [Ni(L)Cl·(H 2 O) 2 ].5H 2 O, [Cu(L)Cl] and [Zn(L)(CH 3 COO)]. The structures of the isolated compounds have been confirmed and identified by means of different spectral and physicochemical techniques including CHN analysis, 1 H & 13 C NMR, mass spectral analysis, molar conductivity measurement, UV-Vis, infrared, magnetic moment in addition to TGA technique. The infrared spectral results ascertained that the ligand acts as monobasic tridentate binding to the metal centers via deprotonated hydroxyl oxygen, azomethine and imidazole nitrogen atoms. The UV-Vis, magnetic susceptibility and molar conductivity data implied octahedral geometry for Co(II) & Ni(II) complexes, tetrahedral for Zn(II) complex and square planar for Cu(II) complex. X-ray structural analysis of Co(II) complex 1 has been reported and discussed. Moreover, the type of interaction between the ligand & its complexes towards salmon sperm DNA (SS-DNA) has been examined by the measurement of absorption spectra and viscosity which confirmed that the ligand and its complexes interact with DNA via intercalation interaction as concluded from the values of binding constants (K b ). Copyright © 2017 Elsevier B.V. All rights reserved.

Speciation in the aqueous H+/H2VO4-/H2O2/citrate system of biomedical interest.

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Gorzsás, András; Getty, Kendra; Andersson, Ingegärd; Pettersson, Lage

2004-09-21

The speciation in the quaternary aqueous H+/H2VO4-/H2O2/citrate (Cit3-) and H+/H2VO4-/Cit3-/L-(+)-lactate (Lac-) systems has been determined at 25 degrees C in the physiological medium of 0.150 M Na(Cl). A combination of 51V NMR integral intensities and chemical shift (Bruker AMX500) as well as potentiometric data (glass electrode) have been collected and evaluated with the computer program LAKE, which is able to treat multimethod data simultaneously. The pKa-values for citric acid have been determined as 2.94, 4.34 and 5.61. Altogether six vanadate-citrate species have been found in the ternary H+/H2VO4-/Cit3- system in the pH region 2-10, only two of which are mononuclear. Reduction of vanadium(V) becomes more pronounced at pH acidic solutions limited the final model to pH > 4. In the quaternary H+/H2VO4-/Cit3-/Lac- system, two mixed-ligand species have been determined, with the compositions V2CitLac2- and V2CitLac3- (pKa = 5.0). To our knowledge, this is the first time such complexes have been reported for vanadium(V). 51V NMR chemical shifts, compositions and formation constants are given, and equilibrium conditions are illustrated in distribution diagrams as well as the fit of the model to the experimental data. When suitable, structural proposals are given, based on 13C NMR measurements and available literature data of related compounds.

Utilization of plant-derived recombinant human β-defensins (hBD-1 and hBD-2) for averting salmonellosis.

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Patro, Sunita; Maiti, Soumitra; Panda, Santosh Kumar; Dey, Nrisingha

2015-04-01

We describe the use of plant-made β-defensins as effective antimicrobial substances for controlling salmonellosis, a deadly infection caused by Salmonella typhimurium (referred to further as S. typhi). Human β-defensin-1 (hBD-1) and -2 (hBD-2) were expressed under the control of strong constitutive promoters in tobacco plants, and bio-active β-defensins were successfully extracted. In the in vitro studies, enriched recombinant plant-derived human β-defensin-1 (phBD-1) and -2 (phBD-2) obtained from both T1 and T2 transgenic plants showed significant antimicrobial activity against Escherichia coli and S. typhi when used individually and in various combinations. The 2:1 peptide combination of phBD-1:phBD-2 with peptides isolated from T1-and T2-generation plants reduced the growth of S. typhi by 96 and 85 %, respectively. In vivo studies employing the mouse model (Balb/c) of Salmonella infection clearly demonstrated that the administration of plant-derived defensins individually and in different combinations enhanced the mean survival time of Salmonella-infected animals. When treatment consisted of the 2:1 phBD-1:phBD-2 combination, approximately 50 % of the infected mice were still alive at 206 h post-inoculation; the lowest number of viable S. typhi was observed in the liver and spleen of infected animals. We conclude that plant-made recombinant β-defensins (phBD-1 and phBD-2) are promising antimicrobial substances and have the potential to become additional tools against salmonellosis, particularly when used in combination.

Different Dimensional and Structural Variations in Coordination Compounds of Cadmium, Manganese and Nickel Constructed from the Ligand 2,2'-Bipyidine-3,3',6,6'-tetracarboxylic Acid (H{sub 4}bptc)

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Xiang, Jing; Yang, Tiantian; Fu, Lulu; Luo, Ya; Wu, Jiashou [Yangtze Univ., Jingzhou (China)

2013-09-15

The reactions of hydrated CdCl{sub 2}, MnCl{sub 2}, and NiCl{sub 2} with 2,2'-bipyidine-3,3',6,6'-tetracarboxylic acid (H{sub 4}bptc) afforded the mononuclear [Cd{sup II}(H{sub 2}bptc)(H{sub 2}O){sub 3}]·H{sub 2}O (1), linear [Cd(H{sub 2}bptc)(H{sub 2}O)]·3H{sub 2}O{sub n} (2), 3-D hetero-bimetallic [NaCd(Hbptc)(H{sub 2}O)] (3), layer [Mn(H{sub 2}bptc)(H{sub 2}O)]n (4) and a dinuclear compound [Ni{sub 2}(H{sub 2}bptc)-(H{sub 2}O){sub 2}]·6H{sub 2}O (5). These compounds have been characterized by elemental analysis, IR, and their structures have been determined by X-ray crystallography. The thermal stabilities of 1-3 were measured by thermogravimetric analysis (TGA) and their solid state luminescence properties together with the free ligand H{sub 4}bptc were investigated at room temperature.

Diaquabis[2,6-bis(4H-1,2,4-triazol-4-ylpyridine-κN2]bis(selenocyanato-κNcobalt(II

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Yuan-Yuan Liu

2012-08-01

Full Text Available In the title compound, [Co(NCSe2(C9H7N72(H2O2], the Co2+ cation is coordinated by two selenocyanate anions, two 2,6-bis(4H-1,2,4-triazol-4-ylpyridine ligands and two water molecules within a slightly distorted N4O2 octahedron. The asymmetric unit consists of one Co2+ cation, which is located on a center of inversion, as well as one selenocyanate anion, one 2,6-bis(4H-1,2,4-triazol-4-ylpyridine ligand and one water molecule in general positions. Intermolecular O—H...N hydrogen bonds join the complex molecules into layers parallel to the bc plane. The layers are linked by C—H...N and C—H...Se hydrogen bonds into a three-dimensional supramolecular architecture.

Oxidative degradation of the organometallic iron(II) complex [Fe{bis[3-(pyridin-2-yl)-1H-imidazol-1-yl]methane}(MeCN)(PMe3)](PF6)2: structure of the ligand decomposition product trapped via coordination to iron(II).

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Haslinger, Stefan; Pöthig, Alexander; Cokoja, Mirza; Kühn, Fritz E

2015-12-01

Iron is of interest as a catalyst because of its established use in the Haber-Bosch process and because of its high abundance and low toxicity. Nitrogen-heterocyclic carbenes (NHC) are important ligands in homogeneous catalysis and iron-NHC complexes have attracted increasing attention in recent years but still face problems in terms of stability under oxidative conditions. The structure of the iron(II) complex [1,1'-bis(pyridin-2-yl)-2,2-bi(1H-imidazole)-κN(3)][3,3'-bis(pyridin-2-yl-κN)-1,1'-methanediylbi(1H-imidazol-2-yl-κC(2))](trimethylphosphane-κP)iron(II) bis(hexafluoridophosphate), [Fe(C17H14N6)(C16H12N6)(C3H9P)](PF6)2, features coordination by an organic decomposition product of a tetradentate NHC ligand in an axial position. The decomposition product, a C-C-coupled biimidazole, is trapped by coordination to still-intact iron(II) complexes. Insights into the structural features of the organic decomposition products might help to improve the stability of oxidation catalysts under harsh conditions.

Novel aza-analogous ergoline derived scaffolds as potent serotonin 5-HT6 and dopamine D2 receptor ligands

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Krogsgaard-Larsen, Niels; Jensen, Anders A.; Schrøder, T.J.

2014-01-01

By introducing distal substituents on a tetracyclic scaffold resembling the ergoline structure, two series of analogues were achieved exhibiting subnanomolar receptor binding affinities for the dopamine D2 and serotonin 5-HT6 receptor subtype, respectively. While the 5-HT6 ligands were antagonists......, the D2 ligands displayed intrinsic activities ranging from full agonism to partial agonism with low intrinsic activity. These structures could potentially be interesting for treatment of neurological diseases such as schizophrenia, Parkinson’s disease, and cognitive deficits....

Synthesis, Photophysical and Electrochemical Properties of a Mixed Bipyridyl-Phenanthrolyl Ligand Ru(II Heteroleptic Complex Having trans-2-Methyl-2-butenoic Acid Functionalities

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Adewale O. Adeloye

2011-09-01

Full Text Available In this work, two ligands: 4-(trans-2-Methyl-2-butenoic acid-2,2'-bipyridine (L1 and 5-(trans-2-methyl-2-butenoic acid-1,10-phenanthroline (L2, with the corresponding mixed-ligand heteroleptic Ru(II complex were synthesized and characterized by FT-IR, 1H-, 13C-NMR spectroscopy and elemental analysis. The influence of the mixed functionalized polypyridyl ruthenium(II complex on the photophysical and electrochemical properties were investigated and compared to individual single-ligand homoleptic complexes. Interestingly, the mixed-ligand complex formulated as [RuL1L2(NCS2] exhibits broad and intense metal-to-ligand charge transfer (MLCT absorption with a high molar extinction coefficient (λmax = 514 nm, ε = 69,700 M−1 cm−1, better than those of individual single-ligand complexes, [Ru(L12(NCS2] and [Ru(L22(NCS2], and a strong photoluminescence intensity ratio in the red region at λem = 686 nm. The electrochemical properties of the complex indicated that the redox processes are ligand-based.

Zinc(II) halide complexes with 2-methoxyaniline ligand: Synthesis, characterization, thermal analyses, crystal structure determination and luminescent properties

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Amani, Vahid

2018-03-01