Formation of doubly and triply bonded unsaturated compounds HCN, HNC, and CH2NH via N + CH4 low-temperature solid state reaction: from molecular clouds to solar system objects

Science.gov (United States)

Mencos, Alejandro; Krim, Lahouari

2018-06-01

We show in the current study carried out in solid phase at cryogenic temperatures that methane (CH4) ice exposed to nitrogen atoms is a source of two acids HCN, HNC, and their corresponding hydrogenated unsaturated species CH2NH, in addition to CH3, C2H6, CN-, and three nitrogen hydrides NH, NH2, and NH3. The solid state N + CH4 reaction taken in the ground state seems to be strongly temperature dependent. While at temperatures lower than 10 K only CH3, NH, NH2, and NH3 species formation is promoted due to CH bond dissociation and NH bond formation, stable compounds with CN bonds are formed at temperatures ranged between 10 and 40 K. Many of these reaction products, resulting from CH4 + N reaction, have already been observed in N2-rich regions such as the atmospheres of Titan, Kuiper belt objects, and molecular clouds of the interstellar medium. Our results show the power of the solid state N-atom chemistry in the transformation of simple astrochemical relevant species, such as CH4 molecules and N atoms into complex organic molecules which are also potentially prebiotic species.

Molecularly Tuning the Radicaloid N-H···O═C Hydrogen Bond.

Science.gov (United States)

Lu, Norman; Chung, Wei-Cheng; Ley, Rebecca M; Lin, Kwan-Yu; Francisco, Joseph S; Negishi, Ei-Ichi

2016-03-03

Substituent effects on the open shell N-H···O═C hydrogen-bond has never been reported. This study examines how 12 functional groups composed of electron donating groups (EDG), halogen atoms and electron withdrawing groups (EWG) affect the N-H···O═C hydrogen-bond properties in a six-membered cyclic model system of O═C(Y)-CH═C(X)N-H. It is found that group effects on this open shell H-bonding system are significant and have predictive trends when X = H and Y is varied. When Y is an EDG, the N-H···O═C hydrogen-bond is strengthened; and when Y is an EWG, the bond is weakened; whereas the variation in electronic properties of X group do not exhibit a significant impact upon the hydrogen bond strength. The structural impact of the stronger N-H···O═C hydrogen-bond are (1) shorter H and O distance, r(H···O) and (2) a longer N-H bond length, r(NH). The stronger N-H···O═C hydrogen-bond also acts to pull the H and O in toward one another which has an effect on the bond angles. Our findings show that there is a linear relationship between hydrogen-bond angle and N-H···O═C hydrogen-bond energy in this unusual H-bonding system. In addition, there is a linear correlation of the r(H···O) and the hydrogen bond energy. A short r(H···O) distance corresponds to a large hydrogen bond energy when Y is varied. The observed trends and findings have been validated using three different methods (UB3LYP, M06-2X, and UMP2) with two different basis sets.

Cooperativity of hydrogen-bonded networks in 7-azaindole(CH3OH)n (n=2,3) clusters evidenced by IR-UV ion-dip spectroscopy and natural bond orbital analysis.

Science.gov (United States)

Sakota, Kenji; Kageura, Yutaka; Sekiya, Hiroshi

2008-08-07

IR-UV ion-dip spectra of the 7-azaindole (7AI)(CH(3)OH)(n) (n=1-3) clusters have been measured in the hydrogen-bonded NH and OH stretching regions to investigate the stable structures of 7AI(CH(3)OH)(n) (n=1-3) in the S(0) state and the cooperativity of the H-bonding interactions in the H-bonded networks. The comparison of the IR-UV ion-dip spectra with IR spectra obtained by quantum chemistry calculations shows that 7AI(CH(3)OH)(n) (n=1-3) have cyclic H-bonded structures, where the NH group and the heteroaromatic N atom of 7AI act as the proton donor and proton acceptor, respectively. The H-bonded OH stretch fundamental of 7AI(CH(3)OH)(2) is remarkably redshifted from the corresponding fundamental of (CH(3)OH)(2) by 286 cm(-1), which is an experimental manifestation of the cooperativity in H-bonding interaction. Similarly, two localized OH fundamentals of 7AI(CH(3)OH)(3) also exhibit large redshifts. The cooperativity of 7AI(CH(3)OH)(n) (n=2,3) is successfully explained by the donor-acceptor electron delocalization interactions between the lone-pair orbital in the proton acceptor and the antibonding orbital in the proton donor in natural bond orbital (NBO) analyses.

Formation mechanism of Al-depleted bands in MOVPE-AlGaN layer on GaN template with trenches

Energy Technology Data Exchange (ETDEWEB)

Kuwano, Noriyuki [Art, Science and Technology Center for Cooperative Research, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Department of Applied Science for Electronics and Materials, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Ezaki, Tetsuya; Kurogi, Takuya [Department of Applied Science for Electronics and Materials, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Miyake, Hideto; Hiramatsu, Kazumasa [Department of Electrical and Electronic Engineering, Mie University, Tsu, Mie 514-8507 (Japan)

2010-07-15

A microstructure in an AlGaN/GaN layer was analyzed in detail by means of transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with special attention to the formation of steps on the surface. The AlGaN layer was grown by MOVPE on a GaN template with periodic trenches. It was revealed that there formed were Al-depleted bands in the AlGaN layer. These bands were generated from rather lower regions in the AlGaN layer or those above the trenches, and run upwards. Some of them reached the top surface to connect a macro step. The formation mechanism of the Al-depleted region is discussed in terms of thermodynamics. If the total bonding energy of atoms on the macro step of surface is assumed to be smaller than that of atoms on a flat surface, the Al-depletion can be explained provided that the local equilibrium in concentration is conserved during the growth of AlGaN layer. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Determination of wafer bonding mechanisms for plasma activated SiN films with x-ray reflectivity

Energy Technology Data Exchange (ETDEWEB)

Hayashi, S [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Sandhu, R [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Wojtowicz, M [Northrop Grumman Space Technology, Redondo Beach, CA 90278 (United States); Sun, Y [Department of Chemical Engineering, University of California, Los Angeles, CA 90095 (United States); Hicks, R [Department of Chemical Engineering, University of California, Los Angeles, CA 90095 (United States); Goorsky, M S [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States)

2005-05-21

Specular and diffuse x-ray reflectivity measurements were employed for wafer bonding studies of surface and interfacial reactions in {approx}800 A thick SiN films deposited on III-V substrates. CuK{sub {alpha}}{sub 1} radiation was employed for these measurements. The as-deposited films show very low surface roughness and uniform, high density SiN. Reflectivity measurements show that an oxygen plasma treatment converts the nitride surface to a somewhat porous SiO{sub x} layer (67 A thick, at 80% of SiO{sub 2} density), with confirmation of the oxide formation from x-ray photoelectron spectroscopy. Reactions at the bonded interface of two oxygen plasma treated SiN layers were examined using a bonded structure from which one of the III-V wafers is removed. Reflectivity measurements of bonded structures annealed at 150 deg. C and 300 deg. C show an increase in the SiO{sub x} layer density and thickness and even a density gradient across this interface. The increase in density is correlated with an increase in bond strength, where after the 300 deg. C anneal, a high interfacial bond strength, exceeding the bulk strength, was achieved.

Ge nitride formation in N-doped amorphous Ge2Sb2Te5

International Nuclear Information System (INIS)

Jung, M.-C.; Lee, Y. M.; Kim, H.-D.; Kim, M. G.; Shin, H. J.; Kim, K. H.; Song, S. A.; Jeong, H. S.; Ko, C. H.; Han, M.

2007-01-01

The chemical state of N in N-doped amorphous Ge 2 Sb 2 Te 5 (a-GST) samples with 0-14.3 N at. % doping concentrations was investigated by high-resolution x-ray photoelectron spectroscopy (HRXPS) and Ge K-edge x-ray absorption spectroscopy (XAS). HRXPS showed negligible change in the Te 4d and Sb 4d core-level spectra. In the Ge 3d core-level spectra, a Ge nitride (GeN x ) peak developed at the binding energy of 30.2 eV and increased in intensity as the N-doping concentration increased. Generation of GeN x was confirmed by the Ge K-edge absorption spectra. These results indicate that the N atoms bonded with the Ge atoms to form GeN x , rather than bonding with the Te or Sb atoms. It has been suggested that the formation of Ge nitride results in increased resistance and phase-change temperature

Synthesis of 1,2,4-Triazoles via Oxidative Heterocyclization: Selective C-N Bond Over C-S Bond Formation.

Science.gov (United States)

Gogoi, Anupal; Guin, Srimanta; Rajamanickam, Suresh; Rout, Saroj Kumar; Patel, Bhisma K

2015-09-18

The higher propensity of C-N over C-S bond forming ability was demonstrated, through formal C-H functionalization during the construction of 4,5-disubstituted 1,2,4-triazole-3-thiones from arylidenearylthiosemicarbazides catalyzed by Cu(II). However, steric factors imparted by the o-disubstituted substrates tend to change the reaction path giving thiodiazole as the major or an exclusive product. Upon prolonging the reaction time, the in situ generated thiones are transformed to 4,5-disubstituted 1,2,4-triazoles via a desulfurization process. Two classes of heterocycles viz. 4,5-disubstituted 1,2,4-triazole-3-thiones and 4,5-disubstituted 1,2,4-triazoles can be synthesized from arylidenearylthiosemicarbazides by simply adjusting the reaction time. Desulfurization of 1,2,4-triazole-3-thiones is assisted by thiophilic Cu to provide 1,2,4-triazoles with concomitant formation of CuS and polynuclear sulfur anions as confirmed from scanning electron microscope and energy dispersive X-ray spectroscopy measurements. A one-pot synthesis of an antimicrobial compound has been successfully achieved following this strategy.

Interfacial microstructure of partial transient liquid phase bonded Si3N4-to-Inconel 718 joints

International Nuclear Information System (INIS)

Kim, Jae Joong; Park, Jin-Woo; Eagar, Thomas W.

2003-01-01

This work presents transmission electron microscopy (TEM) analysis of the interfacial microstructure in Si 3 N 4 -to-Inconel 718 joints with Ni interlayers produced by partial transient liquid phase bonding (PTLPB). Ti and Cu microfoils have been inserted between Si 3 N 4 and the Ni interlayer and joining has been performed at lower temperatures than previous PTLPBs of Si 3 N 4 with the same insert metals. The TEM work is focused on phase identification of the reaction layers between the Si 3 N 4 and the Ni interlayer. According to the TEM analysis, most of the Cu precipitates without reacting with Ti and Ni. Si diffused in the filler metal and thin reaction layer formed at the interface between Si 3 N 4 and the filler metal producing good bond-formation and hence, high interfacial strength. No interfacial fractures occurred after cooling from the bonding temperature of 900 deg. C, which supports the results observed in the TEM analysis. This work confirms that this joining process can produce a more heat resistant Si 3 N 4 -to-Inconel 718 joint than active brazing using Ag-Cu-Ti alloys

Hydrogen bonding donation of N-methylformamide with dimethylsulfoxide and water

Science.gov (United States)

Borges, Alexandre; Cordeiro, João M. M.

2013-04-01

20% N-methylformamide (NMF) mixtures with water and with dimethylsulfoxide (DMSO) have been studied. A comparison between the hydrogen bonding (H-bond) donation of N-methylformamide with both solvents in the mixtures is presented. Results of radial distribution functions, pair distribution energies, molecular dipole moment correlation, and geometry of the H-bonded species in each case are shown. The results indicate that the NMF - solvent H-bond is significantly stronger with DMSO than with water. The solvation shell is best organized in the DMSO mixture than in the aqueous one.

1H-1H correlations across N-H···N hydrogen bonds in nucleic acids

International Nuclear Information System (INIS)

Majumdar, Ananya; Gosser, Yuying; Patel, Dinshaw J.

2001-01-01

In 2H J NN -COSY experiments, which correlate protons with donor/acceptor nitrogens across N d ···HN a bonds, the receptor nitrogen needs to be assigned in order to unambiguously identify the hydrogen bond. For many situations this is a non-trivial task which is further complicated by poor dispersion of (N a ,N d ) resonances. To address these problems, we present pulse sequences to obtain direct, internucleotide correlations between protons in uniformly 13 C/ 15 N labeled nucleic acids containing N d ···HN a hydrogen bonds. Specifically, the pulse sequence H2(N1N3)H3 correlates H2(A,ω 1 ):H3(U,ω 2 ) protons across Watson-Crick A-U and mismatched G·A base pairs, the sequences H5(N3N1)H1/H6(N3N1)H1 correlate H5(C,ω 1 )/H6(C,ω 1 ):H1(G,ω 2 ) protons across Watson-Crick G-C base pairs, and the H 2 (N2N7)H8 sequence correlates NH 2 (G,A,C;ω 1 ):H8(G,A;ω 2 ) protons across G·G, A·A, sheared G·A and other mismatch pairs. These 1 H- 1 H connectivities circumvent the need for independent assignment of the donor/acceptor nitrogen and related degeneracy issues associated with poorly dispersed nitrogen resonances. The methodology is demonstrated on uniformly 13 C/ 15 N labeled samples of (a) an RNA regulatory element involving the HIV-1 TAR RNA fragment, (b) a multi-stranded DNA architecture involving a G·(C-A) triad-containing G-quadruplex and (c) a peptide-RNA complex involving an evolved peptide bound to the HIV-1 Rev response element (RRE) RNA fragment

Supra-molecular hydrogen-bonding patterns in the N(9)-H protonated and N(7)-H tautomeric form of an N(6) -benzoyl-adenine salt: N (6)-benzoyl-adeninium nitrate.

Science.gov (United States)

Karthikeyan, Ammasai; Jeeva Jasmine, Nithianantham; Thomas Muthiah, Packianathan; Perdih, Franc

2016-02-01

In the title molecular salt, C12H10N5O(+)·NO3 (-), the adenine unit has an N (9)-protonated N(7)-H tautomeric form with non-protonated N(1) and N(3) atoms. The dihedral angle between the adenine ring system and the phenyl ring is 51.10 (10)°. The typical intra-molecular N(7)-H⋯O hydrogen bond with an S(7) graph-set motif is also present. The benzoyl-adeninium cations also form base pairs through N-H⋯O and C-H⋯N hydrogen bonds involving the Watson-Crick face of the adenine ring and the C and O atoms of the benzoyl ring of an adjacent cation, forming a supra-molecular ribbon with R 2 (2)(9) rings. Benzoyl-adeninum cations are also bridged by one of the oxygen atoms of the nitrate anion, which acts as a double acceptor, forming a pair of N-H⋯O hydrogen bonds to generate a second ribbon motif. These ribbons together with π-π stacking inter-actions between the phenyl ring and the five- and six-membered adenine rings of adjacent mol-ecules generate a three-dimensional supra-molecular architecture.

N-Oxide-N-oxide interactions and Cl...Cl halogen bonds in pentachloropyridine N-oxide: the many-body approach to interactions in the crystal state.

Science.gov (United States)

Wzgarda-Raj, Kinga; Rybarczyk-Pirek, Agnieszka J; Wojtulewski, Sławomir; Palusiak, Marcin

2018-02-01

Pentachloropyridine N-oxide, C 5 Cl 5 NO, crystallizes in the monoclinic space group P2 1 /c. In the crystal structure, molecules are linked by C-Cl...Cl halogen bonds into infinite ribbons extending along the crystallographic [100] direction. These molecular aggregates are further stabilized by very short intermolecular N-oxide-N-oxide interactions into herringbone motifs. Computations based on quantum chemistry methods allowed for a more detailed description of the N-oxide-N-oxide interactions and Cl...Cl halogen bonds. For this purpose, Hirshfeld surface analysis and the many-body approach to interaction energy were applied.

Studies of Hydrogen Bonding Between N, N-Dimethylacetamide and Primary Alcohols

Directory of Open Access Journals (Sweden)

M. S. Manjunath

2009-01-01

Full Text Available Hydrogen bonding between N, N-dimethylacetamide (DMA and alcohols has been studied in carbon tetrachloride solution by an X-band Microwave bench at 936GHz. The dielectric relaxation time (τ of the binary system are obtained by both Higasi's method and Gopalakrishna method. The most likely association complex between alcohol and DMA is 1:1 stoichiometric complex through the hydroxyl group of the alcohol and the carbonyl group of amide. The results show that the interaction between alcohols and amides is 1:1 complex through the free hydroxyl group of the alcohol and the carbonyl group of amide and the alkyl chain-length of both the alcohols and amide plays an important role in the determination of the strength of hydrogen bond (O-H: C=O formed and suggests that the proton donating ability of alcohols is in the order: 1-propanol < 1-butanol < 1-pentanol and the accepting ability of DMA.

Renewable Formate from C-H Bond Formation with CO2: Using Iron Carbonyl Clusters as Electrocatalysts.

Science.gov (United States)

Loewen, Natalia D; Neelakantan, Taruna V; Berben, Louise A

2017-09-19

As a society, we are heavily dependent on nonrenewable petroleum-derived fuels and chemical feedstocks. Rapid depletion of these resources and the increasingly evident negative effects of excess atmospheric CO 2 drive our efforts to discover ways of converting excess CO 2 into energy dense chemical fuels through selective C-H bond formation and using renewable energy sources to supply electrons. In this way, a carbon-neutral fuel economy might be realized. To develop a molecular or heterogeneous catalyst for C-H bond formation with CO 2 requires a fundamental understanding of how to generate metal hydrides that selectively donate H - to CO 2 , rather than recombining with H + to liberate H 2 . Our work with a unique series of water-soluble and -stable, low-valent iron electrocatalysts offers mechanistic and thermochemical insights into formate production from CO 2 . Of particular interest are the nitride- and carbide-containing clusters: [Fe 4 N(CO) 12 ] - and its derivatives and [Fe 4 C(CO) 12 ] 2- . In both aqueous and mixed solvent conditions, [Fe 4 N(CO) 12 ] - forms a reduced hydride intermediate, [H-Fe 4 N(CO) 12 ] - , through stepwise electron and proton transfers. This hydride selectively reacts with CO 2 and generates formate with >95% efficiency. The mechanism for this transformation is supported by crystallographic, cyclic voltammetry, and spectroelectrochemical (SEC) evidence. Furthermore, installation of a proton shuttle onto [Fe 4 N(CO) 12 ] - facilitates proton transfer to the active site, successfully intercepting the hydride intermediate before it reacts with CO 2 ; only H 2 is observed in this case. In contrast, isoelectronic [Fe 4 C(CO) 12 ] 2- features a concerted proton-electron transfer mechanism to form [H-Fe 4 C(CO) 12 ] 2- , which is selective for H 2 production even in the presence of CO 2 , in both aqueous and mixed solvent systems. Higher nuclearity clusters were also studied, and all are proton reduction electrocatalysts, but none

The Co-III-C bond in (1-thia-4,7-diazacyclodecyl-kappa N-3(4),N-7,C-10)(1,4,7-triazacyclononane-kappa N-3(1),N-4,N-7)-cobalt(III) dithionate hydrate

DEFF Research Database (Denmark)

Harris, Pernille; Kofod, P.; Song, Y.S.

2003-01-01

In the title compound, [Co(C6H15N3)(C7H15N2S)]S2O6.H2O, the Co-C bond distance is 1.9930 (13) Angstrom, which is shorter than for related compounds with the linear 1,6-diamino-3-thiahexan-4-ide anion in place of the macrocyclic 1-thia-4,7-diazacyclodecan-8-ide anion. The coordinated carbanion pro...... produces an elongation of 0.102 (7) Angstrom of the Co-N bond to the 1,4,7-triazacyclononane N atom in the trans position. This relatively small trans influence is presumably a result of the triamine ligand forming strong bonds to the Co-III atom....

Designing new catalytic C-C and C-N bond formations promoted by organoactinides

International Nuclear Information System (INIS)

Eisen, M.S.; Straub, T.; Haskel, A.

1998-01-01

Organoactinides of the type Cp 2 * AcMe 2 (Cp * =C 5 Me 5 ; Ac=Th; U) are active catalytic precursors for the oligomerization of terminal alkynes HC≡CR (R=alkyl, aryl, SiMe 3 ). The regioselectivity and the extent of oligomerization depend strongly on the alkyne substituent R, whereas the catalytic reactivity is similar for both organoactinides. Reaction with tert-butylacetylene yields regioselectively the E-2,4-disubstituted 1-buten-3-yne dimer whereas trimethylsilylacetylene is regioselective trimerized to the E,E-1,4,6-tris(trimethylsilyl)-1,3-hexa diene-5-yne, with small amounts (3-5%) of the corresponding E-2,4-disubstituted 1-buten-3-yne dimer. Oligomerization with less bulky alkyl and aryl substituted alkynes produces a mixture of higher oligomers with no regioselectivity. Using the Cp 2 * ThMe 2 catalyst, we have recently developed a strategic method to control the extent and in some cases the regioselectivity of the catalyzed oligomerization of nonbulky terminal alkynes to dimers and/or trimers. The metallocene catalytic precursors ensure the selective synthesis of small oligomers by the addition of specific amines. Catalytic ''tailoring'' to dimer and trimers can be achieved by using small or bulky amines, respectively. Kinetic and mechanistic data for the controlling experiments argue that the turnover-limiting step involves the acetylide actinide complex formation with the rapid insertion of the alkyne and protonolysis by the amine. The analog Cp 2 * UMe 2 in the presence of primary amines induce the selective C-N bond formation, producing enamines which are tautomerized to the corresponding imines. (orig.)

Microstructure and Properties of Porous Si3N4/Dense Si3N4 Joints Bonded Using RE–Si–Al–O–N (RE = Y or Yb Glasses

Directory of Open Access Journals (Sweden)

Ling Li

2017-11-01

Full Text Available The joining of porous Si3N4 to dense Si3N4 ceramics has been successfully performed using mixed RE2O3 (RE = Y or Yb, Al2O3, SiO2, and α-Si3N4 powders. The results suggested that the α-Si3N4 powders partly transformed into β-SiAlON and partly dissolved into oxide glass to form oxynitride glass. Thus, composites of glass/β-SiAlON-ceramic formed in the seam of joints. Due to the capillary action of the porous Si3N4 ceramic, the molten glass solder infiltrated into the porous Si3N4 ceramic side during the joining process and formed the “infiltration zone” with a thickness of about 400 μm, which contributed to the heterogeneous distribution of the RE–Si–Al–O–N glasses in the porous Si3N4 substrate. In-situ formation of β-SiAlON in the seam resulted in a high bonding strength. The maximum bending strength of 103 MPa and 88 MPa was reached for the porous Si3N4/dense Si3N4 joints using Y–Si–Al–O–N and Yb–Si–Al–O–N glass solders, respectively.

[Effects of magnetron sputtered ZrN on the bonding strength of titanium porcelain].

Science.gov (United States)

Zhou, Shu; Zhang, Wen-yan; Guang, Han-bing; Xia, Yang; Zhang, Fei-min

2009-04-01

To investigate the effect of magnetron sputtered ZrN on the bonding strength between a low-fusing porcelain (Ti/Vita titankeramik system) and commercially pure cast titanium. Sixteen specimens were randomly assigned to test group and control group (n=8). The control group received no surface treated. Magnetron sputtered ZrN film was deposited on the surface of specimens in the test group. Then the sixteen titanium-porcelain specimens were prepared in a rectangular shape and went through three-point bending test on a universal test machine. The bond strength of Ti/porcelain was recorded. The phase composition of the specimens was analyzed using X-ray diffraction (XRD). The interface at titanium and porcelain and the titanium surface after debonding were observed with a scanning electron microscopy (SEM) and analyzed using energy depressive spectrum (EDS). New phase of ZrN was found with XRD in the test group. Statistical analysis showed higher bond strength following ZrN surface treatment in the test group [(45.991+/-0.648) MPa] than that in the control group [(29.483+/-1.007) MPa] (P=0.000). Bonded ceramic could be observed in test group, the amount of bonded ceramic was more than that in the control group. No obvious bonded ceramic in control group was found. Magnetron sputtered ZrN can improve bond strength of Ti/Vita titankeramik system significantly.

A green non-acid-catalyzed process for direct N=N-C group formation: comprehensive study, modeling, and optimization.

Science.gov (United States)

Khakyzadeh, Vahid; Zolfigol, Mohammad Ali; Derakhshan-Panah, Fatemeh; Jafarian, Majid; Miri, Mir Vahid; Gilandoust, Maryam

2018-01-04

The aim of this work is to introduce, model, and optimize a new non-acid-catalyzed system for a direct N[Formula: see text]N-C bond formation. By reacting naphthols or phenol with anilines in the presence of the sodium nitrite as nitrosonium ([Formula: see text] source and triethylammonium acetate (TEAA), a N[Formula: see text]N-C group can be formed in non-acid media. Modeling and optimization of the reaction conditions were investigated by response surface method. Sodium nitrite, TEAA, and water were chosen as variables, and reaction yield was also monitored. Analysis of variance indicates that a second-order polynomial model with F value of 35.7, a P value of 0.0001, and regression coefficient of 0.93 is able to predict the response. Based on the model, the optimum process conditions were introduced as 2.2 mmol sodium nitrite, 2.2 mL of TEAA, and 0.5 mL [Formula: see text] at room temperature. A quadratic (second-order) polynomial model, by analysis of variance, was able to predict the response for a direct N=N-C group formation. Predicted response values were in good agreement with the experimental values. Electrochemistry studies were done to introduce new Michael acceptor moieties. Broad scope, high yields, short reaction time, and mild conditions are some advantages of the presented method.

The formation of hexagonal-shaped InGaN-nanodisk on GaN-nanowire observed in plasma source molecular beam epitaxy

KAUST Repository

Ng, Tien Khee

2014-03-08

We report on the properties and growth kinetics of defect-free, photoluminescence (PL) efficient mushroom-like nanowires (MNWs) in the form of ~30nm thick hexagonal-shaped InGaN-nanodisk on GaN nanowires, coexisting with the conventional rod-like InGaN-on-GaN nanowires (RNWs) on (111)-silicon-substrate. When characterized using confocal microscopy (CFM) with 458nm laser excitation, while measuring spontaneous-emission at fixed detection wavelengths, the spatial intensity map evolved from having uniform pixelated emission, to having only an emission ring, and then a round emission spot. This corresponds to the PL emission with increasing indium composition; starting from emission mainly from the RNW, and then the 540 nm emission from one MNWs ensemble, followed by the 590 nm emission from a different MNW ensemble, respectively. These hexagonal-shaped InGaN-nano-disks ensembles were obtained during molecular-beam-epitaxy (MBE) growth. On the other hand, the regular rod-like InGaN-on-GaN nanowires (RNWs) were emitting at a shorter peak wavelength of 490 nm. While the formation of InGaN rod-like nanowire is well-understood, the formation of the hexagonal-shaped InGaN-nanodisk-on-GaN-nanowire requires further investigation. It was postulated to arise from the highly sensitive growth kinetics during plasma-assisted MBE of InGaN at low temperature, i.e. when the substrate temperature was reduced from 800 °C (GaN growth) to <600 °C (InGaN growth), during which sparsely populated metal-droplet formation prevails and further accumulated more indium adatoms due to a higher cohesive bond between metallic molecules. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Efficient C-O and C-N bond forming cross-coupling reactions catalyzed by core-shell structured Cu/Cu2O nanowires

KAUST Repository

Elshewy, Ahmed M.

2013-12-01

Oxygen and Nitrogen containing compounds are of utmost importance due to their interesting and diverse biological activities. The construction of the C-O and C–N bonds is of significance as it opens avenues for the introduction of ether and amine linkages in organic molecules. Despite significant advancements in this field, the construction of C-O and C–N bonds is still a major challenge for organic chemists, due to the involvement of harsh reaction conditions or the use of expensive catalysts or ligands in many cases. Thus, it is a challenge to develop alternative, milder, cheaper and more reproducible methodologies for the construction of these types of bonds. Herein, we introduce a new efficient ligand free catalytic system for C-O and C-N bond formation reactions.

Tug-of-war between classical and multicenter bonds in H-(Be)n-H species

Science.gov (United States)

Lundell, Katie A.; Boldyrev, Alexander I.

2018-05-01

Quantum chemical calculations were performed for beryllium homocatenated compounds [H-(Be)n-H]. Global minimum structures were found using machine searches (Coalescence Kick method) with density functional theory. Chemical bonding analysis was performed with the Adaptive Natural Density Partitioning method. It was found that H-(Be)2-H and H-(Be)3-H clusters are linear with classical two-center two-electron bonds, while for n > 3, three-dimensional structures are more stable with multicenter bonding. Thus, at n = 4, multicenter bonding wins the tug-of-war vs. the classical bonding.

Theoretical study of the mechanism of formation of a chemical bond between two ions: A+ and B+. Application to CO++. Interpretation of N2O++ photo-dissociation mechanisms

International Nuclear Information System (INIS)

Levasseur, Nathalie

1989-01-01

This research thesis reports the theoretical study of the mechanism of formation of a chemical bond between two positively charged species, within the frame of the valence-bond theory and in the CO model case. The analysis in terms of orthogonal and non orthogonal orbitals leads to two very different interpretations, and allows potential curves of doubly charged diatomic ions to be simply explained, the generally evoked model to be put into question again, and a predictive model to be developed. The theoretical determination of N 2 O potential energy surfaces and of the first states of N 2 O ++ ( 3 Σ - , 1 Δ, 1 Σ + et 3 Π) allowed experimental results of N 2 O ++ photo-dissociation to be at least qualitatively understood and interpreted. Moreover, the study of electronic configurations involved in dissociation, showed that the model elaborated for a diatomic molecule is also valid for a triatomic system [fr

Barrier reduction via implementation of InGaN interlayer in wafer-bonded current aperture vertical electron transistors consisting of InGaAs channel and N-polar GaN drain

International Nuclear Information System (INIS)

Kim, Jeonghee; Laurent, Matthew A.; Li, Haoran; Lal, Shalini; Mishra, Umesh K.

2015-01-01

This letter reports the influence of the added InGaN interlayer on reducing the inherent interfacial barrier and hence improving the electrical characteristics of wafer-bonded current aperture vertical electron transistors consisting of an InGaAs channel and N-polar GaN drain. The current-voltage characteristics of the transistors show that the implementation of N-polar InGaN interlayer effectively reduces the barrier to electron transport across the wafer-bonded interface most likely due to its polarization induced downward band bending, which increases the electron tunneling probability. Fully functional wafer-bonded transistors with nearly 600 mA/mm of drain current at V GS  = 0 V and L go  = 2 μm have been achieved, and thus demonstrate the feasibility of using wafer-bonded heterostructures for applications that require active carrier transport through both materials

14N NQR study of hydrogen bonded complexes of 1,4 diazabicyclo [2,2,2] octane (ted) with phenols and thiourea

Science.gov (United States)

Murgich, Juan; Magaly, Santana R.; Diaz, Olga E.

The 14N NQR spectra of H bonded complexes of 1,4 diazabicyclo [2,2,2] octane, also known as triethylenediamine (TED), with phenol (1:2), p-chlorophenol (1:2), p-nitrophenol (1:2), hydroquinone (1:1), resorcinol (1:1) and thiourea (1:2) were observed at 77 K. The 14N frequency shifts produced by the H bonds in the TED complexes were approximately two times larger than those found for similar complexes of Hexamethylenetetramine (HMT). Such change was explained by the effect on the remaining N atoms of the increase in the number of -CH 2- groups and the decrease in N atoms in passing from HMT to TED. From the above results it seems that the inductive effect plays an important role in the formation of H bonds in tertiary amines like HMT and TED.

Molecularly oriented surface relief formation in polymethacrylates comprising N-benzylideneaniline derivative side groups

Science.gov (United States)

Kawatsuki, Nobuhiro; Hosoda, Risa; Kondo, Mizuho; Sasaki, Tomoyuki; Ono, Hiroshi

2014-12-01

Molecularly oriented surface relief (SR) formation in polymethacrylates with N-benzylideneaniline (NBA) derivative side groups is investigated by holographic exposure using a 325 nm He-Cd laser. Because the NBA moieties show a photoinduced orientation perpendicular to the polarization of light, polarization holography successfully forms a molecularly oriented SR structure in accordance with the polarization distribution that includes p-polarized components. Although intensity holography induces molecular orientation, it does not generate a satisfactory SR structure. In all the holographic modes, the SR depth depends on the direction of the C=N bonds in the NBA moieties and the photoproducts affect the SR formation ability.

Crystal structure of N′′-benzyl-N′′-[3-(benzyldimethylazaniumylpropyl]-N,N,N′,N′-tetramethylguanidinium bis(tetraphenylborate

Directory of Open Access Journals (Sweden)

Ioannis Tiritiris

2015-12-01

Full Text Available In the crystal structure of the title salt, C24H38N42+·2C24H20B−, the C—N bond lengths in the central CN3 unit of the guanidinium ion are 1.3364 (13, 1.3407 (13 and 1.3539 (13 Å, indicating partial double-bond character. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry and the positive charge is delocalized in the CN3 plane. The bonds between the N atoms and the terminal methyl groups of the guanidinium moiety and the four C—N bonds to the central N atom of the (benzyldimethylazaniumylpropyl group have single-bond character. In the crystal, C—H...π interactions between the guanidinium H atoms and the phenyl C atoms of the tetraphenylborate ions are present, leading to the formation of a two-dimensional supramolecular pattern parallel to the ac plane.

Ionic ASi{sub 2}N{sub 3} (A=Li, Na, K and Rb) stabilized by the covalent Si–N bonding: First-principles calculations

Energy Technology Data Exchange (ETDEWEB)

Zhang, Huijun [College of Information Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Ren, Jiadong, E-mail: jdren@ysu.edu.cn [College of Information Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Wu, Lailei [Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Zhang, Jingwu, E-mail: zjw@ysu.edu.cn [Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004 (China)

2017-01-15

The structural, elastic and electronic properties of LiSi{sub 2}N{sub 3} and its substitutions by Na, K and Rb were investigated through first-principles computations. The expansion of lattice parameters of ASi{sub 2}N{sub 3} from Li, Na, K to Rb is found to be determined by the bond angle of Si–N1–Si, which suggests a possible way to improve the lithium ionic conductivity by substitutions. ASi{sub 2}N{sub 3} (A=Li, Na, K and Rb) shows the similar elastic behaviors, while the electronic band gap gradually decreases from 5.1 to 3.4 eV from LiSi{sub 2}N{sub 3} to RbSi{sub 2}N{sub 3}. Interestingly, the analysis of electronic structure, crystal orbital Hamiltonian populations and Bader charges shows that the covalence of Si–N bonding is critical for the stability of ASi{sub 2}N{sub 3} phase. Among ASi{sub 2}N{sub 3} phases, there is a relatively high ionicity in NaSi{sub 2}N{sub 3}; the Si–N bond strength in [Si{sub 2}N{sub 3}]{sup −} net for KSi{sub 2}N{sub 3} and RbSi{sub 2}N{sub 3} is comparable to LiSi{sub 2}N{sub 3}, but stronger than NaSi{sub 2}N{sub 3}. - Graphic abstract: Universal trend of structural and electronic properties in alkaline metal silicon nitrides, ASi{sub 2}N{sub 3}, A=Li, Na, K and Rb. - Highlights: • Trend in structure, electronic and mechanical properties of ASi{sub 2}N{sub 3} (A=Li-Rb) were predicted. • Lattice expansion of ASi{sub 2}N{sub 3} induced by the bond angle of Si–N1–Si was found. • Calculated band gap decreases from 5.1 to 3.4 eV from LiSi{sub 2}N{sub 3} to RbSi{sub 2}N{sub 3}. • Covalent Si–N bonding is critical for the stability of ASi{sub 2}N{sub 3}.

Computational and Empirical Trans-hydrogen Bond Deuterium Isotope Shifts Suggest that N1-N3 A:U Hydrogen Bonds of RNA are Shorter than those of A:T Hydrogen Bonds of DNA

International Nuclear Information System (INIS)

Kim, Yong-Ick; Manalo, Marlon N.; Perez, Lisa M.; LiWang, Andy

2006-01-01

Density functional theory calculations of isolated Watson-Crick A:U and A:T base pairs predict that adenine 13 C2 trans-hydrogen bond deuterium isotope shifts due to isotopic substitution at the pyrimidine H3, 2h Δ 13 C2, are sensitive to the hydrogen-bond distance between the N1 of adenine and the N3 of uracil or thymine, which supports the notion that 2h Δ 13 C2 is sensitive to hydrogen-bond strength. Calculated 2h Δ 13 C2 values at a given N1-N3 distance are the same for isolated A:U and A:T base pairs. Replacing uridine residues in RNA with 5-methyl uridine and substituting deoxythymidines in DNA with deoxyuridines do not statistically shift empirical 2h Δ 13 C2 values. Thus, we show experimentally and computationally that the C7 methyl group of thymine has no measurable affect on 2h Δ 13 C2 values. Furthermore, 2h Δ 13 C2 values of modified and unmodified RNA are more negative than those of modified and unmodified DNA, which supports our hypothesis that RNA hydrogen bonds are stronger than those of DNA. It is also shown here that 2h Δ 13 C2 is context dependent and that this dependence is similar for RNA and DNA

26 CFR 1.103(n)-1T - Limitation on aggregrate amount of private activity bonds (temporary).

Science.gov (United States)

2010-04-01

... activity bonds (temporary). 1.103(n)-1T Section 1.103(n)-1T Internal Revenue INTERNAL REVENUE SERVICE... Excluded from Gross Income § 1.103(n)-1T Limitation on aggregrate amount of private activity bonds (temporary). Q-1: What does section 103(n) provide? A-1: Interest on an issue of private activity bonds will...

Ab Initio Calculations on Halogen Bond Between N-Br and Electron-donating Groups

Institute of Scientific and Technical Information of China (English)

WANG Yan-hua; CHEN Xue-song; ZOU Jian-wei; YU Qing-sen

2007-01-01

Ab initio calculations of complexes formed between N-bromosuccinimide and a series of electron-donating groups were performed at the level of MP2/Lanl2DZ* to gain a deeper insight into the nature of the N-Br halogen stronger halogen-bonding complex than the C-Br. A comparison of neutral hydrogen bond complex series reveals that the electron-donating capacities of the atoms decrease in the order, N＞O＞S; O(sp3)＞O(sp2), which is adequate for the C-Br halogen bonding. Interaction energies, in conjunction with the geometrical parameters show that the affinitive capacity of trihalide anions X-3 with N-bromosuccinimide are markedly lower than that of the corresponding X- with N-bromosuccinimide, even lower than those of neutral molecules with N-bromosuccinimide. AIM analyses further confirmed the above results.

Crystal structures of bis(cyanido)bis(N,N Prime -diethylthiourea-{kappa}S) mercury(II) and bis(cyanido)bis(N,N Prime -dipropylthiourea-{kappa}S) mercury(II)

Energy Technology Data Exchange (ETDEWEB)

Ahmad, Saeed, E-mail: saeed_a786@hotmail.com; Sadaf, Haseeba [University of Engineering and Technology, Department of Chemistry (Pakistan); Altaf, Muhammad; Stoeckli-Evans, Helen [University of Neuchatel, Institute of Physics (Switzerland); Seerat-ur-Rehman [University of Engineering and Technology, Department of Chemistry (Pakistan); Bashir, Sarfaraz Ahmed [Government College Asghar Mall, Department of Chemistry (Pakistan)

2013-09-15

Two mercury(II) complexes containing cyanide and, N,N Prime -diethylthiourea (detu) and N,N Prime -dipropylthiourea (dprtu) ligands, [(detu){sub 2}Hg(CN){sub 2}] (1) and [(dprtu){sub 2}Hg(CN){sub 2}] (2), respectively, have been prepared and characterized by X-ray crystallography. In the both complexes Hg atom lies on a 2-fold rotation axis, and is coordinated to the sulfur atoms of two thiourea ligands and to two cyanide carbon atoms. Both have a distorted tetrahedral environment with bond angles about the Hg atoms in the range of 93.41(4) Degree-Sign -146.75(19) Degree-Sign . In the crystal structures symmetry related molecules are linked via N-H-N hydrogen bonds resulting in the formation of a two-dimensional network in 1, while in 2 a double stranded one-dimensional chain is formed.

Observation of internucleotide NH...N hydrogen bonds in the absence of directly detectable protons

International Nuclear Information System (INIS)

Majumdar, Ananya; Kettani, Abdelali; Skripkin, Eugene; Patel, Dinshaw J.

1999-01-01

Several structural motifs found in nucleic acids involve N-H ... N hydrogen bonds in which the donor hydrogens are broadened to extinction due to chemical or conformational exchange. In such situations, it is impossible to use the well-established HNN-COSY or soft HNN-COSY experiments, which report the presence of the hydrogen bond directly on the donor proton(s). We present a pulse sequence, H(CN)N(H), for alleviating this problem in hydrogen bonds of the type N d H ... N a -CH, in which the donor N d nitrogen is correlated with the corresponding non-exchangeable C-H proton associated with the acceptor N a nitrogen. In this way, missing N d H ... N a correlations in an HNN-COSY spectrum may be recovered from CH-N d correlations in the H(CN)N(H) spectrum. By correlating a different set of nuclei relative to the HNN-COSY class of experiments, the H(CN)N(H) experiment also serves to remove ambiguities associated with degeneracies in HNN-COSY spectra. The technique is demonstrated on d(GGAGGAG) 4 ,a quadruplex containing a novel A . (G . G . G . G) . A hexad and on d(GGGCAGGT) 4 , containing a G . C . G . C tetrad, in which missing NH 2 ... N7 correlations are retrieved via H8-(N2,N6) correlations in the H(CN)N(H) spectrum

Trends in Strong Chemical Bonding in C2, CN, CN-, CO, N2, NO, NO+, and O2

DEFF Research Database (Denmark)

Kepp, Kasper Planeta

2017-01-01

The strong chemical bonds between C, N, and O play a central role in chemistry, and their formation and cleavage are critical steps in very many catalytic processes. The close-lying molecular orbital energies and large correlation effects pose a challenge to electronic structure calculations and ...

Formation of a Six-Coordinate fac-[Re(Co)3]+ Complex by the N-C bond cleavage of a potentially tetradentate ligand

International Nuclear Information System (INIS)

Booysen, I.; Gerber, T. I. A.; Hosten, E.; Mayer, P.

2008-01-01

The rhenium(I) compound fac-[Re(CO) 3 (daa)]. Hpab.H 2 O (Hpab N,N'-(l,2-phenylene)bis(2'-aminobenzamide); Hdaa 2-amino-N-(2-aminophenyl)benzamide) was synthesized from the reaction of [Re(CO) 5 ,Br] with two equivalent of Hpab in toluene. The monoanionic tridentate ligand daa was formed by the rhenium-mediated cleavage of an amido N-C bond of the potentially tetradentate ligand Hpab. The compound was characterized by IR spectroscopy and X-ray crystallography, and daa is coordinated as a diamino amide via three nitrogen-donor atoms

A combined experimental and theoretical approach to the study of hydrogen bond interaction in the binary mixture of N-methylimidazole with water

International Nuclear Information System (INIS)

Huang, Rongyi; Du, Rongbin; Liu, Guangxiang; Zhao, Xiuqin; Ye, Shiyong; Wu, Genhua

2012-01-01

Highlights: ► Densities of N-methylimidazole with water binary mixture were measured. ► Excess molar volumes were fitted to Redlich–Kister polynomial equation. ► Excess molar volumes are negative in the whole mole fraction range. ► 1:1 Hydrogen complex formation between the unlike components was observed. ► Formation of hydrogen bonds in the binary mixture was confirmed by DFT//B3LYP. - Abstract: The intermolecular hydrogen bond interactions in the N-methylimidazole (MeIm) with water binary mixture have been studied by a combined experimental and theoretical approach. The densities of the binary mixture have been measured at T = (288.15 to 323.15) K and at atmospheric pressure. From the experimental data, excess molar volumes were determined as a function of composition at each temperature. The results reveal the formation of 1:1 hydrogen bond complex between MeIm with water at the maximal excess molar volume. Meanwhile, the formation of hydrogen bonds in the binary mixture was further confirmed by high level theoretical calculation. The structures, interactional energies and bond characteristics of the hydrogen bond complexes were calculated in the gas phase using density functional theory (DFT) at the B3LYP/6-311++G(d, p) theory levels. The changes of thermodynamic properties from the monomers to hydrogen bond complexes with the temperature ranging from (288.15 to 323.15) K were obtained using the statistical thermodynamic method. Thermodynamic analyses have been interpreted in terms of intermolecular interactions and excess molar volume changes in the binary mixture. It was also found that the formation reaction of the hydrogen bond complex of MeIm with water was an exothermic, entropy reduced and spontaneous thermodynamic process at all the temperature studied.

π-Stacking and hydrogen bonding in catena-poly[[4,4 '-bipyridine-κN)-dioxouranium(VI)]-di-μ-hydroxo

International Nuclear Information System (INIS)

Thuery, P.

2007-01-01

The title compound, [UO 2 (OH) 2 (C 10 H 8 N 2 )] n , was obtained under hydrothermal conditions. The U atom is seven-coordinated and its environment is pentagonal bipyramidal, with the oxo atoms in axial positions, and one N atom and four hydroxide groups in the equatorial plane. The hydroxide ions are bridging, which results in the formation of infinite chains with the bipyridine molecules alternately located on either side. Neighbouring chains interpenetrate so that each bipyridine ligand is involved both in hydrogen bonds with two hydroxide ions and in π-stacking with its two neighbours from the next chain. (authors)

ZrC zone structure and features of electronic structure of solid solutions on the base ZrC, ZrN, TiC and TiN

International Nuclear Information System (INIS)

Mokhracheva, L.P.; Gel'd, P.V.; Tskhaj, V.A.

1983-01-01

The results of ZrC zone structure calculation conducted using the strong bond method in the three-centre variant are given. Essentially higher degree of M-C chemical bond ionicity than in TiC is shown to take place for it. Solid solution formation in TiC-ZrC, TiN-ZrC and ZrC-ZrN systems differing from TiC-TiN, TiN-ZrN and TiC-TiN is stated to be followed by essential deformation of component zone structures that, obviously, should prevent formation of solid solutions without vacancies in sublatices in these systems

FEM thermal and stress analysis of bonded GaN-on-diamond substrate

Science.gov (United States)

Zhai, Wenbo; Zhang, Jingwen; Chen, Xudong; Bu, Renan; Wang, Hongxing; Hou, Xun

2017-09-01

A three-dimensional thermal and stress analysis of bonded GaN on diamond substrate is investigated using finite element method. The transition layer thickness, thermal conductivity of transition layer, diamond substrate thickness and the area ratio of diamond and GaN are considered and treated appropriately in the numerical simulation. The maximum channel temperature of GaN is set as a constant value and its corresponding heat power densities under different conditions are calculated to evaluate the influences that the diamond substrate and transition layer have on GaN. The results indicate the existence of transition layer will result in a decrease in the heat power density and the thickness and area of diamond substrate have certain impact on the magnitude of channel temperature and stress distribution. Channel temperature reduces with increasing diamond thickness but with a decreasing trend. The stress is reduced by increasing diamond thickness and the area ratio of diamond and GaN. The study of mechanical and thermal properties of bonded GaN on diamond substrate is useful for optimal designs of efficient heat spreader for GaN HEMT.

N,N,N′,N′-Tetramethyl-N′′-[2-(trimethylazaniumylethyl]guanidinium bis(tetraphenylborate acetone disolvate

Directory of Open Access Journals (Sweden)

Ioannis Tiritiris

2016-02-01

Full Text Available The asymmetric unit of the title solvated salt, C10H26N42+·2C24H20B−·2C3H6O, comprises one cation, two tetraphenylborate ions and two acetone solvent molecules. The N and methyl C atoms of the terminal trimethylammonium group are disordered over two sets of sites, with a refined occupancy ratio of 0.846 (3:0.154 (3. The C—N bond lengths in the central C3N unit of the guanidinium ion range between 1.3308 (16 and 1.3508 (16 Å, indicating a degree of double-bond character. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry and the positive charge is delocalized in the CN3 plane. The C—N bond lengths in the terminal trimethylammonium group have values close to that of a typical single bond, and the second positive charge is localized there. In the crystal, the guanidinium ion is connected by N—H...O and C—H...O hydrogen bonds with the acetone molecules. C—H...π interactions are present between the guanidinium H atoms and the phenyl rings of the tetraphenylborate ions, leading to the formation of a two-dimensional supramolecular pattern along the bc plane.

Molecular recognition at methyl methacrylate/n-butyl acrylate (MMA/nBA) monomer unit boundaries of phospholipids at p-MMA/nBA copolymer surfaces.

Science.gov (United States)

Yu, Min; Urban, Marek W; Sheng, Yinghong; Leszczynski, Jerzy

2008-09-16

Lipid structural features and their interactions with proteins provide a useful vehicle for further advances in membrane proteins research. To mimic one of potential lipid-protein interactions we synthesized poly(methyl methacrylate/ n-butyl acrylate) (p-MMA/nBA) colloidal particles that were stabilized by phospholipid (PLs). Upon the particle coalescence, PL stratification resulted in the formation of surface localized ionic clusters (SLICs). These entities are capable of recognizing MMA/nBA monomer interfaces along the p-MMA/nBA copolymer backbone and form crystalline SLICs at the monomer interface. By utilizing attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy and selected area electron diffraction (SAD) combined with ab initio calculations, studies were conducted that identified the origin of SLICs as well as their structural features formed on the surface of p-MMA/nBA copolymer films stabilized by 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) PL. Specific entities responsible for SLIC formation are selective noncovalent bonds of anionic phosphate and cationic quaternary ammonium segments of DLPC that interact with two neighboring carbonyl groups of nBA and MMA monomers of the p-MMA/nBA polymer backbone. To the best of our knowledge this is the first example of molecular recognition facilitated by coalescence of copolymer colloidal particles and the ability of PLs to form SLICs at the boundaries of the neighboring MMA and nBA monomer units of the p-MMA/nBA chain. The dominating noncovalent bonds responsible for the molecular recognition is a combination of H-bonding and electrostatic interactions.

FEM thermal and stress analysis of bonded GaN-on-diamond substrate

Directory of Open Access Journals (Sweden)

Wenbo Zhai

2017-09-01

Full Text Available A three-dimensional thermal and stress analysis of bonded GaN on diamond substrate is investigated using finite element method. The transition layer thickness, thermal conductivity of transition layer, diamond substrate thickness and the area ratio of diamond and GaN are considered and treated appropriately in the numerical simulation. The maximum channel temperature of GaN is set as a constant value and its corresponding heat power densities under different conditions are calculated to evaluate the influences that the diamond substrate and transition layer have on GaN. The results indicate the existence of transition layer will result in a decrease in the heat power density and the thickness and area of diamond substrate have certain impact on the magnitude of channel temperature and stress distribution. Channel temperature reduces with increasing diamond thickness but with a decreasing trend. The stress is reduced by increasing diamond thickness and the area ratio of diamond and GaN. The study of mechanical and thermal properties of bonded GaN on diamond substrate is useful for optimal designs of efficient heat spreader for GaN HEMT.

26 CFR 1.103(n)-4T - Elective carryforward of unused private activity bond limit (temporary).

Science.gov (United States)

2010-04-01

... bond limit (temporary). 1.103(n)-4T Section 1.103(n)-4T Internal Revenue INTERNAL REVENUE SERVICE... Excluded from Gross Income § 1.103(n)-4T Elective carryforward of unused private activity bond limit... carryforward for any one or more projects described in A-5 of this § 1.103(n)-4T (carryforward projects). Q-2...

Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles

Directory of Open Access Journals (Sweden)

Zong Guan

2014-04-01

Full Text Available Deprotonation of indazolium salts at low temperatures gives N-heterocyclic carbenes of indazoles (indazol-3-ylidenes which can be trapped as rhodium complexes (X-ray analysis. In the absence of Rh, the indazol-3-ylidenes spontaneously dimerize under ring cleavage of one of the N,N-bonds and ring closure to an indazole–indole spiro compound which possesses an exocyclic imine group. The E/Z isomers of the imines can be separated by column chromatography when methanol is used as eluent. We present results of a single crystal X-ray analysis of one of the E-isomers, which equilibrate in solution as well as in the solid state. Heating of the indazole–indole spiro compounds results in the formation of quinazolines by a ring-cleavage/ring-closure sequence (X-ray analysis. Results of DFT calculations are presented.

A new efficient method for the preparation of 99mTc-radiopharmaceuticals containing the Tc≡N multiple bond

International Nuclear Information System (INIS)

Pasqualini, R.; Comazzi, V.; Bellande, E.; Duatti, A.; Marchi, A.

1992-01-01

An improved method for the preparation of 99m Tc-radiopharmaceuticals containing the Tc≡N multiple bond, in sterile and apyrogen conditions, is described. This method is based on the reaction of [ 99m Tc] pertechnetate with ligands derived from S-methyl dithiocarbazate [H 2 N-N(R)-C(=S)SCH 3 (R = H, CH 3 )] in the presence of HC1 and tertiary phosphines. It was found that these derivatives can behave both as sources of nitride nitrogen ions (N 3- ) and as coordinating ligands. The reaction leads to the formation of intermediate technetium-nitrido complexes in high yield. These intermediate species can be used as suitable prereduced substrates for the preparation of technetium-nitrido radiopharmaceuticals through simple substitution reactions with appropriate exchanging ligands. (Author)

Magnetic Properties of NdFe10Mo2-N Bonded Magnet

Science.gov (United States)

Zhang, Hong-Wei; Hu, Bo-Ping; Han, Zhong-Fan; Jin, Han-Min; Fu, Quan

1997-06-01

The dependence of remanence and coercivity on the magnetizing field is studied for isotropic and anisotropic epoxy resin bonded magnets. It was found that the coercivity of the NdFe10Mo2-N bonded magnet is mainly controlled by nucleation of reversed magnetic domains. Variation of iHc with Zn content and heat treatment conditions is studied. The value of 0 iHc obtained in the best Zn-bonded condition is about 0.15 T higher than before bonding. The variation of the amount of α-Fe with processing conditions is demonstrated for anisotropic Zn-bonded magnets.

Bis(dicyanamido-κN[tris(3-aminopropylamine-κ4N]nickel(II

Directory of Open Access Journals (Sweden)

Jun Luo

2013-07-01

Full Text Available In the title complex, [Ni(C2N32(C9H24N4], the NiII atom is coordinated in a distorted octahedral geometry by one tris(3-aminopropylamine (trisapa ligand and two dicyanamide (dca ligands [one of them disordered in a 0.681 (19:0319 (19 ratio]. Intermolecular N—H...N hydrogen bonds involving the N atoms of the dca anions and the trisapa amine H atoms result in the formation of a three-dimensional network.

Synthesis and structure of unprecedented samarium complex with bulky bis-iminopyrrolyl ligand via intramolecular C=N bond activation

Energy Technology Data Exchange (ETDEWEB)

Das, Suman; Anga, Srinivas; Harinath, Adimulam; Panda, Tarun K. [Department of Chemistry, Indian Institute of Technology, Hyderabad (India); Pada Nayek, Hari [Department of Applied Chemistry, Indian Institute of Technology, (ISM) Dhanbad, Jharkhand (India)

2017-12-29

An unprecedentate samarium complex of the molecular composition [{κ"3-{(Ph_2CH)N=CH}{sub 2}C{sub 4}H{sub 2}N}{κ"3-{(Ph_2CHN=CH)(Ph_2CHNCH)C_4H_2N}Sm}{sub 2}] (2), which was isolated by the reaction of a potassium salt of 2,5-bis{N-(diphenylmethyl)-iminomethyl}pyrrolyl ligand [K(THF){sub 2}{(Ph_2CH)N=CH}{sub 2}C{sub 4}H{sub 2}N] (1) with anhydrous samarium diiodide in THF at 60 C through the in situ reduction of imine bond is presented. The homoleptic samarium complex [[κ{sup 3}-{(Ph_2CH)-N=CH}{sub 2}C{sub 4}H{sub 2}N]{sub 3}Sm] (3) can also be obtained from the reaction of compound 1 with anhydrous samarium triiodide (SmI{sub 3}) in THF at 60 C. The molecular structures of complexes 2 and 3 were established by single-crystal X-ray diffraction analysis. The molecular structure of complex 2 reveals the formation of a C-C bond in the 2,5-bis{N-(diphenylmethyl)iminomethyl}pyrrole ligand moiety (Ph{sub 2}Py{sup -}). However, complex 3 is a homoleptic samarium complex of three bis-iminopyrrolyl ligands. In complex 2, the samarium ion adopts an octahedral arrangement, whereas in complex 3, a distorted three face-centered trigonal prismatic mode of nine coordination is observed around the metal ion. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Bonding Characteristics and Chemical Inertness of Zr–Si–N Coatings with a High Si Content in Glass Molding

Directory of Open Access Journals (Sweden)

Li-Chun Chang

2018-05-01

Full Text Available High-Si-content transition metal nitride coatings, which exhibited an X-ray amorphous phase, were proposed as protective coatings on glass molding dies. In a previous study, the Zr–Si–N coatings with Si contents of 24–30 at.% exhibited the hardness of Si3N4, which was higher than those of the middle-Si-content (19 at.% coatings. In this study, the bonding characteristics of the constituent elements of Zr–Si–N coatings were evaluated through X-ray photoelectron spectroscopy. Results indicated that the Zr 3d5/2 levels were 179.14–180.22 and 180.75–181.61 eV for the Zr–N bonds in ZrN and Zr3N4 compounds, respectively. Moreover, the percentage of Zr–N bond in the Zr3N4 compound increased with increasing Si content in the Zr–Si–N coatings. The Zr–N bond of Zr3N4 dominated when the Si content was >24 at.%. Therefore, high Si content can stabilize the Zr–N compound in the M3N4 bonding structure. Furthermore, the thermal stability and chemical inertness of Zr–Si–N coatings were evaluated by conducting thermal cycle annealing at 270 °C and 600 °C in a 15-ppm O2–N2 atmosphere. The results indicated that a Zr22Si29N49/Ti/WC assembly was suitable as a protective coating against SiO2–B2O3–BaO-based glass for 450 thermal cycles.

Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides.

Science.gov (United States)

Mphahlele, Malose Jack; Maluleka, Marole Maria; Rhyman, Lydia; Ramasami, Ponnadurai; Mampa, Richard Mokome

2017-01-04

The structures of the mono- and the dihalogenated N -unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (¹H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(O)-NH₂ single bond resulted in non-equivalence of the amide protons and therefore two distinct resonances of different chemical shift values in the ¹H-NMR spectra of these compounds were observed. 2-Amino-5-bromobenzamide ( ABB ) as a model confirmed the presence of strong intramolecular hydrogen bonds between oxygen and the amine hydrogen. However, intramolecular hydrogen bonding between the carbonyl oxygen and the amine protons was not observed in the solution phase due to a rapid exchange of these two protons with the solvent and fast rotation of the Ar-NH₂ single bond. XRD also revealed the ability of the amide unit of these compounds to function as a hydrogen bond donor and acceptor simultaneously to form strong intermolecular hydrogen bonding between oxygen of one molecule and the NH moiety of the amine or amide group of the other molecule and between the amine nitrogen and the amide hydrogen of different molecules. DFT calculations using the B3LYP/6-311++G(d,p) basis set revealed that the conformer ( A ) with oxygen and 2-amine on the same side predominates possibly due to the formation of a six-membered intramolecular ring, which is assisted by hydrogen bonding as observed in the single crystal XRD structure.

Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides

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Malose Jack Mphahlele

2017-01-01

Full Text Available The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (1H-NMR, UV-Vis, FT-IR, and FT-Raman and X-ray crystallographic techniques complemented with a density functional theory (DFT method. The hindered rotation of the C(O–NH2 single bond resulted in non-equivalence of the amide protons and therefore two distinct resonances of different chemical shift values in the 1H-NMR spectra of these compounds were observed. 2-Amino-5-bromobenzamide (ABB as a model confirmed the presence of strong intramolecular hydrogen bonds between oxygen and the amine hydrogen. However, intramolecular hydrogen bonding between the carbonyl oxygen and the amine protons was not observed in the solution phase due to a rapid exchange of these two protons with the solvent and fast rotation of the Ar–NH2 single bond. XRD also revealed the ability of the amide unit of these compounds to function as a hydrogen bond donor and acceptor simultaneously to form strong intermolecular hydrogen bonding between oxygen of one molecule and the NH moiety of the amine or amide group of the other molecule and between the amine nitrogen and the amide hydrogen of different molecules. DFT calculations using the B3LYP/6-311++G(d,p basis set revealed that the conformer (A with oxygen and 2-amine on the same side predominates possibly due to the formation of a six-membered intramolecular ring, which is assisted by hydrogen bonding as observed in the single crystal XRD structure.

Vapour pressures of 1-methyl derivatives of benzimidazole, pyrazole and indole. The energy of the intermolecular hydrogen bond N-H⋯N

International Nuclear Information System (INIS)

Almeida, Ana R.R.P.; Monte, Manuel J.S.

2014-01-01

Highlights: • Vapour pressures of 1-methyl derivatives of benzimidazole, pyrazole and indole. • Enthalpies, entropies and Gibbs free energies of sublimation/vaporisation were derived. • Temperatures and enthalpies of fusion were determined. • Energy of the intermolecular hydrogen bond N-H⋯N was estimated. - Abstract: The vapour pressures of the liquid phase of 1-methylpyrazole, 1-methylbenzimidazole and 1-methylindole were measured over the temperature ranges (253.9 to 293.3) K, (303.2 to 372.5) K, and (268.6 to 341.9) K, respectively, using a static method. The vapour pressures of the crystalline phase of the two latter compounds were also measured at temperatures between (301.2 to 328.9) K and (267.6 to 275.5) K, respectively. The results obtained enabled the determination of the standard molar enthalpies and entropies of sublimation and of vaporisation at the mean temperatures of the measurements and at T = 298.15 K. The temperatures and molar enthalpies of fusion were determined using differential scanning calorimetry. The enthalpies of the intermolecular hydrogen bonds N-H⋯N in the crystalline phase of benzimidazole and pyrazole were determined and compared with the result previously determined for the energy of the intermolecular hydrogen bond in crystalline imidazole

(Z)-N,N-Dimethyl-2-[phen­yl(pyridin-2-yl)methyl­idene]hydrazinecarbothio­amide

Science.gov (United States)

Jayakumar, K.; Sithambaresan, M.; Prathapachandra Kurup, M. R.

2011-01-01

The title compound, C15H16N4S, exists in the Z conformation with the thionyl S atom lying cis to the azomethine N atom. The shortening of the N—N distance [1.3697 (17) Å] is due to extensive delocalization with the pyridine ring. The hydrazine–carbothio­amide unit is almost planar, with a maximum deviation of 0.013 (2) Å for the amide N atom. The stability of this conformation is favoured by the formation of an intra­molecular N—H⋯N hydrogen bond. The packing of the mol­ecules involves no classical inter­molecular hydrogen-bonding inter­actions; however, a C—H⋯π inter­action occurs. PMID:22199715

Crystal structure of N-[3-(dimethylazaniumylpropyl]-N′,N′,N′′,N′′-tetramethyl-N-(N,N,N′,N′-tetramethylformamidiniumylguanidinium dibromide hydroxide monohydrate

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Ioannis Tiritiris

2015-12-01

Full Text Available The asymmetric unit of the title hydrated salt, C15H37N63+·2Br−·OH−·H2O, contains one cation, three partial-occupancy bromide ions, one hydroxide ion and one water molecule. Refinement of the site-occupancy factors of the three disordered bromide ions converges with occupancies 0.701 (2, 0.831 (2 and 0.456 (2 summing to approximately two bromide ions per formula unit. The structure was refined as a two-component inversion twin with volume fractions 0.109 (8:0.891 (8 for the two domains. The central C3N unit of the bisamidinium ion is linked to the aliphatic propyl chain by a C—N single bond. The other two bonds in this unit have double-bond character as have the four C—N bonds to the outer NMe2 groups. In contrast, the three C—N bonds to the central N atom of the (dimethylazaniumylpropyl group have single-bond character. Delocalization of the two positive charges occurs in the N/C/N and C/N/C planes, while the third positive charge is localized on the dimethylammonium group. The crystal structure is stabilized by O—H...O, N—H...Br, O—H...Br and C—H...Br hydrogen bonds, forming a three-dimensional network.

N,N,N′,N′,N′′-Pentamethyl-N′′-[2-(trimethylazaniumylethyl]guanidinium bis(tetraphenylborate acetone monosolvate

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Ioannis Tiritiris

2016-02-01

Full Text Available The asymmetric unit of the title solvated salt, C11H28N42+·2C24H20B−·C3H6O, comprises two cations, four tetraphenylborate anions and two acetone molecules. One cation shows an orientational disorder at the CN3 moiety and two sets of N-atom positions were found related by a 60° rotation, with a refined occupancy ratio of 0.935 (1:0.065 (1. The respective nitrogen-bonded –CH2 and –CH3 groups are included in the disorder model. The C—N bond lengths in the central CN3 units of both guanidinium ions range between 1.3329 (17 and 1.364 (16 Å, indicating a degree of double-bond character. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry and one positive charge is delocalized in the CN3 plane. The C—N bond lengths in the terminal trimethylammonium groups have values close to a typical single bond, and the second positive charge is localized there. In the crystal, the guanidinium ions are connected by C—H...O hydrogen bonds with the acetone molecules. C—H...π interactions are present between the guanidinium and acetone hydrogen atoms and the phenyl rings of the tetraphenylborate ions, leading to the formation of a two-dimensional supramolecular pattern along the bc plane.

Evidence of amino acid precursors: C-N bond coupling in simulated interstellar CO2/NH3 ices

Science.gov (United States)

Esmaili, Sasan

2015-08-01

Low energy secondary electrons are abundantly produced in astrophysical or planetary ices by the numerous ionizing radiation fields typically encountered in space environments and may thus play a role in the radiation processing of such ices [1]. One approach to determine their chemical effect is to irradiate nanometer thick molecular solids of simple molecular constituents, with energy selected electron beams and to monitor changes in film chemistry with the surface analytical techniques [2].Of particular interest is the formation of HCN, which is a signature of dense gases in interstellar clouds, and is ubiquitous in the ISM. Moreover, the chemistry of HCN radiolysis products such as CN- may be essential to understand of the formation of amino acids [3] and purine DNA bases. Here we present new results on the irradiation of multilayer films of CO2 and NH3 with 70 eV electrons, leading to CN bond formations. The electron stimulated desorption (ESD) yields of cations and anions are recorded as a function of electron fluence. The prompt desorption of cationic reaction/scattering products [4], is observed at low fluence (~4x1013 electrons/cm2). Detected ions include C2+, C2O2+, C2O+, CO3+, C2O3+ or CO4+ from pure CO2, and N+, NH+, NH2+, NH3+, NH4+, N2+, N2H+ from pure NH3, and NO+, NOH+ from CO2/NH3 mixtures. Most saliently, increasing signals of negative ion products desorbing during prolonged irradiation of CO2/NH3 films included C2-, C2H-, C2H2-, as well as CN-, HCN- and H2CN-. The identification of particular product ions was accomplished by using 13CO2 and 15NH3 isotopes. The chemistry induced by electrons in pure films of CO2 and NH3 and mixtures with composition ratios (3:1), (1:1), and (1:3), was also studied by X-ray photoelectron spectroscopy (XPS). Irradiation of CO2/NH3 mixed films at 22 K produces species containing the following bonds/functional groups identified by XPS: C=O, O-H, C-C, C-O, C=N and N=O. (This work has been funded by NSERC).

BONDING CAPITAL, EXPLOTACIÓN DE CONOCIMIENTO E INNOVACIÓN INCREMENTAL EN LOS CLUSTERS DE TURISMO CULTURAL: LAS CIUDADES PATRIMONIO DE LA HUMANIDAD EN ESPAÑA

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Elche-Hortelano, Dioni

2015-09-01

Full Text Available En este trabajo analizamos el papel de la estrategia de conocimiento en explotación para explicar la relación entre capital social en su dimensión bonding y la innovación incremental en el ámbito de los clusters. Hemos aplicado un modelo estructural sobre una muestra de 215 empresas del sector de turismo cultural de las Ciudades Patrimonio de la Humanidad de Espana. Los resultados revelan la existencia de un efecto indirecto significativo del bonding capital sobre la innovación incremental a través del desarrollo de una estrategia de conocimiento en explotación. Estos resultados sugieren que si las empresas de un cluster de turismo cultural son capaces de aprovechar sus redes densas y vínculos fuertes para implantar estrategias de conocimiento en explotación, tenderán a desarrollar mayores innovaciones incrementales.

4-Bromo-N-(di-n-propylcarbamothioylbenzamide

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2009-03-01

Full Text Available The synthesis of the title compound, C14H19BrN2OS, involves the reaction of 4-bromobenzoyl chloride with potassium thiocyanate in acetone followed by condensation of the resulting 4-bromobenzoyl isothiocyanate with di-n-propylamine. Typical thiourea carbonyl and thiocarbonyl double bonds, as well as shortened C—N bonds, are observed in the title compound. The short C—N bond lengths in the centre of the molecule reveal the effects of resonance in this part of the molecule. The asymmetric unit of the title compound contains two crystallographically independent molecules, A and B. There is very little difference between the bond lengths and angles of these molecules. In molecule B, one di-n-propyl group is twisted in a −antiperiplanar conformation with C—C—C—H = −179.1 (3° and the other adopts a −synclinal conformation with C—C—C—H = −56.7 (4°; in molecule A the two di-n-propyl groups are twisted in + and −antiperiplanar conformations, with C—C—C—H = −179.9 (3 and 178.2 (3°, respectively. In the crystal, the molecules are linked into dimeric pairs via pairs of N—H...S hydrogen bonds.

Cytochrome P-450 inactivation by 3-alkylsydnones. Mechanistic implications of N-alkyl and N-alkenyl heme adduct formation

International Nuclear Information System (INIS)

Grab, L.A.; Swanson, B.A.; Ortiz de Montellano, P.R.

1988-01-01

Incubation of 3-(2-phenylethyl)-4-methylsydnone (PMS) with liver microsomes from phenobarbital-pretreated rats or with reconstituted cytochrome P-450b results in loss of the enzyme chromophore. Chromophore loss is NADPH-dependent even though the sydnone decomposes by an oxygen- but not enzyme-dependent process to give pyruvic acid and, presumably, the (2-phenylethyl)diazonium cation. N-(2-Phenylethyl)protoporphyrin IX and N-(2-phenylethenyl)protoporphyrin IX have been isolated from the livers of rats treated with PMS. Both deuteriums are retained in the N-(2-phenylethyl) adduct derived from 3-(2-phenyl[1,1- 2 H]ethyl)-4-methylsydnone, but one deuterium is lost in the N-(2-phenylethenyl) adduct. The N-(2-phenylethyl) to N-(2-phenylethenyl) adduct ratio is increased by deuterium substitution. Electron paramagnetic resonance (EPR)-spin trapping studies show that carbon radicals are formed in incubations of the sydnones with liver microsomes but by a process that is independent of chromophore destruction. It is proposed that the 2-phenylethyl radical formed by electron transfer to the sydnone-derived (2-phenylethyl)diazonium cation adds to the prosthetic heme group to give the N-(2-phenylethyl) adduct. This alkylation reaction is similar to that observed with (2-phenylethyl)hydrazine. Autoxidation of the Fe-CH(CH 2 Ph)-N bridged species expected from insertion of 2-phenyldiazoethane into one of the heme Fe-N bonds is proposed to explain the unprecedented introduction of a double bond into the N-(2-phenylethenyl)adduct

Intermolecular and very strong intramolecular C-SeO/N chalcogen bonds in nitrophenyl selenocyanate crystals.

Science.gov (United States)

Wang, Hui; Liu, Ju; Wang, Weizhou

2018-02-14

Single-crystal X-ray diffraction reveals that polymorphic ortho-nitrophenyl selenocyanate (o-NSC, crystals 1a and 1b) and monomorphic para-nitrophenyl selenocyanate (p-NSC, crystal 2) crystals are all stabilized mainly by intermolecular and very strong intramolecular C-SeO/N chalcogen bonds, as well as by other different interactions. Thermogravimetric (TG) and differential scanning calorimetry thermogram (DSC) analyses show that the starting decomposition temperatures and melting points of the three crystals are different, following the order 1b > 1a > 2, which is consistent with the structural characteristics of the crystals. In addition, atoms in molecules (AIM) and natural bond orbital (NBO) analyses indicate that the total strengths of the C-SeO and C-SeN chalcogen bonds decrease in the order 1b > 1a > 2. This study could be significant for engineering functional crystals based on robust C-SeO and C-SeN chalcogen bonds, and for designing drugs containing selenium as well as understanding their interaction in biosystems.

Pressure-induced structural transition and thermodynamic properties of RhN2 and the effect of metallic bonding on its hardness

International Nuclear Information System (INIS)

Liu Jun; Kuang Xiao-Yu; Wang Zhen-Hua; Huang Xiao-Fen

2012-01-01

The elastic constant, structural phase transition, and effect of metallic bonding on the hardness of RhN 2 under high pressure are investigated through the first-principles calculation by means of the pseudopotential plane-wave method. Three structures are chosen to investigate for RhN 2 , namely, simple hexagonal P6/mmm (denoted as SH), orthorhombic Pnnm (marcasite), and simple tetragonal P4/mbm (denoted as ST). Our calculations show that the SH phase is energetically more stable than the other two phases at zero pressure. On the basis of the third-order Birch—Murnaghan equation of states, we find that the phase transition pressures from an SH to a marcasite structure and from a marcasite to an ST structure are 1.09 GPa and 354.57 GPa, respectively. Elastic constants, formation enthalpies, shear modulus, Young's modulus, and Debye temperature of RhN 2 are derived. The calculated values are, generally speaking, in good agreement with the previous theoretical results. Meanwhile, it is found that the pressure has an important influence on physical properties. Moreover, the effect of metallic bonding on the hardness of RhN 2 is investigated. This is a quantitative investigation on the structural properties of RhN 2 , and it still awaits experimental confirmation. (condensed matter: structural, mechanical, and thermal properties)

Interfacial bonding and electronic structure of GaN/GaAs interface: A first-principles study

International Nuclear Information System (INIS)

Cao, Ruyue; Zhang, Zhaofu; Wang, Changhong; Li, Haobo; Dong, Hong; Liu, Hui; Wang, Weichao; Xie, Xinjian

2015-01-01

Understanding of GaN interfacing with GaAs is crucial for GaN to be an effective interfacial layer between high-k oxides and III-V materials with the application in high-mobility metal-oxide-semiconductor field effect transistor (MOSFET) devices. Utilizing first principles calculations, here, we investigate the structural and electronic properties of the GaN/GaAs interface with respect to the interfacial nitrogen contents. The decrease of interfacial N contents leads to more Ga dangling bonds and As-As dimers. At the N-rich limit, the interface with N concentration of 87.5% shows the most stability. Furthermore, a strong band offsets dependence on the interfacial N concentration is also observed. The valance band offset of N7 with hybrid functional calculation is 0.51 eV. The electronic structure analysis shows that significant interface states exist in all the GaN/GaAs models with various N contents, which originate from the interfacial dangling bonds and some unsaturated Ga and N atoms. These large amounts of gap states result in Fermi level pinning and essentially degrade the device performance

GaN microring waveguide resonators bonded to silicon substrate by a two-step polymer process.

Science.gov (United States)

Hashida, Ryohei; Sasaki, Takashi; Hane, Kazuhiro

2018-03-20

Using a polymer bonding technique, GaN microring waveguide resonators were fabricated on a Si substrate for future hybrid integration of GaN and Si photonic devices. The designed GaN microring consisted of a rib waveguide having a core of 510 nm in thickness, 1000 nm in width, and a clad of 240 nm in thickness. A GaN crystalline layer of 1000 nm in thickness was grown on a Si(111) substrate by metal organic chemical vapor deposition using a buffer layer of 300 nm in thickness for the compensation of lattice constant mismatch between GaN and Si crystals. The GaN/Si wafer was bonded to a Si(100) wafer by a two-step polymer process to prevent it from trapping air bubbles. The bonded GaN layer was thinned from the backside by a fast atom beam etching to remove the buffer layer and to generate the rib waveguides. The transmission characteristics of the GaN microring waveguide resonators were measured. The losses of the straight waveguides were measured to be 4.0±1.7  dB/mm around a wavelength of 1.55 μm. The microring radii ranged from 30 to 60 μm, where the measured free-spectral ranges varied from 2.58 to 5.30 nm. The quality factors of the microring waveguide resonators were from 1710 to 2820.

Dimethyl N-cyanodithioiminocarbonate

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Mouhamadou Birame Diop

2016-03-01

Full Text Available The title compound, C4H6N2S2, crystallizes with four independent molecules in the asymmetric unit. Two of the molecules are disordered about a pseudo twofold rotation axis. The mean values of the C—N bonds are 1.143 (5 Å for C[triple-bond]N, 1.302 (5 Å for C=N and 1.341 (5 Å for the C—N single bond. In the crystal, molecules are linked via C—H...N hydrogen bonds, forming slabs parallel to the bc plane.

Smart supramolecular sensing with cucurbit[n]urils: probing hydrogen bonding with SERS.

Science.gov (United States)

de Nijs, Bart; Kamp, Marlous; Szabó, Istvan; Barrow, Steven J; Benz, Felix; Wu, Guanglu; Carnegie, Cloudy; Chikkaraddy, Rohit; Wang, Wenting; Deacon, William M; Rosta, Edina; Baumberg, Jeremy J; Scherman, Oren A

2017-12-04

Rigid gap nano-aggregates of Au nanoparticles formed using cucurbit[n]uril (CB[n]) molecules are used to investigate the competitive binding of ethanol and methanol in an aqueous environment. We show it is possible to detect as little as 0.1% methanol in water and a ten times higher affinity to methanol over ethanol, making this a useful technology for quality control in alcohol production. We demonstrate strong interaction effects in the SERS peaks, which we demonstrate are likely from the hydrogen bonding of water complexes in the vicinity of the CB[n]s.

Divergent Pathways Involving 1,3-Dipolar Addition and N-N Bond Splitting of an Organic Azide across a Zirconium Methylidene.

Science.gov (United States)

Kurogi, Takashi; Mane, Manoj V; Zheng, Shuai; Carroll, Patrick J; Baik, Mu-Hyun; Mindiola, Daniel J

2018-02-12

The zirconium methylidene (PNP)Zr=CH 2 (OAr) (1) reacts with N 3 Ad to give two products (PNP)Zr=NAd(OAr) (2) and (PNP)Zr(η 2 -N=NAd)(N=CH 2 )(OAr) (3), both resulting from a common cycloaddition intermediate (PNP)Zr(CH 2 N 3 Ad)(OAr) (A). Using a series of control experiments in combination with DFT calculations, it was found that 2 results from a nitrene by a carbene metathesis reaction in which N 2 acts as a delivery vehicle and forms N 2 CH 2 as a side product. In the case of 3, N-N bond splitting of the azide at the α-position allowed the isolation of a rare example of a parent ketimide complex of zirconium. Isotopic labeling studies and solid-state X-ray analysis are presented for 2 and 3, in addition to an independent synthesis for the former. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Conformational properties of oxazole-amino acids: effect of the intramolecular N-H···N hydrogen bond.

Science.gov (United States)

Siodłak, Dawid; Staś, Monika; Broda, Małgorzata A; Bujak, Maciej; Lis, Tadeusz

2014-03-06

Oxazole ring occurs in numerous natural peptides, but conformational properties of the amino acid residue containing the oxazole ring in place of the C-terminal amide bond are poorly recognized. A series of model compounds constituted by the oxazole-amino acids occurring in nature, that is, oxazole-alanine (L-Ala-Ozl), oxazole-dehydroalanine (ΔAla-Ozl), and oxazole-dehydrobutyrine ((Z)-ΔAbu-Ozl), was investigated using theoretical calculations supported by FTIR and NMR spectra and single-crystal X-ray diffraction. It was found that the main feature of the studied oxazole-amino acids is the stable conformation β2 with the torsion angles φ and ψ of -150°, -10° for L-Ala-Ozl, -180°, 0° for ΔAla-Ozl, and -120°, 0° for (Z)-ΔAbu-Ozl, respectively. The conformation β2 is stabilized by the intramolecular N-H···N hydrogen bond and predominates in the low polar environment. In the case of the oxazole-dehydroamino acids, the π-electron conjugation that is spread on the oxazole ring and C(α)═C(β) double bond is an additional stabilizing interaction. The tendency to adopt the conformation β2 clearly decreases with increasing the polarity of environment, but still the oxazole-dehydroamino acids are considered to be more rigid and resistant to conformational changes.

Orbital localization criterion as a complementary tool in the bonding analysis by means of electron localization function: study of the Si(n)(BH)(5-n)(2-) (n = 0-5) clusters.

Science.gov (United States)

Oña, Ofelia B; Alcoba, Diego R; Torre, Alicia; Lain, Luis; Torres-Vega, Juan J; Tiznado, William

2013-12-05

A recently proposed molecular orbital localization procedure, based on the electron localization function (ELF) technique, has been used to describe chemical bonding in the cluster series Sin(BH)(5-n)(2-) (n = 0-5). The method combines the chemically intuitive information obtained from the traditional ELF analysis with the flexibility and generality of canonical molecular orbital theory. This procedure attempts to localize the molecular orbitals in regions that have the highest probability for finding a pair of electrons, providing a chemical bonding description according to the classical Lewis theory. The results confirm that conservation of the structures upon isoelectronic replacement of a B-H group by a Si atom, allowing evolution from B5H5(2-) to Si5(2-), is in total agreement with the preservation of the chemical bonding pattern.

N,N,N′,N′,N′′,N′′,N′′′,N′′′-Octamethyl(but-2-ynebisamidinium bis(tetraphenylborate

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Ioannis Tiritiris

2016-02-01

Full Text Available The asymmetric unit of the title salt, C12H24N42+.2C24H20B−, comprises half a cation and one tetraphenylborate ion. An inversion centre is situated at the mid-point of the triple C[triple-bond]C bond in the cation. The bisamidinium C—N bonds [1.3249 (11 and 1.3267 (11 Å] have double-bond character and both positive charges are delocalized between the dimethylamino groups. The bonds between the N atoms and the terminal C-methyl groups all have values characteristic for a typical single bond [1.4656 (12–1.4687 (12 Å]. The acetylenic bond length [1.1889 (18 Å] is consistent with a triple C[triple-bond]C bond and the butyne carbon chain is almost linear. C—H...π interactions between the bisamidinium methyl H atoms and the phenyl C atoms of the tetraphenylborate ions are present. The phenyl rings form aromatic pockets, in which the cations are embedded. This leads to the formation of a two-dimensional supramolecular pattern in the ab plane.

Scaffold Diversity from N-Acyliminium Ions

DEFF Research Database (Denmark)

Wu, Peng; Nielsen, Thomas E

2017-01-01

N-Acyliminium ions are powerful reactive species for the formation of carbon-carbon and carbon-heteroatom bonds. Strategies relying on intramolecular reactions of N-acyliminium intermediates, also referred to as N-acyliminium ion cyclization reactions, have been employed for the construction...... of structurally diverse scaffolds, ranging from simple bicyclic skeletons to complex polycyclic systems and natural-product-like compounds. This review aims to provide an overview of cyclization reactions of N-acyliminium ions derived from various precursors for the assembly of structurally diverse scaffolds...

2-[N-(3-Amino-4-nitrophenylcarboximidoyl]phenol

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Gholam Hossein Shahverdizadeh

2011-11-01

Full Text Available The title compound, C13H11N3O3, is essentially planar (r.m.s. for the 19 non-H atoms = 0.031 Å, a conformation stabilized in part by intramolecular O—H...N and N—H...O hydrogen bonds. The configuration about the imine bond [1.2919 (12 Å] is E. The presence of N—H...O(nitro hydrogen bonds leads to the formation of supramolecular tapes in the crystal structure. These are connected into layers by π–π interactions [centroid–centroid distance = 3.6046 (6 Å] occurring between the hydroxy- and amino-substituted benzene rings.

A multivariate relationship for the impact sensitivities of energetic N-nitrocompounds based on bond dissociation energy.

Science.gov (United States)

Li, Jinshan

2010-02-15

The ZPE-corrected N-NO(2) bond dissociation energies (BDEs(ZPE)) of a series of model N-nitrocompounds and typical energetic N-nitrocompounds have been calculated using density functional theory methods. Computed results show that using the 6-31G** basis set the UB3LYP calculated BDE(ZPE) is similar to the B3PW91 but is less than the UB3P86 and that for both UB3P86 and UB3PW91 methods the 6-31G(**) calculated BDE(ZPE) is close to the 6-31++G(**). For the series of model N-nitrocompounds it is drawn from the NBO analysis that at the UB3LYP/6-31G(**) level the order of BDE(ZPE) is not only in line with that of bond order but also with that of the energy gap between N-NO(2) bond and antibond orbitals. For the typical energetic N-nitrocompounds the impact sensitivity is strongly related to the BDE(ZPE) indeed, and based on the BDEs(ZPE) calculated at different density functional theory levels this work has established a good multivariate correlation of impact sensitivity with molecular parameters, which provides a method to address the sensitivity problem.

Hydrogen bonding properties and intermediate structure of N-(2-carboxyphenyl)salicylidenimine

NARCIS (Netherlands)

Ligtenbarg, Alette G.J.; Hage, Ronald; Meetsma, Auke; Feringa, Ben L.

1999-01-01

The hydrogen bonding properties, the nature of the tautomeric structure and dimerization of N-(2-carboxyphenyl)salicylidenimine 1 has been studied. The crystal and molecular structure of 1 has been determined by single-crystal X-ray diffraction analysis. This compound forms a dimer in the solid

Role of N defects in paramagnetic CrN at finite temperatures from first principles

Science.gov (United States)

Mozafari, E.; Alling, B.; Steneteg, P.; Abrikosov, Igor A.

2015-03-01

Simulations of defects in paramagnetic materials at high temperature constitute a formidable challenge to solid-state theory due to the interaction of magnetic disorder, vibrations, and structural relaxations. CrN is a material where these effects are particularly large due to a strong magnetolattice coupling and a tendency for deviations from the nominal 1:1 stoichiometry. In this work, we present a first-principles study of nitrogen vacancies and nitrogen interstitials in CrN at elevated temperature. We report on formation energetics, the geometry of interstitial nitrogen dimers, and the impact on the electronic structure caused by the defects. We find a vacancy formation energy of 2.28 eV with a small effect of temperature, i.e., a formation energy for N interstitial in the form of a -oriented split bond of 3.77 eV with an increase to 3.97 at 1000 K. Vacancies are found to add three electrons, while split-bond interstitial adds one electron to the conduction band. The band gap of defect-free CrN is smeared out due to vibrations, although it is difficult to draw a conclusion about the exact temperature at which the band gap closes from our calculations. However, it is clear that at 900 K there is a nonzero density of electronic states at the Fermi level. At 300 K, our results indicate a border case where the band gap is about to close.

4-Bromo-N-(di-n-propyl-carbamothioyl)-benzamide.

Science.gov (United States)

Binzet, Gün; Flörke, Ulrich; Külcü, Nevzat; Arslan, Hakan

2009-02-04

The synthesis of the title compound, C(14)H(19)BrN(2)OS, involves the reaction of 4-bromo-benzoyl chloride with potassium thio-cyanate in acetone followed by condensation of the resulting 4-bromo-benzoyl isothio-cyanate with di-n-propyl-amine. Typical thio-urea carbonyl and thio-carbonyl double bonds, as well as shortened C-N bonds, are observed in the title compound. The short C-N bond lengths in the centre of the mol-ecule reveal the effects of resonance in this part of the mol-ecule. The asymmetric unit of the title compound contains two crystallographically independent mol-ecules, A and B. There is very little difference between the bond lengths and angles of these mol-ecules. In mol-ecule B, one di-n-propyl group is twisted in a -anti-periplanar conformation with C-C-C-H = -179.1 (3)° and the other adopts a -synclinal conformation with C-C-C-H = -56.7 (4)°; in mol-ecule A the two di-n-propyl groups are twisted in + and -anti-periplanar conformations, with C-C-C-H = -179.9 (3) and 178.2 (3)°, respectively. In the crystal, the mol-ecules are linked into dimeric pairs via pairs of N-H⋯S hydrogen bonds.

N-(N-[2-(3,5-Difluorophenyl)acetyl]-(S)-alanyl)-(S)-phenylglycine tert-butyl ester (DAPT): an inhibitor of γ-secretase, revealing fine electronic and hydrogen-bonding features

Energy Technology Data Exchange (ETDEWEB)

Czerwinski, Andrzej; Valenzuela, Francisco [Peptides International Inc., 11621 Electron Drive, Louisville, KY 40299 (United States); Afonine, Pavel [Lawrence Berkeley National Laboratory, One Cyclotron Road, Building 64R0121, Berkeley, CA 94720 (United States); Dauter, Miroslawa, E-mail: dauter@anl.gov [Basic Research Program, SAIC-Frederick Inc., Synchrotron Radiation Research Section, MCL, NCI, Argonne National Laboratory, Biosciences Division, Building 202, Argonne, IL 60439 (United States); Dauter, Zbigniew [Synchrotron Radiation Research Section, MCL, NCI, Argonne National Laboratory, Biosciences Division, Building 202, Argonne, IL 60439 (United States); Peptides International Inc., 11621 Electron Drive, Louisville, KY 40299 (United States)

2010-12-01

The title compound, C{sub 23}H{sub 26}F{sub 2}N{sub 2}O{sub 4}, is a dipeptidic inhibitor of γ-secretase, one of the enzymes involved in Alzheimer’s dis@@ease. The mol@@ecule adopts a compact conformation, without intra@@molecular hydrogen bonds. In the crystal structure, one of the amide N atoms forms the only inter@@molecular N—H⋯O hydrogen bond; the second amide N atom does not form hydrogen bonds. High-resolution synchrotron diffraction data permitted the unequivocal location and refinement without restraints of all H atoms, and the identification of the characteristic shift of the amide H atom engaged in the hydrogen bond from its ideal position, resulting in a more linear hydrogen bond. Significant residual densities for bonding electrons were revealed after the usual SHELXL refinement, and modeling of these features as additional inter@@atomic scatterers (IAS) using the program PHENIX led to a significant decrease in the R factor from 0.0411 to 0.0325 and diminished the r.m.s. deviation level of noise in the final difference Fourier map from 0.063 to 0.037 e Å{sup −3}.

Enthalpies of solution of N,N,N',N'-tetramethylurea in amides, dimethylsulphoxide, and acetone at 298.15 K

International Nuclear Information System (INIS)

Ivanov, Evgeniy V.; Smirnov, Valeriy I.

2008-01-01

The enthalpies of solution Δ sol H m m were determined for N,N,N',N'-tetramethylurea in formamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, and acetone. Measurements were made at 298.15 K and molalities m = (0.004 to 0.031) mol . kg -1 with a precise isoperibol ampoule-type calorimeter. Standard enthalpies of solution Δ sol H m 0 and transfer Δ tr H m 0 from one solvent to another were computed. The enthalpies of solution of the solute in the hydrogen-non-bonding media were found to be endothermic and weak depending on the nature of methylation in a solvent molecule. It was concluded that the solvent proton-donor ability and existing steric hindrances for hydrogen bonding and other intermolecular interactions play the key role in solvation of tetramethylurea

A comparative computational study of Csbnd N and Csbnd C bonding visible to NIR absorbing croconines

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Chetti, Prabhakar; Tripathi, Anuj

2018-03-01

The lowest electronic excitations and charge transfer properties in two series of croconine dyes; 1) molecules with Csbnd N bonding, having an absorption in the visible region (400-600 nm) and 2) molecules with Csbnd C bonding, showing absorption in visible to near infrared (NIR) region (600-1100 nm) are analyzed by quantum-chemical calculations. The absorption maxima in Csbnd C bonding croconines (CCR) are always having 200-300 nm red shifted than its corresponding Csbnd N bonding croconines (NCR). The reason for this drastic red shift in CCR series than its corresponding NCR has been systematically studied by DFT, TDDFT and SAC-CI methods. It is found that, CCR series are with less charge transfer in nature and are having larger diradical character, whereas NCR series molecules showing larger charge transfer with lower diradical character. The change in bonding mode of central five membered croconate ring, from Csbnd N to Csbnd C, destabilization and/stabilization of HOMO LUMO levels were observed. This study may helpful in the design and synthesis of new visible to NIR absorbing croconine dyes which are useful in materials applications.

Crystal structures of N2,N3,N5,N6-tetrakis(pyridin-2-ylmethylpyrazine-2,3,5,6-tetracarboxamide and N2,N3,N5,N6-tetrakis(pyridin-4-ylmethylpyrazine-2,3,5,6-tetracarboxamide

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Dilovan S. Cati

2017-02-01

Full Text Available The title compounds, C32H28N10O4· unknown solvent, (I, and C32H28N10O4, (II, are pyrazine-2,3,5,6-tetracarboxamide derivatives. In (I, the substituents are (pyridin-2-ylmethylcarboxamide, while in (II, the substituents are (pyridin-4-ylmethylcarboxamide. Both compounds crystallize in the monoclinic space group P21/n, with Z′ = 1 for (I, and Z′ = 0.5 for (II. The whole molecule of (II is generated by inversion symmetry, the pyrazine ring being situated about a center of inversion. In (I, the four pyridine rings are inclined to the pyrazine ring by 83.9 (2, 82.16 (18, 82.73 (19 and 17.65 (19°. This last dihedral angle involves a pyridine ring that is linked to the adjacent carboxamide O atom by an intramolecular C—H...O hydrogen bond. In compound (II, the unique pyridine rings are inclined to the pyrazine ring by 33.3 (3 and 81.71 (10°. There are two symmetrical intramolecular C—H...O hydrogen bonds present in (II. In the crystal of (I, molecules are linked by N—H...O and N—H...N hydrogen bonds, forming layers parallel to (10-1. The layers are linked by C—H...O and C—H...N hydrogen bonds, forming a three-dimensional framework. In the crystal of (II, molecules are linked by N—H...N hydrogen bonds, forming chains propagating along the [010] direction. The chains are linked by a weaker N—H...N hydrogen bond, forming layers parallel to the (101 plane, which are in turn linked by C—H...O hydrogen bonds, forming a three-dimensional structure. In the crystal of compound (I, a region of disordered electron density was treated with the SQUEEZE routine in PLATON [Spek (2015. Acta Cryst. C71, 9–18]. Their contribution was not taken into account during refinement. In compound (II, one of the pyridine rings is positionally disordered, and the refined occupancy ratio for the disordered Car—Car—Npy atoms is 0.58 (3:0.42 (3.

Deuterium and 15N fractionation in N2H+ during the formation of a Sun-like star

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De Simone, M.; Fontani, F.; Codella, C.; Ceccarelli, C.; Lefloch, B.; Bachiller, R.; López-Sepulcre, A.; Caux, E.; Vastel, C.; Soldateschi, J.

2018-05-01

Although chemical models predict that the deuterium fractionation in N2H+ is a good evolutionary tracer in the star formation process, the fractionation of nitrogen is still a poorly understood process. Recent models have questioned the similar evolutionary trend expected for the two fractionation mechanisms in N2H+, based on a classical scenario in which ion-neutral reactions occurring in cold gas should have caused an enhancement of the abundance of N2D+, 15NNH+, and N15NH+. In the framework of the ASAI IRAM-30m large program, we have investigated the fractionation of deuterium and 15N in N2H+ in the best known representatives of the different evolutionary stages of the Sun-like star formation process. The goal is to ultimately confirm (or deny) the classical `ion-neutral reactions' scenario that predicts a similar trend for D and 15N fractionation. We do not find any evolutionary trend of the 14N/15N ratio from both the 15NNH+ and N15NH+ isotopologues. Therefore, our findings confirm that, during the formation of a Sun-like star, the core evolution is irrelevant in the fractionation of 15N. The independence of the 14N/15N ratio with time, found also in high-mass star-forming cores, indicates that the enrichment in 15N revealed in comets and protoplanetary discs is unlikely to happen at core scales. Nevertheless, we have firmly confirmed the evolutionary trend expected for the H/D ratio, with the N2H+/N2D+ ratio decreasing before the pre-stellar core phase, and increasing monotonically during the protostellar phase. We have also confirmed clearly that the two fractionation mechanisms are not related.

trans-Bis(N,N-diethylethylenediaminenickel(II dibromide

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James P. Donahue

2011-01-01

Full Text Available The structure of the title compound, [Ni(C6H16N22]Br2 or [Ni(Et2en2]Br2 (Et2en is asymmetric N,N-diethylethylenediamine, containing an NiII atom (site symmetry overline{1} in square-planar NiN4 coordination, is described and contrasted with related structures containing NiII in octahedral coordination with axial X− ligands (X− = variable anions. The dialkylated N atom has an appreciably longer bond length to the NiII atom [1.9666 (13 Å] than does the unsubstituted N atom [1.9202 (14 Å]. The Ni—N bond lengths in [Ni(Et2en2]Br2 are significantly shorter than corresponding values in tetragonally distorted [Ni(Et2en2X2] compounds (X = −O2CCF3, OH2, or −NCS, which have a triplet ground state. The electronic configuration in these axially ligated [Ni(Et2en2X2] compounds populates the metal-based dx2-y2 orbital, which is Ni—N antibonding in character. Each Et2en ligand in each [Ni(Et2en2]2+ cation forms a pair of N—H...Br hydrogen bonds to the Br− anions, one above and below the NiN4 square plane. Thus, a ribbon of alternating Br− pairs and [Ni(Et2en2]2+ cations that are canted at 65° relative to one another is formed by hydrogen bonds.

Experimental and theoretical investigation of the production of cations containing C-N bonds in the reaction of benzene with atomic nitrogen ions

International Nuclear Information System (INIS)

Di Stefano, Marco; Rosi, Marzio; Sgamellotti, Antonio; Ascenzi, Daniela; Bassi, Davide; Franceschi, Pietro; Tosi, Paolo

2003-01-01

In the last few years, astronomical spectra have revealed the presence of aromatic and polyaromatic molecules in extraterrestrial environments, near carbon stars, in molecular clouds and meteorites. Moreover, the recent observation of benzene in interstellar space has noticeably increased the interest in the entire class of molecules and in their chemical behavior. In this work, we have investigated the reaction between the benzene molecule and the atomic nitrogen cation and, in particular, the mechanisms by which the reactants are converted into cationic products containing at least one C-N bond, according to the general scheme C 6 H 6 +N + →H m C n N + +C x H y . We have measured the energy dependence of the cross section in a guided ion beam tandem mass spectrometer. Relevant stationary points of the potential energy surface have been studied by using the density functional theory hybrid functional B3LYP with the 6-31G* basis set. Thermochemical calculations, and the comparison with experimental results, allow us to distinguish between exoergic and endoergic processes and to obtain a detailed description of the reaction mechanisms. We show that aromatic hydrocarbons may be converted into organic-nitrogen compounds via the insertion of N + into the benzene ring and the formation of C-N bonds from C-C ring reactants

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

Science.gov (United States)

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

2017-06-01

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

rac-N-[Hydroxy(4-pyridylmethyl]picolinamide: a hemiamidal

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Muhammad Altaf

2010-07-01

Full Text Available The title compound, C12H11N3O2, a hemiamidal, was synthesized by solvent-free aldol condensation at room temperature by grinding picolinamide with isonicotinaldehyde in a 1:1 molar ratio. In the molecule, the two pyridine rings are inclined to one another by 58.75 (6°. They are linked, at positions 2 and 4, by the hemiamidal bridge (–CO—NH—CHOH–. The NH-group H atom forms an intramolecular hydrogen bond with the N atom of the picolinamide pyridine ring. In the crystal, symmetry-related molecules are linked via N—H...O hydrogen bonds, involving the NH group H atom of the hemiamidal bridge and the hydroxy O atom, forming inversion-related dimers, with graph-set R22(8. Adjacent molecules are also linked via O—H...N hydrogen bonds, involving the hydroxy substituent and the 4-pyridine N atom. Together these interactions lead to the formation of double-stranded ribbon-like hydrogen-bonded polymers propagating in [010]. The latter are further connected via C—H...O hydrogen bonds involving the carbonyl O atom, so forming a two-dimensional network in (011.

Thermochemistry of 1,1'-di-n-butyluranocene

International Nuclear Information System (INIS)

Kuznetsov, N.T.; Mitin, V.A.; Kir'yanov, K.V.; Sevast'yanov, V.G.; Bogdanov, V.A.

1987-01-01

Combustion enthalpy, temperature dependence of saturated vapor of uranium 1,1'-di-n-butylcyclooctatetraene (1,1'-di-n-butyluranocene) are determined for the first time and its thermal behaviour is studied using DTA and high temperature spectrophotometry. Melting and thermal decomposition beginning temperatures; melting and vaporization enthalpies; standard formation enthalpies in a condensed and gaseous states; mean dissociation energy of uranium bond to n-butylcyclooctatetraene are calculated according to the data obtained

Enhanced photocatalytic degradation of Amaranth dye on mesoporous anatase TiO2: evidence of C-N, N[double bond, length as m-dash]N bond cleavage and identification of new intermediates.

Science.gov (United States)

Naik, Amarja P; Salkar, Akshay V; Majik, Mahesh S; Morajkar, Pranay P

2017-07-01

The photocatalytic degradation mechanism of Amaranth, a recalcitrant carcinogenic azo dye, was investigated using mesoporous anatase TiO 2 under sunlight. Mesoporous anatase TiO 2 of a high photocatalytic activity has been synthesized using a sol-gel method and its photocatalytic activity for the degradation of Amaranth dye has been evaluated with respect to Degussa P25. The effect of bi-dentate complexing agents like oxalic acid, ethylene glycol and urea on the surface properties of TiO 2 catalyst has been investigated using TG-DTA, FTIR, HR-TEM, SAED, PXRD, EDS, UV-DRS, PL, BET N 2 adsorption-desorption isotherm studies and BJH analysis. The influence of catalyst properties such as the mesoporous network, pore volume and surface area on the kinetics of degradation of Amaranth as a function of irradiation time under natural sunlight has been monitored using UV-Vis spectroscopy. The highest rate constant value of 0.069 min -1 was obtained for the photocatalytic degradation of Amaranth using TiO 2 synthesized via a urea assisted sol-gel synthesis method. The effect of the reaction conditions such as pH, TiO 2 concentration and Amaranth concentration on the photodegradation rate has been investigated. The enhanced photocatalytic activity of synthesized TiO 2 in comparison with P25 is attributed to the mesoporous nature of the catalyst leading to increased pore diameter, pore volume, surface area and enhanced charge carrier separation efficiency. New intermediates of photocatalytic degradation of Amaranth, namely, sodium-3-hydroxynaphthalene-2,7-disulphonate, 3-hydroxynaphthalene, sodium-4-aminonaphthalenesulphonate and sodium-4-aminobenzenesulphonate have been identified using LC-ESI-MS for the very first time, providing direct evidence for simultaneous bond cleavage pathways (-C-N-) and (-N[double bond, length as m-dash]N-). A new plausible mechanism of TiO 2 catalysed photodegradation of Amaranth along with the comparison of its toxicity to that of its degradation

C-N bond cleavage of anilines by a (salen)ruthenium(VI) nitrido complex.

Science.gov (United States)

Man, Wai-Lun; Xie, Jianhui; Pan, Yi; Lam, William W Y; Kwong, Hoi-Ki; Ip, Kwok-Wa; Yiu, Shek-Man; Lau, Kai-Chung; Lau, Tai-Chu

2013-04-17

We report experimental and computational studies of the facile oxidative C-N bond cleavage of anilines by a (salen)ruthenium(VI) nitrido complex. We provide evidence that the initial step involves nucleophilic attack of aniline at the nitrido ligand of the ruthenium complex, which is followed by proton and electron transfer to afford a (salen)ruthenium(II) diazonium intermediate. This intermediate then undergoes unimolecular decomposition to generate benzene and N2.

Propiedades mecánicas de uniones obtenidas mediante soldadura por difusión dinámica en un acero de media aleación

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Gómez de Salazar, J. M.

2001-04-01

Full Text Available Mechanical properties in Dynamic Diffusion Bonded (DDB in a A.S.T.M. 1045 steel (0.45 %C joints were studied. The thermomechanical cycle added to the process, favours both the initial deformation stage and probably the diffusion mechanism which participate in bond formation.

En el presente trabajo se estudian las propiedades mecánicas de uniones obtenidas mediante Soldadura por Difusión Dinámica (SDD en un acero ASTM 1045 (0,45 %C. La aplicación de ciclos termomecánicos en el proceso favorece las etapas iniciales de deformación y, probablemente, los mecanismos difusivos que participan en la formación de la unión.

4-Bromo-N-(di-n-propyl­carbamothioyl)­benzamide

OpenAIRE

Binzet, Gün; Flörke, Ulrich; Külcü, Nevzat; Arslan, Hakan

2009-01-01

The synthesis of the title compound, C14H19BrN2OS, involves the reaction of 4-bromo­benzoyl chloride with potassium thio­cyanate in acetone followed by condensation of the resulting 4-bromo­benzoyl isothio­cyanate with di-n-propyl­amine. Typical thio­urea carbonyl and thio­carbonyl double bonds, as well as shortened C—N bonds, are observed in the title compound. The short C—N bond lengths in the centre of the mol­ecule reveal the effects of resonance in this part of the mol­ecule. The asymmet...

Twisted Amides: From Obscurity to Broadly Useful Transition-Metal-Catalyzed Reactions by N-C Amide Bond Activation.

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Liu, Chengwei; Szostak, Michal

2017-05-29

The concept of using amide bond distortion to modulate amidic resonance has been known for more than 75 years. Two classic twisted amides (bridged lactams) ingeniously designed and synthesized by Kirby and Stoltz to feature fully perpendicular amide bonds, and as a consequence emanate amino-ketone-like reactivity, are now routinely recognized in all organic chemistry textbooks. However, only recently the use of amide bond twist (distortion) has advanced to the general organic chemistry mainstream enabling a host of highly attractive N-C amide bond cross-coupling reactions of broad synthetic relevance. In this Minireview, we discuss recent progress in this area and present a detailed overview of the prominent role of amide bond destabilization as a driving force in the development of transition-metal-catalyzed cross-coupling reactions by N-C bond activation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

N-(4-Chlorophenyl-2-(hydroxyiminoacetamide

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Jie Sun

2009-09-01

Full Text Available The title compound, C8H7ClN2O2, is an intermediate in the synthesis of 5-chloroisatin, which can be further transformed to 5-chloro-2-indolinone via a Wolff–Kishne reduction. The C2N acetamide plane forms a dihedral angle of 6.3 (3° with the benzene ring. An intramolecular C—H...O interaction results in the formation of a six-membered ring. In the crystal, intermolecular N—H...O, N—H...N and O—H...O hydrogen bonds link the molecules into multimers, forming sheets.

N,N′-Bis(4-bromophenyl-N,N′-dimethylurea

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Alexandre Pocinho

2018-02-01

Full Text Available The structure of the title compound, C15H14Br2N2O, at 180 K has monoclinic (P21/n symmetry. It was obtained unexpectedly from the decomposition of the parent 4-bromo-N-tert-butoxycarbonyl-N-methyl-aniline. It exhibits an `endo' conformation with angles between the two aromatic rings slightly lower than the average values found for similar compounds on the Cambridge Structural Database. In the crystal, C—H...O hydrogen bonds and short Br...Br halogen bonds [3.444 (1 Å] are observed.

Ab initio investigations of the electronic structure and chemical bonding of Li2ZrN2

International Nuclear Information System (INIS)

Matar, S.F.; Pöttgen, R.; Al Alam, A.F.; Ouaini, N.

2012-01-01

The electronic structure of the ternary nitride Li 2 ZrN 2 is examined from ab initio with DFT computations for an assessment of the properties of chemical bonding. The compound is found insulating with 1.8 eV band gap; it becomes metallic and less ionic upon removal of one equivalent of Li. The chemical interaction is found mainly between Zr and N on one hand and Li and N on the other hand. While all pair interactions are bonding, antibonding N–N interactions are found dominant at the top of the valence band of Li 2 ZrN 2 and they become less intense upon removal of Li. From energy differences the partial delithiation leading to Li 2−x ZrN 2 (x=∼1) is favored. - Graphical abstract: Trigonal structure of Li 2 ZrN 2 showing the Zr–N–Li layers along the c-axis. Highlights: ► Li 2 ZrN 2 calculated insulating with a 1.8 eV gap in agreement with its light green color. ► Lithium de-intercalation is energetically favored for one out of two Li equivalents. ► Li plays little role in the change of the structure, ensured by Zr and N binding. ► Similar changes in the electronic structure as for various intercalated phases of ZrN.

Formation of InN phase by sequential ion implantation

International Nuclear Information System (INIS)

Santhana Raman, P.; Ravichandran, V.; Nair, K.G.M.; Kesavamoorthy, R.; Kalavathi, S.; Panigrahi, B.K.; Dhara, S.

2006-01-01

Formation of InN phase by sequentially implanting nitrogen on indium implanted silica was demonstrated. The growth of embedded InN phase on as-implanted and post-implantation annealed sample was studied using Glancing Incidence X-Ray Diffraction (GIXRD) and Raman spectroscopy. Existence of both cubic and hexagonal phases of InN was observed. Results of irradiation induced ripening of In nanoclusters due to N + ion implantation was also studied. (author)

Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

Science.gov (United States)

Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

2016-02-01

This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

EI/MS/MS SPECTRA OF N-MONOSUBS-TITUTED CYANOACETAMIDES

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NATAŠA ILIĆ

2010-12-01

Full Text Available The electron-ionization induced mass spectra of twenty six N-monosubstituted cyanoacetamides were recorded and their fragmentation patterns were stu¬died. The effect of N-alkyl and N-aryl substituents to the fragmentation of the investigated compounds was discussed. Mechanistic generalization lead to a conclusion that fission of the carbon-carbon bonds next to carbonyl function or nitrogen were processes common for N-alkyl and N-(4-substituted phenyl cya¬noacetamides. In some amides, the elimination of the acyl group by a ketene fragment gave rise to the more stable ion. Cycloalkyl amides could not frag¬ment by single carbon-carbon bond fission, but subsequent rearrangement resulted in formation of stable even electron ion. N-(4-substituted phenyl cyanoacetamides were more stable showing also characteristic fragmentation depending on substituent present at phenyl ring.

Hemoglobin as a nitrite anhydrase: modeling methemoglobin-mediated N2O3 formation.

Science.gov (United States)

Hopmann, Kathrin H; Cardey, Bruno; Gladwin, Mark T; Kim-Shapiro, Daniel B; Ghosh, Abhik

2011-05-27

Nitrite has recently been recognized as a storage form of NO in blood and as playing a key role in hypoxic vasodilation. The nitrite ion is readily reduced to NO by hemoglobin in red blood cells, which, as it happens, also presents a conundrum. Given NO's enormous affinity for ferrous heme, a key question concerns how it escapes capture by hemoglobin as it diffuses out of the red cells and to the endothelium, where vasodilation takes place. Dinitrogen trioxide (N(2)O(3)) has been proposed as a vehicle that transports NO to the endothelium, where it dissociates to NO and NO(2). Although N(2)O(3) formation might be readily explained by the reaction Hb-Fe(3+)+NO(2)(-)+NO⇌Hb-Fe(2+)+N(2)O(3), the exact manner in which methemoglobin (Hb-Fe(3+)), nitrite and NO interact with one another is unclear. Both an "Hb-Fe(3+)-NO(2)(-)+NO" pathway and an "Hb-Fe(3+)-NO+NO(2)(-) " pathway have been proposed. Neither pathway has been established experimentally. Nor has there been any attempt until now to theoretically model N(2)O(3) formation, the so-called nitrite anhydrase reaction. Both pathways have been examined here in a detailed density functional theory (DFT, B3LYP/TZP) study and both have been found to be feasible based on energetics criteria. Modeling the "Hb-Fe(3+)-NO(2)(-)+NO" pathway proved complex. Not only are multiple linkage-isomeric (N- and O-coordinated) structures conceivable for methemoglobin-nitrite, multiple isomeric forms are also possible for N(2)O(3) (the lowest-energy state has an N-N-bonded nitronitrosyl structure, O(2)N-NO). We considered multiple spin states of methemoglobin-nitrite as well as ferromagnetic and antiferromagnetic coupling of the Fe(3+) and NO spins. Together, the isomerism and spin variables result in a diabolically complex combinatorial space of reaction pathways. Fortunately, transition states could be successfully calculated for the vast majority of these reaction channels, both M(S)=0 and M(S)=1. For a six-coordinate Fe(3+)-O

N,N'-Dimethylthiourea dioxide formation from N,N'-dimethylthiourea reflects hydrogen peroxide concentrations in simple biological systems

International Nuclear Information System (INIS)

Curtis, W.E.; Muldrow, M.E.; Parker, N.B.; Barkley, R.; Linas, S.L.; Repine, J.E.

1988-01-01

The authors hypothesized that measurement of a specific product from reaction of N,N'-dimethylthiourea (Me 2 TU) and H 2 O 2 would provide a good indication of the H 2 O 2 scavenging and protection seen after addition of Me 2 TU to biological systems. They found that addition of H 2 O 2 to Me 2 TU yielded a single stable product, Me 2 TU dioxide. Me 2 TU dioxide formation correlated with Me 2 TU consumption as a function of added H 2 O 2 concentration and was prevented by simultaneous addition of catalase (but not boiled catalase), superoxide dismutase, dimethyl sulfoxide, mannitol, or sodium benzoate. Me 2 TU dioxide formation, Me 2 TU consumption, and H 2 O 2 concentration increases occurred in mixtures containing phorbol 12-myristate 13-acetate (PMA) and normal human neutrophils but not in mixtures containing PMA and neutrophils from patients with chronic granulomatous disease or in mixtures containing PMA and normal neutrophils and catalase. Me 2 TU dioxide formation also occurred in isolated rat lungs perfused with Me 2 TU and H 2 O 2 but not in lungs perfused with Me 2 TU and elastase, histamine, or oleic acid. In contrast, Me 2 TU dioxide formation did not occur after exposure of Me 2 TU to 60 Co-generated hydroxyl radical or hypochlorous acid in the presence of catalase. The results indicate that reaction of Me 2 TU with H 2 O 2 selectively forms Me 2 TU may be useful for assessing the presence and significance of H 2 O 2 in biological systems

Diverse Cd(II) compounds based on N-benzoyl-L-glutamic acid and N-donor ligands: Structures and photoluminescent properties

International Nuclear Information System (INIS)

Ma, Ning; Guo, Wei-Ying; Song, Hui-Hua; Yu, Hai-Tao

2016-01-01

Five new Cd(II) coordination polymers with N-benzoyl-L-glutamic acid (H_2bzgluO) and different N-donor ligands, [Cd(bzgluO)(2,2′-bipy)(H_2O)]_n (1), [Cd(bzgluO)(2,4′-bipy)_2(H_2O)·3H_2O]_n (2), [Cd(bzgluO)(phen)·H_2O]_n (3), [Cd(bzgluO)(4,4′-bipy)(H_2O)]_n (4), [Cd(bzgluO)(bpp)(H_2O)·2H_2O]_n (5) were synthesized (2,2′-bipy=2,2′-bipyridine, 2,4′-bipy=2,4′-bipyridine, phen=1,10-phenanthroline, 4,4′-bipy=4,4′-bipyridine, bpp=1,3-di(4-pyridyl)propane). Compounds 1–2 exhibit a 1D single-chain structure. Compound 1 generates a 2D supramolecular structure via π–π stacking and hydrogen bonding, 3D architecture of compound 2 is formed by hydrogen bonding. Compound 3 features a 1D double-chain structure, which are linked by π–π interactions into a 2D supramolecular layer. Compounds 4-5 display a 2D network structure. Neighboring layers of 4 are extended into a 3D supramolecular architecture through hydrogen bonding. The structural diversity of these compounds is attributed to the effect of ancillary N-donor ligands and coordination modes of H_2bzgluO. Luminescent properties of 1–5 were studied at room temperature. Circular dichroism of compounds 1, 2 and 5 were investigated. - Graphical abstract: Five new Cd(II) metal coordination compounds with H_2bzgluO and different N-donor ligands were synthesized and characterized. Compounds 1, 2 and 3 present 1D structures, compounds 4 and 5 display 2D networks. Results indicate that auxiliary ligands and coordination modes of H_2bzgluO play an important role in governing the formation of final frameworks, and the hydrogen-bonding and π–π stacking interactions contribute the formation of the diverse supramolecular architectures. Furthermore, the different crystal structures influence the emission spectra significantly. - Highlights: • It is rarely reported that complexes prepared with N-benzoyl-L-glutamic acid. • Each complex displays diverse structures and different supramolecular

Palladium-catalyzed Suzuki-Miyaura coupling of amides by carbon-nitrogen cleavage: general strategy for amide N-C bond activation.

Science.gov (United States)

Meng, Guangrong; Szostak, Michal

2016-06-15

The first palladium-catalyzed Suzuki-Miyaura cross-coupling of amides with boronic acids for the synthesis of ketones by sterically-controlled N-C bond activation is reported. The transformation is characterized by operational simplicity using bench-stable, commercial reagents and catalysts, and a broad substrate scope, including substrates with electron-donating and withdrawing groups on both coupling partners, steric-hindrance, heterocycles, halides, esters and ketones. The scope and limitations are presented in the synthesis of >60 functionalized ketones. Mechanistic studies provide insight into the catalytic cycle of the cross-coupling, including the first experimental evidence for Pd insertion into the amide N-C bond. The synthetic utility is showcased by a gram-scale cross-coupling and cross-coupling at room temperature. Most importantly, this process provides a blueprint for the development of a plethora of metal catalyzed reactions of typically inert amide bonds via acyl-metal intermediates. A unified strategy for amide bond activation to enable metal insertion into N-C amide bond is outlined ().

Formation of scandium nitride (ScN) layer on gallium arsenide (GaAs) substrate using a combined technique of e-beam evaporator and ammonia annealing treatment

Energy Technology Data Exchange (ETDEWEB)

Yong Shee Meng, Alvin [Institute of Nano Optoelectronics Research and Technology (INOR), sains@usm, Persiaran Bukit Jambul, 11900 Bayan Lepas, Penang (Malaysia); Zainal, Norzaini, E-mail: norzaini@usm.my [Nano Optoelectronics Research and Laboratory, Universiti Sains Malaysia, sains@usm, Persiaran Bukit Jambul, 11900, Bayan Lepas, Penang (Malaysia); Hassan, Zainuriah; Ibrahim, Kamarulazizi [Institute of Nano Optoelectronics Research and Technology (INOR), sains@usm, Persiaran Bukit Jambul, 11900 Bayan Lepas, Penang (Malaysia)

2015-12-30

Graphical abstract: - Highlights: • Forming ScN layer using electron e-beam evaporator with successive NH{sub 3} annealing thermal has been successfully demonstrated. • NH{sub 3} annealing played the role in changing the grain structure of the ScN layer. • The existence of Sc−N bonds was confirmed by XPS measurement. • The 900 °C annealed ScN layer showed the best structural and optical characteristics. • ScN layer annealed at 980 °C exhibited poor structural and optical characteristics. - Abstract: A demonstration on a new technique of growing ScN using electron beam (e-beam) evaporator, coupled with successive ammonia (NH{sub 3}) annealing treatment is presented in this paper. The annealing temperature was varied at 750, 800, 850, 900 and 980 °C in order to obtain the best ScN layer. It was found that as the annealing temperature increased, the surface morphology of the ScN layer changed and ScN grains formed abundantly on the surface. The best surface of ScN layer was found in the 900 °C annealed sample. However, the roughness of the ScN increased with temperature. The photoluminescence (PL) peak of the near-to-band-edge (NBE) of ScN was observable in all samples and its intensity was the highest in the 900 °C annealed sample. Note that when the annealing treatment was conducted at 980 °C, the GaN PL peak is observable. Raman peaks of TO(X) of ScN were much evident at the annealing temperature above 900 °C. The formation of Sc−N bonds was confirmed by X-ray spectroscopy (XPS) measurement. In the end of this work, we propose that the formation of ScN using the above techniques was successful, with thermal annealing at the temperature of 900 °C.

Formation of scandium nitride (ScN) layer on gallium arsenide (GaAs) substrate using a combined technique of e-beam evaporator and ammonia annealing treatment

International Nuclear Information System (INIS)

Yong Shee Meng, Alvin; Zainal, Norzaini; Hassan, Zainuriah; Ibrahim, Kamarulazizi

2015-01-01

Graphical abstract: - Highlights: • Forming ScN layer using electron e-beam evaporator with successive NH_3 annealing thermal has been successfully demonstrated. • NH_3 annealing played the role in changing the grain structure of the ScN layer. • The existence of Sc−N bonds was confirmed by XPS measurement. • The 900 °C annealed ScN layer showed the best structural and optical characteristics. • ScN layer annealed at 980 °C exhibited poor structural and optical characteristics. - Abstract: A demonstration on a new technique of growing ScN using electron beam (e-beam) evaporator, coupled with successive ammonia (NH_3) annealing treatment is presented in this paper. The annealing temperature was varied at 750, 800, 850, 900 and 980 °C in order to obtain the best ScN layer. It was found that as the annealing temperature increased, the surface morphology of the ScN layer changed and ScN grains formed abundantly on the surface. The best surface of ScN layer was found in the 900 °C annealed sample. However, the roughness of the ScN increased with temperature. The photoluminescence (PL) peak of the near-to-band-edge (NBE) of ScN was observable in all samples and its intensity was the highest in the 900 °C annealed sample. Note that when the annealing treatment was conducted at 980 °C, the GaN PL peak is observable. Raman peaks of TO(X) of ScN were much evident at the annealing temperature above 900 °C. The formation of Sc−N bonds was confirmed by X-ray spectroscopy (XPS) measurement. In the end of this work, we propose that the formation of ScN using the above techniques was successful, with thermal annealing at the temperature of 900 °C.

C=C bond cleavage on neutral VO3(V2O5)n clusters.

Science.gov (United States)

Dong, Feng; Heinbuch, Scott; Xie, Yan; Bernstein, Elliot R; Rocca, Jorge J; Wang, Zhe-Chen; Ding, Xun-Lei; He, Sheng-Gui

2009-01-28

The reactions of neutral vanadium oxide clusters with alkenes (ethylene, propylene, 1-butene, and 1,3-butadiene) are investigated by experiments and density function theory (DFT) calculations. Single photon ionization through extreme ultraviolet radiation (EUV, 46.9 nm, 26.5 eV) is used to detect neutral cluster distributions and reaction products. In the experiments, we observe products (V(2)O(5))(n)VO(2)CH(2), (V(2)O(5))(n)VO(2)C(2)H(4), (V(2)O(5))(n)VO(2)C(3)H(4), and (V(2)O(5))(n)VO(2)C(3)H(6), for neural V(m)O(n) clusters in reactions with C(2)H(4), C(3)H(6), C(4)H(6), and C(4)H(8), respectively. The observation of these products indicates that the C=C bonds of alkenes can be broken on neutral oxygen rich vanadium oxide clusters with the general structure VO(3)(V(2)O(5))(n=0,1,2...). DFT calculations demonstrate that the reaction VO(3) + C(3)H(6) --> VO(2)C(2)H(4) + H(2)CO is thermodynamically favorable and overall barrierless at room temperature. They also provide a mechanistic explanation for the general reaction in which the C=C double bond of alkenes is broken on VO(3)(V(2)O(5))(n=0,1,2...) clusters. A catalytic cycle for alkene oxidation on vanadium oxide is suggested based on our experimental and theoretical investigations. The reactions of V(m)O(n) with C(6)H(6) and C(2)F(4) are also investigated by experiments. The products VO(2)(V(2)O(5))(n)C(6)H(4) are observed for dehydration reactions between V(m)O(n) clusters and C(6)H(6). No product is detected for V(m)O(n) clusters reacting with C(2)F(4). The mechanisms of the reactions between VO(3) and C(2)F(4)/C(6)H(6) are also investigated by calculations at the B3LYP/TZVP level.

Formation of a dinuclear copper(II) complex through the cleavage of CBond' name='Single-Bond' value='Single-Bond'/>N bond of 1-benzoyl-3-(pyridin-2-yl)-1H-pyrazole

Energy Technology Data Exchange (ETDEWEB)

Shardin, Rosidah; Pui, Law Kung; Yamin, Bohari M. [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM 43600 Bangi, Selangor (Malaysia); Kassim, Mohammad B. [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM 43600 Bangi, Selangor, Malaysia and Fuel Cell Institute, Universiti Kebangsaan Malaysia, UKM 43600 Bangi, Selangor (Malaysia)

2014-09-03

A simple mononuclear octahedral copper(II) complex was attempted from the reaction of three moles of 1-benzoyl-3-(pyridin-2-yl)-1H-pyrazole and one mole of copper(II) perchlorate hexahydrate in methanol. However, the product of the reaction was confirmed to be a dinuclear copper(II) complex with μ-(3-(pyridin-2-yl)-pyrazolato) and 3-(pyridin-2-yl)-1H-pyrazole ligands attached to each of the Cu(II) centre atom. The copper(II) ion assisted the cleavage of the C{sub benzoyl}Bond' name='Single-Bond' value='Single-Bond'/>N bond afforded a 3-(pyridin-2-yl)-1H-pyrazole molecule. Deprotonation of the 3-(pyridin-2-yl)-1H-pyrazole gave a 3-(pyridin-2-yl)-pyrazolato, which subsequently reacted with the Cu(II) ion to give the (3-(pyridin-2-yl)-pyrazolato)(3-(pyridin-2-yl)-1H-pyrazole)Cu(II) product moiety. The structure of the dinuclear complex was confirmed by x-ray crystallography. The complex crystallized in a monoclinic crystal system with P2(1)/n space group and cell dimensions of a = 12.2029(8) Å, b = 11.4010(7) Å, c = 14.4052(9) Å and β = 102.414(2)°. The compound was further characterized by mass spectrometry, CHN elemental analysis, infrared and UV-visible spectroscopy and the results concurred with the x-ray structure. The presence of d-d transition at 671 nm (ε = 116 dm{sup 3} mol{sup −1} cm{sup −1}) supports the presence of Cu(II) centres.

Crystal structure of trans-(1,8-dibutyl-1,3,6,8,10,13-hexaazacyclotetradecane-κ4N3,N6,N10,N13bis(isonicotinato-κOcopper(II from synchrotron data

Directory of Open Access Journals (Sweden)

Jong Won Shin

2015-02-01

Full Text Available The title compound, [Cu(C6H4NO22(C16H38N6] has been synthesized and characterized by structure analysis based on synchrotron data and by FT–IR spectroscopy. The asymmetric unit consists of half of the CuII complex, the other half being completed by inversion symmetry. The CuII ion has a tetragonally distorted octahedral coordination sphere with four secondary N atoms of the azamacrocyclic ligand in the equatorial plane [Cu—Neq = 2.018 (12 Å] and two O atoms of the isonicotinate anions at the axial positions [Cu—Oax = 2.4100 (11 Å]. Intramolecular N—H...O hydrogen bonds between one of the secondary amine N—H groups of the azamacrocyclic ligand and the non-coordinating O atom of the isonicotinate ions stabilize the molecular structure. Intermolecular N—H...N hydrogen bonds between the other macrocyclic N—H group and the pyridine N atom of an adjacent isonicotinate anion as well as π–π interactions [centroid-to-centroid distance 3.711 (2 Å] lead to the formation of rods parallel to [001].

Assembly of phosphonic acids on GaN and AlGaN

Energy Technology Data Exchange (ETDEWEB)

Simpkins, B S; Stine, R; Theodore, N D; Pehrsson, P E [Chemistry Division, Naval Research Laboratory, Washington DC (United States); Hong, S [Thomas Jefferson High School, McClean, VA (United States); Maekinen, A J [Optical Sciences Division, Naval Research Laboratory, Washington, DC (United States); Mastro, M A; Eddy, C R Jr [Electronics Science and Technology Division, Naval Research Laboratory, Washington, DC (United States)

2010-01-13

Self-assembled monolayers of octadecylphosphonic acid and 16-phosphonohexadecanoic acid (PHDA) were formed on the semiconductor substrates gallium nitride (GaN) and aluminium gallium nitride (AlGaN). The presence of the molecular layers was verified through x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Structural information was acquired with infrared spectroscopy which verified the bonding orientation of the carboxyl-containing PHDA. The impact of the molecular layers on the channel conductivity and the surface electronic structure of an AlGaN/GaN heterostructure was measured. Our results indicate that pinning of the surface Fermi level prohibits modification of the channel conductivity by the layer. However, a surface dipole of {approx}0.8 eV is present and associated with both phosphonic acid layers. These results are of direct relevance to field-effect-based biochemical sensors and metal-semiconductor contact formation for this system and provide a fundamental basis for further applications of GaN and AlGaN technology in the fields of biosensing and microelectronics.

Theoretical study of the interaction of N2 with water molecules. (H2O)/sub n/:N2, n = 1--8

International Nuclear Information System (INIS)

Curtiss, L.A.; Eisgruber, C.L.

1984-01-01

Ab initio molecular orbital calculations including correlation energy have been carried out on the interaction of a single H 2 O molecule with N 2 . The potential energy surface for H 2 O:N 2 is found to have a minimum corresponding to a HOH xxx N 2 structure with a weak ( -1 ) hydrogen bond. A second, less stable, configuration corresponding to a H 2 O xxx N 2 structure with N 2 bonded side on to the oxygen of H 2 O was found to be either a minimum or a saddle point in the potential energy surface depending on the level of calculation. The minimal STO-3G basis set was used to investigate the interaction of up to eight H 2 O molecules with N 2 . Two types of clusters, one containing only HOH xxx N 2 interactions and the other containing both HOH xxxN 2 and H 2 O xxx N 2 interactions, were investigated for [N 2 :(H 2 O)/sub n/, n = 2--8

Reductive Elimination Leading to C-C Bond Formation in Gold(III) Complexes: A Mechanistic and Computational Study.

Science.gov (United States)

Rocchigiani, Luca; Fernandez-Cestau, Julio; Budzelaar, Peter H M; Bochmann, Manfred

2018-06-21

The factors affecting the rates of reductive C-C cross-coupling reactions in gold(III) aryls were studied by using complexes that allow easy access to a series of electronically modified aryl ligands, as well as to gold methyl and vinyl complexes, by using the pincer compounds [(C^N^C)AuR] (R=C 6 F 5 , CH=CMe 2 , Me and p-C 6 H 4 X, where X=OMe, F, H, tBu, Cl, CF 3 , or NO 2 ) as starting materials (C^N^C=2,6-(4'-tBuC 6 H 3 ) 2 pyridine dianion). Protodeauration followed by addition of one equivalent SMe 2 leads to the quantitative generation of the thioether complexes [(C^N-CH)AuR(SMe 2 )] + . Upon addition of a second SMe 2 pyridine is displaced, which triggers the reductive aryl-R elimination. The rates for these cross-couplings increase in the sequence k(vinyl)>k(aryl)≫k(C 6 F 5 )>k(Me). Vinyl-aryl coupling is particularly fast, 1.15×10 -3  L mol -1  s -1 at 221 K, whereas both C 6 F 5 and Me couplings encountered higher barriers for the C-C bond forming step. The use of P(p-tol) 3 in place of SMe 2 greatly accelerates the C-C couplings. Computational modelling shows that in the C^N-bonded compounds displacement of N by a donor L is required before the aryl ligands can adopt a conformation suitable for C-C bond formation, so that elimination takes place from a four-coordinate intermediate. The C-C bond formation is the rate-limiting step. In the non-chelating case, reductive C(sp 2 )-C(sp 2 ) elimination from three-coordinate ions [(Ar 1 )(Ar 2 )AuL] + is almost barrier-free, particularly if L=phosphine. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organocatalysis by hydrogen-bonding: a new approach to controlled/living polymerization of α-amino acid N-carboxyanhydrides

KAUST Repository

Zhao, Wei; Gnanou, Yves; Hadjichristidis, Nikolaos

2015-01-01

A new method, based on hydrogen-bonding organocatalysis, was developed to achieve living ring-opening polymerization of N-carboxyanhydride of α-amino acids using aminoalcohols as initiators in the presence of N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea (TU-S). The thiourea provides, through hydrogen bonding, simultaneous activation of NCA monomers/reversible deactivation of polymer chain-ends/silencing of the tertiary amine and thus allows the polymerization to proceed in a highly controllable mode. For example, by using N,N-dimethyl ethanolamine (DMEA), as an initiator in the presence of TU-S, a series of well-defined linear polypeptides with differently designed Mns (3.01 × 104-18.10 × 104) and low PDI values (1.02-1.05) were successfully synthesized. This general strategy was also extended to the synthesis of well-defined di- and multi-armed polypeptides by using di-, tri-, or tetra-aminoalcohol initiators (methyldiethanolamine (MDEA), triethanolamine (TEA) or N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (THEED)) in the presence of TU-S. © The Royal Society of Chemistry 2015.

Defect Formation and Electronic Transport at AlGaN/GaN Interfaces

International Nuclear Information System (INIS)

Haller, E.E.; Hsu, Leonardo; Walukiewicz, W.

1997-01-01

We have calculated the effects of charged defects located near an Al x Ga 1-x N/GaN heterointerface on the transport properties of the two dimensional electron gas confined at the interface and also determined the distribution of those defects taking into consideration the dependence of the formation energy on the Fermi level. In addition, we have investigated the effects of hydrostatic pressure on such modulation doped heterostructures and find that pressure can be used to make the determination of the properties of the two dimensional electron gas easier by eliminating parallel three dimensional conduction paths

MOLECULAR COMPLEXES OF SULPHUR DIOXIDE WITH N,O-CONTAINING ORGANIC BASES (REVIEW

Directory of Open Access Journals (Sweden)

R. E. Khoma

2016-10-01

Full Text Available The literature data on the synthesis, stoichiometry, structure and relative stability of molecular  complexes of sulphur dioxide with N,O-containing organic bases have been systematized and  generalized. It was shown that the yield of the reaction product of sulfur dioxide with organic  bases (such as amines are strongly influenced by the conditions of synthesis: the nature of  the solvent (basicity, polarity, the temperature and SO2:L ratio in the reaction medium. The stoichiometry of SO2*nL molecular complexes depends on ligand denticity, as well as its  ability to H-bonding. The reaction of the sulfur oxide (IV with organic bases can give S←N and S←O complexes. With the increase of the value of base proton affinity the decrease ΔrSN values has been marked. Characteristic parameter Δr SN = r SN – a1(rS+ rN (where rSNis the S←N donor-acceptor bond length has been determined by microwave spectroscopy and X-ray analysis, rSand rNwere the tabulated values of the homopolar covalent radii of sulphur and nitrogen heteroatoms. The dependence of formation enthalpy of molecular complexes of basic amines and spectral characteristics has been noted; enthalpy-entropy compensation for S←N and S←O complex-es has been stated. Despite the limited experimental data on the thermodynamics of complex formation and the lengths of donor-acceptor bonds for the same compounds it has been found bond S←N strength in SO2 molecular complexes to depend on the intrinsic value of ΔrSN. The contribution of van der Waals forces and charge transfer forces to the formation of molecular complexes of sulphur dioxide has been stated.

N,N′-(Ethane-1,2-diyldi-o-phenylenebis(pyridine-2-carboxamide

Directory of Open Access Journals (Sweden)

Shuranjan Sarkar

2011-11-01

Full Text Available The title molecule, C26H22N4O2, is centrosymmetric and adopts an anti conformation. Two intramolecular hydrogen bonds, viz. amide–pyridine N—H...N and phenyl–amide C—H...O, stabilize the trans conformation of the (pyridine-2-carboxamidophenyl group about the amide plane. In the crystal, the presence of weak intermolecular C—H...O hydrogen bonds results in the formation of a three-dimensional network.

Molecular dynamics studies of defect formation during heteroepitaxial growth of InGaN alloys on (0001) GaN surfaces.

Science.gov (United States)

Gruber, J; Zhou, X W; Jones, R E; Lee, S R; Tucker, G J

2017-05-21

We investigate the formation of extended defects during molecular-dynamics (MD) simulations of GaN and InGaN growth on (0001) and ([Formula: see text]) wurtzite-GaN surfaces. The simulated growths are conducted on an atypically large scale by sequentially injecting nearly a million individual vapor-phase atoms towards a fixed GaN surface; we apply time-and-position-dependent boundary constraints that vary the ensemble treatments of the vapor-phase, the near-surface solid-phase, and the bulk-like regions of the growing layer. The simulations employ newly optimized Stillinger-Weber In-Ga-N-system potentials, wherein multiple binary and ternary structures are included in the underlying density-functional-theory training sets, allowing improved treatment of In-Ga-related atomic interactions. To examine the effect of growth conditions, we study a matrix of >30 different MD-growth simulations for a range of In x Ga 1-x N-alloy compositions (0 ≤  x  ≤ 0.4) and homologous growth temperatures [0.50 ≤  T/T * m ( x ) ≤ 0.90], where T * m ( x ) is the simulated melting point. Growths conducted on polar (0001) GaN substrates exhibit the formation of various extended defects including stacking faults/polymorphism, associated domain boundaries, surface roughness, dislocations, and voids. In contrast, selected growths conducted on semi-polar ([Formula: see text]) GaN, where the wurtzite-phase stacking sequence is revealed at the surface, exhibit the formation of far fewer stacking faults. We discuss variations in the defect formation with the MD growth conditions, and we compare the resulting simulated films to existing experimental observations in InGaN/GaN. While the palette of defects observed by MD closely resembles those observed in the past experiments, further work is needed to achieve truly predictive large-scale simulations of InGaN/GaN crystal growth using MD methodologies.

Antiferromagnetic MnN layer on the MnGa(001) surface

Energy Technology Data Exchange (ETDEWEB)

Guerrero-Sánchez, J., E-mail: guerrero@cnyn.unam.mx; Takeuchi, Noboru

2016-12-30

Highlights: • A ferromagnetic Gallium terminated surface is stable before N incorporation. • After N incorporation, an antiferromagnetic MnN layer becomes stable in a wide range of chemical potential. • Spin density distribution shows an antiferromagnetic/ferromagnetic (MnN/MnGa) arrangement at the surface. - Abstract: Spin polarized first principles total energy calculations have been applied to study the stability and magnetic properties of the MnGa(001) surface and the formation of a topmost MnN layer with the deposit of nitrogen. Before nitrogen adsorption, surface formation energies show a stable gallium terminated ferromagnetic surface. After incorporation of nitrogen atoms, the antiferromagnetic manganese terminated surface becomes stable due to the formation of a MnN layer (Mn-N bonding at the surface). Spin density distribution shows a ferromagnetic/antiferromagnetic arrangement in the first surface layers. This thermodynamically stable structure may be exploited to growth MnGa/MnN magnetic heterostructures as well as to look for exchange biased systems.

Ground-State Distortion in N-Acyl-tert-butyl-carbamates (Boc) and N-Acyl-tosylamides (Ts): Twisted Amides of Relevance to Amide N-C Cross-Coupling.

Science.gov (United States)

Szostak, Roman; Shi, Shicheng; Meng, Guangrong; Lalancette, Roger; Szostak, Michal

2016-09-02

Amide N-C(O) bonds are generally unreactive in cross-coupling reactions employing low-valent transition metals due to nN → π*C═O resonance. Herein we demonstrate that N-acyl-tert-butyl-carbamates (Boc) and N-acyl-tosylamides (Ts), two classes of acyclic amides that have recently enabled the development of elusive amide bond N-C cross-coupling reactions with organometallic reagents, are intrinsically twisted around the N-C(O) axis. The data have important implications for the design of new amide cross-coupling reactions with the N-C(O) amide bond cleavage as a key step.

Iodide, azide, and cyanide complexes of (N,C), (N,N), and (N,O) metallacycles of tetra- and pentavalent uranium

International Nuclear Information System (INIS)

Benaud, Olivier; Berthet, Jean-Claude; Thuery, Pierre; Ephritikhine, Michel

2011-01-01

In contrast to the neutral macrocycle [UN* 2 (N,C)] (1) [N* = N(SiMe 3 ) 3 ; N,C = CH 2 SiMe 2 N-(SiMe 3 )] which was quite inert toward I 2 , the anionic bismetallacycle [NaUN*(N,C) 2 ] (2) was readily transformed into the enlarged monometallacycle [UN*(N,N)I] (4) [N,N = (Me 3 Si)NSiMe 2 CH 2 CH 2 SiMe 2 N(SiMe 3 )] resulting from C-C coupling of the two CH 2 groups, and [NaUN*(N,O) 2 ] (3) [N,O = OC(=CH 2 )SiMe 2 N(SiMe 3 )], which is devoid of any U-C bond, was oxidized into the UV bismetallacycle [Na{UN*(N,O) 2 }2(μ-I)] (5). Sodium amalgam reduction of 4 gave the U(III) compound [UN*(N,N)] (6). Addition of MN 3 or MCN to the (N,C), (N,N), and (N,O) metallacycles 1, 4, and 5 led to the formation of the anionic azide or cyanide derivatives M[UN* 2 (N,C)(N 3 )] [M = Na, 7a or Na(15-crown-5), 7b], M[UN* 2 (N,C)(CN)] [M = NEt 4 , 8a or Na(15-crown-5), 8b or K(18-crown-6), 8c], M[UN*(N,N)(N 3 ) 2 ] [M = Na, 9a or Na(THF)4, 9b], [NEt 4 ][UN*(N,N)(CN) 2 ] (10), M[UN*(N,O) 2 (N 3 )] [M = Na, 11a or Na(15-crown-5), 11b], M[UN*(N,O) 2 (CN)] [M = NEt 4 , 12a or Na(15-crown-5), 12b]. In the presence of excess iodine in THF, the cyanide 12a was converted back into the iodide 5, while the azide 11a was transformed into the neutral UV complex [U(N{SiMe 3 }-SiMe 2 C{CHI}O) 2 I(THF)] (13). The X-ray crystal structures of 4, 7b, 8a-c, 9b, 10, 12b, and 13 were determined. (authors)

Stability analysis and structural rules of titanium dioxide clusters (TiO2)n with n = 1-9

International Nuclear Information System (INIS)

Zhang Weiwei; Han Ye; Yao Shuyu; Sun Haiqing

2011-01-01

Highlights: · We investigated the structure and stability of (TiO 2 ) n clusters with n = 1-9. · Some initial structures are introduced and proved to be the real global minimum. · We summarized the structural rules for small (TiO 2 ) n clusters. · The bonding features for the energy increment or decrement of the clusters are investigated. · A general shift of stability and reactivity with size for (TiO 2 ) n clusters. - Abstract: Atomic clusters have been considered as models for fundamental mechanistic insight into complex surfaces and catalysts. The structure and stability of (TiO 2 ) n clusters with n = 1-9 are investigated using the b3lyp hybrid density functional method in this paper. Some of the clusters are proposed initially and proved to be the real global minima. The stability and band gap of the clusters as a function of size are also investigated. The structural rules of the clusters are first summarized. The lowest-lying (TiO 2 ) n isomers tend to form some compact rather than quasi-linear or circular structures. The oxygen atom in 4-fold coordination and the titanium atom in 4-fold coordination favor the cluster stability. The 5-fold coordinated Ti-atom, the Ti-Ti bond and the terminal Ti-O bond lead to stability penalty for the clusters. No evidence for a regular variation in stability or reactivity with size of the clusters has shown. The structural rules can serve as guiding factors for formation research and structure design of (TiO 2 ) n and other transition metal oxide clusters.

Accurate characterization and understanding of interface trap density trends between atomic layer deposited dielectrics and AlGaN/GaN with bonding constraint theory

Energy Technology Data Exchange (ETDEWEB)

Ramanan, Narayanan; Lee, Bongmook; Misra, Veena, E-mail: vmisra@ncsu.edu [Department of Electrical and Computer Engineering, North Carolina State University, 2410 Campus Shore Drive, Raleigh, North Carolina 27695 (United States)

2015-06-15

Many dielectrics have been proposed for the gate stack or passivation of AlGaN/GaN based metal oxide semiconductor heterojunction field effect transistors, to reduce gate leakage and current collapse, both for power and RF applications. Atomic Layer Deposition (ALD) is preferred for dielectric deposition as it provides uniform, conformal, and high quality films with precise monolayer control of film thickness. Identification of the optimum ALD dielectric for the gate stack or passivation requires a critical investigation of traps created at the dielectric/AlGaN interface. In this work, a pulsed-IV traps characterization method has been used for accurate characterization of interface traps with a variety of ALD dielectrics. High-k dielectrics (HfO{sub 2}, HfAlO, and Al{sub 2}O{sub 3}) are found to host a high density of interface traps with AlGaN. In contrast, ALD SiO{sub 2} shows the lowest interface trap density (<2 × 10{sup 12 }cm{sup −2}) after annealing above 600 °C in N{sub 2} for 60 s. The trend in observed trap densities is subsequently explained with bonding constraint theory, which predicts a high density of interface traps due to a higher coordination state and bond strain in high-k dielectrics.

Collision-Induced Dissociation Study of Strong Hydrogen-Bonded Cluster Ions Y-(HF) n (Y=F, O2) Using Atmospheric Pressure Corona Discharge Ionization Mass Spectrometry Combined with a HF Generator.

Science.gov (United States)

Sakamoto, Kenya; Sekimoto, Kanako; Takayama, Mitsuo

2017-01-01

Hydrogen fluoride (HF) was produced by a homemade HF generator in order to investigate the properties of strong hydrogen-bonded clusters such as (HF) n . The HF molecules were ionized in the form of complex ions associated with the negative core ions Y - produced by atmospheric pressure corona discharge ionization (APCDI). The use of APCDI in combination with the homemade HF generator led to the formation of negative-ion HF clusters Y - (HF) n (Y=F, O 2 ), where larger clusters with n ≥4 were not detected. The mechanisms for the formation of the HF, F - (HF) n , and O 2 - (HF) n species were discussed from the standpoints of the HF generator and APCDI MS. By performing energy-resolved collision-induced dissociation (CID) experiments on the cluster ions F - (HF) n ( n =1-3), the energies for the loss of HF from F - (HF) 3 , F - (HF) 2 , and F - (HF) were evaluated to be 1 eV or lower, 1 eV or higher, and 2 eV, respectively, on the basis of their center-of-mass energy ( E CM ). These E CM values were consistent with the values of 0.995, 1.308, and 2.048 eV, respectively, obtained by ab initio calculations. The stability of [O 2 (HF) n ] - ( n =1-4) was discussed on the basis of the bond lengths of O 2 H-F - (HF) n and O 2 - H-F(HF) n obtained by ab initio calculations. The calculations indicated that [O 2 (HF) 4 ] - separated into O 2 H and F - (HF) 3 .

A density functional theory study of the TMG adsorption on the GaN surface

Energy Technology Data Exchange (ETDEWEB)

Ptasinska, Maria; Soltys, Jakub; Piechota, Jacek [Interdisciplinary Centre for Materials Modelling, University of Warsaw, ul. Pawinskiego 5a, 02-106 Warszawa (Poland); Krukowski, Stanislaw [Interdisciplinary Centre for Materials Modelling, University of Warsaw, ul. Pawinskiego 5a, 02-106 Warszawa (Poland); Institute of High Pressure Physics, Polish Academy of Sciences, ul. Sokolowska 29/37, 01-142 Warsaw (Poland)

2011-07-01

TMG (trimetylogallium) and NH{sub 3} (ammonia) are widely used reactants in the metal organic chemical vapor deposition (MOCVD) technique used in the growth of the GaN thin films. We have recently examined theoretically, with the help of the density functional theory (DFT), TMG adsorption on the GaN(0001) surface in order to study formation of bonds between Ga and N. Dangling bonds on the GaN(0001) surface were saturated with the hydrogen atoms. The slab polarization, which is due to the dangling bonds present on the GaN(0001) surface, and energy of the system in the vicinity of TMG was computed for different distances between the surface atoms and TMG. We also studied TMG diffusion on the GaN surface. As a result, the energy path for diffusion from Top N to Hollow was obtained.

Electrochemical formation of AlN in molten LiCl-KCl-Li{sub 3}N systems

Energy Technology Data Exchange (ETDEWEB)

Goto, Takuya [Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University, Sakyo, Kyoto 606-8501 (Japan)]. E-mail: goto@energy.kyoto-u.ac.jp; Iwaki, Takayuki [Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University, Sakyo, Kyoto 606-8501 (Japan); Ito, Yasuhiko [Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University, Sakyo, Kyoto 606-8501 (Japan)

2005-01-30

Electrochemical formation of aluminum nitride was investigated in molten LiCl-KCl-Li{sub 3}N systems at 723 K. When Al was anodically polarized at 1.0 V (versus Li{sup +}/Li), oxidation of nitride ions proceeded to form adsorbed nitrogen atoms, which reacted with the surface to form AlN film. The obtained nitrided film had a thickness of sub-micron order. The obtained nitrided layer consisted of two regions; the outer layer involving AlN and aluminum oxynitride and the inner layer involving metallic Al and AlN. When Al electrode was anodically polarized at 2.0 V, anodic dissolution of Al electrode occurred to give aluminum ions, which reacted with nitride ions in the melt to produce AlN particles (1-5 {mu}m of diameter) of wurtzite structure.

Bonded exciplex formation: electronic and stereoelectronic effects.

Science.gov (United States)

Wang, Yingsheng; Haze, Olesya; Dinnocenzo, Joseph P; Farid, Samir; Farid, Ramy S; Gould, Ian R

2008-12-18

As recently proposed, the singlet-excited states of several cyanoaromatics react with pyridine via bonded-exciplex formation, a novel concept in photochemical charge transfer reactions. Presented here are electronic and steric effects on the quenching rate constants, which provide valuable support for the model. Additionally, excited-state quenching in poly(vinylpyridine) is strongly inhibited both relative to that in neat pyridine and also to conventional exciplex formation in polymers, consistent with a restrictive orientational requirement for the formation of bonded exciplexes. Examples of competing reactions to form both conventional and bonded exciplexes are presented, which illustrate the delicate balance between these two processes when their reaction energetics are similar. Experimental and computational evidence is provided for the formation of a bonded exciplex in the reaction of the singlet excited state of 2,6,9,10-tetracyanoanthracene (TCA) with an oxygen-substituted donor, dioxane, thus expanding the scope of bonded exciplexes.

Diverse Cd(II) compounds based on N-benzoyl-L-glutamic acid and N-donor ligands: Structures and photoluminescent properties

Energy Technology Data Exchange (ETDEWEB)

Ma, Ning; Guo, Wei-Ying; Song, Hui-Hua, E-mail: songhuihua@mail.hebtu.edu.cn; Yu, Hai-Tao, E-mail: haitaoyu@mail.hebtu.edu.cn

2016-01-15

Five new Cd(II) coordination polymers with N-benzoyl-L-glutamic acid (H{sub 2}bzgluO) and different N-donor ligands, [Cd(bzgluO)(2,2′-bipy)(H{sub 2}O)]{sub n} (1), [Cd(bzgluO)(2,4′-bipy){sub 2}(H{sub 2}O)·3H{sub 2}O]{sub n} (2), [Cd(bzgluO)(phen)·H{sub 2}O]{sub n} (3), [Cd(bzgluO)(4,4′-bipy)(H{sub 2}O)]{sub n} (4), [Cd(bzgluO)(bpp)(H{sub 2}O)·2H{sub 2}O]{sub n} (5) were synthesized (2,2′-bipy=2,2′-bipyridine, 2,4′-bipy=2,4′-bipyridine, phen=1,10-phenanthroline, 4,4′-bipy=4,4′-bipyridine, bpp=1,3-di(4-pyridyl)propane). Compounds 1–2 exhibit a 1D single-chain structure. Compound 1 generates a 2D supramolecular structure via π–π stacking and hydrogen bonding, 3D architecture of compound 2 is formed by hydrogen bonding. Compound 3 features a 1D double-chain structure, which are linked by π–π interactions into a 2D supramolecular layer. Compounds 4-5 display a 2D network structure. Neighboring layers of 4 are extended into a 3D supramolecular architecture through hydrogen bonding. The structural diversity of these compounds is attributed to the effect of ancillary N-donor ligands and coordination modes of H{sub 2}bzgluO. Luminescent properties of 1–5 were studied at room temperature. Circular dichroism of compounds 1, 2 and 5 were investigated. - Graphical abstract: Five new Cd(II) metal coordination compounds with H{sub 2}bzgluO and different N-donor ligands were synthesized and characterized. Compounds 1, 2 and 3 present 1D structures, compounds 4 and 5 display 2D networks. Results indicate that auxiliary ligands and coordination modes of H{sub 2}bzgluO play an important role in governing the formation of final frameworks, and the hydrogen-bonding and π–π stacking interactions contribute the formation of the diverse supramolecular architectures. Furthermore, the different crystal structures influence the emission spectra significantly. - Highlights: • It is rarely reported that complexes prepared with N-benzoyl-L-glutamic acid

Influences of argon gas shielding on diffusion bonding of Ti-6Al-4V alloy to aluminum; Influencia del argón como gas protector en la difusión durante el proceso de unión de la aleación Ti6Al4V con el aluminio

Energy Technology Data Exchange (ETDEWEB)

Akcaa, A.; Gursela, A.

2017-09-01

This study presents a diffusion bonding process of commercially pure aluminum to Ti-6Al-4V alloy. Prepared samples were exposed to temperature of 560, 600 and 640 °C for the bonding time of 30, 45 and 60 min at the atmosphere of argon gas and non-argon. Diffusion bonding is a dissimilar metal welding process which can be applied to the materials without causing any physical deformations. The processed samples were also metallographically prepared, optically examined followed by Vickers microhardness test in order to determine joint strength. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used in this work to investigate the compositional changes in order to observe the influence of atmosphere shielding in the transition zone. The result of tests and analyses were tried to be compared with the effect of argon shielding. The significant influences have been observed in the argon shielding during diffusion bonding process. [Spanish] Este estudio presenta los procesos de difusión durante la unión de aluminio puro con la aleación Ti6Al4V. Se expusieron probetas a las temperaturas de 560, 600 y 640 ºC durante un tiempo de unión de 30, 45 y 60 min en una atmósfera en presencia y ausencia de gas argón. La unión por difusión es un proceso de soldadura entre metales distintos que puede ser aplicado a los materiales sin causar deformaciones físicas. Las probetas procesadas fueron preparadas también metalográficamente, examinadas por miscroscopía óptica, seguido de ensayos de microdureza Vickers para determinar el límite elástico. Se utilizó microscopía electrónica de barrido (SEM) y espectroscopía de energias dispersivas (EDS) para determinar los cambios en la composición y estudiar la influencia del argón como gas protector en la zona de transición. La influencia más importante se ha observado durante el proceso de difusión en estado sólido.

Autoformación: una perspectiva diferente Self-formation: a different perspective

Directory of Open Access Journals (Sweden)

Ángel García del Dujo

2007-12-01

Full Text Available El objetivo de este trabajo es el de mostrar que una de las competencias que hoy día deben fomentarse, si queremos responder realmente a las demandas laborales desde una perspectiva socioeducativa, es la de la autoformación. Nadie pone en duda que el modelo de desarrollo que se pretende implementar en la sociedad actual requiere una mayor masa formativa, un mayor nivel de formación en cada individuo. No obstante, pensamos que también requiere un modelo de formación, sino diferente sí, al menos, complementario. Más allá de una pedagogía individualista, mentalista, aislacionista y abstracta, basada en una lógica de conocimientos e instituciones, pensamos que el sistema formativo debe recuperar una visión más social y global de los procesos de producción y de la vida. Una lógica que esté apoyada en los modos de acción que tienen lugar en el mundo de la vida y del trabajo. Sobreponiéndonos a los simples listados de competencias, nos hemos preguntado por la forma como se generan, adquieren y desarrollan las competencias, concluyendo que el enfoque de la autoformación responde no sólo a determinadas tendencias económicas sino a las transformaciones que viene conociendo la sociedad en la última década. Teniendo en cuenta que el ser humano es algo más que un nódulo productivo, laboral, y la autofor-mación es una característica que se predica del sujeto en cuanto tal, en su totalidad y en relación con su entorno, concluimos el trabajo presentando la autoformación como competencia clave y como modelo de formación para la sociedad del siglo XXI.The objective of this work is to show that one of the competences that nowadays must be fostered, if we really want to respond to the demands for workforce from a socioeducational perspective, is that of self-formation. There is little doubt that the development model that society currently wants to implement requires a larger formative volume, a higher level of formation of each

DFT study of small fullerene dimer complexes C_2_0-N_m@C_n (m = 1-6 and n = 24, 28, 32, 36 and 40)

International Nuclear Information System (INIS)

Kaur, Sandeep; Sharma, Amrish; Mudahar, Isha

2016-01-01

First principle calculations based on density functional theory were performed to calculate the structural and electronic properties of C_2_0-N_m@C_n dimer complexes. The calculated binding energies of the complexes formed are comparable to C_6_0 dimer which ensures their stability. The bond lengths of these dimer complexes were found to be nearly same as pure complexes C_2_0-C_n. Further, nitrogen (N) atoms were encapsulated inside the secondary cage (C_n) of dimer complexes and the number of N atoms depends on diameter of the cage. The HOMO-LUMO gaps of new proposed complexes indicate the increase in gap as compared to pure complexes. Mulliken charge analysis of these complexes has been studied which shows the significant charge transfer from the N atoms to the secondary cage of these complexes. The study propose the formation of the new dimer complexes which are stable and are able to encapsulate atoms which are otherwise reactive in free space.

Location of protons in N-H···N hydrogen-bonded systems: a theoretical study on intramolecular pyridine-dihydropyridine and pyridine-pyridinium pairs.

Science.gov (United States)

Mori, Yukie; Takano, Keiko

2012-08-21

Two-dimensional potential energy surfaces (PESs) were calculated for the degenerate intramolecular proton transfer (PT) in two N-H···N hydrogen-bonded systems, (Z)-2-(2-pyridylmethylidene)-1,2-dihydropyridine (1) and monoprotonated di(2-pyridyl) ether (2), at the MP2/cc-pVDZ level of theory. The calculated PES had two minima in both cases. The energy barrier in 1 was higher than the zero-point energy (ZPE) level, while that in 2 was close to the ZPE. Vibrational wavefunctions were obtained by solving time-independent Schrödinger equations with the calculated PESs. The maximum points of the probability density were shifted from the energy minima towards the region where the covalent N-H bond was elongated and the N···N distance shortened. The effects of a polar solvent on the PES were investigated with the continuum or cluster models in such a way that the solute-solvent electrostatic interactions could be taken into account under non-equilibrated conditions. A solvated contact ion-pair was modelled by a cluster consisting of one cation 2, one chloride ion and 26 molecules of acetonitrile. The calculation with this model suggested that the bridging proton is localised in the deeper well due to the significant asymmetry of the PES and the high potential barrier.

Molecular Cloud Structures and Massive Star Formation in N159

Science.gov (United States)

Nayak, O.; Meixner, M.; Fukui, Y.; Tachihara, K.; Onishi, T.; Saigo, K.; Tokuda, K.; Harada, R.

2018-02-01

The N159 star-forming region is one of the most massive giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC). We show the 12CO, 13CO, CS molecular gas lines observed with ALMA in N159 west (N159W) and N159 east (N159E). We relate the structure of the gas clumps to the properties of 24 massive young stellar objects (YSOs) that include 10 newly identified YSOs based on our search. We use dendrogram analysis to identify properties of the molecular clumps, such as flux, mass, linewidth, size, and virial parameter. We relate the YSO properties to the molecular gas properties. We find that the CS gas clumps have a steeper size–linewidth relation than the 12CO or 13CO gas clumps. This larger slope could potentially occur if the CS gas is tracing shocks. The virial parameters of the 13CO gas clumps in N159W and N159E are low (<1). The threshold for massive star formation in N159W is 501 M ⊙ pc‑2, and the threshold for massive star formation in N159E is 794 M ⊙ pc‑2. We find that 13CO is more photodissociated in N159E than N159W. The most massive YSO in N159E has cleared out a molecular gas hole in its vicinity. All the massive YSO candidates in N159E have a more evolved spectral energy distribution type in comparison to the YSO candidates in N159W. These differences lead us to conclude that the giant molecular cloud complex in N159E is more evolved than the giant molecular cloud complex in N159W.

Crystal structure of N′′-(2-ethoxy-2-oxoethyl-N,N,N′,N′-tetramethyl-N′′-[3-(1,3,3-trimethylureidopropyl]guanidinium tetraphenylborate

Directory of Open Access Journals (Sweden)

Ioannis Tiritiris

2015-12-01

Full Text Available In the title salt, C16H34N5O3+·C24H20B−, the C—N bond lengths in the cation are 1.3368 (16, 1.3375 (18 and 1.3594 (17 Å, indicating partial double-bond character. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry and the positive charge is delocalized in the CN3 plane. In the crystal, weak C—H...O contacts are observed between neighbouring guanidinium ions and between guanidinium ions and tetraphenylborate anions. In addition, C—H...π interactions involving guanidinium H atoms and aromatic rings of the anion are present. The phenyl rings form aromatic pockets, in which the cations are embedded. This leads to the formation of a two-dimensional supramolecular pattern along the ab plane.

C-H Bond Functionalization via Hydride Transfer: Formation of α-Arylated Piperidines and 1,2,3,4-Tetrahydroisoquinolines via Stereoselective Intramolecular Amination of Benzylic C-H Bonds

OpenAIRE

Vadola, Paul A.; Carrera, Ignacio; Sames, Dalibor

2012-01-01

We here report a study of the intramolecular amination of sp3 C-H bonds via the hydride transfer cyclization of N-tosylimines (HT-amination). In this transformation, 5-aryl-aldehydes are subjected to N-toluenesulfonamide in the presence of BF3•OEt2 to effect imine formation and HT-cyclization, leading to 2-aryl-piperidines and 3-aryl-1,2,3,4-tetrahydroisoquinolines in a one-pot procedure. We examined the reactivity of a range of aldehyde substrates as a function of their conformational flexib...

Microsolvation of the acetanilide cation (AA(+)) in a nonpolar solvent: IR spectra of AA(+)-L(n) clusters (L = He, Ar, N2; n ≤ 10).

Science.gov (United States)

Schmies, Matthias; Patzer, Alexander; Schütz, Markus; Miyazaki, Mitsuhiko; Fujii, Masaaki; Dopfer, Otto

2014-05-07

Infrared photodissociation (IRPD) spectra of mass-selected cluster ions of acetanilide (N-phenylacetamide), AA(+)-Ln, with the ligands L = He (n = 1-2), Ar (n = 1-7), and N2 (n = 1-10) are recorded in the hydride stretch (amide A, νNH, νCH) and fingerprint (amide I-III) ranges of AA(+) in its (2)A'' ground electronic state. Cold AA(+)-Ln clusters are generated in an electron impact ion source, which predominantly produces the most stable isomer of a given cluster ion. Systematic vibrational frequency shifts of the N-H stretch fundamentals (νNH) provide detailed information about the sequential microsolvation process of AA(+) in a nonpolar (L = He and Ar) and quadrupolar (L = N2) solvent. In the most stable AA(+)-Ln clusters, the first ligand forms a hydrogen bond (H-bond) with the N-H proton of trans-AA(+) (t-AA(+)), whereas further ligands bind weakly to the aromatic ring (π-stacking). There is no experimental evidence for complexes with the less stable cis-AA(+) isomer. Quantum chemical calculations at the M06-2X/aug-cc-pVTZ level confirm the cluster growth sequence derived from the IR spectra. The calculated binding energies of De(H) = 720 and 1227 cm(-1) for H-bonded and De(π) = 585 and 715 cm(-1) for π-bonded Ar and N2 ligands in t-AA(+)-L are consistent with the observed photofragmentation branching ratios of AA(+)-Ln. Comparison between charged and neutral AA((+))-L dimers indicates that ionization switches the preferred ion-ligand binding motif from π-stacking to H-bonding. Electron removal from the HOMO of AA(+) delocalized over both the aromatic ring and the amide group significantly strengthens the C[double bond, length as m-dash]O bond and weakens the N-H bond of the amide group.

Ab-initio studies of the Sc adsorption and the ScN thin film formation on the GaN(000-1)-(2 × 2) surface

International Nuclear Information System (INIS)

Guerrero-Sánchez, J.; Sánchez-Ochoa, F.; Cocoletzi, Gregorio H.; Rivas-Silva, J.F.; Takeuchi, Noboru

2013-01-01

First principles total energy calculations have been performed to investigate the initial stages of the Sc adsorption and ScN thin film formation on the GaN(000-1)-(2 × 2) surface. Studies are done within the periodic density functional theory as implemented in the PWscf code of the Quantum ESPRESSO package. The Sc adsorption at high symmetry sites results in the bridge site as the most stable structure. When a Sc monolayer is deposited above the surface the T4 site results as the most stable geometry. The Sc migration into the first Ga monolayer induces the Ga displaced ad-atom to be adsorbed at the T4-2 site. A ScN bilayer may be obtained under the Ga monolayer. Finally a ScN bilayer may be formed in the wurtzite phase above the surface. The formation energy plots show that in the moderate Ga-rich conditions we obtain the formation of a ScN bilayer under the gallium monolayer. However at N-rich conditions the formation of ScN bilayer above the surface is the most favorable structure. We report the density of states to explain the electronic structure of the most favorable geometries. - Highlights: • Studies of the initial stages in the formation of Sc and ScN structures on GaN • In the adsorption of Sc on the GaN the Br site is the most favorable geometry. • When a Sc replaces a Ga of the first monolayer the displaced Ga occupies a T4-2 site. • For Ga-rich conditions there is formation of ScN under the Ga monolayer. • In N-rich conditions there is formation of ScN in the wurtzite phase

Valence bond solids for SU(n) spin chains: Exact models, spinon confinement, and the Haldane gap

International Nuclear Information System (INIS)

Greiter, Martin; Rachel, Stephan

2007-01-01

To begin with, we introduce several exact models for SU(3) spin chains: First is a translationally invariant parent Hamiltonian involving four-site interactions for the trimer chain, with a threefold degenerate ground state. We provide numerical evidence that the elementary excitations of this model transform under representation 3 of SU(3) if the original spins of the model transform under representation 3. Second is a family of parent Hamiltonians for valence bond solids of SU(3) chains with spin representations 6, 10, and 8 on each lattice site. We argue that of these three models, only the latter two exhibit spinon confinement and, hence, a Haldane gap in the excitation spectrum. We generalize some of our models to SU(n). Finally, we use the emerging rules for the construction of valence bond solid states to argue that models of antiferromagnetic chains of SU(n) spins, in general, possess a Haldane gap if the spins transform under a representation corresponding to a Young tableau consisting of a number of boxes λ which is divisible by n. If λ and n have no common divisor, the spin chain will support deconfined spinons and not exhibit a Haldane gap. If λ and n have a common divisor different from n, it will depend on the specifics of the model including the range of the interaction

Ab initio investigations of the electronic structure and chemical bonding of Li{sub 2}ZrN{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Matar, S.F., E-mail: matar@icmcb-bordeaux.cnrs.fr [CNRS, Universite de Bordeaux, ICMCB, 87 Avenue du Docteur Albert Schweitzer, 33600 Pessac (France); Poettgen, R., E-mail: pottgen@uni-muenster.de [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany); Al Alam, A.F., E-mail: adelalalam@usek.edu.lb [Universite Saint Esprit de Kaslik (USEK), Faculte des Sciences, URA GREVE (CNRS/USEK/UL), Jounieh (Lebanon); Ouaini, N., E-mail: naimouaini@usek.edu.lb [Universite Saint Esprit de Kaslik (USEK), Faculte des Sciences, URA GREVE (CNRS/USEK/UL), Jounieh (Lebanon)

2012-06-15

The electronic structure of the ternary nitride Li{sub 2}ZrN{sub 2} is examined from ab initio with DFT computations for an assessment of the properties of chemical bonding. The compound is found insulating with 1.8 eV band gap; it becomes metallic and less ionic upon removal of one equivalent of Li. The chemical interaction is found mainly between Zr and N on one hand and Li and N on the other hand. While all pair interactions are bonding, antibonding N-N interactions are found dominant at the top of the valence band of Li{sub 2}ZrN{sub 2} and they become less intense upon removal of Li. From energy differences the partial delithiation leading to Li{sub 2-x}ZrN{sub 2} (x={approx}1) is favored. - Graphical abstract: Trigonal structure of Li{sub 2}ZrN{sub 2} showing the Zr-N-Li layers along the c-axis. Highlights: Black-Right-Pointing-Pointer Li{sub 2}ZrN{sub 2} calculated insulating with a 1.8 eV gap in agreement with its light green color. Black-Right-Pointing-Pointer Lithium de-intercalation is energetically favored for one out of two Li equivalents. Black-Right-Pointing-Pointer Li plays little role in the change of the structure, ensured by Zr and N binding. Black-Right-Pointing-Pointer Similar changes in the electronic structure as for various intercalated phases of ZrN.

Evolution of Electrically Active Defects in n-GaN During Heat Treatment Typical for Ohmic Contact Formation

DEFF Research Database (Denmark)

Boturchuk, Ievgen; Scheffler, Leopold Julian; Larsen, Arne Nylandsted

2018-01-01

Ohmic contact formation to n-type GaN often involves high temperature steps, for example sintering at about 800 °C in the case of Ti-based contacts. Such processing steps might cause changes in the distribution, concentration, and properties of the defects. The present work aims at contributing...... to the knowledge about defect evolution in GaN upon processing at different temperatures. The processing temperatures are selected according to fabrication procedures for commonly used ohmic contacts to n-GaN: 300 °C (In-based), 550 °C (Ta-based), and 800 °C (Ti-based). Properties and concentration of the defects...

Recognition of a novel type X═N-Hal···Hal (X = C, S, P; Hal = F, Cl, Br, I) halogen bonding.

Science.gov (United States)

Gushchin, Pavel V; Kuznetsov, Maxim L; Haukka, Matti; Kukushkin, Vadim Yu

2013-04-04

The chlorination of the eight-membered platinum(II) chelates [PtCl2{NH═C(NR2)N(Ph)C(═NH)N(Ph)C(NR2)═NH}] (R = Me (1); R2 = (CH2)5 (2)) with uncomplexed imino group with Cl2 gives complexes bearing the ═N-Cl moiety [PtCl4{NH═C(NR2)N(Ph)C(═NCl)N(Ph)C(NR2)═NH}] (R = Me (3); R2 = (CH2)5 (4)). X-ray study for 3 revealed a novel type intermolecular halogen bonding ═N-Cl···Cl(-), formed between the Cl atom of the chlorinated imine and the chloride bound to the platinum(IV) center. The processing relevant structural data retrieved from the Cambridge Structural Database (CSDB) shows that this type of halogen bonding is realized in 18 more molecular species having X═N-Hal moieties (X = C, P, S, V, W; Hal = Cl, Br, I), but this weak ═N-Hal···Hal(-) bonding was totally neglected in the previous works. The presence of the halogen bonding in 3 was confirmed by theoretical calculations at the density functional theory (DFT, M06-2X) level, and its nature was analyzed.

Dichloridobis(N,N,N′,N′-tetramethylthiourea-κSmercury(II

Directory of Open Access Journals (Sweden)

Sidra Nawaz

2010-08-01

Full Text Available In the title compound, [HgCl2(C5H12N2S2], the HgII atom is located on a twofold rotation axis and is bonded in a distorted tetrahedral coordination mode to two chloride ions and to two tetramethylthiourea (tmtu molecules through their S atoms. The crystal structure is stabilized by C—H...N and C—H...S hydrogen bonds.

Effects of nano TiN addition on the microstructure and mechanical properties of TiC based steel bonded carbides

Institute of Scientific and Technical Information of China (English)

WANG Zhi'an; DAI Haiyang; ZOU Yu

2008-01-01

TiC based steel bonded carbides with the addition of nano TiN were prepared by vicuum sintering techniques.The microstructure was investigated using scanning electron microscopy(SEM)and transmission electron microscopy (TEM),and the mechanical properties,such as bending strength,impact toughness,hardness,and density,were measured.The results indicate that the grain size becomes small and there is uniformity in the steel bonded carbide with nano addition;several smaller carbide particles are also found to be inlaid in the rim of the larger carbide grains and prevent the coalescence of TiC grains.The smaller and larger carbide grains joint firmly,and then the reduction of the average size of the grains leads to the increase in the mechanical properties of the steel bonded carbides with nano addition.But the mechanical properties do not increase monotonously with an increase in nano addition.When the nano TiN addition accounts for 6-8 wt.% of the amount of steel bonded carbides.the mechanical properties reach the maximum values and then decrease with further increase in nano TiN addition.

N-H···S Interaction Continues To Be an Enigma: Experimental and Computational Investigations of Hydrogen-Bonded Complexes of Benzimidazole with Thioethers.

Science.gov (United States)

Wategaonkar, Sanjay; Bhattacherjee, Aditi

2018-05-03

The N-H···S hydrogen bond, even though classified as an unconventional hydrogen bond, is found to bear important structural implications on protein structure and folding. In this article, we report a gas-phase study of the N-H···S hydrogen bond between the model compounds of histidine (benzimidazole, denoted BIM) and methionine (dimethyl sulfide, diethyl sulfide, and tetrahydrothiophene, denoted Me 2 S, Et 2 S, and THT, respectively). A combination of laser spectroscopic methods such as laser-induced fluorescence (LIF), two-color resonant two-photon ionization (2cR2PI), and fluorescence depletion by infrared spectroscopy (FDIR) is used in conjunction with DFT and ab initio calculations to characterize the nature of this prevalent H-bonding interaction in simple bimolecular complexes. A single conformer was found to exist for the BIM-Me 2 S complex, whereas the BIM-Et 2 S and BIM-THT complexes showed the presence of three and two conformers, respectively. These conformers were characterized on the basis of IR spectroscopic results and electronic structure calculations. Quantum theory of atoms in molecules (QTAIM), natural bond orbital (NBO), and energy decomposition (NEDA) analyses were performed to investigate the nature of the N-H···S H-bond. Comparison of the results with the N-H···O type of interactions in BIM and indole revealed that the strength of the N-H···S H-bond is similar to N-H···O in these binary gas-phase complexes.

Conversion of Amides to Esters by the Nickel-Catalyzed Activation of Amide C–N Bonds

Science.gov (United States)

Hie, Liana; Fine Nathel, Noah F.; Shah, Tejas K.; Baker, Emma L.; Hong, Xin; Yang, Yun-Fang; Liu, Peng; Houk, K. N.; Garg, Neil K.

2015-01-01

Amides are common functional groups that have been well studied for more than a century.1 They serve as the key building blocks of proteins and are present in an broad range of other natural and synthetic compounds. Amides are known to be poor electrophiles, which is typically attributed to resonance stability of the amide bond.1,2 Whereas Nature can easily cleave amides through the action of enzymes, such as proteases,3 the ability to selectively break the C–N bond of an amide using synthetic chemistry is quite difficult. In this manuscript, we demonstrate that amide C–N bonds can be activated and cleaved using nickel catalysts. We have used this methodology to convert amides to esters, which is a challenging and underdeveloped transformation. The reaction methodology proceeds under exceptionally mild reaction conditions, and avoids the use of a large excess of an alcohol nucleophile. Density functional theory (DFT) calculations provide insight into the thermodynamics and catalytic cycle of this unusual transformation. Our results provide a new strategy to harness amide functional groups as synthons and are expected fuel the further use of amides for the construction of carbon–heteroatom or carbon–carbon bonds using non-precious metal catalysis. PMID:26200342

n-Electrons of heteroatoms in hydrogen bond and luminescence

International Nuclear Information System (INIS)

Karyakin, A.V.

1985-01-01

Hydrogen bond energy in the process of interaction between water molecules, water molecules and heteroatoms of organic solvents, water molecules and inorganic compounds, is determined, its mechanism being studied. On the basis of X-ray structure and IR-spectroscopic data water state in easily hydrolized compounds of zirconium and hafnium, including sulfates, nitrates, oxychlorides etc. is analyzed. Water state in uranyl nitrate hydrates, the structure of the compounds and their behaviour when they are extracted by TBP, are considered. The reasons for stability of uranyl nitrate hydrates are discussed. The effect of n-electrons of heteroatoms of simple aromatic compound on structural spectra of luminescence in aliphatic and inorganic matrices is investigated

1D and 2D assembly structures by imidazole···chloride hydrogen bonds of iron(II) complexes [Fe(II)(HL(n-Pr))3]Cl·Y (HL(n-Pr) = 2-methylimidazol-4-yl-methylideneamino-n-propyl; Y = AsF6, BF4) and their spin states.

Science.gov (United States)

Fujinami, Takeshi; Nishi, Koshiro; Matsumoto, Naohide; Iijima, Seiichiro; Halcrow, Malcolm A; Sunatsuki, Yukinari; Kojima, Masaaki

2011-12-07

Two Fe(II) complexes fac-[Fe(II)(HL(n-Pr))(3)]Cl·Y (Y = AsF(6) (1) and BF(4) (2)) were synthesized, where HL(n-Pr) is 2-methylimidazole-4-yl-methylideneamino-n-propyl. Each complex-cation has the same octahedral N(6) geometry coordinated by three bidentate ligands and assumes facial-isomerism, fac-[Fe(II)(HL(n-Pr))(3)](2+) with Δ- and Λ-enantiomorphs. Three imidazole groups per Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) are hydrogen-bonded to three Cl(-) ions or, from the viewpoint of the Cl(-) ion, one Cl(-) ion is hydrogen-bonded to three neighbouring fac-[Fe(II)(HL(n-Pr))(3)](2+) cations. The 3 : 3 NH···Cl(-) hydrogen bonds between Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) and Cl(-) generate two kinds of assembly structures. The directions of the 3 : 3 NH···Cl(-) hydrogen bonds and hence the resulting assembly structures are determined by the size of the anion Y, though Y is not involved into the network structure and just accommodated in the cavity. Compound 1 has a 1D ladder structure giving a larger cavity, in which the Δ- and Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) enantiomorphs are bridged by two NH···Cl(-) hydrogen bonds. Compound 2 has a 2D network structure with a net unit of a cyclic trimer of {fac-[Fe(II)(HL(n-Pr))(3)](2+)···Cl(-)}(3) giving a smaller cavity, in which Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) species with the same chirality are linked by NH···Cl(-) hydrogen bonds to give a homochiral 2D network structure. Magnetic susceptibility and Mössbauer spectral measurements demonstrated that compound 1 showed an abrupt one-step spin crossover with 4.0 K thermal hysteresis of T(c↓) = 125.5 K and T(c↑) = 129.5 K and compound 2 showed no spin transition and stayed in the high-spin state over the 5-300 K temperature range.

Nitrogen-oxy compounds formation in moist - N2 gaseous systems

International Nuclear Information System (INIS)

Dey, G.R.; Das, Tomi Nath

2015-01-01

In any high ionizing radiation zone continuous generation of nitrogen compounds such as NO 2 , NO 2 - and NO 3 - in aqueous and gas phase is a normal phenomena. Their formation mechanisms, and the control processes still pose a challenge with reference to the resulting corrosive environment generated, and it's effect on various structural materials used in nuclear industry. The source(s) of nitrogen for these products are mainly air which ingresses into the system, and/or nitrogen compounds such as ammonia, hydrazine, volatile amines used in different parts of the nuclear power plants to control pH and scavenge dissolved oxygen in coolant/moderator systems. Under high radiation environment their subsequent chemistry leads to the formation of various N-O compounds. With the objective to elucidate such reaction mechanisms, we studied and compared the chemistry of nitrogen in water and moist-nitrogen systems under the complimentary initiation techniques of cold plasma, wherein free electrons in eV energy range initiate the radical induced chemistry. In the gas phase, cold plasma produced NO and NO 2 which were confirmed on-line by respective absorbance measurement at 204, 214.5, 226 and 400 nm, while NO 2 - was analyzed as additional product after wet-chemical sampling in sulphanalic acid (0.5%) and N (1-naphthyl) ethylene diamine dihydrochloride (0.1%) mixed solution followed by absorbance measurement at 540 nm. This work was explored in three different systems: (i) N 2 from commercial high purity N 2 gas cylinder, (ii) N 2 from such source pretreated with activated silica gel (to reduce/minimize moisture concentration further) and (iii) N 2 bubbled through water (saturated moisture in N 2 system). The observed concentration of NO 2 - was found to be higher in moisture saturated N 2 system. In this presentation a brief summary of the results on various aspect of the formation of different N-O compounds during radiolysis of aqueous systems and gas phase cold

Cross-Dehydrogenative Coupling Reactions Between P(O)-H and X-H (X = S, N, O, P) Bonds.

Science.gov (United States)

Hosseinian, Akram; Farshbaf, Sepideh; Fekri, Leila Zare; Nikpassand, Mohammad; Vessally, Esmail

2018-05-26

P(O)-X (X = S, N, O, P) bond-containing compounds have extensive application in medicinal chemistry, agrochemistry, and material chemistry. These useful organophosphorus compounds also have many applications in organic synthesis. In light of the importance of titled compounds, there is continuing interest in the development of synthetic methods for P(O)-X bonds construction. In the last 4 years, the direct coupling reaction of P(O)-H compounds with thiols, alcohols, and amines/amides has received much attention because of the atom-economic character. This review aims to give an overview of new developments in cross-dehydrogenative coupling reactions between P(O)-H and X-H (X = S, N, O, P) bonds, with special emphasis on the mechanistic aspects of the reactions.

A comprehensive experimental and kinetic modeling study of n -propylbenzene combustion

KAUST Repository

Yuan, Wenhao

2017-09-05

This work presents a comprehensive experimental and kinetic modeling study on the combustion of n-propylbenzene. Flow reactor pyrolysis of n-propylbenzene at 0.04, 0.2 and 1 atm and laminar premixed flames of n-propylbenzene at 0.04 atm with equivalence ratios of 0.75 and 1.00 were investigated with synchrotron vacuum ultraviolet photoionization mass spectrometry. Jet stirred reactor (JSR) oxidation of n-propylbenzene at 10 atm with equivalence ratios of 0.5, 1.0, 1.5 and 2.0 was investigated with gas chromatography. A detailed kinetic model for n-propylbenzene combustion with 340 species and 2069 reactions was developed and validated against the data measured in this work. Model analyses such as rate of production analysis and sensitivity analysis were also performed to reveal the key pathways in the consumption of fuel and formation of polycyclic aromatic hydrocarbons (PAHs). The analysis results demonstrate that the benzylic Csingle bondC bond dissociation reaction is crucial for the decomposition of n-propylbenzene in the pyrolysis and rich flame. Low temperature oxidation reactions play important roles in the high pressure JSR oxidation of n-propylbenzene. In addition, the formation pathways of PAHs are strongly related to the fuel structure, especially for the formation of bicyclic PAHs such as indene and naphthalene. Furthermore, the present model was also validated against previous experimental data of n-propylbenzene combustion under a wide range of conditions, including ignition delay times, laminar flame speeds, extinction strain rates, speciation profiles in atmospheric pressure JSR oxidation, flow reactor oxidation and high pressure shock tube pyrolysis and oxidation.

A comprehensive experimental and kinetic modeling study of n -propylbenzene combustion

KAUST Repository

Yuan, Wenhao; Li, Yuyang; Dagaut, Philippe; Wang, Yizun; Wang, Zhandong; Qi, Fei

2017-01-01

This work presents a comprehensive experimental and kinetic modeling study on the combustion of n-propylbenzene. Flow reactor pyrolysis of n-propylbenzene at 0.04, 0.2 and 1 atm and laminar premixed flames of n-propylbenzene at 0.04 atm with equivalence ratios of 0.75 and 1.00 were investigated with synchrotron vacuum ultraviolet photoionization mass spectrometry. Jet stirred reactor (JSR) oxidation of n-propylbenzene at 10 atm with equivalence ratios of 0.5, 1.0, 1.5 and 2.0 was investigated with gas chromatography. A detailed kinetic model for n-propylbenzene combustion with 340 species and 2069 reactions was developed and validated against the data measured in this work. Model analyses such as rate of production analysis and sensitivity analysis were also performed to reveal the key pathways in the consumption of fuel and formation of polycyclic aromatic hydrocarbons (PAHs). The analysis results demonstrate that the benzylic Csingle bondC bond dissociation reaction is crucial for the decomposition of n-propylbenzene in the pyrolysis and rich flame. Low temperature oxidation reactions play important roles in the high pressure JSR oxidation of n-propylbenzene. In addition, the formation pathways of PAHs are strongly related to the fuel structure, especially for the formation of bicyclic PAHs such as indene and naphthalene. Furthermore, the present model was also validated against previous experimental data of n-propylbenzene combustion under a wide range of conditions, including ignition delay times, laminar flame speeds, extinction strain rates, speciation profiles in atmospheric pressure JSR oxidation, flow reactor oxidation and high pressure shock tube pyrolysis and oxidation.

Search for a metallic dangling-bond wire on n-doped H-passivated semiconductor surfaces

DEFF Research Database (Denmark)

Engelund, Mads; Papior, Nick Rübner; Brandimarte, Pedro

2016-01-01

We have theoretically investigated the electronic properties of neutral and n-doped dangling bond (DB) quasi-one-dimensional structures (lines) in the Si(001):H and Ge(001):H substrates with the aim of identifying atomic-scale interconnects exhibiting metallic conduction for use in on-surface cir...

Quantification of the selective activation of C--H bonds in short chain alkanes: The reactivity of ethane, propane, isobutane, n-butane, and neopentane on Ir(111)

International Nuclear Information System (INIS)

Johnson, D.F.; Weinberg, W.H.

1995-01-01

The initial probabilities of precursor-mediated, dissociative chemisorption of the saturated hydrocarbons 13 C-labeled ethane, propane, isobutane, n-butane, and neopentane on the close-packed Ir(111) surface have been measured. The selective activation of primary (1 degree), secondary (2 degree), and tertiary (3 degree) C--H bonds has been quantified by examining the reactivities of the selectively deuterated isotopomers of propane, C 3 H 8 , CH 3 CD 2 CH 3 , and C 3 D 8 , and of isobutane, (CH 3 ) 3 CH, (CH 3 ) 3 CD, and (CD 3 ) 3 CH. With respect to the bottom of the physically adsorbed well for each hydrocarbon, the apparent C--H bond activation energies have been found to be 10.4±0.3 kcal/mol (ethane), 11.4±0.3 kcal/mol (propane), 11.5±0.3 kcal/mol (n-butane), 11.3±0.3 kcal/mol (i-butane), and 11.3±0.3 kcal/mol (neopentane). For all the alkanes examined, the ratios of the preexponential factors of the rate coefficients of reaction and desorption are 1x10 -2 . The C--D bond activation energies are higher than the corresponding C--H bond activation energies by 480 cal/mol (ethane), 630 cal/mol (propane), and 660 cal/mol (i-butane). By analyzing the primary kinetic isotope effects for the selectively deuterated isotopomers of propane and isobutane, the 2 degree C--H bond activation energy is found to be 310±160 cal/mol less than the 1 degree C--H bond activation energy on this surface, and similarly, 3 degree C--H bond cleavage is less by 80±70 cal/mol. The quantification of the branching ratios within the C--H bond activation channel for propane and isobutane on this surface shows that the formation of 1 degree-alkyl intermediates is, in general, favored over the formation of either 2 degree- or 3 degree-alkyl intermediates. (Abstract Truncated)

Metallic and/or oxygen ion implantation into AlN ceramics as a method of preparation for its direct bonding with copper

International Nuclear Information System (INIS)

Barlak, M.; Borkowska, K.; Olesinska, W.; Kalinski, D.; Piekoszewski, J.; Werner, Z.; Jagielski, J.; Sartowska, B.

2006-01-01

Direct bonding (DB) process is recently getting an increasing interest as a method for producing high quality joints between aluminum nitride (AlN) ceramics and copper. The metallic ions were implanted using an MEVVA type TITAN implanter with unseparated beam. Oxygen ions were implanted using a semi-industrial ion implanter without mass separation equipped with a gaseous ion source. The substrate temperature did not exceed 200 o C. Ions were implanted at two acceleration voltages, i.e. 15 and 70 kV. The fluence range was between 1·E16 and 1·E18 cm -2 . After implantation, some of the samples were characterized by the Rutherford backscattering (RBS) method. In conclusion: (a) The investigations performed in the present work confirm an assumption that ion implantation is a very promising technique as a pretreatment of AlN ceramics for the formation of the joints with copper in direct bonding process. (b) It has been shown that titanium implantation gives the best results in comparison to other metals examined (Fe, Cr, Cu) but also in comparison to double Ti+O and O+Ti implantations

tri-n-butyltin hydride-mediated radical reaction of a 2-iodobenzamide: formation of an unexpected carbon-tin bond

International Nuclear Information System (INIS)

Oliveira, Marcelo T.; Alves, Rosemeire B.; Cesar, Amary; Prado, Maria Auxiliadora F.; Alves, Ricardo J.; Queiroga, Carla G.; Santos, Leonardo S.; Eberlin, Marcos N.

2007-01-01

The tri-n-butyltin hydride-mediated reaction of methyl 2,3-di-O-benzyl-4-O-trans-cinnamyl- 6-deoxy-6-(2-iodobenzoylamino)-α-D-galactopyranoside afforded an unexpected aryltributyltin compound. The structure of this new tetraorganotin(IV) product has been elucidated by 1 H, 13 C NMR spectroscopy, COSY and HMQC experiments and electrospray ionization mass spectrometry (ESI-MS). The formation of this new compound via a radical coupling reaction and a radical addition-elimination process is discussed. (author)

Measurement of formation cross-section of 99Mo from the 98Mo(n,γ) and 100Mo(n,2n) reactions.

Science.gov (United States)

Badwar, Sylvia; Ghosh, Reetuparna; Lawriniang, Bioletty M; Vansola, Vibha; Sheela, Y S; Naik, Haladhara; Naik, Yeshwant; Suryanarayana, Saraswatula V; Jyrwa, Betylda; Ganesan, Srinivasan

2017-11-01

The formation cross-section of medical isotope 99 Mo from the 98 Mo(n,γ) reaction at the neutron energy of 0.025eV and from the 100 Mo(n,2n) reaction at the neutron energies of 11.9 and 15.75MeV have been determined by using activation and off-line γ-ray spectrometric technique. The thermal neutron energy of 0.025eV was used from the reactor critical facility at BARC, Mumbai, whereas the average neutron energies of 11.9 and 15.75MeV were generated using 7 Li(p,n) reaction in the Pelletron facility at TIFR, Mumbai. The experimentally determined cross-sections were compared with the evaluated nuclear data libraries of ENDF/B-VII.1, CENDL-3.1, JENDL-4.0 and JEFF-3.2 and are found to be in close agreement. The 100 Mo(n,2n) 99 Mo reaction cross-sections were also calculated theoretically by using TALYS-1.8 and EMPIRE-3.2 computer codes and compared with the experimental data. Copyright © 2017 Elsevier Ltd. All rights reserved.

Influence of Si and N additions on structure and phase stability of Ge(2)Sb(2)Te(5) thin films.

Science.gov (United States)

Kölpin, Helmut; Music, Denis; Laptyeva, Galyna; Ghadimi, Reza; Merget, Florian; Richter, Silvia; Mykhaylonka, Ruslàn; Mayer, Joachim; Schneider, Jochen M

2009-10-28

The influence of Si and N in Ge(2)Sb(2)Te(5) (space group [Formula: see text]) on structure and phase stability thereof was studied experimentally by thin film growth and characterization as well as theoretically by ab initio calculations. It was found that Si and N most probably accumulate in the amorphous matrix embedding Ge(2)Sb(2)Te(5) grains. The incorporation of Si and N in these samples causes an increase of the crystallization temperature and the formation of finer grains. N is more efficient in increasing the crystallization temperature and in reducing the grain size than Si which can be understood based on the bonding analysis. The incorporation of both Si and N in Ge(2)Sb(2)Te(5) is energetically unfavourable, leading to finer grains and larger crystallization temperatures. While in the case of Si additions no significant changes in bonding are observed, N additions appear to enable the formation of strong Te-N bonds in the amorphous matrix, which are shown to be almost twice as strong as the strongest bonds in unalloyed Ge(2)Sb(2)Te(5).

Influence of Si and N additions on structure and phase stability of Ge2Sb2Te5 thin films

International Nuclear Information System (INIS)

Koelpin, Helmut; Music, Denis; Mykhaylonka, Ruslan; Schneider, Jochen M; Laptyeva, Galyna; Ghadimi, Reza; Richter, Silvia; Mayer, Joachim; Merget, Florian

2009-01-01

The influence of Si and N in Ge 2 Sb 2 Te 5 (space group Fm3-barm) on structure and phase stability thereof was studied experimentally by thin film growth and characterization as well as theoretically by ab initio calculations. It was found that Si and N most probably accumulate in the amorphous matrix embedding Ge 2 Sb 2 Te 5 grains. The incorporation of Si and N in these samples causes an increase of the crystallization temperature and the formation of finer grains. N is more efficient in increasing the crystallization temperature and in reducing the grain size than Si which can be understood based on the bonding analysis. The incorporation of both Si and N in Ge 2 Sb 2 Te 5 is energetically unfavourable, leading to finer grains and larger crystallization temperatures. While in the case of Si additions no significant changes in bonding are observed, N additions appear to enable the formation of strong Te-N bonds in the amorphous matrix, which are shown to be almost twice as strong as the strongest bonds in unalloyed Ge 2 Sb 2 Te 5 .

The first N-terminal unprotected (Gly-Aib)n peptide: H-Gly-Aib-Gly-Aib-OtBu.

Science.gov (United States)

Gessmann, Renate; Brückner, Hans; Petratos, Kyriacos

2015-12-01

Glycine (Gly) is incorporated in roughly half of all known peptaibiotic (nonribosomally biosynthesized antibiotic peptides of fungal origin) sequences and is the residue with the greatest conformational flexibility. The conformational space of Aib (α-aminoisobutyric acid) is severely restricted by the second methyl group attached to the Cα atom. Most of the crystal structures containing Aib are N-terminal protected. Deprotection of the N- or C-terminus of peptides may alter the hydrogen-bonding scheme and/or the structure and may facilitate crystallization. The structure reported here for glycyl-α-aminoisobutyrylglycyl-α-aminoisobutyric acid tert-butyl ester, C16H30N4O5, describes the first N-terminal-unprotected (Gly-Aib)n peptide. The achiral peptide could form an intramolecular hydrogen bond between the C=O group of Gly1 and the N-H group of Aib4. This hydrogen bond is found in all tetrapeptides and N-terminal-protected tripeptides containing Aib, apart from one exception. In the present work, this hydrogen bond is not observed (N...O = 5.88 Å). Instead, every molecule is hydrogen bonded to six other symmetry-related molecules with a total of eight hydrogen bonds per molecule. The backbone conformation starts in the right-handed helical region (and the left-handed helical region for the inverted molecule) and reverses the screw sense in the last two residues.

The formation of hexagonal-shaped InGaN-nanodisk on GaN-nanowire observed in plasma source molecular beam epitaxy

KAUST Repository

Ng, Tien Khee; Gasim, Anwar; Cha, Dong Kyu; Janjua, Bilal; Yang, Yang; Jahangir, Shafat; Zhao, Chao; Bhattacharya, Pallab; Ooi, Boon S.

2014-01-01

sensitive growth kinetics during plasma-assisted MBE of InGaN at low temperature, i.e. when the substrate temperature was reduced from 800 °C (GaN growth) to <600 °C (InGaN growth), during which sparsely populated metal-droplet formation prevails and further

Specific and total N-nitrosamines formation potentials of nitrogenous micropollutants during chloramination.

Science.gov (United States)

Piazzoli, Andrea; Breider, Florian; Aquillon, Caroline Gachet; Antonelli, Manuela; von Gunten, Urs

2018-05-15

N-nitrosamines are a group of potent human carcinogens that can be formed during oxidative treatment of drinking water and wastewater. Many tertiary and quaternary amines present in consumer products (e.g., pharmaceuticals, personal care and household products) are known to be N-nitrosodimethylamine (NDMA) precursors during chloramination, but the formation of other N-nitrosamines has been rarely studied. This study investigates the specific and total N-nitrosamine (TONO) formation potential (FP) of various precursors from nitrogen-containing micropollutants (chlorhexidine, metformin, benzalkonium chloride and cetyltrimethylammonium chloride) and tertiary and quaternary model amines (trimethyl amine, N,N-dimethylbutyl amine, N,N-dimethylbenzyl amine and tetramethyl ammonium). All the studied nitrogenous micropollutants displayed quantifiable TONO FP, with molar yields in the range 0.04-11.92%. However, the observed TONO pools constituted mostly of uncharacterized species, not included in US-EPA 8270 N-nitrosamines standard mix. Only the quaternary ammonium compound benzalkonium chloride showed quantifiable NDMA FP (0.56% molar yield), however, explaining only a minor fraction of the observed TONO FP. The studied model amines showed molar NDMA yields from 0.10% (trimethyl amine) to 5.05% (N,N-dimethylbenzyl amine), very similar to the molar TONO yields. The comparison of the FPs of micropollutants and model compounds showed that the presence of electron donating functional groups (such as a benzyl group) in tertiary and quaternary amine precursors leads to a higher formation of NDMA and uncharacterized N-nitrosamines, respectively. LC-qTOF screening of a list of proposed N-nitrosamine structures has enabled to identify a novel N-nitrosamine (N-nitroso-N-methyldodecylamine) from the chloramination of benzalkonium chloride. This finding supports the hypothesis that different functional groups in quaternary amines can act as leaving groups during chloramination and

Study of Diffusion Barrier for Solder/ n-Type Bi2Te3 and Bonding Strength for p- and n-Type Thermoelectric Modules

Science.gov (United States)

Lin, Wen-Chih; Li, Ying-Sih; Wu, Albert T.

2018-01-01

This paper investigates the interfacial reaction between Sn and Sn3Ag0.5Cu (SAC305) solder on n-type Bi2Te3 thermoelectric material. An electroless Ni-P layer successfully suppressed the formation of porous SnTe intermetallic compound at the interface. The formation of the layers between Bi2Te3 and Ni-P indicates that Te is the dominant diffusing species. Shear tests were conducted on both Sn and SAC305 solder on n- and p-type Bi2Te3 with and without a Ni-P barrier layer. Without a Ni-P layer, porous SnTe would result in a more brittle fracture. A comparison of joint strength for n- and p-type thermoelectric modules is evaluated by the shear test. Adding a diffusion barrier increases the mechanical strength by 19.4% in n-type and 74.0% in p-type thermoelectric modules.

Magnesium substituted hydroxyapatite formation on (Ti,Mg)N coatings produced by cathodic arc PVD technique

International Nuclear Information System (INIS)

Onder, Sakip; Kok, Fatma Nese; Kazmanli, Kursat; Urgen, Mustafa

2013-01-01

In this study, formation of magnesium substituted hydroxyapatite (Ca 10−x Mg x (PO 4 ) 6 (OH) 2 ) on (Ti,Mg)N and TiN coating surfaces were investigated. The (Ti 1−x ,Mg x )N (x = 0.064) coatings were deposited on titanium substrates by using cathodic arc physical vapor deposition technique. TiN coated grade 2 titanium substrates were used as reference to understand the role of magnesium on hydroxyapatite (HA) formation. The HA formation experiments was carried out in simulated body fluids (SBF) with three different concentrations (1X SBF, 5X SBF and 5X SBF without magnesium ions) at 37 °C. The coatings and hydroxyapatite films formed were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and FTIR Spectroscopy techniques. The energy dispersive X-ray spectroscopy (EDS) analyses and XRD investigations of the coatings indicated that magnesium was incorporated in the TiN structure rather than forming a separate phase. The comparison between the TiN and (Ti, Mg)N coatings showed that the presence of magnesium in TiN structure facilitated magnesium substituted HA formation on the surface. The (Ti,Mg)N coatings can potentially be used to accelerate the HA formation in vivo conditions without any prior hydroxyapatite coating procedure. - Highlights: • Mg incorporated in (Ti,Mg)N coating structure and did not form a separate phase • Mg dissolution in SBF solution facilitated Mg-substituted hydroxyapatite formation • (Ti,Mg)N acted as Mg-source for Mg-substituted hydroxyapatite formation in SBF

THE APPREHENSION MEDICAL METHOD IN THE FORMATION OF VALUE / EL MÉTODO APREHENSIÓN MÉDICA EN LA FORMACIÓN DE VALORES

Directory of Open Access Journals (Sweden)

Mirna León Acebo

2012-10-01

Full Text Available This work responds to one of the main tendencies in the Cuban medical formation which consists of the formation of physicians in the setting of primary health attention; it gives hierarchy to the job education as a main organization form in the medicine career. The design of the apprehension medical method contributes to integrate practical and theoretical knowledge due to the use of different areas from the formative context in the universitary policlinic. It is identified as the nucleus of the system of medical methods of the medicine care. During the formation of this value, the medical students move across two phases, the identity identification and identity consciousness.ResumenEste trabajo responde a una de las principales tendencias en la formación médica cubana actual que consiste en la formación del médico en los escenarios de la atención primaria, jerarquizando a la educación en el trabajo como forma fundamental de organización de la Carrera de Medicina. El diseño del método aprehensión médica, que contribuye a integrar los conocimientos teóricos con los prácticos al utilizar las diferentes áreas del contexto formativo del policlínico universitario, se identifica como el núcleo del sistema de métodos de la Carrera de Medicina, contribuye a formar el valor identidad profesional médica; durante la formación de este valor el estudiante de medicina transita por dos fases, la de identificación identitaria y la de concientización identitaria.

Evaluation of N-Nitrosamine Formation in Routine Potato Cooking

Directory of Open Access Journals (Sweden)

Qajarbeygi

2015-08-01

Full Text Available Background Nitrosamine is amongst carcinogen chemical compounds, which can enter the human body through consumption of food. Potatoes are a root vegetable consumed by many people around the world, however their potential for nitrosamine formation during cooking processes needs to be considered for public health matters. Objectives In this study we evaluated the effect of conventional potato cooking method on N-nitrosamine compound formation. Materials and Methods The amounts of four nitrosamines, namely N-nitrosodimethylamine (NDMA, N-nitrosodiethylamine (NDEA, N-nitrosopiperidine (NPIP and N-nitrosopyrrolidine (NPYR were determined in four different potato-baking methods. Sixty potato samples were randomly collected from Hamadan city. Fried potato samples were roasted at 180°C and boiled potato samples were scalded at 120°C. Nitrosamine levels were measured using gas chromatography coupled with electronic ionization detector (GC-EID, and spectrophotometry was used for measuring nitrite. Results Fried samples that were measured by the gas chromatography method had the highest average levels of nitrosamine compounds; NDMA, 5.09 ng kg-1, and NDEA, 8.66 ng kg-1. Low levels of nitrosamine compounds were associated with raw potatoes, in which no nitrosamine compound was detected. Based on the analysis of the potato samples by spectrophotometry, the highest levels of nitrite was found in raw potatoes with a mean of 2.43 mg kg-1 and the lowest levels of nitrite were detected in boiled potatoes with an average of 1.172 mg kg-1. Conclusions Nitrosamine was formed with conventional potato baking methods with the most nitrosamine formation found on the surface fried samples. Nitrites amount in baked potatoes decreased. Generally, the amount of nitrosamine in baked potato samples was lower than acceptable limits.

Crystal structure of N,N-diethylbenzene-1,4-diaminium dinitrate

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Yasmina Bouaoud

2014-11-01

Full Text Available In the structure of the title molecular salt, C10H18N22+·2NO3−, the dinitrate salt of 4-(N,N-diethylaminoaniline, the two ethyl groups lie almost perpendicular to the plane of the benzene ring [the ring-to-ethyl C—C—N—C torsion angles are −59.5 (2 and 67.5 (3°]. The aminium groups of the cation form inter-species N—H...O hydrogen bonds with the nitro O-atom acceptors of both anions, giving rise to chain substructures lying along c. The chains are linked via further N—H...O hydrogen bonds, forming two-dimensional networks lying parallel to (010. These sheets are linked by C—H...O hydrogen bonds, forming a three-dimensional structure.

Bis{N-[5-(4-methoxyphenyl-1,3,4-oxadiazol-2-yl]ethanimidamidato}copper(II

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Yacine Djebli

2010-04-01

Full Text Available The title compound, [Cu(C11H11N4O22], was prepared by solvothermal synthesis using 2-amino-5-(4-methoxyphenyl-1,3,4-oxadiazole and copper sulfate pentahydrate in an acetonitrile solution. The CuII atom lies on an inversion center and is four-coordinated in a slightly distorted square-planar geometry by four N atoms of the ligands obtained from the formation of a bond between the amine N atom of the oxadiazole molecule and the nitrile C atom of the solvent. In the crystal structure an intermolecular N—H...N hydrogen bond links inversion-related molecules.

Alkali metal control over N-N cleavage in iron complexes.

Science.gov (United States)

Grubel, Katarzyna; Brennessel, William W; Mercado, Brandon Q; Holland, Patrick L

2014-12-03

Though N2 cleavage on K-promoted Fe surfaces is important in the large-scale Haber-Bosch process, there is still ambiguity about the number of Fe atoms involved during the N-N cleaving step and the interactions responsible for the promoting ability of K. This work explores a molecular Fe system for N2 reduction, particularly focusing on the differences in the results obtained using different alkali metals as reductants (Na, K, Rb, Cs). The products of these reactions feature new types of Fe-N2 and Fe-nitride cores. Surprisingly, adding more equivalents of reductant to the system gives a product in which the N-N bond is not cleaved, indicating that the reducing power is not the most important factor that determines the extent of N2 activation. On the other hand, the results suggest that the size of the alkali metal cation can control the number of Fe atoms that can approach N2, which in turn controls the ability to achieve N2 cleavage. The accumulated results indicate that cleaving the triple N-N bond to nitrides is facilitated by simultaneous approach of least three low-valent Fe atoms to a single molecule of N2.

Theoretical investigation of inclusion complex formation of Gold (III – Dimethyldithiocarbamate anticancer agents with cucurbit[n = 5,6]urils

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Zabiollah Mahdavifar

2014-09-01

Full Text Available Gold (III-N,N-dimethyldithiocarbamate [DMDT(AuX2] complexes have recently gained increasing attention as potential anticancer agents because of their strong tumor cell growth–inhibitory effects, generally achieved by exploiting non-cisplatin-like mechanisms of action. The goal of our research work is to encapsulate the gold(III dimethyldithiocarbamate complexes as anticancer with cucurbit[n]urils (CB[n = 5, 6] by accurate calculations, to predict the inclusion complex formation of gold(III species with cucurbiturils (CB[n = 5, 6]. The calculations were carried out just for the 1:1 stoichiometric complexes. Upon encapsulation, binding energy, thermodynamic parameters, structural parameters and electronic structures of complexes are investigated. The results of the thermodynamic calculations and the binding energy show that the inclusion process is exothermic and the CB[6]/[DMDT(AuBr2] complex is more stable than other complexes. The final geometry of CB[n]/drugs indicates that the drugs were expelled from the cavity of CB[n]. NBO calculations reveal that the hydrogen bonding between CB[n] and drugs and electrostatic interactions are the major factors contributing to the overall stabilities of the complexes.

Crystal structure of N,N,N′,N′,N′′,N′′-hexamethylguanidinium cyanate 1.5-hydrate

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Ioannis Tiritiris

2015-12-01

Full Text Available The title hydrated salt, C7H18N3+·OCN−.1.5H2O, was synthesized starting from N,N,N′,N′,N′′,N′′-hexamethylguanidinium chloride by a twofold anion-exchange reaction. The asymmetric unit contains two cations, two cyanate anions and three water molecules. One cation shows orientational disorder and two sets of N-atom positions were found related by a 60° rotation, with an occupancy ratio of 0.852 (6:0.148 (6. The C—N bond lengths in both guanidinium ions range from 1.329 (2 to 1.358 (10 Å, indicating double-bond character, pointing towards charge delocalization within the NCN planes. Strong O—H...N hydrogen bonds between the crystal water molecules and the cyanate ions and strong O—H...O hydrogen bonds between the water molecules are present, resulting in a two-dimensional hydrogen bonded network running parallel to the (001 plane. The hexamethylguanidinium ions are packed in between the layers built up by water molecules and cyanate ions.

A PEG/copper(i) halide cluster as an eco-friendly catalytic system for C-N bond formation.

Science.gov (United States)

Li, Cheng-An; Ji, Wei; Qu, Jian; Jing, Su; Gao, Fei; Zhu, Dun-Ru

2018-05-22

The catalytic activities of eight copper(i) halide clusters assembled from copper(i) halide and ferrocenyltelluroethers, 1-8, were investigated in C-N formation under various conditions. A catalytic procedure using poly(ethylene glycol) (PEG-400) as a greener alternative organic solvent has been developed. The PEG-400/5 system can achieve 99% targeted yield with a mild reaction temperature and short reaction time. After the isolation of the products by extraction with diethyl ether, this PEG-400/cluster system could be easily recycled. Spectroscopic studies elucidate a stepwise mechanism: firstly, proton-coupled electron transfer (PCET) involving the transfer of an electron from Cu+ and a proton from imidazole results in the formation of a labile penta-coordinated Cu2+ and aryl radical; the following effective electron transfer from the ferrocene unit reduces Cu2+ and forms the target product; finally, the ferrocenium unit is reduced by the I- anion. The merits of this eco-friendly synthesis are the efficient utilization of reagents and easy recyclability.

Generalized valence bond description of the ground states (X(1)Σg(+)) of homonuclear pnictogen diatomic molecules: N2, P2, and As2.

Science.gov (United States)

Xu, Lu T; Dunning, Thom H

2015-06-09

The ground state, X1Σg+, of N2 is a textbook example of a molecule with a triple bond consisting of one σ and two π bonds. This assignment, which is usually rationalized using molecular orbital (MO) theory, implicitly assumes that the spins of the three pairs of electrons involved in the bonds are singlet-coupled (perfect pairing). However, for a six-electron singlet state, there are five distinct ways to couple the electron spins. The generalized valence bond (GVB) wave function lifts this restriction, including all of the five spin functions for the six electrons involved in the bond. For N2, we find that the perfect pairing spin function is indeed dominant at Re but that it becomes progressively less so from N2 to P2 and As2. Although the perfect pairing spin function is still the most important spin function in P2, the importance of a quasi-atomic spin function, which singlet couples the spins of the electrons in the σ orbitals while high spin coupling those of the electrons in the π orbitals on each center, has significantly increased relative to N2 and, in As2, the perfect pairing and quasi-atomic spin couplings are on essentially the same footing. This change in the spin coupling of the electrons in the bonding orbitals down the periodic table may contribute to the rather dramatic decrease in the strengths of the Pn2 bonds from N2 to As2 as well as in the increase in their chemical reactivity and should be taken into account in more detailed analyses of the bond energies in these species. We also compare the spin coupling in N2 with that in C2, where the quasi-atomic spin coupling dominants around Re.

Supramolecular structures in N-isonicotinoyl arylaldehydehydrazones: multiple hydrogen-bonding modes in series of geometric isomers.

Science.gov (United States)

Wardell, Solange M S V; de Souza, Marcus V N; Wardell, James L; Low, John N; Glidewell, Christopher

2007-12-01

Sixteen N-isonicotinoyl arylaldehydehydrazones, NC(5)H(4)CONHN=CHC(6)H(4)R, have been studied and the structures of 14 of them have been determined, including the unsubstituted parent compound with R = H, and the complete sets of 2-, 3- and 4-substituted geometric isomers for R = F, Br and OMe, and two of the three isomers for R = Cl and OEt. The 2-chloro and 3-chloro derivatives are isostructural with the corresponding bromo isomers, and all compounds contain trans amide groups apart from the isostructural pair where R = 2-Cl and 2-Br, which contain cis amide groups. The structures exhibit a wide range of direction-specific intermolecular interactions, including eight types of hydrogen bonds, N-H...N, N-H...O, O-H...O, O-H...N, C-H...N, C-H...O, C-H...pi(arene) and C-H...pi(pyridyl), as well as pi...pi stacking interactions. The structures exhibit a very broad range of combinations of these interactions: the resulting hydrogen-bonded supramolecular structures range from one-dimensional when R = 2-F, 2-OMe or 2-OEt, via two-dimensional when R = 4-F, 3-Cl, 3-Br, 4-OMe or 3-OEt, to three-dimensional when R = H, 3-F, 2-Cl, 2-Br, 4-Br or 3-OMe. Minor changes in either the identity of the substituent or its location can lead to substantial changes in the pattern of supramolecular aggregation, posing significant problems of predictability. The new structures are compared with the recently published structures of the isomeric series having R = NO(2), with several monosubstituted analogues containing 2-pyridyl or 3-pyridyl units rather than 4-pyridyl, and with a number of examples having two or three substituents in the aryl ring: some 30 structures in all are discussed.

Spectroscopic Identification of the Au-C Bond Formation upon Electroreduction of an Aryl Diazonium Salt on Gold.

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Guo, Limin; Ma, Lipo; Zhang, Yelong; Cheng, Xun; Xu, Ye; Wang, Jin; Wang, Erkang; Peng, Zhangquan

2016-11-08

Electroreduction of aryl diazonium salts on gold can produce organic films that are more robust than their analogous self-assembled monolayers formed from chemical adsorption of organic thiols on gold. However, whether the enhanced stability is due to the Au-C bond formation remains debated. In this work, we report the electroreduction of an aryl diazonium salt of 4,4'-disulfanediyldibenzenediazonium on gold forming a multilayer of Au-(Ar-S-S-Ar) n , which can be further degraded to a monolayer of Au-Ar-S - by electrochemical cleavage of the S-S moieties within the multilayer. By conducting an in situ surface-enhanced Raman spectroscopic study of both the multilayer formation/degradation and the monolayer reduction/oxidation processes, coupled to density functional theory calculations, we provide compelling evidence that an Au-C bond does form upon electroreduction of aryl diazonium salts on gold and that the enhanced stability of the electrografted organic films is due to the Au-C bond being intrinsically stronger than the Au-S bond for a given phenylthiolate compound by ca. 0.4 eV.

Sequential plasma activation methods for hydrophilic direct bonding at sub-200 °C

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He, Ran; Yamauchi, Akira; Suga, Tadatomo

2018-02-01

We present our newly developed sequential plasma activation methods for hydrophilic direct bonding of silica glasses and thermally grown SiO2 films. N2 plasma was employed to introduce a metastable oxynitride layer on wafer surfaces for the improvement of bond energy. By using either O2-plasma/N2-plasma/N-radical or N2-plasma/N-radical sequential activation, the quartz-quartz bond energy was increased from 2.7 J/m2 to close to the quartz bulk fracture energy that was estimated to be around 9.0 J/m2 after post-bonding annealing at 200 °C. The silicon bulklike bond energy between thermal SiO2 films was also obtained. We suggest that the improvement is attributable to surface modification such as N-related defect formation and asperity softening by the N2 plasma surface treatment.

Thermophysical properties of N, N-dimethylacetamide mixtures with n-butanol

Science.gov (United States)

Maharolkar, Aruna P.; Murugkar, A. G.; Khirade, P. W.; Mehrotra, S. C.

2017-09-01

The refraction, dielectric, viscosity, density, data of the binary mixtures of N, N-dimethylacetamide (DMA) with n-butanol at 308.15 and 313.15 K. The measured parameters used to obtain derived properties like Bruggeman factor, molar refraction and excess static dielectric constant, excess inverse relaxation time, excess molar volume and excess viscosity, excess molar refraction. The variation in magnitude with composition and temperature of these quantities has been used to discuss the type, strength and nature of binary interactions. Results confirm that there are strong hydrogen-bond interactions between unlike molecules of DMA+ n-butanol mixtures and that 1: 1 complexes are formed and strength of intermolecular interaction increases with temperature.

Formation dynamics of FeN thin films on Cu(100)

KAUST Repository

Heryadi, Dodi

2012-01-01

To investigate the structural and magnetic properties of thin films of FeN we have performed ab initio molecular dynamics simulations of their formation on Cu(100) substrates. The iron nitride layers exhibit a p4gm(2 × 2) reconstruction and order ferromagnetically in agreement with experiment. We establish the dynamics and time scale of the film formation as a function of the film thickness. The process is split in two phases: formation of almost flat FeN layers and optimization of the distance to the substrate. Our calculated magnetic moments are 1.67 μ B, 2.14 μ B, and 2.21 μ B for one, two, and three monolayers of iron nitride. © 2011 Elsevier B.V. All rights reserved.

[μ-1,1′-(Butane-1,4-diyldi-1H-benzimidazole-κ2N3:N3′]bis{[N,N′-bis(carboxymethylethylenediamine-N,N′-diacetato-κ5O,O′,O′′,N,N′]mercury(II} methanol disolvate

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Gang-Sen Li

2009-08-01

Full Text Available The binuclear title complex, [Hg2(C10H14N2O82(C18H18N4]·2CH3OH, lies on an inversion center with the unique HgII ion coordinated in a disorted octahedral environment with one Hg—N bond significantly shorter than the other two. In the crystal structure, intermolecular O—H...O hydrogen bonds link complex and solvent molecules into a three-dimensional network.

A graded nano-TiN coating on biomedical Ti alloy: Low friction coefficient, good bonding and biocompatibility

Energy Technology Data Exchange (ETDEWEB)

Cui, Wenfang [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Material Science and Engineering, Northeastern University, Shenyang 110819 (China); Qin, Gaowu, E-mail: qingw@smm.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Material Science and Engineering, Northeastern University, Shenyang 110819 (China); Duan, Jingzhu; Wang, Huan [Spinal surgery, Shengjing Hospital, China Medical University, Shenyang 110004 (China)

2017-02-01

In order to solve wear resistance of Ti alloy biomaterials, the concept of a graded nano-TiN coating has been proposed. The coating was prepared on Ti-6Al-4V bio-alloy by DC reactive magnetron sputtering. The wear performance of the coated specimens was measured in Hank's solution under the load of 10 N, and the biocompatibility was evaluated according to ISO-10993-4 standard. The results show that the gradient coating exhibits a gradual change in compositions and microstructures along the direction of film growth. Nano-TiN with the size of several to dozens nanometers and Ti{sub 4}N{sub 3−x} transitional phase with variable composition form a graded composite structure, which significantly improves adhesion strength (L{sub c1} = 80 N, L{sub c2} = 120 N), hardness (21 GPa) and anti-wear performance (6.2 × 10{sup −7} mm{sup 3}/Nm). The excellent bonding and wear resistance result from a good match of mechanical properties at substrate/coating interface and the strengthening and toughening effects of the nanocrystalline composite. The nano-TiN coating has also been proved to have good biocompatibility through in-vitro cytotoxicity, hemocompatibility and general toxicity tests. And thus, the proposed graded nano-TiN coating is a good candidate improving wear resistance of many implant medical devices. - Highlights: • A graded nano-TiN coating was prepared on biomedical Ti alloy by PVD. • The combination of hard and soft phase increases hardness and toughness. • The coating exhibits high bonding, low coefficient of friction and wear rate. • The new coating has good bio-safety and great clinical application prospect.

Magnesium substituted hydroxyapatite formation on (Ti,Mg)N coatings produced by cathodic arc PVD technique.

Science.gov (United States)

Onder, Sakip; Kok, Fatma Nese; Kazmanli, Kursat; Urgen, Mustafa

2013-10-01

In this study, formation of magnesium substituted hydroxyapatite (Ca10-xMgx(PO4)6(OH)2) on (Ti,Mg)N and TiN coating surfaces were investigated. The (Ti1-x,Mgx)N (x=0.064) coatings were deposited on titanium substrates by using cathodic arc physical vapor deposition technique. TiN coated grade 2 titanium substrates were used as reference to understand the role of magnesium on hydroxyapatite (HA) formation. The HA formation experiments was carried out in simulated body fluids (SBF) with three different concentrations (1X SBF, 5X SBF and 5X SBF without magnesium ions) at 37 °C. The coatings and hydroxyapatite films formed were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and FTIR Spectroscopy techniques. The energy dispersive X-ray spectroscopy (EDS) analyses and XRD investigations of the coatings indicated that magnesium was incorporated in the TiN structure rather than forming a separate phase. The comparison between the TiN and (Ti, Mg)N coatings showed that the presence of magnesium in TiN structure facilitated magnesium substituted HA formation on the surface. The (Ti,Mg)N coatings can potentially be used to accelerate the HA formation in vivo conditions without any prior hydroxyapatite coating procedure. © 2013.

Characterization of N-nitrosodimethylamine formation from the ozonation of ranitidine.

Science.gov (United States)

Lv, Juan; Wang, Lin; Li, Yongmei

2017-08-01

N-nitrosodimethylamine (NDMA) is an emerging disinfection by-product which is formed during water disinfection in the presence of amine-based precursors. Ranitidine, as one kind of amine-based pharmaceuticals, has been identified as NDMA precursor with high NDMA molar conversion during chloramination. This study focused on the characterization of NDMA formation during ozonation of ranitidine. Influences of operational variables (ozone dose, pH value) and water matrix on NDMA generation as well as ranitidine degradation were evaluated. The results indicate high reactivity of ranitidine with ozone. Dimethylamine (DMA) and NDMA were generated due to ranitidine oxidation. High pH value caused more NDMA accumulation. NDMA formation was inhibited under acid conditions (pH≤5) mainly due to the protonation of amines. Water matrix such as HCO 3 - and humic acid impacted NDMA generation due to OH scavenging. Compared with OH, ozone molecules dominated the productions of DMA and NDMA. However, OH was a critical factor in NDMA degradation. Transformation products of ranitidine during ozonation were identified using gas chromatography-mass spectrometry. Among these products, just DMA and N,N-dimethylformamide could contribute to NDMA formation due to the DMA group in the molecular structures. The NDMA formation pathway from ranitidine ozonation was also proposed. Copyright © 2017. Published by Elsevier B.V.

Novel ethylenediamine-gallium phosphate containing 6-fold coordinated gallium atoms with unusual four equatorial Ga–N bonds

Energy Technology Data Exchange (ETDEWEB)

Torre-Fernández, Laura [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, 33006 Oviedo (Spain); Espina, Aránzazu; Khainakov, Sergei A.; Amghouz, Zakariae [Servicios Científico Técnicos, Universidad de Oviedo, 33006 Oviedo (Spain); García, José R. [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, 33006 Oviedo (Spain); García-Granda, Santiago, E-mail: sgg@uniovi.es [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, 33006 Oviedo (Spain)

2014-07-01

A novel ethylenediamine-gallium phosphate, formulated as Ga(H{sub 2}NCH{sub 2}CH{sub 2}NH{sub 2}){sub 2}PO{sub 4}·2H{sub 2}O, was synthesized under hydrothermal conditions. The crystal structure, including hydrogen positions, was determined using single-crystal X-ray diffraction data (monoclinic, a=9.4886(3) Å, b=6.0374(2) Å, c=10.2874(3) Å, and β=104.226(3)°, space group Pc) and the bulk was characterized by chemical (Ga–P–C–H–N) and thermal analysis (TG–MS and DSC), including activation energy data of its thermo-oxidative degradation, powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (SS-NMR) measurements, and transmission electron microscopy (TEM, SAED/NBD, and STEM BF-EDX). The crystal structure is built up of infinite zig-zag chains running along the c-axis, formed by vertex-shared (PO{sub 4}) and (GaO{sub 2}N{sub 4}) polyhedra. The new compound is characterized by unusual four equatorial Ga–N bonds coming from two nonequivalent ethylenediamine molecules and exhibits strong blue emission at 430 nm (λ{sub ex}=350 nm) in the solid state at room temperature. - Graphical abstract: Single crystals of a new ethylenediamine-gallium phosphate, Ga(H{sub 2}NCH{sub 2}CH{sub 2}NH{sub 2}){sub 2}PO{sub 4}·2H{sub 2}O, were obtained and the structural features presented. This structure is one of the scarce examples of GaPO with Ga–N bonds reported. - Highlights: • A novel ethylenediamine-gallium phosphate was hydrothermally synthesized. • The new compound is characterized by unusual four equatorial Ga–N bonds. • Void-volume analysis shows cages and channels with sizes ideally suited to accommodate small molecules. • The new compound exhibits strong blue emission.

Molecular orbital calculations for the formation of GaN layers on ultra-thin AlN/6H-SiC surface using alternating pulsative supply of gaseous trimethyl gallium (TMG) and NH3

International Nuclear Information System (INIS)

Seong, See Yearl; Hwang, Jin Soo

2001-01-01

The steps for the generation of very thin GaN films on ultrathin AlN/6H-SiC surface by alternating a pulsative supply (APS) of trimethyl gallium and NH 3 gases have been examined by ASED-MO calculations. We postulate that the gallium clusters was formed with the evaporation of CH 4 gases via the decomposition of trimethyl gallium (TMG), dimethyl gallium (DMG), and monomethyl gallium (MMG). During the injection of NH 3 gas into the reactor, the atomic hydrogens were produced from the thermal decomposition of NH 3 molecule. These hydrogen gases activated the Ga-C bond cleavage. An energetically stable GaN nucleation site was formed via nitrogen incorporation into the layer of gallium cluster. The nitrogen atoms produced from the thermal degradation of NH 3 were expected to incorporate into the edge of the gallium cluster since the galliums bind weakly to each other (0.19 eV). The structure was stabilized by 2.08 eV, as an adsorbed N atom incorporated into a tetrahedral site of the Ga cluster. This suggests that the adhesion of the initial layer can be reinforced by the incorporation of nitrogen atom through the formation of large grain boundary GaN crystals at the early stage of GaN film growth

Evolution of C-O-H-N volatile species in the magma ocean during core formation.

Science.gov (United States)

Dalou, C.; Le Losq, C.; Hirschmann, M. M.; Jacobsen, S. D.; Fueri, E.

2017-12-01

The composition of the Hadean atmosphere affected how life began on Earth. Magma ocean degassing of C, O, H, and N was a key influence on the composition of the Hadean atmosphere. To identify the nature of degassed C-O-H-N species, we determined their speciation in reduced basaltic glasses (in equilibrium with Fe-C-N metal alloy, synthetized at 1400 and 1600 ºC and 1.2-3 GPa) via Raman spectroscopy. We addressed the effect of oxygen fugacity (fO2) on C-O-H-N speciation between IW-2.3 and IW-0.4, representing the evolution of the shallow upper mantle fO2 during the Hadean. We observe H2, NH2, NH3, CH3, CH4, CO, N2, and OH species in all glasses. With increasing ƒO2, our results support the formation of OH groups at the expense of N-H and C-H bonds in the melt, implying the equilibria at IW-2: (1) 2OH- (melt) + ½ N2 (melt) ↔ NH2 (melt) + 2 O2- (melt) , (2) 2OH- (melt) + ½ N2 (melt) + ½ H2 (melt) ↔ NH3 (melt) + 2 O2- (melt) . With increasing fO2, eqs. (1) and (2) shift to the left. From IW-2 to IW, we also observe an increase in the intensity of the NH2 peak relative to NH3. Carbon is present as CH3, CH4, and CO in all our glasses. While CO is likely the main carbon specie under reduced conditions (e.g., Armstrong et al. 2015), CH species should remain stable from moderately (IW-0.4) to very reduced (IW-3; Ardia et al. 2014; Kadik et al. 2015, 2017) conditions in hydrous silicate glasses following the equilibria: (3) 3OH- (melt) + C (graphite) ↔ CH3 (melt) + 3O2- (melt) , (4) 4OH- (melt) + C (graphite) ↔ CH4 (melt) + 4O2- (melt) . With increasing fO2, eqs. (3) and (4) shift to the left. As metal segregation and core formation drove the ƒO2 of the magma ocean from IW-4 to IW during the Hadean (Rubie et al. 2011), the nature of species degassed by the magma ocean should have evolved during that time. The C-O-H-N species we observe dissolved in our reduced glasses may not directly correspond to those degassed (Schaeffer and Fegley, 2007), but a better

Calculations of radiation defect formation cross sections in reactor materials in (n,p) and (n,α) reactions

International Nuclear Information System (INIS)

Kupchishin, A.A.; Kupchishin, A.I.; Omarbekova, Zh.

2001-01-01

In the work an experimental data analysis by integral σ(E 1 ) and differential [dσ(E 1 ,E 2 )]/dE 2 neutron interaction cross sections with reactor materials with the secondary protons and alpha particles generation as well as with the primarily knock-on atoms production in such reactions are carried out. It is shown, that in the (n,p) and (n',α) reactions the recoil nuclei receive essential energy portion and they are the patriarchs for atom-atom cascades in the substance. Nuclear reactions with formation of the secondary α-particles and and recoil nuclei are considered. It is shown, that these reactions are effectively proceeding within neutrons energy range 0.3-15 MeV. The nuclear reactions kinematics of above mentioned processes is studied. Energy conservation law for these reaction is applied. Deferential cross section conservation and transformation law for radiation defect formation in the (n,α) reaction are considered as well

n-Type Azaacenes Containing B←N Units.

Science.gov (United States)

Min, Yang; Dou, Chuandong; Tian, Hongkun; Geng, Yanhou; Liu, Jun; Wang, Lixiang

2018-02-12

We disclose a novel strategy to design n-type acenes through the introduction of boron-nitrogen coordination bonds (B←N). We synthesized two azaacenes composed of two B←N units and six/eight linearly annelated rings. The B←N unit significantly perturbed the electronic structures of the azaacenes: Unique LUMOs delocalized over the entire acene skeletons and decreased aromaticity of the B←N-adjacent rings. Most importantly, these B←N-containing azaacenes exhibited low-lying LUMO energy levels and high electron affinities, thus leading to n-type character. The solution-processed organic field-effect transistor based on one such azaacene exhibited unipolar n-type characteristics with an electron mobility of 0.21 cm 2  V -1  s -1 . © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Unusually short chalcogen bonds involving organoselenium: insights into the Se-N bond cleavage mechanism of the antioxidant ebselen and analogues.

Science.gov (United States)

Thomas, Sajesh P; Satheeshkumar, K; Mugesh, Govindasamy; Guru Row, T N

2015-04-27

Structural studies on the polymorphs of the organoselenium antioxidant ebselen and its derivative show the potential of organic selenium to form unusually short Se⋅⋅⋅O chalcogen bonds that lead to conserved supramolecular recognition units. Se⋅⋅⋅O interactions observed in these polymorphs are the shortest such chalcogen bonds known for organoselenium compounds. The FTIR spectral evolution characteristics of this interaction from solution state to solid crystalline state further validates the robustness of this class of supramolecular recognition units. The strength and electronic nature of the Se⋅⋅⋅O chalcogen bonds were explored using high-resolution X-ray charge density analysis and atons-in-molecules (AIM) theoretical analysis. A charge density study unravels the strong electrostatic nature of Se⋅⋅⋅O chalcogen bonding and soft-metal-like behavior of organoselenium. An analysis of the charge density around Se-N and Se-C covalent bonds in conjunction with the Se⋅⋅⋅O chalcogen bonding modes in ebselen and its analogues provides insights into the mechanism of drug action in this class of organoselenium antioxidants. The potential role of the intermolecular Se⋅⋅⋅O chalcogen bonding in forming the intermediate supramolecular assembly that leads to the bond cleavage mechanism has been proposed in terms of electron density topological parameters in a series of molecular complexes of ebselen with reactive oxygen species (ROS). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electronic Transport Mechanism for Schottky Diodes Formed by Au/HVPE a-Plane GaN Templates Grown via In Situ GaN Nanodot Formation

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Moonsang Lee

2018-06-01

Full Text Available We investigate the electrical characteristics of Schottky contacts for an Au/hydride vapor phase epitaxy (HVPE a-plane GaN template grown via in situ GaN nanodot formation. Although the Schottky diodes present excellent rectifying characteristics, their Schottky barrier height and ideality factor are highly dependent upon temperature variation. The relationship between the barrier height, ideality factor, and conventional Richardson plot reveals that the Schottky diodes exhibit an inhomogeneous barrier height, attributed to the interface states between the metal and a-plane GaN film and to point defects within the a-plane GaN layers grown via in situ nanodot formation. Also, we confirm that the current transport mechanism of HVPE a-plane GaN Schottky diodes grown via in situ nanodot formation prefers a thermionic field emission model rather than a thermionic emission (TE one, implying that Poole–Frenkel emission dominates the conduction mechanism over the entire range of measured temperatures. The deep-level transient spectroscopy (DLTS results prove the presence of noninteracting point-defect-assisted tunneling, which plays an important role in the transport mechanism. These electrical characteristics indicate that this method possesses a great throughput advantage for various applications, compared with Schottky contact to a-plane GaN grown using other methods. We expect that HVPE a-plane GaN Schottky diodes supported by in situ nanodot formation will open further opportunities for the development of nonpolar GaN-based high-performance devices.

Unexpected formation and crystal structure of tetrakis(1H-pyrazole-κN2palladium(II dichloride

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Thomas Wagner

2014-12-01

Full Text Available The title salt, [Pd(C3H4N24]Cl2, was obtained unexpectedly by the reaction of palladium(II dichloride with equimolar amounts of 1-chloro-1-nitro-2,2,2-tris(pyrazolylethane in methanol solution. The Pd2+ cation is located on an inversion centre and has a square-planar coordination sphere defined by four N atoms of four neutral pyrazole ligands. The average Pd—N distance is 2.000 (2 Å. The two chloride anions are not coordinating to Pd2+. They are connected to the complex cations through N—H...Cl hydrogen bonds. In addition, C—H...Cl hydrogen bonds are observed, leading to a three-dimensional linkage of cations and anions.

The intermetallic bonding between a ring carrier and aluminum piston alloy

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Manasijevic, Srećko

2015-09-01

Full Text Available This paper presents the results of investigating the formation of intermetallic bond between a ring carrier and aluminum piston alloy. The ring carrier is made of austenitic cast iron (Ni-Resist in order to increase the wear resistance of the first ring groove and applied in highly loaded diesel engines. Metallographic examination of the quality of alfin bond was done. A metallographic investigation using an optical microscope in combination with the SEM/EDS analysis of the quality of the intermetallic bonding layer was done. The test results show that can be made successfully as well as the formation of metal connection (alfin bond between the ring carrier and aluminum piston alloy.El artículo presenta los resultados de la investigación sobre la formación de una unión intermetálica entre el portasegmento y la aleación de aluminio del pistón. El portasegmento es una fundición de hierro austenítico (Ni-Resist con el fin de aumentar la resistencia al desgaste de la unión Al-fin del primer segmento y se utiliza en motores diésel altamente cargados. Se realizó un examen metalográfico de la unión intermetálica, mediante un microscopio óptico en combinación con SEM/EDS. Los satisfactorios resultados obtenidos muestran la formación de contacto metálico (unión Al-fin del primer segmento entre el portasegmento y la aleación de aluminio del pistón.

N-(4-Methoxyphenyl-tert-butanesulfinamide

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Mrityunjoy Datta

2009-11-01

Full Text Available In the title compound, C11H17NO2S, the molecules interact head-to-tail through N—H...OS hydrogen bonds, giving discrete centrosymmetric cyclic dimers. The N—Caryl bond length [1.4225 (14 Å] is intermediate between that in N-phenyl-tert-butanesulfinamide [1.4083 (12 Å] and the N—Calkyl bond lengths in N-alkylalkanesulfinamides (1.470–1.530 Å, suggesting weaker delocalization of electrons over the N atom and the aromatic ring due to the presence of the 4-methoxy group.

N-Methylamino Pyrimidyl Amides (MAPA): Highly Reactive, Electronically-Activated Amides in Catalytic N-C(O) Cleavage.

Science.gov (United States)

Meng, Guangrong; Lalancette, Roger; Szostak, Roman; Szostak, Michal

2017-09-01

Despite recent progress in catalytic cross-coupling technologies, the direct activation of N-alkyl-N-aryl amides has been a challenging transformation. Here, we report the first Suzuki cross-coupling of N-methylamino pyrimidyl amides (MAPA) enabled by the controlled n N → π Ar conjugation and the resulting remodeling of the partial double bond character of the amide bond. The new mode of amide activation is suitable for generating acyl-metal intermediates from unactivated primary and secondary amides.

Nitrogen-tuned bonding mechanism of Li and Ti adatom embedded graphene

International Nuclear Information System (INIS)

Lee, Sangho; Chung, Yong-Chae

2013-01-01

The effects of nitrogen defects on the bonding mechanism and resultant binding energy between the metal and graphene layer were investigated using density functional theory (DFT) calculations. For the graphitic N-doped graphene, Li adatom exhibited ionic bonding character, while Ti adatom showed features of covalent bonding similar to that of pristine graphene. However, in the cases of pyridinic and pyrrolic structures, partially covalent bonding characteristic occurred around N atoms in the process of binding with metals, and this particular bond formation enhanced the bond strength of metal on the graphene layer as much as it exceeded the cohesive energy of the metal bulk. Thus, Li and Ti metals are expected to be dispersed with atomic accuracy on the pyridinic and pyrrolic N-doped graphene layers. These results demonstrate that the bonding mechanism of metal–graphene complex can change according to the type of N defect, and this also affects the binding results. - Graphical abstract: Display Omitted - Highlights: • Nitrogen defects changed the bonding mechanism between metal and graphene. • Bonding character and binding results were investigated using DFT calculations. • Covalent bonding character occurred around pyridinic and pyrrolic N-doped graphene. • Pyridinic and pyrrolic N atoms are effective for metal dispersion on the graphene

N,N,N′-Trimethyl-N′′-(4-nitrophenyl-N′-phenylguanidine

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Ioannis Tiritiris

2014-05-01

Full Text Available The C—N bond lengths in the guanidine unit of the title compound, C16H18N4O2, are 1.298 (2, 1.353 (2 and 1.401 (3 Å, indicating double- and single-bond character. The N—C—N angles are 115.81 (16, 118.90 (18 and 125.16 (18°, showing a deviation of the CN3 plane from an ideal trigonal–planar geometry. In the crystal, C—H...O hydrogen bonds are observed between the methyl- and aromatic-H atoms and nitro-O atoms. One H atom of the phenyl ring and of the NMe2 group associate with the O atoms of the nitro group, giving chains along the a- and b-axis directions. Cross-linking of these two chains results in a two-dimensional network along bc.

The stereochemistry of the addition of chlorotitanium enolates of N-acyl oxazolidin-2-ones to 5- and 6- membered N-acyliminium ions

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Pilli Ronaldo A.

2001-01-01

Full Text Available The stereoselective addition of chiral and achiral titanium enolates derived from the corresponding N-acyl oxazolidin-2-ones to 5- and 6- membered N-acyliminium ions afforded 2-substituted pyrrolidines in moderate to good diastereoisomeric ratio (5:1 to 14:1 while lower diastereoselection was generally observed in the formation of the corresponding 2-substituted piperidines. The stereochemical outcome was found to be modulated by the nature of the cyclic N-acyliminium ion (5- or 6-membered and of its carbamate and by the N-acyl group in the enolate precursor. The preferential lk approach seems to be dictated mainly by the minimization of non-bonding interactions between the N-acyl group in the chlorotitanium (IV enolate and the carbamate and methylene groups in the cyclic N-acyliminium ion.

A study on poly (N-vinyl-2-pyrrolidone covalently bonded NiTi surface for inhibiting protein adsorption

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Hongyan Yu

2016-12-01

Full Text Available Near equiatomic NiTi alloys have been extensively applied as biomaterials owing to its unique shape memory effect, superelasticity and biocompatibility. It has been demonstrated that surfaces capable of preventing plasma protein adsorption could reduce the reactivity of biomaterials with human blood. This motivated a lot of researches on the surface modification of NiTi alloy. In the present work, following heat and alkaline treatment and silanization by trichlorovinylsilane (TCVS, coating of poly (N-vinyl-2-pyrrolidone (PVP was produced on the NiTi alloy by gamma ray induced chemical bonding. The structures and properties of modified NiTi were characterized and in vitro biocompatibility of plasma protein adsorption was investigated. The results indicated that heat treatment at 823 K for 1 h could result in the formation of a protective TiO2 layer with “Ni-free” zone on NiTi surface. It was found that PVP was covalently bonded on NiTi surface to create a hydrophilic layer for inhibiting protein adsorption on the surface. The present work offers a green approach to introduce a bioorganic surface on metal and other polymeric or inorganic substrates by gamma irradiation.

From Stable ZnO and GaN Clusters to Novel Double Bubbles and Frameworks

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Matthew R. Farrow

2014-05-01

Full Text Available A bottom up approach is employed in the design of novel materials: first, gas-phase “double bubble” clusters are constructed from high symmetry, Th, 24 and 96 atom, single bubbles of ZnO and GaN. These are used to construct bulk frameworks. Upon geometry optimization—minimisation of energies and forces computed using density functional theory—the symmetry of the double bubble clusters is reduced to either C1 or C2, and the average bond lengths for the outer bubbles are 1.9 Å, whereas the average bonds for the inner bubble are larger for ZnO than for GaN; 2.0 Å and 1.9 Å, respectively. A careful analysis of the bond distributions reveals that the inter-bubble bonds are bi-modal, and that there is a greater distortion for ZnO. Similar bond distributions are found for the corresponding frameworks. The distortion of the ZnO double bubble is found to be related to the increased flexibility of the outer bubble when composed of ZnO rather than GaN, which is reflected in their bulk moduli. The energetics suggest that (ZnO12@(GaN48 is more stable both in gas phase and bulk frameworks than (ZnO12@(ZnO48 and (GaN12@(GaN48. Formation enthalpies are similar to those found for carbon fullerenes.

(μ-trans-1,2-Di-4-pyridylethylene-κ2N:N′bis[bis(N,N-diisopropyldithiocarbamato-κ2S,S′zinc(II

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Hadi D. Arman

2009-11-01

Full Text Available The dinuclear title compound, [Zn2(C7H14NS24(C12H10N2], is centrosymmetric about the central C=C bond. The five-coordinate Zn atom is bonded to two asymmetrically chelating dithiocarbamate ligands and a pyridine N atom to define an NS4 coordination geometry tending towards a square pyramid, with the N atom in the apical site. In the crystal structure, C—H...S contacts lead to supramolecular chains.

Amide Bond Formation Assisted by Vicinal Alkylthio Migration in Enaminones: Metal- and CO-Free Synthesis of α,β-Unsaturated Amides.

Science.gov (United States)

Liu, Zhuqing; Huang, Fei; Wu, Ping; Wang, Quannan; Yu, Zhengkun

2018-05-18

Amide bond formation is one of the most important transformations in organic synthesis, drug development, and materials science. Efficient construction of amides has been among the most challenging tasks for organic chemists. Herein, we report a concise methodology for amide bond (-CONH-) formation assisted by vicinal group migration in alkylthio-functionalized enaminones (α-oxo ketene N, S-acetals) under mild conditions. Simple treatment of such enaminones with PhI(OAc) 2 at ambient temperature in air afforded diverse multiply functionalized α,β-unsaturated amides including β-cyclopropylated acrylamides, in which a wide array of functional groups such as aryl, (hetero)aryl, alkenyl, and alkyl can be conveniently introduced to a ketene moiety. The reaction mechanism was investigated by exploring the origins of the amide oxygen and carbon atoms as well as isolation and structural characterization of the reaction intermediates. The amide bond formation reactions could also be efficiently performed under solventless mechanical milling conditions.

Evaluación in vitro de la filtración marginal de diferentes sistemas de adhesión dentinaria: Gluma frente a Mirage

OpenAIRE

Navarro Majó, José Luis; Roig Cayón, Miguel; Basilio Monné, J.; Jané Noblom, L.; Sentís Vilalta, Juan; Brau Aguadé, Esteban

1992-01-01

Los autores realizaron un estudio comparativo, in vitro, de la capacidad de prevenir la filtración marginal de dos adhesivos dentinarios, el Gluma-Bond y el Mirage-Bond, en cavidades de clases V y II. Se tallaron dichas cavidades en premolares humanos recién extraídos y se obturaron con un composite híbrido. A continuación se procedió al termociclado de las muestras y a su inmersión en azul de metileno, y tras seccionarlas se procedió a su estudio mediante un estereomicroscopio. Pese a lograr...

Early-transition-metal ketenimine complexes. Synthesis, reactivity, and structural characterization of complexes with. eta. sup 2 (C,N)-ketenimine groups bound to the halogenobis((trimethylsilyl)cyclopentadienyl)niobium unit. X-ray structure of Nb(. eta. sup 5 -C sub 5 H sub 4 SiMe sub 3 ) sub 2 Cl(. eta. sup 2 (C,N)-PhN double bond C double bond CPh sub 2 )

Energy Technology Data Exchange (ETDEWEB)

Antinolo, A.; Fajardo, M.; Lopez Mardomingo, C.; Otero, A. (Univ. de Alcala de Henares (Spain)); Mourad, Y.; Mugnier, Y. (Centre National de la Recherche Scientifique, Dijon (France)); Sanz-Aparicio, J.; Fonseca, I.; Florencio, F. (CSIC, Madrid (Spain))

1990-11-01

The reaction of Nb({eta}{sup 5}-C{sub 5}H{sub 4}SiMe{sub 3}){sub 2}X (X = Cl, Br) with 1 equiv of various ketenimines, R{sup 1}N{double bond}C{double bond}CR{sup 2}R{sup 3}, leads to the niobium derivatives Nb({eta}{sup 5}-C{sub 5}H{sub 4}SiMe{sub 3}){sub 2}X({eta}{sup 2}(C,N)-R{sup 1}N{double bond}C{double bond}CR{sup 2}R{sup 3}) (1, X = Cl, R{sup 1} = R{sup 2} = R{sup 3} = C{sub 6}H{sub 5}; 2, X = Cl, R{sup 1} = p-CH{sub 3}-C{sub 6}H{sub 4}, R{sup 2} = R{sup 3} = C{sub 6}H{sub 5}; 3, X = Br, R{sup 1} = R{sup 2} = R{sup 3} = C{sub 6}H{sub 5}; 4, X = Br, R{sup 1} = p-CH{sub 3}-C{sub 6}H{sub 4}, R{sup 2} = R{sup 3} = C{sub 6}H{sub 5}; 5, X = Cl, R{sup 1} = R{sup 2} = C{sub 6}H{sub 5}, R{sup 3} = CH{sub 3}; 6, X = Br, R{sup 1} = R{sup 2} = C{sub 6}H{sub 5}, R{sup 3} = CH{sub 3}) with the expected ketenimine C{double bond}N bonding mode. Reduction of 1 with 1 equiv of Na/Hg gives the complex Nb({eta}{sup 5}-C{sub 5}H{sub 4}SiMe{sub 3}){sub 2}({eta}{sup 2}(C,N)-PhN{double bond}C{double bond}CPh{sub 2}) (9) as a paramagnetic compound. The reduction of 9 with 1 equiv of Na/Hg and the subsequent addition of a proton source (ethanol) leads to the iminoacyl compound Nb({eta}{sup 5}-C{sub 5}H{sub 4}SiMe{sub 3}){sub 2}(CRNR{sup 1}) (10, R = CH(Ph{sub 2}), R{sup 1} = Ph). The one- and two-electron reductions of 1 have been studied by cyclic voltammetry experiments. The structure of 1 was determined by single-crystal X-ray diffractometry: a = 24.4904 (14) {angstrom}, b = 11.0435 (04) {angstrom}, c = 26.6130 (15) {angstrom}, {beta} = 109.890 (5){degree}, monoclinic, space group C2/c, Z = 8, V = 6,768.4 (5) {angstrom}{sup 3}, {rho}{sub calcd} = 1.3194 g/mL, R = 0.048, R{sub w} = 0.060 based on 4,806 observed reflections. The structure contains a niobium atom bonded to two cyclopentadienyl rings in a {eta}{sup 5} fashion; the coordination of the metal is completed by a Cl atom and a {eta}{sup 2}(C,N)-bonded ketenimine ligand.

Ribonucleocapsid Formation of SARS-COV Through Molecular Action of the N-Terminal Domain of N Protein

Energy Technology Data Exchange (ETDEWEB)

Saikatendu, K.S.; Joseph, J.S.; Subramanian, V.; Neuman, B.W.; Buchmeier, M.J.; Stevens, R.C.; Kuhn, P.; /Scripps Res. Inst.

2007-07-12

Conserved amongst all coronaviruses are four structural proteins, the matrix (M), small envelope (E) and spike (S) that are embedded in the viral membrane and the nucleocapsid phosphoprotein (N), which exists in a ribonucleoprotein complex in their lumen. The N terminal domain of coronaviral N proteins (N-NTD) provides a scaffold for RNA binding while the C-terminal domain (N-CTD) mainly acts as oligomerization modules during assembly. The C-terminus of N protein anchors it to the viral membrane by associating with M protein. We characterized the structures of N-NTD from severe acute respiratory syndrome coronavirus (SARS-CoV) in two crystal forms, at 1.17A (monoclinic) and 1.85 A (cubic) respectively, solved by molecular replacement using the homologous avian infectious bronchitis virus (IBV) structure. Flexible loops in the solution structure of SARS-CoV N-NTD are now shown to be well ordered around the beta-sheet core. The functionally important positively charged beta-hairpin protrudes out of the core and is oriented similar to that in the IBV N-NTD and is involved in crystal packing in the monoclinic form. In the cubic form, the monomers form trimeric units that stack in a helical array. Comparison of crystal packing of SARS-CoV and IBV N-NTDs suggest a common mode of RNA recognition, but probably associate differently in vivo during the formation of the ribonucleoprotein complex. Electrostatic potential distribution on the surface of homology models of related coronaviral N-NTDs hints that they employ different modes of both RNA recognition as well as oligomeric assembly, perhaps explaining why their nucleocapsids have different morphologies.

Influence of Si and N additions on structure and phase stability of Ge{sub 2}Sb{sub 2}Te{sub 5} thin films

Energy Technology Data Exchange (ETDEWEB)

Koelpin, Helmut; Music, Denis; Mykhaylonka, Ruslan; Schneider, Jochen M [Materials Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Laptyeva, Galyna; Ghadimi, Reza; Richter, Silvia; Mayer, Joachim [Central Facility for Electron Microscopy, RWTH Aachen University, Ahornstrasse 55, D-52074 Aachen (Germany); Merget, Florian [Institute of Semiconductor Electronics, RWTH Aachen University, Sommerfeldstrasse 24, D-52074 Aachen (Germany)

2009-10-28

The influence of Si and N in Ge{sub 2}Sb{sub 2}Te{sub 5} (space group Fm3-barm) on structure and phase stability thereof was studied experimentally by thin film growth and characterization as well as theoretically by ab initio calculations. It was found that Si and N most probably accumulate in the amorphous matrix embedding Ge{sub 2}Sb{sub 2}Te{sub 5} grains. The incorporation of Si and N in these samples causes an increase of the crystallization temperature and the formation of finer grains. N is more efficient in increasing the crystallization temperature and in reducing the grain size than Si which can be understood based on the bonding analysis. The incorporation of both Si and N in Ge{sub 2}Sb{sub 2}Te{sub 5} is energetically unfavourable, leading to finer grains and larger crystallization temperatures. While in the case of Si additions no significant changes in bonding are observed, N additions appear to enable the formation of strong Te-N bonds in the amorphous matrix, which are shown to be almost twice as strong as the strongest bonds in unalloyed Ge{sub 2}Sb{sub 2}Te{sub 5}.

N-(2-Chlorophenyl-2-methylbenzamide

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B. Thimme Gowda

2008-08-01

Full Text Available In the structure of the title compound (N2CP2MBA, C14H12ClNO, the conformations of the N—H and C=O bonds are trans to each other. Furthermore, the conformation of the N—H bond is syn to the ortho-chloro group in the aniline ring and the C=O bond is syn to the ortho-methyl substituent in the benzoyl ring, similar to what is observed in 2-chloro-N-(2-chlorophenylbenzamide and 2-methyl-N-phenylbenzamide. The amide group makes almost the same dihedral angles of 41.2 (14 and 42.2 (13° with the aniline and benzoyl rings, respectively, while the dihedral angle between the benzoyl and aniline rings is only 7.4 (3°. The molecules in N2CP2MBA are packed into chains through N—H...O hydrogen bonds.

Experimental and theoretical studies of solvent effects on the hydrogen bonds in homoconjugated cations of substituted 4-halo (Cl, Br) pyridine N-oxide derivatives

International Nuclear Information System (INIS)

Gurzynski, Lukasz; Puszko, Aniela; Makowski, Mariusz; Chmurzynski, Lech

2007-01-01

Hydrogen bond OHO-type bridges formed between six substituted 4-halo (Cl, Br) pyridine N-oxide systems and their simple cations have been investigated by using the potentiometric titration method. The formation constants of these complexes (expressed as lgK BHB + ) have been determined in two non-aqueous aprotic solvents with different polarity, i.e., acetone (AC) and acetonitrile (AN). It has been observed that tri- and tetra-substituted pyridine N-oxides [B] and their cationic acids [BH + ] form stable homocomplexed cations [BHB + ] stabilized by O...H...O bridges in both solvents used. It has been found that the most stable homocomplexed system is formed by 3,5-dimethyl-4-chloropyridine N-oxide (3,5Me 2 4ClPyO). The lgK BHB + values for this compound in acetone and acetonitrile are 3.15 and 2.82, respectively. Furthermore, by using ab initio methods at the RHF and MP2 levels utilizing the Gaussian 6-31++G ** basis set, the energies of formation of the homocomplexed cations and Gibbs free energies have been determined in vacuo. The calculated energy parameters in vacuo have been compared with the cationic homoconjugation constants determined potentiometrically in acetone and acetonitrile to establish a correlation between these magnitudes. Additionally, the results of potentiometric measurements have been used to determine the acidity constants of the conjugate acids of N-oxides

Mechanisms of nitrous oxide (N2 O) formation and reduction in denitrifying biofilms.

Science.gov (United States)

Sabba, Fabrizio; Picioreanu, Cristian; Nerenberg, Robert

2017-12-01

Nitrous oxide (N 2 O) is a potent greenhouse gas that can be formed in wastewater treatment processes by ammonium oxidizing and denitrifying microorganisms. While N 2 O emissions from suspended growth systems have been extensively studied, and some recent studies have addressed emissions from nitrifying biofilms, much less is known about N 2 O emissions from denitrifying biofilm processes. This research used modeling to evaluate the mechanisms of N 2 O formation and reduction in denitrifying biofilms. The kinetic model included formation and consumption of key denitrification species, including nitrate (NO3-), nitrite (NO2-), nitric oxide (NO), and N 2 O. The model showed that, in presence of excess of electron donor, denitrifying biofilms have two distinct layers of activity: an outer layer where there is net production of N 2 O and an inner layer where there is net consumption. The presence of oxygen (O 2 ) had an important effect on N 2 O emission from suspended growth systems, but a smaller effect on biofilm systems. The effects of NO3- and O 2 differed significantly based on the biofilm thickness. Overall, the effects of biofilm thickness and bulk substrate concentrations on N 2 O emissions are complex and not always intuitive. A key mechanism for denitrifying biofilms is the diffusion of N 2 O and other intermediates from one zone of the biofilm to another. This leads to zones of N 2 O formation or consumption transformations that would not exist in suspended growth systems. © 2017 Wiley Periodicals, Inc.

cis-Dichlorido(dimethyl sulfoxide-κS(N,N,N′,N′-tetramethylguanidine-κN′′platinum(II

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Ivan I. Eliseev

2013-02-01

Full Text Available In the title compound, cis-[PtCl2(C5H13N3(C2H6OS], the four-coordinate PtII atom is bonded to one N atom of the N,N,N′,N′-tetramethylguanidine ligand, one dimethyl sulfoxide S atom and two chloride ligands, forming a cis-square-planar geometry. The bond lengths and angles of the N—Pt—Cl functionality are typical for imine dichloridoplatinum(II complexes. The H atom of the imino group is oriented towards the O atom of the sulfoxide group of a neighboring molecule and forms an N—H...O hydrogen bond.

Formation of N{sub 2} during the fixed-bed pyrolysis of coals

Energy Technology Data Exchange (ETDEWEB)

Wu, Zhiheng; Ohtsuka, Yasuo [Tohoku Univ., Sendai (Japan); Furimsky, E. [Natural Resources Canada, Ottawa, Ontario (Canada)

1995-12-31

Research on the fate of the nitrogen in coal during pyrolysis has attracted increased attention, since it is related with the NO{sub x} and N{sub 2}O emissions during subsequent combustion. It has been reported that coal nitrogen is initially released as tar, which is then converted to HCN and NH{sub 3} through secondary decomposition reactions. However, little attention to N{sub 2} has been paid so far. We have recently found that N{sub 2} is the dominant product in slow heating rate pyrolysis of a subbituminous coal, and that the finely dispersed iron catalyst promotes drastically the formation of N{sub 2} from a brown coal. If coal nitrogen can be removed efficiently as N{sub 2} during pyrolysis, this method would contribute to the reduction of the NO{sub x} and N{sub 2}O emissions, since such pollutants originate mostly from coal nitrogen. Therefore the present study aims at making clear the influence of coal type, pyrolysis conditions, demineralization, and iron catalyst on the formation of N{sub 2} during the fix-bed pyrolysis of several coals with different ranks.

Room-Temperature Synthesis of Thiostannates from {[Ni(tren)]2[Sn2S6]}n.

Science.gov (United States)

Hilbert, Jessica; Näther, Christian; Weihrich, Richard; Bensch, Wolfgang

2016-08-15

The compound {[Ni(tren)]2[Sn2S6]}n (1) (tren = tris(2-aminoethyl)amine, C6H18N4) was successfully applied as source for the room-temperature synthesis of the new thiostannates [Ni(tren)(ma)(H2O)]2[Sn2S6]·4H2O (2) (ma = methylamine, CH5N) and [Ni(tren)(1,2-dap)]2[Sn2S6]·2H2O (3) (1,2-dap = 1,2-diaminopropane, C3H10N2). The Ni-S bonds in the Ni2S2N8 bioctahedron in the structure of 1 are analyzed with density functional theory calculations demonstrating significantly differing Ni-S bond strengths. Because of this asymmetry they are easily broken in the presence of an excess of ma or 1,2-dap immediately followed by Ni-N bond formation to N donor atoms of the amine ligands thus generating [Ni(tren)(amine)](2+) complexes. The chemical reactions are fast, and compounds 2 and 3 are formed within 1 h. The synthesis concept presented here opens hitherto unknown possibilities for preparation of new thiostannates.

Ohmic contacts to n+-GaN capped AlGaN/AlN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Wang Liang; Mohammed, Fitih M.; Ofuonye, Benedict; Adesida, Ilesanmi

2007-01-01

Investigations of Ti/Al/Mo/Au Ohmic contact formation, premetallization plasma treatment effects, and interfacial reactions for n + -GaN capped AlGaN/AlN/GaN heterostructures are presented. Ti thickness played an important role in determining contact performance. Transmission electron microscopy studies confirmed that thick Ti layer was necessary to fully consume the GaN cap and the top of AlGaN to enable a higher tunneling current flow. A direct correlation of plasma treatment conditions with I-V linearity, current level, and contact performance was established. The plasma-affected region is believed to extend over 20 nm into the AlGaN and GaN

Surface properties and bond strength measurements of N-vinylcaprolactam (NVC)-containing glass-ionomer cements.

Science.gov (United States)

Moshaverinia, Alireza; Chee, Winston W; Brantley, William A; Schricker, Scott R

2011-03-01

N-vinylcaprolactam (NVC)-containing glass ionomers are promising dental restorative materials with improved mechanical properties; however, little information is available on other physical characteristics of these types of modified glass ionomers, especially their surface properties. Understanding the surface characteristics and behavior of glass ionomers is important for understanding their clinical behavior and predictability as dental restorative materials. The purpose of this study was to investigate the effect of NVC-containing terpolymers on the surface properties and bond strength to dentin of GIC (glass-ionomer cement), and to evaluate the effect of NVC-containing terpolymer as a dentin conditioner. The terpolymer of acrylic acid (AA)-itaconic acid (IA)-N-vinylcaprolactam (NVC) with a molar ratio of 8:1:1 (AA:IA:NVC) was synthesized by free radical polymerization and characterized using nuclear magnetic resonance ((1)H-NMR) and Fourier transform infrared spectroscopy (FTIR). The synthesized terpolymer was used in glass-ionomer cement formulations (Fuji IX GP). Ten disc-shaped specimens (12 × 1 mm) were mixed and fabricated at room temperature. Surface properties (wettability) of modified cements were studied by contact angle measurements as a function of time. Work of adhesion values of different surfaces were also determined. The effect of NVC-modified polyacid on the bond strength of glass-ionomer cement to dentin was investigated. The mean data obtained from contact angle and bonding strength measurements were subjected to t test and 2-way ANOVA (α=.05). NVC-modified glass-ionomer cements showed significantly (Pcement also showed significantly higher values for shear bond strength to dentin (8.7 ±0.15 MPa after 1 month) when compared to the control group (8.4 ±0.13 MPa after 1 month). NVC-containing terpolymers may enhance the surface properties of GICs and increase their bond strength to the dentin. Furthermore, NVC-containing polyelectrolytes are

Through-bond interaction in the radical cation of N,N-dimethylpiperazine

DEFF Research Database (Denmark)

Brouwer, A.M.; Langkilde, F.W.; Bajdor, K.

1994-01-01

The radical cation of N,N-dimethylpiperazine is investigated by resonance Raman spectroscopy and ab initio calculations. The calculations strongly support the assignment of the vibrational spectrum to a chair conformation. It is shown that a dramatic geometry relaxation following ionization allows...

Standard molar enthalpies of formation of three N-benzoylthiocarbamic-O-alkylesters

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Santos, Luis M.N.B.F.; Schroeder, Bernd; Dietze, Frank; Beyer, Lothar

2004-01-01

The standard (p 0 =0.1 MPa) molar enthalpies of combustion in oxygen of three crystalline N-benzoylthiocarbamic-O-alkylesters, PhCONHCSOR, R=Et (Hbtcee), n-Bu (Hbtcbe), n-Hex (Hbtche), were measured at T=298.15 K by rotating bomb calorimetry. The standard molar enthalpies of sublimation of the three compounds were measured using Calvet microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous phases, respectively

(N,N,N′,N′-Tetramethylethylenediamine-κNbis(2,4,6-trimethylphenolato-κOgermanium(II

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Eduard Rusanov

2012-03-01

Full Text Available In the title compound, [Ge(C9H11O2(C6H16N2], the GeII atom is coordinated in a distorted trigonal–pyramidal geometry by two O atoms belonging to two 2,4,6-trimethylphenolate ligands and one N atom of a tetramethylethylenediamine ligand. Comparing the structure with published data of similar compounds shows that the Ge—O bonds are covalent and the Ge—N bond is coordinated.

(Pyridine-2-aldoximato-κ2N,N′bis[2-(pyridin-2-ylphenyl-κ2C1,N]iridium(III

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Bimal Chandra Singh

2013-03-01

Full Text Available In the title complex, [Ir(C11H8N2(C6H5N2O], the octahedrally coordinated IrIII atom is bonded to two 2-(pyridin-2-ylphenyl ligands, through two phenyl C and two pydidine N atoms, and to one pyridine-2-aldoxime ligand through a pyridine N and an oxime N atom. The oxime O atom of the aldoxime unit forms intermolecular C—H...O hydrogen bonds, which result in a two-dimensional hydrogen-bonded polymeric network parallel to (100. C—H...π interactions are also observed.

Ab initio molecular dynamics studies on effect of Zr on oxidation resistance of TiAlN coatings

Energy Technology Data Exchange (ETDEWEB)

Pi, Jingwu [State Key Lab of Powder Metallurgy, Central South University, Changsha,Hunan 410083 (China); Kong, Yi, E-mail: yikong@csu.edu.cn [State Key Lab of Powder Metallurgy, Central South University, Changsha,Hunan 410083 (China); Chen, Li [State Key Lab of Powder Metallurgy, Central South University, Changsha,Hunan 410083 (China); Zhuzhou Cemented Carbide Cutting Tools Co., Ltd., Zhuzhou, Hunan 412007 (China); Du, Yong [State Key Lab of Powder Metallurgy, Central South University, Changsha,Hunan 410083 (China)

2016-08-15

Highlights: • The lowest bonding energy sequence for dimers in the vacuum: Zr−O < Ti−O < Al−O. • The lowest bonding energy sequence for oxygen above the surface: Ti−O < Zr−O < Al−O. • At 300 K, the addition of Zr benefitting the formation of vacancy and TiO{sub 2}. • At 1123 K, the addition of Zr leading to a more stable surface. • Our findings explain that the oxidation resistance of TiAlZrN superior to TiAlN at 1123 K as well as TiAlZrN at 300 K. - Abstract: It was demonstrated experimentally that doping Zr into TiAlN coatings at room temperature will detriment its oxidation resistance. On the other hand, there are evidences that doping Zr into TiAlN at high temperature will improve coating's oxidation resistance. In the present work, we address the effect of Zr on the oxidation resistance of TiAlN by means of ab initio molecular dynamics simulations. The TiAlN and TiAlZrN (1 Zr atom replacing 1 Ti atom) surfaces covered with 4 oxygen atoms at 300 K and 1123 K were simulated. Based on the analysis of the atomic motion, bond formation after relaxation, and the charge density difference maps we find that at 300 K, the addition of Zr induces escape of Ti atoms from the surface, resulting in formation of surface vacancies and subsequently TiO{sub 2}. Comparison of metal-oxygen dimers in the vacuum and above the TiAlZrN surface further shows that the addition of Zr in the TiAlN surface will change the lowest bonding energy sequence from Zr−O < Ti−O < Al−O in the vacuum to Ti−O < Zr−O < Al−O above the TiAlZrN surface. From Molecular Dynamics simulations at 1123 K, it is find that no Ti vacancies were generated in the surface. Moreover, less charge is transferred from metal to N atoms and the bond lengths between Ti and O atoms become shorter at 1123 K as compared with 300 K, suggesting that the addition of Zr atom promotes the interaction of Ti and O at TiAlZrN surface at 1123 K, leading to a more stable surface. Our simulation

High pressure stability analysis and chemical bonding of Ti1-xZrxN alloy: A first principle study

International Nuclear Information System (INIS)

Chauhan, Mamta; Gupta, Dinesh C.

2016-01-01

First-principles pseudo-potential calculations have been performed to analyze the stability of Ti 1-x Zr x N alloy under high pressures. The first order phase transition from B1 to B2 phase has been observed in this alloy at high pressure. The variation of lattice parameter with the change in concentration of Zr atom in Ti 1-x Zr x N is also reported in both the phases. The calculations for density of states have been performed to understand the alloying effects on chemical bonding of Ti-Zr-N alloy.

Formation of reactive oxygen by N2O decomposition over binuclear cationic sites of Fe-ferrierite zeolite: Periodic DFT + U study

Science.gov (United States)

Avdeev, Vasilii I.; Bedilo, Alexander F.

2018-03-01

The electronic nature of sites over Fe-ferrierite zeolite stabilizing active α-oxygen is analyzed by the periodic DFT + U approach. It is shown that two antiferromagnetically coupled Fe2+ cations with bridging OH-bonds form a stable bi-nuclear site of the [Fe2+Fe2+] doped FER complex. Frontier orbitals of this complex populated by two electrons with minority spins are localized in the bandgap. As a result, [Fe2+Fe2+] unit acquires the properties of a binuclear Lewis acid dipolarophile for 1,3-dipole N2O. First reaction step of N2O decomposition follows the Huisgen‧s concept of the 1,3-dipolar cycloaddition concept followed by the formation of reactive oxygen species Fesbnd O.

The Role of Hydroxylamine as a Nitrification Intermediate in N-nitrosamine Formation

Science.gov (United States)

The formation of N-nitrosamines, and in particular N-nitrosodimethylamine (NDMA), in drinking water systems that use chloramines is a concern because of their potential carcinogenicity and occurrences in finished waters at toxicologically relevant levels. The widely accepted mech...

Intramolecular hydrogen bonding in N-salicylideneaniline: FT-IR spectrum and quantum chemical calculations

Science.gov (United States)

Moosavi-Tekyeh, Zainab; Dastani, Najmeh

2015-12-01

FT-IR and FT-Raman spectra of N-salicylideneaniline (SAn) and its deuterated analogue (D-SAn) are recorded, and the theoretical calculations are performed on their molecular structures and vibrational frequencies. The same calculations are performed for SAn in different solutions using the polarizable conductor continuum model (CPCM) method. Comparisons between the spectra obtained and the corresponding theoretical calculations are used to assign the vibrational frequencies for these compounds. The spectral behavior of SAn upon deuteration is also used to distinguish the positions of OH vibrational frequencies. The hydrogen bond strength of SAn is investigated by applying the atoms-in-molecules (AIM) theory, natural bond orbital (NBO) analysis, and geometry calculations. The harmonic vibrational frequencies of SAn are calculated at B3LYP and X3LYP levels of theory using 6-31G*, 6-311G**, and 6-311++G** basis sets. The AIM results support a medium hydrogen bonding in SAn. The observed νOH/νOD and γOH/γOD for SAn appear at 2940/2122 and 830/589 cm-1, respectively.

Formation and mitigation of N-nitrosamines in nitrite preserved cooked sausages

DEFF Research Database (Denmark)

Herrmann, Susan Strange; Granby, Kit; Duedahl-Olesen, Lene

2015-01-01

Literature on formation and mitigation of N-nitrosamine (NA) and especially non-volatile NA (NVNA) in meat products is scarce and the present study is therefore a relevant contribution to the field. We found positive correlation between the levels of N-nitrosopiperidine (NPIP), N-nitrosohydroxypr...... and a combination of the two provided no further protection. Increasing the black pepper content increased the levels of NPIP and NMTCA. Only slight effects of increased fat content and addition of tripolyphosphate were observed....

Unusual C-C bond cleavage in the formation of amine-bis(phenoxy) group 4 benzyl complexes: Mechanism of formation and application to stereospecific polymerization

KAUST Repository

Gowda, Ravikumar R.

2014-08-11

Group 4 tetrabenzyl compounds MBn4 (M = Zr, Ti), upon protonolysis with an equimolar amount of the tetradentate amine-tris(phenol) ligand N[(2,4-tBu2C6H2(CH 2)OH]3 in toluene from -30 to 25 °C, unexpectedly lead to amine-bis(phenoxy) dibenzyl complexes, BnCH2N[(2,4- tBu2C6H2(CH2)O] 2MBn2 (M = Zr (1), Ti (2)) in 80% (1) and 75% (2) yields. This reaction involves an apparent cleavage of the >NCH2-ArOH bond (loss of the phenol in the ligand) and formation of the >NCH 2-CH2Bn bond (gain of the benzyl group in the ligand). Structural characterization of 1 by X-ray diffraction analysis confirms that the complex formed is a bis(benzyl) complex of Zr coordinated by a newly derived tridentate amine-bis(phenoxy) ligand arranged in a mer configuration in the solid state. The abstractive activation of 1 and 2 with B(C6F 5)3·THF in CD2Cl2 at room temperature generates the corresponding benzyl cations {BnCH2N[(2,4- tBu2C6H2(CH2)O] 2MBn(THF)}+[BnB(C6F5) 3]- (M = Zr (3), Ti, (4)). These cationic complexes, along with their analogues derived from (imino)phenoxy tri- and dibenzyl complexes, [(2,6-iPr2C6H3)N=C(3,5- tBu2C6H2)O]ZrBn3 (5) and [2,4-Br2C6H2(O)(6-CH2(NC 5H9))CH2N=CH(2-adamantyl-4-MeC 6H2O)]ZrBn2 (6), have been found to effectively polymerize the biomass-derived renewable β-methyl-α-methylene- γ-butyrolactone (βMMBL) at room temperature into the highly stereoregular polymer PβMMBL with an isotacticity up to 99% mm. A combined experimental and DFT study has yielded a mechanistic pathway for the observed unusual C-C bond cleavage in the present protonolysis reaction between ZrBn4 and N[(2,4-tBu2C 6H2(CH2)OH]3 for the formation of complex 1, which involves the benzyl radical and the Zr(III) species, resulting from thermal and photochemical decomposition of ZrBn4, followed by a series of reaction sequences consisting of protonolysis, tautomerization, H-transfer, oxidation, elimination, and radical coupling. © 2014 American Chemical Society.

Supramolecular packing and polymorph screening of N-isonicotinoyl arylketone hydrazones with phenol and amino modifications

Science.gov (United States)

Hean, Duane; Michael, Joseph P.; Lemmerer, Andreas

2018-04-01

Thirteen structural variants based on the (E)-N‧-(1-arylethylidene)pyridohydrazide template were prepared, investigated and screened for possible polymorphic behaviour. Four variants showed from Differential Scanning Calorimetry Scans thermal events indicative of new solid-state phases. The thirteen variants included substituents R = sbnd OH or sbnd NH2 placed at ortho, meta and para positions on the phenyl ring; and shifting the pyridyl nitrogen between positions 4-, 3- and 2-. The crystal structures of twelve of the compounds were determined to explore their supramolecular structures. The outcomes of these modifications demonstrated that the pyridyl nitrogen at the 2- position is 'locked' by forming a hydrogen bond with the amide hydrogen; while placing the pyridyl nitrogen at positions 3- and 4- offers a greater opportunity for hydrogen bonding with neighbouring molecules. Such interactions include Osbnd H⋯N, Nsbnd H⋯N, Osbnd H⋯O, Nsbnd H⋯O, Nsbnd H⋯π, π⋯π stacking, as well as other weaker interactions such as Csbnd H⋯N, Csbnd H⋯O, Csbnd H⋯N(pyridyl). When OH or NH2 donors are placed in the ortho position, an intramolecular hydrogen bond is formed between the acceptor hydrazone nitrogen and the respective donor. The meta- and para-positioned donors form an unpredictable array of supramolecular structures by forming hydrogen-bonded chains with the pyridyl nitrogen and carbonyl acceptors respectively. In addition to the intramolecular and chain hydrogen bond formation demonstrated throughout the crystal structures under investigation, larger order hydrogen-bonded rings were also observed in some of the supramolecular aggregations. The extent of the hydrogen-bonded ring formations range from two to six molecular participants depending on the specific crystal structure.

A hybrid neutron diffraction and computer simulation study on the solvation of N-methylformamide in dimethylsulfoxide

Science.gov (United States)

Cordeiro, João M. M.; Soper, Alan K.

2013-01-01

The solvation of N-methylformamide (NMF) by dimethylsulfoxide (DMSO) in a 20% NMF/DMSO liquid mixture is investigated using a combination of neutron diffraction augmented with isotopic substitution and Monte Carlo simulations. The aim is to investigate the solute-solvent interactions and the structure of the solution. The results point to the formation of a hydrogen bond (H-bond) between the H bonded to the N of the amine group of NMF and the O of DMSO particularly strong when compared with other H-bonded liquids. Moreover, a second cooperative H-bond is identified with the S atom of DMSO. As a consequence of these H-bonds, molecules of NMF and DMSO are rather rigidly connected, establishing very stable dimmers in the mixture and very well organized first and second solvation shells.

N,N,N′,N′,N′′,N′′-Hexamethylguanidinium 1,1,3,3-tetracyanoprop-2-en-1-ide

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Ioannis Tiritiris

2016-03-01

Full Text Available The asymmetric unit of the title salt, C7H18N3+·C7HN4−, comprises one cation and one anion. The N,N,N′,N′,N′′,N′′-hexamethylguanidinium ion shows orientational disorder and two sets of N- and C-atom positions were found, with an occupancy ratio of 0.535 (3:0.465 (3. The C—N bond lengths in the guanidinium ion range from 1.339 (16 to 1.35 (2 Å, indicating partial double-bond character pointing towards charge delocalization within the NCN planes. The negative charge in the 1,1,3,3-tetracyanoprop-2-en-1-ide ion is delocalized within the CCC planes with the C—C bonds ranging in length from 1.379 (3 to 1.427 (3 Å, also indicating partial double-bond character.

N,N-Diethyl-4-[(E-(pyridin-3-yldiazenyl]aniline

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Tatiana V. Timofeeva

2013-08-01

Full Text Available The molecule of the title compound, C15H18N4, adopts a trans conformation with respect to the diazo N=N bond. The dihedral angle between the benzene and pyridine rings in the molecule is 8.03 (5°. In the crystal, a weak C—H...π interaction arranges the molecules into a corrugated ribbon, with an antiparallel orientation of neighboring molecules propagating in the [100] direction.

N-Benzyl-N-[2-(N-benzyl-N′,N′,N′′,N′′-tetramethylguanidiniumylethyl]-N′,N′,N′′,N′′-tetramethylguanidinium dibromide 1.5-hydrate

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Ioannis Tiritiris

2016-01-01

Full Text Available The asymmetric unit of the hydrated title compound, C26H42N62+·2Br−·1.5H2O, comprises one cation, two bromide anions and one and a half water molecules, as one water molecule is fully occupied and the other is only half occupied [0.500 (6]. Both bromide ions are disordered over two sites with refined occupancies of 0.938 (3:0.062 (3 and 0.520 (9:0.480 (9. The C—N bond lengths in both central C3N units of the bisguanidinium ion range between 1.336 (3 and 1.349 (3 Å, indicating a degree of double-bond character. The central C atoms are bonded to the three N atoms in a nearly ideal trigonal–planar geometry and the positive charges are delocalized in both CN3 planes. The crystal structure is stabilized by a three-dimensional network of O—H...O, O—H...Br and C—H...Br hydrogen bonds.

Computational Study of Pincer Iridium Catalytic Systems: C-H, N-H, and C-C Bond Activation and C-C Coupling Reactions

Science.gov (United States)

Zhou, Tian

Computational chemistry has achieved vast progress in the last decades in the field, which was considered to be only experimental before. DFT (density functional theory) calculations have been proven to be able to be applied to large systems, while maintaining high accuracy. One of the most important achievements of DFT calculations is in exploring the mechanism of bond activation reactions catalyzed by organometallic complexes. In this dissertation, we discuss DFT studies of several catalytic systems explored in the lab of Professor Alan S. Goldman. Headlines in the work are: (1) (R4PCP)Ir alkane dehydrogenation catalysts are highly selective and different from ( R4POCOP)Ir catalysts, predicting different rate-/selectivity-determining steps; (2) The study of the mechanism for double C-H addition/cyclometalation of phenanthrene or biphenyl by (tBu4PCP)Ir(I) and ( iPr4PCP)Ir illustrates that neutral Ir(III) C-H addition products can undergo a very facile second C-H addition, particularly in the case of sterically less-crowded Ir(I) complexes; (3) (iPr4PCP)Ir pure solid phase catalyst is highly effective in producing high yields of alpha-olefin products, since the activation enthalpy for dehydrogenation is higher than that for isomerization via an allyl pathway; higher temperatures favor the dehydrogenation/isomerization ratio; (4) (PCP)Ir(H)2(N2H4) complex follows a hydrogen transfer mechanism to undergo both dehydrogenation to form N 2 and H2, as well as hydrogen transfer followed by N-N bond cleavage to form NH3, N2, and H2; (5) The key for the catalytic effect of solvent molecule in CO insertion reaction for RMn(CO)5 is hydrogen bond assisted interaction. The basicity of the solvent determines the strength of the hydrogen bond interaction during the catalytic path and determines the catalytic power of the solvent; and (6) Dehydrogenative coupling of unactivated C-H bonds (intermolecular vinyl-vinyl, intramolecular vinyl-benzyl) is catalyzed by precursors of the

Experimental and theoretical studies of solvent effects on the hydrogen bonds in homoconjugated cations of substituted 4-halo (Cl, Br) pyridine N-oxide derivatives

Energy Technology Data Exchange (ETDEWEB)

Gurzynski, Lukasz [Department of General and Inorganic Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Puszko, Aniela [Department of Organic Chemistry, School of Economics, Wroclaw (Poland); Makowski, Mariusz [Department of General and Inorganic Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Chmurzynski, Lech [Department of General and Inorganic Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland)], E-mail: lech@chem.univ.gda.pl

2007-09-15

Hydrogen bond OHO-type bridges formed between six substituted 4-halo (Cl, Br) pyridine N-oxide systems and their simple cations have been investigated by using the potentiometric titration method. The formation constants of these complexes (expressed as lgK{sub BHB{sup +}}) have been determined in two non-aqueous aprotic solvents with different polarity, i.e., acetone (AC) and acetonitrile (AN). It has been observed that tri- and tetra-substituted pyridine N-oxides [B] and their cationic acids [BH{sup +}] form stable homocomplexed cations [BHB{sup +}] stabilized by O...H...O bridges in both solvents used. It has been found that the most stable homocomplexed system is formed by 3,5-dimethyl-4-chloropyridine N-oxide (3,5Me{sub 2}4ClPyO). The lgK{sub BHB{sup +}} values for this compound in acetone and acetonitrile are 3.15 and 2.82, respectively. Furthermore, by using ab initio methods at the RHF and MP2 levels utilizing the Gaussian 6-31++G{sup **} basis set, the energies of formation of the homocomplexed cations and Gibbs free energies have been determined in vacuo. The calculated energy parameters in vacuo have been compared with the cationic homoconjugation constants determined potentiometrically in acetone and acetonitrile to establish a correlation between these magnitudes. Additionally, the results of potentiometric measurements have been used to determine the acidity constants of the conjugate acids of N-oxides.

Diazido{(S-1-phenyl-N,N-bis[(2-pyridylmethyl]ethanamine}copper(II

Directory of Open Access Journals (Sweden)

Sankara Rao Rowthu

2011-07-01

Full Text Available In the title compound, [Cu(N32(C20H21N3], the CuII ion is coordinated by the three N atoms of the (S-1-phenyl-N,N-bis[(2-pyridylmethyl]ethanamine ligand and two N atoms from two azide anions, resulting in a distorted square-pyramidal environment. A weak intermolecular C—H...N hydrogen-bonding interaction between one pyridine group of the ligand and an azide N atom of an adjacent complex unit gives a one-dimensional chain structure parallel to the c axis.

Crystal structures of 5-amino-N-phenyl-3H-1,2,4-di-thia-zol-3-iminium chloride and 5-amino-N-(4-chloro-phen-yl)-3H-1,2,4-di-thia-zol-3-iminium chloride monohydrate.

Science.gov (United States)

Yeo, Chien Ing; Tan, Yee Seng; Tiekink, Edward R T

2015-10-01

The crystal and mol-ecular structures of the title salt, C8H8N3S2 (+)·Cl(-), (I), and salt hydrate, C8H7ClN3S2 (+)·Cl(-)·H2O, (II), are described. The heterocyclic ring in (I) is statistically planar and forms a dihedral angle of 9.05 (12)° with the pendant phenyl ring. The comparable angle in (II) is 15.60 (12)°, indicating a greater twist in this cation. An evaluation of the bond lengths in the H2N-C-N-C-N sequence of each cation indicates significant delocalization of π-electron density over these atoms. The common feature of the crystal packing in (I) and (II) is the formation of charge-assisted amino-N-H⋯Cl(-) hydrogen bonds, leading to helical chains in (I) and zigzag chains in (II). In (I), these are linked by chains mediated by charge-assisted iminium-N(+)-H⋯Cl(-) hydrogen bonds into a three-dimensional architecture. In (II), the chains are linked into a layer by charge-assisted water-O-H⋯Cl(-) and water-O-H⋯O(water) hydrogen bonds with charge-assisted iminium-N(+)-H⋯O(water) hydrogen bonds providing the connections between the layers to generate the three-dimensional packing. In (II), the chloride anion and water mol-ecules are resolved into two proximate sites with the major component being present with a site occupancy factor of 0.9327 (18).

Investigation of the flatband voltage (V(FB)) shift of Al2O3 on N2 plasma treated Si substrate.

Science.gov (United States)

Kim, Hyungchul; Lee, Jaesang; Jeon, Heeyoung; Park, Jingyu; Jeon, Hyeongtag

2013-09-01

The relationships between the physical and electrical characteristics of films treated with N2 plasma followed by forming gas annealing (FGA) were investigated. The Si substrates were treated with various radio frequency (RF) power levels under a N2 ambient. Al2O3 films were then deposited on Si substrates via remote plasma atomic-layer deposition. The plasma characteristics, such as the radical and ion density, were investigated using optical emission spectroscopy. Through X-ray photoelectron spectroscopy, the chemical-bonding configurations of the samples treated with N2 plasma and FGA were examined. The quantity of Si-N bonds increased as the RF power was increased, and Si--O--N bonds were generated after FGA. The flatband voltage (VFB) was shifted in the negative direction with increasing RF power, but the VFB values of the samples after FGA shifted in the positive direction due to the formation of Si--O--N bonds. N2 plasma treatment with various RF power levels slightly increased the leakage current due to the generation of defect sites.

Size-dependent disproportionation (in 2-20 nm regime) and hybrid Bond Valence derived interatomic potentials for BaTaO2N

Science.gov (United States)

Anbalagan, Kousika; Thomas, Tiju

2018-05-01

Interatomic potentials for complex materials (like ceramic systems) are important for realistic molecular dynamics (MD) simulations. Such simulations are relevant for understanding equilibrium, transport and dynamical properties of materials, especially in the nanoregime. Here we derive a hybrid interatomic potential (based on bond valence (BV) derived Morse and Coulomb terms), for modeling a complex ceramic, barium tantalum oxynitride (BaTaO2N). This material has been chosen due to its relevance for capacitive and photoactive applications. However, the material presents processing challenges such as the emergence of non-stoichiometric phases during processing, demonstrating complex processing-property correlations. This makes MD investigations of this material both scientifically and technologically relevant. The BV based hybrid potential presented here has been used for simulating sintering of BaTaO2N nanoparticles ( 2-20 nm) under different conditions (using the relevant canonical ensemble). Notably, we show that sintering of particles of diameter 10 nm in size results in the formation of a cluster of tantalum and oxygen atoms at the interface of the BaTaO2N particles. This is in agreement with the experimental reports. The results presented here suggest that the potential proposed can be used to explore dynamical properties of BaTaO2N and related systems. This work will also open avenues for development of nanoscience-enabled aid-free sintering approaches to this and related materials.

Effects of multiple substitution upon the P...N noncovalent interaction

International Nuclear Information System (INIS)

Scheiner, Steve

2011-01-01

Graphical abstract: The presence of one halogen opposite the N results in strong attraction between P and N. This force is little affected by identity of Y atoms, whether H or halogen. Highlights: → Strong attractive force directly between trivalent P and N atoms. → P...N force is unlike H-bonds or halogen bonds, but stronger than both. → Multiple halogenation beyond a single atom on P slightly weakens the interaction. - Abstract: The attractive noncovalent interaction of a P atom with N is derived primarily from two sources. Charge transfer from the N lone pair into the σ * antibonding orbital of a P-X bond that is turned away from the N atom combines with attractive Coulombic forces. As in the case of H-bonding, which is parallel in some ways to P...N attraction, placement of an electron-withdrawing substituent on the P atom enhances both of these components, and strengthens the overall interaction. However, in stark contrast with H-bonding, halogenation beyond monosubstitution does not lead to any further strengthening of the P...N noncovalent bond. Indeed, di and tri-substitution lead to small reductions in the interaction energy. In all cases, the geometry which contains a P...N bond is more stable than other candidate structures, some of which contain hydrogen or halogen bonds.

A Relativity Enhanced, Medium-Strong Au(I)···H-N Hydrogen Bond in a Protonated Phenylpyridine-Gold(I) Thiolate.

Science.gov (United States)

Berger, Raphael J F; Schoiber, Jürgen; Monkowius, Uwe

2017-01-17

Gold is an electron-rich metal with a high electronegativity comparable to that of sulfur. Hence, hydrogen bonds of the Au(I)···H-E (E = electronegative element) type should be possible, but their existence is still under debate. Experimental results are scarce and often contradictory. As guidance for possible preparative work, we have theoretically investigated (ppyH)Au(SPh) (ppy = 2-phenylpyridine) bearing two monoanionic ligands which are not strongly electronegative at the same time to further increase the charge density on the gold(I) atom. The protonated pyridine nitrogen atom in ppy is geometrically ideally suited to place a proton in close proximity to the gold atom in a favorable geometry for a classical hydrogen bond arrangement. Indeed, the results of the calculations indicate that the hydrogen bonded conformation of (ppyH)Au(SPh) represents a minimum geometry with bond metrics in the expected range for medium-strong hydrogen bonds [r(N-H) = 1.043 Å, r(H···Au) = 2.060 Å, a(N-H···Au) = 141.4°]. The energy difference between the conformer containing the H···Au bond and another conformer without a hydrogen bond amounts to 7.8 kcal mol -1 , which might serve as an estimate of the hydrogen bond strength. Spectroscopic properties were calculated, yielding further characteristics of such hydrogen bonded gold species.

Hydroxyl Radical-Mediated Novel Modification of Peptides: N-Terminal Cyclization through the Formation of α-Ketoamide.

Science.gov (United States)

Lee, Seon Hwa; Kyung, Hyunsook; Yokota, Ryo; Goto, Takaaki; Oe, Tomoyuki

2015-01-20

The hydroxyl radical-mediated oxidation of peptides and proteins constitutes a large group of post-translational modifications that can result in structural and functional changes. These oxidations can lead to hydroxylation, sulfoxidation, or carbonylation of certain amino acid residues and cleavage of peptide bonds. In addition, hydroxyl radicals can convert the N-terminus of peptides to an α-ketoamide via abstraction of the N-terminal α-hydrogen and hydrolysis of the ketimine intermediate. In the present study, we identified N-terminal cyclization as a novel modification mediated by a hydroxyl radical. The reaction of angiotensin (Ang) II (DRVYIHPF) and the hydroxyl radical generated by the Cu(II)/ascorbic acid (AA) system or UV/hydrogen peroxide system produced N-terminal cyclized-Ang II (Ang C) and pyruvamide-Ang II (Ang P, CH3COCONH-RVYIHPF). The structure of Ang C was confirmed by mass spectrometry and comparison to an authentic standard. The subsequent incubation of isolated Ang P in the presence of Cu(II)/AA revealed that Ang P was the direct precursor of Ang C. The proposed mechanism involves the formation of a nitrogen-centered (aminyl) radical, which cyclizes to form a five-membered ring containing the alkoxy radical. The subsequent β-scission reaction of the alkoxyl radical results in the cleavage of the terminal CH3CO group. The initial aminyl radical can be stabilized by chelation to the Cu(II) ions. The affinity of Ang C toward the Ang II type 1 receptor was significantly lower than that of Ang II or Ang P. Ang C was not further metabolized by aminopeptidase A, which converts Ang II to Ang III. Hydroxyl radical-mediated N-terminal cyclization was also observed in other Ang peptides containing N-terminal alanine, arginine, valine, and amyloid β 1-11 (DAEFRHDSGYE).

N-nitrosamine formation by monochloramine, free chlorine, and peracetic acid disinfection with presence of amine precursors in drinking water system.

Science.gov (United States)

West, Danielle M; Wu, Qihua; Donovan, Ariel; Shi, Honglan; Ma, Yinfa; Jiang, Hua; Wang, Jianmin

2016-06-01

In this study, the formation of eight N-nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine, N-nitrosomethylamine, N-nitrosodi-n-propylamine, N-nitrosodi-n-butylamine, N-Nitrosopiperidine, N-Nitrosopyrrolidine, N-Nitrosomorpholine, were systematically evaluated with respect to seven N-nitrosamine precursors (dimethylamine, trimethylamine, 3-(dimethylaminomethyl)indole, 4-dimethylaminoantipyrine, ethylmethylamine, diethylamine, dipropylamine) and three disinfectants (monochloramine, free chlorine, peracetic acid) under variable dosages, exposure times, and pH in a drinking water system. Without the presence of the seven selected N-nitrosamine precursors N-nitrosamine formation was not observed under any tested condition except very low levels of N-Nitrosopyrrolidine under some conditions. With selected N-nitrosamine precursors present N-nitrosamines formed at different levels under different conditions. The highest N-nitrosamine formation was NDMA with a maximum concentration of 1180 ng/L by monochloramine disinfection with precursors present; much lower levels of N-nitrosamines were formed by free chlorine disinfection; and no detectable level of N-nitrosamines were observed by peracetic acid disinfection except low level of N-Nitrosodi-n-propylamine under some conditions. NDMA formation was not affected by pH while four other N-nitrosamine formations were slightly affected by sample pH tested between 7 and 9, with formation decreasing with increasing pH. Monochloramine exposure time study displayed fast formation of N-nitrosamines, largely formed in four hours of exposure and maximized after seven days. This was a systematic study on the N-nitrosamine formation with the seven major N-nitrosamine precursors presence and absence under different conditions, including peracetic acid disinfection which has not been studied elsewhere. Copyright © 2016 Elsevier Ltd. All rights reserved.

Formation of oriented nitrides by N+ ion implantation in iron single crystals

International Nuclear Information System (INIS)

Costa, A.R.G.; Silva, R.C. da; Ferreira, L.P.; Carvalho, M.D.; Silva, C.; Franco, N.; Godinho, M.

2014-01-01

Iron single crystals were implanted with nitrogen at room temperature, with a fluence of 5×10 17 cm −2 and 50 keV energy, to produce iron nitride phases and characterize the influence of the crystal orientation. The stability and evolution of the nitride phases and diffusion of implanted nitrogen were studied as a function of successive annealing treatments at 250 °C in vacuum. The composition, structure and magnetic properties were characterized using RBS/channeling, X-Ray Diffraction, Magnetic Force Microscopy, Magneto-optical Kerr Effect and Conversion Electron Mössbauer Spectroscopy. In the as-implanted state the formation of Fe 2 N phase was clearly identified in all single crystals. This phase is not stable at 250 °C and annealing at this temperature promotes the formation of ε-Fe 3 N, or γ′-Fe 4 N, depending on the orientation of the substrate. - Highlights: • Oriented magnetic iron nitrides were obtained by nitrogen implantation into iron single crystals. • The stable magnetic nitride phase at 250 °C depends on the orientation of the host single crystal, being γ'-Fe 4 N or ε-Fe 3 N. • The easy magnetization axis was found to lay in the (100) plane for cubic γ'-Fe 4 N and out of (100) plane for hexagonal ε-Fe 3 N

Crystal structure of mer-tris{2,6-difluoro-3-[5-(2-fluorophenylpyridin-2-yl-κN]pyridin-4-yl-κC4}iridium(III dichloromethane hemisolvate n-hexane hemisolvate

Directory of Open Access Journals (Sweden)

Youngjin Kang

2017-12-01

Full Text Available The asymmetric unit of the title compound, [Ir(C17H11F2N23]·0.5CH3(CH24CH3·0.5CH2Cl2, comprises one IrIII atom, three 2,6-difluoro-3-[5-(2-fluorophenylpyridin-2-yl]pyridin-4-yl ligands and half each of an n-hexane and a dichloromethane solvent molecule located about crystallographic inversion centres. The IrIII atom displays a distorted octahedral coordination geometry, having three C,N-chelating 2,6-difluoro-3-[5-(2-fluorophenylpyridin-2-yl]pyridin-4-yl ligands arranged in a meridional manner. The IrIII ion lies almost in the equatorial plane [deviation = 0.0069 (15 Å]. The average distance [2.041 (3 Å] of Ir—C bonds is slightly shorter than that [2.076 (3 Å] of Ir—N bonds. A variety of intra- and intermolecular C—H...F and C—H...π hydrogen bonds, as well as intermolecular C—F...π interactions, contribute to the stabilization of the molecular and crystal structures, and result in the formation of a two-dimensional network parallel to the ab plane. No interactions between n-hexane solvent molecules and the other components in the title compound are observed.

Particle Number Dependence of the N-body Simulations of Moon Formation

Science.gov (United States)

Sasaki, Takanori; Hosono, Natsuki

2018-04-01

The formation of the Moon from the circumterrestrial disk has been investigated by using N-body simulations with the number N of particles limited from 104 to 105. We develop an N-body simulation code on multiple Pezy-SC processors and deploy Framework for Developing Particle Simulators to deal with large number of particles. We execute several high- and extra-high-resolution N-body simulations of lunar accretion from a circumterrestrial disk of debris generated by a giant impact on Earth. The number of particles is up to 107, in which 1 particle corresponds to a 10 km sized satellitesimal. We find that the spiral structures inside the Roche limit radius differ between low-resolution simulations (N ≤ 105) and high-resolution simulations (N ≥ 106). According to this difference, angular momentum fluxes, which determine the accretion timescale of the Moon also depend on the numerical resolution.

Copper(I)-catalyzed olefination of N-sulfonylhydrazones with sulfones.

Science.gov (United States)

Xu, Shuai; Gao, Yunpeng; Chen, Ri; Wang, Kang; Zhang, Yan; Wang, Jianbo

2016-03-25

The Cu(I)-catalyzed olefination of N-sulfonylhydrazones with sulfones via metal carbene intermediates is reported. This reaction uses readily available starting materials and is operationally simple, thus representing a practical method for the construction of carbon-carbon double bonds. Mechanistically, Cu(I) carbene formation and subsequent carbene migratory insertion are proposed as the key steps.

Effect of pressure on the solution structure and hydrogen bond properties of aqueous N-methylacetamide

International Nuclear Information System (INIS)

Sarma, Rahul; Paul, Sandip

2012-01-01

Highlights: ► NMA molecules are associated mostly through their hydrophobic methyl groups. ► High pressure reduces association propensity causing dispersion of these moieties. ► Orientational polarization of vicinal water molecules near O and H atoms of NMA. ► NMA prefers to be a H-bond acceptor rather than a donor in interaction with water. ► Energy of these hydrogen bonds reduces slightly at high pressure. -- Abstract: Effects of high pressure on hydrophobic and hydrogen bonding interactions are investigated by employing molecular dynamics (MD) simulations of aqueous N-methylacetamide (NMA) solutions. Such systems are of interest mainly because high pressure causes protein denaturation and NMA is a computationally effective model to understand the atomic-level picture of pressure-induced structural transitions of protein. Simulations are performed for five different pressure values ranging from 1 atm to 8000 atm. We find that NMA molecules are associated mostly through their hydrophobic methyl groups and high pressure reduces this association propensity, causing dispersion of these moieties. At high pressure, structural void decreases and the packing efficiency of water molecules around NMA molecules increases. Hydrogen bond properties calculations show favorable NMA–NMA hydrogen bonds as compared to those of NMA–water hydrogen bonds and preference of NMA to be a hydrogen bond acceptor rather than a donor in interaction with water.

Effect of GaN buffer polarization on electron distribution of AlGaN/GaN heterostructure

International Nuclear Information System (INIS)

He, Xiaoguang; Zhao, Degang; Liu, Wei; Yang, Jing; Li, Xiaojing; Li, Xiang

2016-01-01

The formation of 2DEG in AlGaN/GaN heterostructure is discussed in detail. A misunderstanding about the 2DEG sheet density expression is clarified. It is predicted by theoretical analysis and validated by self-consistent Schrodinger–Poisson numerical simulation that under the force of GaN polarization, large amounts of electrons will accumulate at the GaN/substrate interface in AlGaN/GaN/substrate HEMT structure. - Highlights: • The formation of 2DEG in AlGaN/GaN heterostructure is discussed in detail. • Self-consistent Schrodinger–Poisson numerical simulation is used to modulate the AlGaN/GaN/substrate structure. • It is predicted by that large amounts of electrons will accumulate at the GaN/substrate interface.

Effect of GaN buffer polarization on electron distribution of AlGaN/GaN heterostructure

Energy Technology Data Exchange (ETDEWEB)

He, Xiaoguang; Zhao, Degang, E-mail: dgzhao@red.semi.ac.cn; Liu, Wei; Yang, Jing; Li, Xiaojing; Li, Xiang

2016-06-15

The formation of 2DEG in AlGaN/GaN heterostructure is discussed in detail. A misunderstanding about the 2DEG sheet density expression is clarified. It is predicted by theoretical analysis and validated by self-consistent Schrodinger–Poisson numerical simulation that under the force of GaN polarization, large amounts of electrons will accumulate at the GaN/substrate interface in AlGaN/GaN/substrate HEMT structure. - Highlights: • The formation of 2DEG in AlGaN/GaN heterostructure is discussed in detail. • Self-consistent Schrodinger–Poisson numerical simulation is used to modulate the AlGaN/GaN/substrate structure. • It is predicted by that large amounts of electrons will accumulate at the GaN/substrate interface.

Selective bond cleavage in potassium collisions with pyrimidine bases of DNA.

Science.gov (United States)

Almeida, Diogo; Ferreira da Silva, Filipe; García, Gustavo; Limão-Vieira, Paulo

2013-01-11

Electron transfer in alkali-molecule collisions to gas phase thymine and uracil yielding H- formation is selectively controlled in the energy range between 5.3 and 66.1 eV. By tuning the collision energy, electron transfer from the alkali to partly deuterated thymine, methylated thymine at the N1 and methylated uracil at the N3 positions, H- loss proceeds not only through the breaking of the (C-H) against (N-H) bonds but also through N1 against N3 sites. Such selectivity, as far as bond and site are concerned, is here reported for the first time by electron transfer induced dissociation experiments in alkali-molecule collisions.

Bis[N,N-bis(1-allyl-1H-benzimidazol-2-ylmethyl-κN3benzylamine-κN]cadmium dipicrate

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Jing-Kun Yuan

2011-06-01

Full Text Available The crystal structure of the title compound, [Cd(C29H29N52](C6H2N3O72, consists of CdII complex cations and picrate anions. In the complex cation, the CdII ion is chelated by two bis(1-allylbenzimidazol-2-ylmethylbenzylamine (babb ligands in a distorted octahedral geometry. Extensive C—H...O hydrogen bonding occurs between cations and anions in the crystal structure.

Analysis of Disulfide Bond Formation

NARCIS (Netherlands)

Braakman, Ineke; Lamriben, Lydia; van Zadelhoff, Guus; Hebert, Daniel N.

2017-01-01

In this unit, protocols are provided for detection of disulfide bond formation in cultures of intact cells and in an in vitro translation system containing isolated microsomes or semi-permeabilized cells. First, the newly synthesized protein of interest is biosynthetically labeled with radioactive

Ti, Al and N adatom adsorption and diffusion on rocksalt cubic AlN (001) and (011) surfaces: Ab initio calculations

Science.gov (United States)

Mastail, C.; David, M.; Nita, F.; Michel, A.; Abadias, G.

2017-11-01

We use ab initio calculations to determine the preferred nucleation sites and migration pathways of Ti, Al and N adatoms on cubic NaCl-structure (B1) AlN surfaces, primary inputs towards a further thin film growth modelling of the TiAlN alloy system. The potential energy landscape is mapped out for both metallic species and nitrogen adatoms for two different AlN surface orientations, (001) and (110), using density functional theory. For all species, the adsorption energies on AlN(011) surface are larger than on AlN(001) surface. Ti and Al adatom adsorption energy landscapes determined at 0 K by ab initio show similar features, with stable binding sites being located in, or near, epitaxial surface positions, with Ti showing a stronger binding compared to Al. In direct contrast, N adatoms (Nad) adsorb preferentially close to N surface atoms (Nsurf), thus forming strong N2-molecule-like bonds on both AlN(001) and (011). Similar to N2 desorption mechanisms reported for other cubic transition metal nitride surfaces, in the present work we investigate Nad/Nsurf desorption on AlN(011) using a drag calculation method. We show that this process leaves a Nsurf vacancy accompanied with a spontaneous surface reconstruction, highlighting faceting formation during growth.

Crystal structure of 2-hydroxy-N-(2-hydroxyethyl-N-{2-hydroxy-3-[(E-N-hydroxyethanimidoyl]-5-methylbenzyl}ethanaminium acetate monohydrate

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Gary S. Nichol

2015-03-01

Full Text Available The structure of the title hydrated molecular salt, C14H23N2O4+·C2H3O2−·H2O, was determined as part of a wider study on the use of the molecule as a polydentate ligand in the synthesis of MnIII clusters with magnetic properties. The cation features intramolecular O—H...N and N—H...O hydrogen-bond interactions. The crystal structure features a range of intermolecular hydrogen-bonding interactions, principally O—H...O interactions between all three species in the asymmetric unit. An R24(8 graph-set hydrogen-bonding motif between the anion and water molecules serves as a unit which links to the cation via the diethanolamine group. Each O atom of the acetate anion accepts two hydrogen bonds.

Electronic structures and thermochemical properties of the small silicon-doped boron clusters B(n)Si (n=1-7) and their anions.

Science.gov (United States)

Tai, Truong Ba; Kadłubański, Paweł; Roszak, Szczepan; Majumdar, Devashis; Leszczynski, Jerzy; Nguyen, Minh Tho

2011-11-18

We perform a systematic investigation on small silicon-doped boron clusters B(n)Si (n=1-7) in both neutral and anionic states using density functional (DFT) and coupled-cluster (CCSD(T)) theories. The global minima of these B(n)Si(0/-) clusters are characterized together with their growth mechanisms. The planar structures are dominant for small B(n)Si clusters with n≤5. The B(6)Si molecule represents a geometrical transition with a quasi-planar geometry, and the first 3D global minimum is found for the B(7)Si cluster. The small neutral B(n)Si clusters can be formed by substituting the single boron atom of B(n+1) by silicon. The Si atom prefers the external position of the skeleton and tends to form bonds with its two neighboring B atoms. The larger B(7)Si cluster is constructed by doping Si-atoms on the symmetry axis of the B(n) host, which leads to the bonding of the silicon to the ring boron atoms through a number of hyper-coordination. Calculations of the thermochemical properties of B(n)Si(0/-) clusters, such as binding energies (BE), heats of formation at 0 K (ΔH(f)(0)) and 298 K (ΔH(f)([298])), adiabatic (ADE) and vertical (VDE) detachment energies, and dissociation energies (D(e)), are performed using the high accuracy G4 and complete basis-set extrapolation (CCSD(T)/CBS) approaches. The differences of heats of formation (at 0 K) between the G4 and CBS approaches for the B(n)Si clusters vary in the range of 0.0-4.6 kcal mol(-1). The largest difference between two approaches for ADE values is 0.15 eV. Our theoretical predictions also indicate that the species B(2)Si, B(4)Si, B(3)Si(-) and B(7)Si(-) are systems with enhanced stability, exhibiting each a double (σ and π) aromaticity. B(5)Si(-) and B(6)Si are doubly antiaromatic (σ and π) with lower stability. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal structure of N-(quinolin-6-ylhydroxylamine

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Anuruddha Rajapakse

2014-11-01

Full Text Available The title compound, C9H8N2O, crystallized with four independent molecules in the asymmetric unit. The four molecules are linked via one O—H...N and two N—H...N hydrogen bonds, forming a tetramer-like unit. In the crystal, molecules are further linked by O—H...N and N—H...O hydrogen bonds forming layers parallel to (001. These layers are linked via C—H...O hydrogen bonds and a number of weak C—H...π interactions, forming a three-dimensional structure. The crystal was refined as a non-merohedral twin with a minor twin component of 0.319.

Glutamate stimulates the formation of N-acylphosphatidylethanolamine in cortical neurons in culture

DEFF Research Database (Denmark)

Hansen, Harald S.; Lauritzen, L.; Strand, A.M.

1995-01-01

The formation of anandamide (N-arachidonoylethanolamine), N-acylethanolamine, and N-acylphosphatidylethanolamine was studied in primary cultures of rat cortical neurons. The cells were incubated for 22 h with [C]ethanolamine, [U-C]arachidonic acid, [H]arachidonic acid, [P]phosphate, [C]stearic acid......-acylethanolamine. Compound I could be labelled with [C]stearic acid and [H]myristic acid, but not with [H]- or [C]arachidonic acid. Exogenous [H]anandamide was metabolised with a t( 1/2 ) of 2.6 h. The labelling of the two compounds identified as N-acylethanolamine and N-acylphosphatidylethanolamine were more pronounced......, or [H]myristic acid. The lipids from the cells and media were separated by thin layer chromatography. [C]Ethanolamine labelling revealed two compounds (I and II), which on different thin layer chromatography systems migrated as N-acylethanolamine (0.06-0.55% of total radioactivity) and N...

Quadruple metal-metal bonds with strong donor ligands. Ultraviolet photoelectron spectroscopy of M{sub 2}(form){sub 4} (M = Cr, Mo, W; form = N,N{prime}-diphenylformamidinate)

Energy Technology Data Exchange (ETDEWEB)

Lichtenberger, D.L.; Lynn, M.A.; Chisholm, M.H.

1999-12-29

The He I photoelectron spectra of M{sub 2}(form){sub 4}(M = Cr, Mo, W; form - N,N{prime}-diphenylformamidinate) and Mo{sub 2}(cyform){sub 4} (cyform = N,N{prime}-dicyclohexylformamidinate) are presented. For comparison, the Ne I, He I, and He II photoelectron spectra of Mo{sub 2}(p-CH{sub 3}-form){sub 4} have also been obtained. The valence ionization features of these molecules are interpreted based on (1) the changes that occur with the metal and ligand substitutions, (2) the changes in photoelectron cross sections with excitation source, and (3) the changes from previously studied dimetal complexes. These photoelectron spectra are useful for revealing the effects that better electron donor ligands have on the valence electronic structure of M{sub 2}(L-L){sub 4} systems. Comparison with the He I spectra of the isoelectronic M{sub 2}(O{sub 2}CCH{sub 3}){sub 4} compounds is particularly revealing. Unlike with the more electron-withdrawing acetate ligand, several formamidinate-based ionizations derived from the nitrogen p{sub {pi}} orbitals occur among the metal-metal {sigma}, {pi}, and {delta} ionization bands. Although these formamidinate-based levels are close in energy to the occupied metal-metal bonds, they have little direct mixing interaction with them. The shift of the metal-metal bond ionizations to lower ionization energies for the formamidinate systems is primarily a consequence of the lower electronegativity of the ligand and the better {pi} donation into empty metal levels. The metal-metal {delta} orbital experiences some additional net bonding interaction with ligand orbitals of the same symmetry. Also, an additional bonding interaction from ligand-to-metal electron donation to the {delta}* orbital is identified. These spectra suggest a greater degree of metal-ligand covalency than in the related M{sub 2}(O{sub 2}CCH{sub 3}){sub 4} systems. Fenske-Hall molecular orbital and density functional (ADF) calculations agree with the assignment and

Theoretical Study on Interactions between N-Butylpyridinium Nitrate and Thiophenic Compounds

International Nuclear Information System (INIS)

Lue, Renqing; Wang, Shutao; Lu, Yukun; Liu, Dong

2013-01-01

By using density functional theory calculations, we have performed a systemic study on the electronic structures and topological properties of interactions between N-butylpyridinium nitrate ([BPY] + [NO 3 ] - ) and thiophene (TS), benzothiophene (BT), dibenzothiophene (DBT), naphthalene (NAP). The most stable structure of [BPY] + [NO 3 ] - ion pair indicates that hydrogen bonding interactions between oxygen atoms on [NO 3 ] - anion and C2-H2 on pyridinium ring play a dominating role in the formation of ion pair. The occurrence of hydrogen bonding, π···H-C, and π···π interactions between [BPY] + [NO 3 ] - and TS, BT, DBT, NAP has been corroborated at the molecular level. But hydrogen bonding and π···π interactions between [BPY] + [NO 3 ] - and NAP are weak in terms of structural properties and NBO, AIM analyses. DBT is prior to adsorption on N-butylpyridinium nitrate ionic liquid

Measurement and modelling of hydrogen bonding in 1-alkanol plus n-alkane binary mixtures

DEFF Research Database (Denmark)

von Solms, Nicolas; Jensen, Lars; Kofod, Jonas L.

2007-01-01

Two equations of state (simplified PC-SAFT and CPA) are used to predict the monomer fraction of 1-alkanols in binary mixtures with n-alkanes. It is found that the choice of parameters and association schemes significantly affects the ability of a model to predict hydrogen bonding in mixtures, eve...... studies, which is clarified in the present work. New hydrogen bonding data based on infrared spectroscopy are reported for seven binary mixtures of alcohols and alkanes. (C) 2007 Elsevier B.V. All rights reserved....... though pure-component liquid densities and vapour pressures are predicted equally accurately for the associating compound. As was the case in the study of pure components, there exists some confusion in the literature about the correct interpretation and comparison of experimental data and theoretical...

Análisis comparativo in vitro del grado de microfiltración entre un sistema adhesivo de quinta y séptima generación

Directory of Open Access Journals (Sweden)

Gabriela Alvarado Ordoñez

2016-01-01

Full Text Available El objetivo de este estudio fue comparar el grado de microfiltración en adhesivos de quinta generación Adper Single Bond (3M ESPE y séptima generación Gc G-Bond (Gc Corp por medio de infiltración de colorantes y observación microscópica. Metodología: Se seleccionaron 30 piezas dentales sanas correspondientes a premolares y terceros molares. Las piezas dentarias fueron limpiadas y almacenadas en agua destilada. Se realizaron las preparaciones de una cavidad clase V en la superficie vestibular y lingual de cada diente. Se empleó el adhesivo Adper Single Bond (3M ESPE, quinta generación en la cavidad vestibular y Gc G-Bond (Gc Corp, séptima generación en la cavidad lingual, todas las piezas dentarias fueron restauradas con resina compuesta Valux Plus A3 (3M ESPE. La muestra fue sometida a penetración de colorante, azul de metileno al 2%, por 24 horas y se efectuó un corte en sentido mesiodistal y analizadas con microscopia óptica. Se empleó la prueba estadística t-student para muestras independientes y el análisis de las diferencias en los niveles de microfiltración marginal, con un nivel de significancia estadística del 95%(= 0.05. Los resultados se analizaron mediante el software SPSS. Resultados: Al analizar la resultados se observa que existe una diferencia significativa (P= 0,033 entre los sistemas adhesivos de quinta y séptima generación. Presentando los adhesivos de séptima generación (Gc G-Bond - Gc Corp valores menores de microfiltración. Conclusión: De los resultados obtenidos se puede concluir que adhesivos de quita generación (Adper Single Bond - 3M ESPE, como los de séptima generación (Gc G-Bond - Gc Corp presentan microfiltración al colorante. Presenta una microfiltración significativa menor el adhesivo Gc G-Bond.

Análisis comparativo in vitro del grado de microfiltración entre un sistema adhesivo de quinta y séptima generación

Directory of Open Access Journals (Sweden)

Gabriela Alvarado Ordoñez

2016-01-01

Full Text Available El objetivo de este estudio fue comparar el grado de microfiltración en adhesivos de quinta generación Adper Single Bond (3M ESPE y séptima generación Gc G-Bond (Gc Corp por medio de infiltración de colorantes y observación microscópica. Metodología: Se seleccionaron 30 piezas dentales sanas correspondientes a premolares y terceros molares. Las piezas dentarias fueron limpiadas y almacenadas en agua destilada. Se realizaron las preparaciones de una cavidad clase V en la superficie vestibular y lingual de cada diente. Se empleó el adhesivo Adper Single Bond (3M ESPE, quinta generación en la cavidad vestibular y Gc G-Bond (Gc Corp, séptima generación en la cavidad lingual, todas las piezas dentarias fueron restauradas con resina compuesta Valux Plus A3 (3M ESPE. La muestra fue sometida a penetración de colorante, azul de metileno al 2%, por 24 horas y se efectuó un corte en sentido mesiodistal y analizadas con microscopia óptica. Se empleó la prueba estadística t-student para muestras independientes y el análisis de las diferencias en los niveles de microfiltración marginal, con un nivel de significancia estadística del 95%(p<= 0.05. Los resultados se analizaron mediante el software SPSS. Resultados: Al analizar la resultados se observa que existe una diferencia significativa (P= 0,033 entre los sistemas adhesivos de quinta y séptima generación. Presentando los adhesivos de séptima generación (Gc G-Bond - Gc Corp valores menores de microfiltración. Conclusión: De los resultados obtenidos se puede concluir que adhesivos de quita generación (Adper Single Bond - 3M ESPE, como los de séptima generación (Gc G-Bond - Gc Corp presentan microfiltración al colorante. Presenta una microfiltración significativa menor el adhesivo Gc G-Bond.

Crystal structure of diaquabis(N,N-diethylnicotinamide-κN1bis(2,4,6-trimethylbenzoato-κO1cobalt(II

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Gülçin Şefiye Aşkın

2016-04-01

Full Text Available The centrosymmetric molecule in the monomeric title cobalt complex, [Co(C10H11O22(C10H14N2O2(H2O2], contains two water molecules, two 2,4,6-trimethylbenzoate (TMB ligands and two diethylnicotinamide (DENA ligands. All ligands coordinate to the CoII atom in a monodentate fashion. The four O atoms around the CoII atom form a slightly distorted square-planar arrangement, with the distorted octahedral coordination sphere completed by two pyridine N atoms of the DENA ligands. The dihedral angle between the planar carboxylate group and the adjacent benzene ring is 84.2 (4°, while the benzene and pyridine rings are oriented at a dihedral angle of 38.87 (10°. The water molecules exhibit both intramolecular (to the non-coordinating carboxylate O atom and intermolecular (to the amide carbonyl O atom O—H...O hydrogen bonds. The latter lead to the formation of layers parallel to (100, enclosing R44(32 ring motifs. These layers are further linked via weak C—H...O hydrogen bonds, resulting in a three-dimensional network. One of the two ethyl groups of the DENA ligand is disordered over two sets of sites with an occupancy ratio of 0.490 (13:0.510 (13.

Catena-poly[[bis(1H-benzotriazole-kappaN3)cobalt(II)]-di-mu-tricyanomethanido-kappa2N:N'] and catena-poly[[bis(3,5-dimethyl-1H-pyrazole-kappaN2)manganese(II)]-di-mu-tricyanomethanido-kappa2N:N'].

Science.gov (United States)

Shao, Ze-Huai; Luo, Jun; Cai, Rui-Fang; Zhou, Xi-Geng; Weng, Lin-Hong; Chen, Zhen-Xia

2004-06-01

Two new one-dimensional coordination polymers, viz. the title compounds, [Co[C(CN)(3)](2)(C(6)H(5)N(3))(2)](n), (I), and [Mn[C(CN)(3)](2)(C(5)H(8)N(2))(2)](n), (II), have been synthesized and characterized by X-ray diffraction. Both complexes consist of linear chains with double 1,5-tricyanomethanide bridges between neighbouring divalent metal ions. The Co and Mn atoms are located on centres of inversion. In (I), the coordination environment of the Co(II) atom is that of an elongated octahedron. The Co(II) atom is coordinated in the equatorial plane by four nitrile N atoms of four bridging tricyanomethanide ions, with Co-N distances of 2.106 (2) and 2.110 (2) A, and in the apical positions by two N atoms from the benzotriazole ligands, with a Co-N distance of 2.149 (2) A. The [Co[C(CN)(3)](2)(C(6)H(5)N(3))(2)] units form infinite chains extending along the a axis. These chains are crosslinked via a hydrogen bond between the uncoordinated nitrile N atom of a tricyanomethanide anion and the H atom on the uncoordinated N atom of a benzotriazole ligand from an adjacent chain, thus forming a three-dimensional network structure. In (II), the Mn(II) atom also adopts a slightly distorted octahedral geometry, with four nitrile N atoms of tricyanomethanide ligands [Mn-N = 2.226 (2) and 2.227 (2) A] in equatorial positions and two N atoms of the monodentate 3,5-dimethylpyrazole ligands [Mn-N = 2.231 (2) A] in the axial sites. In (II), one-dimensional polymeric chains extending along the b axis are formed, with tricyanomethanide anions acting as bidentate bridging ligands. A hydrogen bond between the uncoordinated nitrile N atom of the tricyanomethanide ligand and the H atom on the uncoordinated N atom of a 3,5-dimethylpyrazole group from a neighbouring chain links the molecule into a two-dimensional layered structure.

The Role of Hydroxylamine as a Nitrification Intermediate in N-Nitrosamine Formation- Indianapolis

Science.gov (United States)

The formation of N-nitrosamines, and in particular N-nitrosodimethylamine (NDMA), in drinking water systems that use chloramines is a concern because of their potential carcinogenicity and occurrences in finished waters at toxicologically relevant levels. The widely accepted mech...

In search of a new class of stable nitroxide: synthesis and reactivity of a peri-substituted N,N-bissulfonylhydroxylamine.

Science.gov (United States)

Patel, Bhaven; Carlisle, Julie; Bottle, Steven E; Hanson, Graeme R; Kariuki, Benson M; Male, Louise; McMurtrie, John C; Spencer, Neil; Grainger, Richard S

2011-04-07

Acyclic bissulfonylnitroxides have never been isolated, and degrade through fragmentation. In an approach to stabilising a bissulfonylnitroxide radical, the cyclic, peri-substituted N,N-bissulfonylhydroxylamine, 2-hydroxynaphtho[1,8-de][1,3,2]dithiazine 1,1,3,3-tetraoxide (1), has been prepared by formal nitrogen insertion into the sulfur-sulfur bond of a sulfinylsulfone, naphtho[1,8-cd][1,2]dithiole 1,1,2-trioxide. The heterocyclic ring of 1 is shown to adopt a sofa conformation by X-ray crystallography, with a pseudo-axial hydroxyl group. N,N-Bissulfonylhydroxylamine 1 displays high thermal, photochemical and hydrolytic stability compared to acyclic systems. EPR analysis reveals formation of the corresponding bissulfonylnitroxide 2 upon oxidation of 1 with the Ce(IV) salts CAN and CTAN. Although 2 does not undergo fragmentation, it cannot be isolated, since hydrogen atom abstraction to reform 1 occurs in situ. The stability and reactivity of 1 and 2 are compared with the known cyclic benzo-fused N,N-bissulfonylhydroxylamine, N-hydroxy-O-benzenedisulfonimide (6), for which the X-ray data, and EPR of the corresponding nitroxide 10, are also reported for the first time.

Effects of thin heavily Mg-doped GaN capping layer on ohmic contact formation of p-type GaN

International Nuclear Information System (INIS)

Wu, L L; Zhao, D G; Jiang, D S; Chen, P; Le, L C; Li, L; Liu, Z S; Zhang, S M; Zhu, J J; Wang, H; Zhang, B S; Yang, H

2013-01-01

The growth condition of thin heavily Mg-doped GaN capping layer and its effect on ohmic contact formation of p-type GaN were investigated. It is confirmed that the excessive Mg doping can effectively enhance the Ni/Au contact to p-GaN after annealing at 550 °C. When the flow rate ratio between Mg and Ga gas sources is 6.4% and the layer width is 25 nm, the capping layer grown at 850 °C exhibits the best ohmic contact properties with respect to the specific contact resistivity (ρ c ). This temperature is much lower than the conventional growth temperature of Mg-doped GaN, suggesting that the deep-level-defect induced band may play an important role in the conduction of capping layer. (paper)

A bilayer diffusion barrier of Ru/WSi{sub x}N{sub y} for advanced Cu interconnects

Energy Technology Data Exchange (ETDEWEB)

Eom, Tae-Kwang; Sari, Windu [School of Materials Science and Engineering, Yeungnam University 214-1, Dae-dong, Gyeongsan-si, Gyeongsangbuk-do, 712-749 (Korea, Republic of); Cheon, Taehoon [Center for Core Research Facilities, Daegu Gyeongbuk Institute of Science and Technology, Sang-ri, Hyeonpung-myeon, Dalseong-gun, Daegu, 711-873 (Korea, Republic of); Kim, Soo-Hyun, E-mail: soohyun@ynu.ac.kr [School of Materials Science and Engineering, Yeungnam University 214-1, Dae-dong, Gyeongsan-si, Gyeongsangbuk-do, 712-749 (Korea, Republic of); Kim, Woo Kyoung [School of Chemical Engineering, Yeungnam University 214-1, Dae-dong, Gyeongsan-si, Gyeongsangbuk-do, 712-749 (Korea, Republic of)

2012-10-30

Bilayers of Ru (7 nm)/WSi{sub x}N{sub y} (8 nm) prepared by sputtering were investigated as diffusion barriers between Cu and Si for direct-platable Cu interconnects. Four different WSi{sub x}N{sub y} films were prepared by using various N{sub 2}/Ar flow rate ratios during sputtering of a WSi{sub 2.7} target. Sheet resistance measurements and X-ray diffractometry analysis showed that Ru/WSi{sub x}N{sub y} bilayer diffusion barriers prevented Cu diffusion during 30 min of annealing at temperatures of up to 550-750 Degree-Sign C, while the Ru single layer of the same thickness (15 nm) failed after annealing at 400 Degree-Sign C by the formation of copper silicide due to the diffusion of Cu into Si. It was shown that the performances of bilayer diffusion barriers were improved as the nitrogen content in the WSi{sub x}N{sub y} films was increased, which can be explained based on the results from transmission electron microscopy and X-ray photoelectron spectroscopy analysis of WSi{sub x}N{sub y} films deposited with different N{sub 2}/Ar flow rate ratios. From the results, the Si-N and W-N chemical bonds are strengthened as the N contents in the WSi{sub x}N{sub y} films are increased by increasing the N{sub 2} flow rate during the deposition. The results indicate that the formation of both Si-N and W-N bonds will give an effective diffusion barrier against Cu diffusion.

Bis[μ-(E-N-(pyridin-3-ylmethylidenehydroxyamine]-κ2N1:N3;κ2N3:N1-bis{[(E-N-(pyridin-3-ylmethylidene-κNhydroxyamine]silver(I} dinitrate

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Shan Gao

2012-12-01

Full Text Available In the centrosymmetric dinuclear title AgI compound, [Ag2(C6H6N2O4](NO32, the aromatic amine-coordinated AgI atom is further bridged by two hydroxylamine molecules that use aromatic and oxime N atoms for bridging, and it exists in a distorted trigonal-planar geometry. In the crystal, the nitrate anions link to the dinuclear compound molecules via O—H...O hydrogen bonds, generating a chain running along the a-axis direction.

Study of factors that influence complex-formation of n-alkanes with crystal carbamide

Energy Technology Data Exchange (ETDEWEB)

Dorodnova, V.S.; Korzhov, Yu.A.; Martynenko, A.G.

1982-01-01

Studies effect of temperature, solid phase content in the suspension and amount of MeOH on extent of n-alkane extraction during carbamide deparaffinization. A most thorough extraction of n-alkanes is achieved with a graduated temperature regimen of complex-formation.

Synthesis of Reusable Silica Nanosphere-Supported Pt(IV Complex for Formation of Disulfide Bonds in Peptides

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Xiaonan Hou

2017-02-01

Full Text Available Some peptide-based drugs, including oxytocin, vasopressin, ziconotide, pramlintide, nesiritide, and octreotide, contain one intramolecular disulfide bond. A novel and reusable monodispersed silica nanosphere-supported Pt(IV complex (SiO2@TPEA@Pt(IV; TPEA: N-[3-(trimethoxysilylpropyl]ethylenediamine was synthesized via a four-step procedure and was used for the formation of intramolecular disulfide bonds in peptides. Transmission electron microscopy (TEM and chemical mapping results for the Pt(II intermediates and for SiO2@TPEA@Pt(IV show that the silica nanospheres possess a monodisperse spherical structure and contain uniformly-distributed Si, O, C, N, Cl, and Pt. The valence state of Pt on the silica nanospheres was characterized by X-ray photoelectron spectroscopy (XPS. The Pt(IV loaded on SiO2@TPEA@Pt(IV was 0.15 mmol/g, as determined by UV-VIS spectrometry. The formation of intramolecular disulfides in six dithiol-containing peptides of variable lengths by the use of SiO2@TPEA@Pt(IV was investigated, and the relative oxidation yields were determined by high-performance liquid chromatography (HPLC. In addition, peptide 1 (Ac-CPFC-NH2 was utilized to study the reusability of SiO2@TPEA@Pt(IV. No significant decrease in the relative oxidation yield was observed after ten reaction cycles. Moreover, the structure of SiO2@TPEA@Pt(IV after being used for ten cycles was determined to be similar to its initial one, demonstrating the cycling stability of the complex.

Competing intramolecular N-H⋯O=C hydrogen bonds and extended intermolecular network in 1-(4-chlorobenzoyl)-3-(2-methyl-4-oxopentan-2-yl) thiourea analyzed by experimental and theoretical methods

Energy Technology Data Exchange (ETDEWEB)

Saeed, Aamer, E-mail: aamersaeed@yahoo.com [Department of Chemistry, Quaid-I-Azam University, Islamabad 45320 (Pakistan); Khurshid, Asma [Department of Chemistry, Quaid-I-Azam University, Islamabad 45320 (Pakistan); Jasinski, Jerry P. [Department of Chemistry, Keene State College, 229 Main Street Keene, NH 03435-2001 (United States); Pozzi, C. Gustavo; Fantoni, Adolfo C. [Instituto de Física La Plata, Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 49 y 115, La Plata, Buenos Aires (Argentina); Erben, Mauricio F., E-mail: erben@quimica.unlp.edu.ar [CEQUINOR (UNLP, CONICET-CCT La Plata), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 962, (1900) La Plata, Buenos Aires (Argentina)

2014-03-18

Highlights: • Two distinct N-H⋯O=C intramolecular competing hydrogen bonds are feasible in the title molecule. • Crystal structures and vibrational properties were determined. • The C=O and C=S double bonds of the acyl-thiourea group are mutually oriented in opposite directions. • A strong hyperconjugative lpO1 → σ{sup ∗}(N2-H) remote interaction was detected. • Topological analysis reveals a Cl⋯N interaction playing a relevant role in crystal packing. - Abstract: The synthesis of a novel 1-acyl-thiourea species (C{sub 14}H{sub 17}N{sub 2}O{sub 2}SCl), has been tailored in such a way that two distinct N-H⋯O=C intramolecular competing hydrogen bonds are feasible. The X-ray structure analysis as well as the vibrational (FT-IR and FT-Raman) data reveal that the S conformation is preferred, with the C=O and C=S bonds of the acyl-thiourea group pointing in opposite directions. The preference for the intramolecular N-H⋯O=C hydrogen bond within the -C(O)NHC(S)NH- core is confirmed. The Natural Bond Orbital and the Atom in Molecule approaches demonstrate that a strong hyperconjugative lpO → σ{sup ∗}(N-H) remote interaction between the acyl and the thioamide N-H groups is responsible for the stabilization of the S conformation. Intermolecular interactions have been characterized in the periodic system electron density and the topological analysis reveals the presence of an extended intermolecular network in the crystal, including a Cl⋯N interaction playing a relevant role in crystal packing.

Structural, phase stability, electronic, elastic properties and hardness of IrN{sub 2} and zinc blende IrN: First-principles calculations

Energy Technology Data Exchange (ETDEWEB)

Zhou, Zhaobo [Key Laboratory of Advanced Materials of Yunnan Province & Key Laboratory of Advanced Materials of Non-Ferrous and Precious Rare Metals Ministry of Education, Kunming University of Science and Technology, Kunming 650093 (China); Zhou, Xiaolong, E-mail: kmzxlong@163.com [Key Laboratory of Advanced Materials of Yunnan Province & Key Laboratory of Advanced Materials of Non-Ferrous and Precious Rare Metals Ministry of Education, Kunming University of Science and Technology, Kunming 650093 (China); Zhang, Kunhua [State Key Laboratory of Rare Precious Metals Comprehensive Utilization of New Technologies, Kunming Institute of Precious Metals, Kunming 650106 (China)

2016-12-15

First-principle calculations were performed to investigate the structural, phase stability, electronic, elastic properties and hardness of monoclinic structure IrN{sub 2} (m-IrN{sub 2}), orthorhombic structure IrN{sub 2} (o-IrN{sub 2}) and zinc blende structure IrN (ZB IrN). The results show us that only m-IrN{sub 2} is both thermodynamic and dynamic stability. The calculated band structure and density of states (DOS) curves indicate that o-IrN{sub 2} and ZB Ir-N compounds we calculated have metallic behavior while m-IrN{sub 2} has a small band gap of ~0.3 eV, and exist a common hybridization between Ir-5d and N-2p states, which forming covalent bonding between Ir and N atoms. The difference charge density reveals the electron transfer from Ir atom to N atom for three Ir-N compounds, which forming strong directional covalent bonds. Notable, a strong N-N bond appeared in m-IrN{sub 2} and o-IrN{sub 2}. The ratio of bulk to shear modulus (B/G) indicate that three Ir-N compounds we calculated are ductile, and ZB IrN possesses a better ductility than two types IrN{sub 2}. m-IrN{sub 2} has highest Debye temperature (736 K), illustrating it possesses strongest covalent bonding. The hardness of three Ir-N compounds were also calculated, and the results reveal that m-IrN{sub 2} (18.23 GPa) and o-IrN{sub 2} (18.02 GPa) are ultraincompressible while ZB IrN has a negative value, which may be attributed to phase transition at ca. 1.98 GPa.

Impact of post-deposition annealing on interfacial chemical bonding states between AlGaN and ZrO2 grown by atomic layer deposition

International Nuclear Information System (INIS)

Ye, Gang; Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong; Wang, Hong; Ng, Serene Lay Geok; Ji, Rong; Liu, Zhi Hong

2015-01-01

The effect of post-deposition annealing on chemical bonding states at interface between Al 0.5 Ga 0.5 N and ZrO 2 grown by atomic layer deposition (ALD) is studied by angle-resolved x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that both of Al-O/Al 2p and Ga-O/Ga 3d area ratio decrease at annealing temperatures lower than 500 °C, which could be attributed to “clean up” effect of ALD-ZrO 2 on AlGaN. Compared to Ga spectra, a much larger decrease in Al-O/Al 2p ratio at a smaller take-off angle θ is observed, which indicates higher effectiveness of the passivation of Al-O bond than Ga-O bond through “clean up” effect near the interface. However, degradation of ZrO 2 /AlGaN interface quality due to re-oxidation at higher annealing temperature (>500 °C) is also found. The XPS spectra clearly reveal that Al atoms at ZrO 2 /AlGaN interface are easier to get oxidized as compared with Ga atoms

Distribution of species and Ga–N bonds in silicon co-implanted with gallium and nitrogen ions

International Nuclear Information System (INIS)

Surodin, S. I.; Nikolitchev, D. E.; Kryukov, R. N.; Belov, A. I.; Korolev, D. S.; Mikhaylov, A. N.; Tetelbaum, D. I.

2016-01-01

The concentration profiles of species in silicon subjected to gallium and nitrogen co-implantation and subsequent annealing have been investigated by the method of X-ray photoelectron spectroscopy combined with the layer-by-layer ion etching of the implanted layer. It is shown that practically entire implanted gallium undergoes out-diffusion, but the preliminary implantation of nitrogen for the synthesis of a barrier SiN_x layer makes it possible to avoid the essential loss of gallium. In this case, about 14 % of implanted gallium bond to nitrogen. The obtained data are discussed from the viewpoint of the possibility of ion synthesis of GaN inclusions in silicon matrix.

Distribution of species and Ga–N bonds in silicon co-implanted with gallium and nitrogen ions

Energy Technology Data Exchange (ETDEWEB)

Surodin, S. I., E-mail: surodin.bsn@mail.ru; Nikolitchev, D. E.; Kryukov, R. N.; Belov, A. I.; Korolev, D. S.; Mikhaylov, A. N.; Tetelbaum, D. I., E-mail: tetelbaum@phys.unn.ru [Lobachevsky University, 23 Prospekt Gagarina, Nizhny Novgorod, 603950 (Russian Federation)

2016-06-17

The concentration profiles of species in silicon subjected to gallium and nitrogen co-implantation and subsequent annealing have been investigated by the method of X-ray photoelectron spectroscopy combined with the layer-by-layer ion etching of the implanted layer. It is shown that practically entire implanted gallium undergoes out-diffusion, but the preliminary implantation of nitrogen for the synthesis of a barrier SiN{sub x} layer makes it possible to avoid the essential loss of gallium. In this case, about 14 % of implanted gallium bond to nitrogen. The obtained data are discussed from the viewpoint of the possibility of ion synthesis of GaN inclusions in silicon matrix.

Stability and electronic structure of superlattices (IIIV)n/(IV2)n

International Nuclear Information System (INIS)

Casagrande, D.; Ferraz, A.C.

1996-01-01

Theoretical investigations of atomic relaxation and electronic states have been made for ultrathin superlattices (GaP) n /(Ge 2 ) n , (GaP) n /(Si 2 ) n , (In P) n /(Ge 2 ) n and (In P) n /(Si 2 ) n with period n ≤ 3 in growth directions (001) and (110). The calculations were performed within the momentum-space formalism of the self-consistent ab-initio pseudopotential method and the molecular dynamics approach as proposed by Car and Parrinello. The structures were found to be unstable with respect to the phase separation into the constituent bulk materials. The results for the enthalpy show a metastability as increasing the superlattice period n. The density of nonoctet wrong-bonds play an important role to determine the stability of the structures. (author). 13 refs., 2 figs., 3 tabs

Black hole formation and classicalization in ultra-Planckian 2→N scattering

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G. Dvali

2015-04-01

Full Text Available We establish a connection between the ultra-Planckian scattering amplitudes in field and string theory and unitarization by black hole formation in these scattering processes. Using as a guideline an explicit microscopic theory in which the black hole represents a bound-state of many soft gravitons at the quantum critical point, we were able to identify and compute a set of perturbative amplitudes relevant for black hole formation. These are the tree-level N-graviton scattering S-matrix elements in a kinematical regime (called classicalization limit where the two incoming ultra-Planckian gravitons produce a large number N of soft gravitons. We compute these amplitudes by using the Kawai–Lewellen–Tye relations, as well as scattering equations and string theory techniques. We discover that this limit reveals the key features of the microscopic corpuscular black hole N-portrait. In particular, the perturbative suppression factor of a N-graviton final state, derived from the amplitude, matches the non-perturbative black hole entropy when N reaches the quantum criticality value, whereas final states with different value of N are either suppressed or excluded by non-perturbative corpuscular physics. Thus we identify the microscopic reason behind the black hole dominance over other final states including non-black hole classical object. In the parameterization of the classicalization limit the scattering equations can be solved exactly allowing us to obtain closed expressions for the high-energy limit of the open and closed superstring tree-level scattering amplitudes for a generic number N of external legs. We demonstrate matching and complementarity between the string theory and field theory in different large-s and large-N regimes.

Crystal structures of 5-amino-N-phenyl-3H-1,2,4-dithiazol-3-iminium chloride and 5-amino-N-(4-chlorophenyl-3H-1,2,4-dithiazol-3-iminium chloride monohydrate

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Chien Ing Yeo

2015-10-01

Full Text Available The crystal and molecular structures of the title salt, C8H8N3S2+·Cl−, (I, and salt hydrate, C8H7ClN3S2+·Cl−·H2O, (II, are described. The heterocyclic ring in (I is statistically planar and forms a dihedral angle of 9.05 (12° with the pendant phenyl ring. The comparable angle in (II is 15.60 (12°, indicating a greater twist in this cation. An evaluation of the bond lengths in the H2N—C—N—C—N sequence of each cation indicates significant delocalization of π-electron density over these atoms. The common feature of the crystal packing in (I and (II is the formation of charge-assisted amino-N—H...Cl− hydrogen bonds, leading to helical chains in (I and zigzag chains in (II. In (I, these are linked by chains mediated by charge-assisted iminium-N+—H...Cl− hydrogen bonds into a three-dimensional architecture. In (II, the chains are linked into a layer by charge-assisted water-O—H...Cl− and water-O—H...O(water hydrogen bonds with charge-assisted iminium-N+—H...O(water hydrogen bonds providing the connections between the layers to generate the three-dimensional packing. In (II, the chloride anion and water molecules are resolved into two proximate sites with the major component being present with a site occupancy factor of 0.9327 (18.

Crystal structure of trans-diaquabis(4-cyanobenzoato-κObis(N,N-diethylnicotinamide-κNcadmium

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Nurcan Akduran

2016-12-01

Full Text Available The mononuclear title cadmium complex, [Cd(C10H14N2O2(C8H4NO22(H2O2], is centrosymmetric and contains two water molecules, two 4-cyanobenzoate (CB ligands and two diethylnicotinamide (DENA ligands. All the ligands are coordinated to the CdII atom in a monodentate mode. The four nearest O atoms around the CdII atom form a slightly distorted square-planar arrangement, with the distorted octahedral coordination sphere being completed by the two pyridine N atoms of the DENA ligands at distances of 2.3336 (13 Å. The dihedral angle between the carboxylate group and the adjacent benzene ring is 8.75 (16°, while the benzene and pyridine rings are oriented at a dihedral angle of 57.83 (5°. The water molecules exhibit both intramolecular [to the non-coordinating carboxylate O atom, enclosing an S(6 hydrogen-bonding motif, where O...O = 2.670 (2 Å] and intermolecular [to the amide carbonyl O atom, enclosing an R22(16 ring motif, where O...O = 2.781 (2 Å] O—H...O hydrogen bonds. The latter lead to the formation of supramolecular chains propagating along [110].

(Bipyridine-κ2N,N′chlorido[N-(2-hydroxyethyl-N-isopropyldithiocarbamato-κ2S,S′]zinc(II

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Fatin Allia Mohamad

2012-07-01

Full Text Available The ZnII atom in the title compound, [Zn(C6H12NOS2Cl(C10H8N2], is coordinated by a chelating N-2-hydroxyethyl-N-isopropyldithiocarbamate ligand, a 2,2′-bipyridine ligand and a Cl atom. The resulting ClN2S2 donor set defines a distorted square-pyramidal coordination geometry. Helical supramolecular chains sustained by O—H...S hydrogen bonds and propagating along the b axis feature in the crystal packing. A three-dimensional architecture is stabilized by C—H...O, C—H...S and C—H...Cl interactions.

Diiodidobis(N,N,N′,N′-tetramethylthiourea-κScadmium(II

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Sidra Nawaz

2010-08-01

Full Text Available In the title compound, [CdI2(C5H12N2S2], the CdII ion is located on a twofold rotation axis and is coordinated in a distorted tetrahedral mode by two iodide ions and by two tetramethylthiourea (tmtu ligands through their S atoms. The crystal structure is stabilized by C—H...N and C—H...S hydrogen bonds.

Importance of mother-infant communication for social bond formation in mammals.

Science.gov (United States)

Okabe, Shota; Nagasawa, Miho; Mogi, Kazutaka; Kikusui, Takefumi

2012-06-01

Mother-infant bonding is a universal relationship of all mammalian species. Here, we describe the role of reciprocal communication between mother and infant in the formation of bonding for several mammalian species. Mother-infant bond formation is reinforced by various social cues or stimuli, including communicative signals, such as odor and vocalizations, or tactile stimuli. The mother also develops cross-modal sensory recognition of the infant, during bond formation. Many studies have indicated that the oxytocin neural system plays a pivotal role in bond formation by the mother; however, the underlying neural mechanisms for infants have not yet been clarified. The comparative understanding of cognitive functions of mother and infants may help us understand the biological significance of mother-infant communication in mammalian species. © 2012 The Authors. Animal Science Journal © 2012 Japanese Society of Animal Science.

N-Benzoyl-2-nitrobenzenesulfonamide

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P. A. Suchetan

2012-02-01

Full Text Available In the title compound, C13H10N2O5S, the N—C bond in the C—SO2—NH—C segment has gauche torsion angles with respect to the S=O bonds. The conformation between the N—H bond and the ortho-nitro group in the sulfonyl benzene ring is syn. The molecule is twisted at the S—N bond with a torsion angle of −63.4 (2°. The sulfonyl benzene ring is tilted by 77.1 (1° relative to the —SO2—NH—C—O segment. The dihedral angle between the sulfonyl and the benzoyl benzene rings is 88.6 (1°. In the crystal, pairs of N—H...O(S hydrogen bonds link the molecules into inversion dimers, which are linked by weak C—H...O and C—H...π interactions along the b axis.

Tris(N,N,N′,N′,N′′,N′′-hexaethylguanidinium dodecaiodidotribismuthate(III

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Ioannis Tiritiris

2016-03-01

Full Text Available The asymmetric unit of title compound, (C13H30N33[Bi3I12], comprises one cation and two independent (1/6 fragments of the [Bi3I12]3− ions. The C—N bond lengths in the guanidinium ion range from 1.340 (4 to 1.345 (4 Å, indicating partial double-bond character pointing towards charge delocalization within the NCN planes. The BiIII ions are distorted octahedrally coordinated by six iodide ions, with Bi—I bond lengths ranging from 2.9206 (3 to 3.3507 (3 Å. Three [BiI6]3− octahedra are fused together through face-sharing, forming a trinuclear [Bi3I12]3− unit.

Influence of Ge addition on the morphology and properties of TiN thin films deposited by magnetron sputtering

International Nuclear Information System (INIS)

Sandu, C.S.; Sanjines, R.; Benkahoul, M.; Parlinska-Wojtan, M.; Karimi, A.; Levy, F.

2006-01-01

Thin films of TM-X-N (TM stands for early transition metal and X = Si, Al, etc.) are used as protective coatings. The most investigated among the ternary composite systems is Ti-Si-N. The system Ti-Ge-N has been chosen to extend the knowledge about the formation of nanocomposite films. Ti-Ge-N thin films were deposited by reactive magnetron sputtering on Si and WC-Co substrates at T s = 240 deg. C, from confocal Ti and Ge targets in mixed Ar/N 2 atmosphere. The nitrogen partial pressure and the power on the Ti target were kept constant, while the power on the Ge target was varied in order to obtain various Ge concentrations in the films. No presence of Ge-N bonds was detected, while X-ray photoelectron spectroscopy measurements revealed the presence of Ti-Ge bonds. Transmission Electron Microscopy investigations have shown important changes induced by Ge addition in the morphology and structure of Ti-Ge-N films. Electron Energy-Loss Spectrometry study revealed a significant increase of Ge content at the grain boundaries. The segregation of Ge atoms to the TiN crystallite surface appears to be responsible for limitation of crystal growth and formation of a TiGe y amorphous phase

Formation dynamics of FeN thin films on Cu(100)

KAUST Repository

Heryadi, Dodi; Schwingenschlö gl, Udo

2012-01-01

To investigate the structural and magnetic properties of thin films of FeN we have performed ab initio molecular dynamics simulations of their formation on Cu(100) substrates. The iron nitride layers exhibit a p4gm(2 × 2) reconstruction and order

Deuterium isotope effects on 13C and 15N chemical shifts of intramolecularly hydrogen-bonded enaminocarbonyl derivatives of Meldrum’s and Tetronic acid

Science.gov (United States)

Ullah, Saif; Zhang, Wei; Hansen, Poul Erik

2010-07-01

Secondary deuterium isotope effects on 13C and 15N nuclear shieldings in a series of cyclic enamino-diesters and enamino-esters and acyclic enaminones and enamino-esters have been examined and analysed using NMR and DFT (B3LYP/6-31G(d,p)) methods. One-dimensional and two-dimensional NMR spectra of enaminocarbonyl and their deuterated analogues were recorded in CDCl 3 and CD 2Cl 2 at variable temperatures and assigned. 1JNH coupling constants for the derivatives of Meldrum's and tetronic acids reveal that they exist at the NH-form. It was demonstrated that deuterium isotope effects, for the hydrogen bonded compounds, due to the deuterium substitution at the nitrogen nucleus lead to large one-bond isotope effects at nitrogen, 1Δ 15N(D), and two-bond isotope effects on carbon nuclei, 2ΔC(ND), respectively. A linear correlations exist between 2ΔC(ND) and 1Δ 15N(D) whereas the correlation with δNH is divided into two. A good agreement between the experimentally observed 2ΔC(ND) and calculated dσ 13C/dR NH was obtained. A very good correlation between calculated NH bond lengths and observed NH chemical shifts is found. The observed isotope effects are shown to depend strongly on Resonance Assisted Hydrogen bonding.

Crystal structures of the dioxane hemisolvates of N-(7-bromomethyl-1,8-naphthyridin-2-ylacetamide and bis[N-(7-dibromomethyl-1,8-naphthyridin-2-ylacetamide

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Robert Rosin

2017-10-01

Full Text Available The syntheses and crystal structures of N-(7-bromomethyl-1,8-naphthyridin-2-ylacetamide dioxane hemisolvate, C11H10BrN3O·0.5C4H8O2, (I, and bis[N-(7-dibromomethyl-1,8-naphthyridin-2-ylacetamide] dioxane hemisolvate, 2C11H9Br2N3O·0.5C4H8O2, (II, are described. The molecules adopt a conformation with the N—H hydrogen pointing towards the lone electron pair of the adjacent naphthyridine N atom. The crystals of (I are stabilized by a three-dimensional supramolecular network comprising N—H...N, C—H...N and C—H...O hydrogen bonds, as well as C—Br...π halogen bonds. The crystals of compound (II are stabilized by a three-dimensional supramolecular network comprising N—H...N, C—H...N and C—H...O hydrogen bonds, as well as C—H...π contacts and C—Br...π halogen bonds. The structure of the substituent attached in the 7-position of the naphthyridine skeleton has a fundamental influence on the pattern of intermolecular noncovalent bonding. While the Br atom of (I participates in weak C—Br...Oguest and C—Br...π contacts, the Br atoms of compound (II are involved in host–host interactions via C—Br...O=C, C—Br...N and C—Br...π bonding.

Crystal structure of 2-hy-droxy-imino-2-(pyridin-2-yl)-N'-[1-(pyridin-2-yl)ethyl-idene]acetohydrazide.

Science.gov (United States)

Plutenko, Maxym O; Lampeka, Rostislav D; Haukka, Matti; Nordlander, Ebbe

2014-12-01

The mol-ecule of the title compound, C14H13N5O2, is approximately planar (r.m.s deviation for all non-H atoms = 0.093 Å), with the planes of the two pyridine rings inclined to one another by 5.51 (7)°. The oxime group is syn to the amide group, probably due to the formation of an intra-molecular N-H⋯N hydrogen bond that forms an S(6) ring motif. In the crystal, mol-ecules are linked by pairs of bifurcated O-H⋯(O,N) hydrogen bonds, forming inversion dimers. The latter are linked via C-H⋯O and C-H⋯N hydrogen bonds, forming sheets lying parallel to (502). The sheets are linked via π-π stacking inter-actions [inter-centroid distance = 3.7588 (9) Å], involving the pyridine rings of inversion-related mol-ecules, forming a three-dimensional structure.

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

Low temperature X-ray structure analyses combined with NBO studies of a new heteroleptic octa-coordinated Holmium(III) complex with N,N,N-tridentate hydrazono-phthalazine-type ligand

Science.gov (United States)

Soliman, Saied M.; El-Faham, Ayman

2018-04-01

The new heteroleptic [HoL(H2O)5]Br3 complex, L is hydrazono-phthalazine ligand, is synthesized and its molecular structure aspects were analyzed using single crystal X-ray structure (SCXRD), Hirshfeld (HF) analysis, quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) method. The SCXRD showed that the Ho is octa-coordinated with one N,N,N-tridentate ligand L and five water molecules. The HF analysis is used to analyze the molecular packing in the [HoL(H2O)5]Br3crystal structure. The complex cations are connected via strong Osbnd H⋯Br and Nsbnd H⋯Br H-bonding interactions which have greater importance than the Csbnd H⋯Br contacts. Also, all the Hosbnd N and Hosbnd O bonds have the characteristics of closed shell interactions using QTAIM. The natural orbitals included in these interactions were analyzed using NBO method. The alpha LP*(8)Ho and beta LP*(4)Ho which have mainly s-orbital characters are the most important anti-bonding natural orbitals included in all Ho-N and Hosbnd O bonds. The rest of the Ho anti-bonding orbitals which have either p or d-orbital characters shared partially in the Ho-ligands interactions. Natural charges analysis revealed the presence of significant amount of electron density (0.9225-0.9300 e) transferred from the ligands to Ho (2.0700-2.0775 e). Spherical spin density with ∼4.0 e is predicted over the Ho atom.

[μ-N,N′-Bis(2-aminoethylethane-1,2-diamine-κ4N1,N1′:N2,N2′]bis{[N,N′-bis(2-aminoethylethane-1,2-diamine-κ4N,N′,N′′,N′′′]cadmium} tetrakis(perchlorate

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Hamid Goudarziafshar

2012-09-01

Full Text Available The centrosymmetric dinuclear cadmium title complex, [Cd2(C6H18N43](ClO44, was obtained by the reaction of N,N′-bis(2-aminoethylethane-1,2-diamine (trien with Cd(NO32·4H2O and sodium perchlorate in methanol. The CdII cation is coordinated by four N atoms of a non-bridging trien ligand and by two N atoms of a bridging trien ligand in a slightly distorted octahedral coordination geometry. The bridging ligand shares another two N atoms with a neighboring symmetry-equivalent CdII cation. The structure displays C—H...O and N—H...O hydrogen bonding. The perchlorate anion is disordered over two sets of sites in a 0.854 (7: 0.146 (7 ratio.

A graded nano-TiN coating on biomedical Ti alloy: Low friction coefficient, good bonding and biocompatibility.

Science.gov (United States)

Cui, Wenfang; Qin, Gaowu; Duan, Jingzhu; Wang, Huan

2017-02-01

In order to solve wear resistance of Ti alloy biomaterials, the concept of a graded nano-TiN coating has been proposed. The coating was prepared on Ti-6Al-4V bio-alloy by DC reactive magnetron sputtering. The wear performance of the coated specimens was measured in Hank's solution under the load of 10N, and the biocompatibility was evaluated according to ISO-10993-4 standard. The results show that the gradient coating exhibits a gradual change in compositions and microstructures along the direction of film growth. Nano-TiN with the size of several to dozens nanometers and Ti 4 N 3-x transitional phase with variable composition form a graded composite structure, which significantly improves adhesion strength (L c1 =80N, L c2 =120N), hardness (21GPa) and anti-wear performance (6.2×10 -7 mm 3 /Nm). The excellent bonding and wear resistance result from a good match of mechanical properties at substrate/coating interface and the strengthening and toughening effects of the nanocrystalline composite. The nano-TiN coating has also been proved to have good biocompatibility through in-vitro cytotoxicity, hemocompatibility and general toxicity tests. And thus, the proposed graded nano-TiN coating is a good candidate improving wear resistance of many implant medical devices. Copyright © 2016 Elsevier B.V. All rights reserved.

On the eletronic structure of Be sub(n) (3 < = n < = 10) clusters

International Nuclear Information System (INIS)

Camargo, F.P.; Vianna, J.D.M.

The electronic configurations, bonding energies and molecular orbital energies of Be(sub n) (n = 3, 4, 6, 10) have been calculated by the SCF-MO-CNDO theory parametrized by Boyd and Whitehead (CNDO/BW). Comparisons are made with the theoretical results which are available. (Author) [pt

Cross-sections for the formation of isomeric pair {sup 75}Ge{sup m,g} through (n, 2n), (n, p) and (n, {alpha}) reactions measured over 13.73 MeV to 14.77 MeV and calculated from near threshold to 20 MeV neutron energies

Energy Technology Data Exchange (ETDEWEB)

Attar, F.M.D.; Dhole, S.D. [Department of Physics, University of Pune, Pune-411007 (India); Kailas, S. [Nuclear Physics Division, BARC, Mumbai-400085 (India); Bhoraskar, V.N. [Department of Physics, University of Pune, Pune-411007 (India)], E-mail: vnb@physics.unipune.ernet.in

2009-09-15

The cross-sections for formation of isomeric pair, {sup 75}Ge{sup m}({sigma}{sub m}) and {sup 75}Ge{sup g}({sigma}{sub g}), through {sup 76}Ge(n, 2n), {sup 75}As(n, p) and {sup 78}Se(n, {alpha}) reactions were measured at 13.73 MeV, 14.42 MeV and 14.77 MeV neutrons and also estimated using EMPIRE-II and TALYS codes over neutron energies from near threshold to 20 MeV. For each (n, 2n), (n, p) and (n, {alpha}) reaction, the cross-section initially increases with neutron energy, but starts decreasing as the neutron energy exceeds the respective threshold of (n, 3n), (n, pn) and (n, {alpha}n) reactions. The higher values of {sigma}{sub m} relative to {sigma}{sub g} reveal that the transitions of the excited {sup 75}Ge from higher energy levels to metastable state (7{sup +}/2) are favored as compared to unstable ground state (1{sup -}/2). The present values of cross sections for formation of {sup 75}Ge{sup m,g} through (n, 2n) and (n, {alpha}) reactions are lower, and that of (n, p) reaction are higher compared to most of the corresponding literature cross-sections.

Formation and Control of N-Nitrosodimethylamine (NDMA) in Wastewater Reclaimed for Indirect Potable Reuse

OpenAIRE

Sgroi, Massimiliano

2014-01-01

A large variety of disinfection by-products (DBPs) are formed during water treatment processes using chlorination. Disinfection with chloramines is often used to significantly reduce the formation of regulated DBPs. However, chloramination favours the formation of N-nitrosamines, which are emerging by-products of health concern. Of all the nitrosamines, N-nitrosodimethylamine (NDMA) has been most commonly detected in drinking water and wastewater. Nitrosamines can also be produced using diffe...

Structure and chemistry of the Si(111)/AlN interface

Science.gov (United States)

Radtke, G.; Couillard, M.; Botton, G. A.; Zhu, D.; Humphreys, C. J.

2012-01-01

We investigate the atomic structure and the chemistry of the Si(111)/AlN interface for an AlN film grown at low-temperature (735 °C) by metalorganic vapor phase epitaxy. A heterogeneous interface is formed from the alternation of crystallographically abrupt and partly amorphous regions. The polarity of the AlN film, along with the projected atomic structure of the crystalline interface, is retrieved using high-angle annular dark field imaging, and a model, based on these experimental observations, is proposed for the bonding at the interface. Electron energy-loss spectrum-imaging, however, also reveals a chemical intermixing, placing our growth conditions at the onset of SiNx interlayer formation.

Extracting properties of N,N,N'N'-tetraalkyl-2 alkyl propane -1,3 diamides

International Nuclear Information System (INIS)

Nigond, L.

1992-01-01

N,N,N',N'-tetraalkyl -2 alkyl propane -1,3 diamides (RR'NCO) 2 CHR'' are investigated in the aim to separate actinides from nuclear wastes. N,N'-dimethyl N,N'-dibutyl tetradecylmalonamide (DMDBTDMA) was selected. This molecule can extract trivalent actinides in aliphatic diluents. Americium extraction is faster than iron extraction, hydrolytic degradation and solubility in aqueous phase are satisfactory. In non acidic media, diamides form aggregates, the size of which is function of diluent and diamide concentration. Extraction equilibria of HNO 3 , UO 2 2+ , Pu 4+ , Am 3+ and Fe 3+ are investigated.Four complexes are formed with nitric acid: L 2 HNO 3 , LHNO 3 , L 2 (HNO 3 ) 2 and L(HNO 3 ) 3 with L=DMDBTDMA. UO 2 2+ and Pu 4+ extraction takes place via the formation of neutral complexes: LUO 2 (NO 3 ) 2 , LPu(NO 3 ) 4 and L 2 Pu(NO 3 ) 4 for any nitric acid concentration. Am 3+ extraction takes place via the formation of LAm(NO 3 ) 3 and L 2 Am(NO 3 ) 3 for low nitric acid concentration and L x H y Am(NO 3 ) 3+y at higher acidity. Fe 3+ extraction involves anionic complexes L x HFe(NO 3 ) 4 for any acid concentration. In the presence of metallic cations, two kinds of interactions are observed: in the inner sphere of the metal diamide-metal ion complexation and in the outer sphere diamide-metallic complex interaction. The malonamide DMDBTDMA can be used to separate (III), (IV) and (VI) actinides from radioactive wastes

Copper-catalyzed transformation of ketones to amides via C(CO)-C(alkyl) bond cleavage directed by picolinamide.

Science.gov (United States)

Ma, Haojie; Zhou, Xiaoqiang; Zhan, Zhenzhen; Wei, Daidong; Shi, Chong; Liu, Xingxing; Huang, Guosheng

2017-09-13

Copper catalyzed chemoselective cleavage of the C(CO)-C(alkyl) bond leading to C-N bond formation with chelation assistance of N-containing directing groups is described. Inexpensive Cu(ii)-acetate serves as a convenient catalyst for this transformation. This method highlights the emerging strategy to transform unactivated alkyl ketones into amides in organic synthesis and provides a new strategy for C-C bond cleavage.

A classical trajectory study of the adatom -surface bond dissociation in the collision reaction between an adsorbed H atom and an N2 molecule

International Nuclear Information System (INIS)

Bayhan, U.

2005-01-01

The collisionnal dissociation of the Adatom-Surface bond in the diatomic molecule N2(gas)/H(ads) collision taking place on a W(100) bcc-structure surface have been studied by classical trajectory method over the collision energy ranges (0.1-2.0 eV ) and the attractive well depth (0.19-4.0 eV). of the N2 molecule (gas)/H(ads) interactions. When the energy accumulate into the adatom bond, thus leading to a a large dissociation probability

Continuous formation of N-chloro-N,N-dialkylamine solutions in well-mixed meso-scale flow reactors

Science.gov (United States)

Jolley, Katherine E

2015-01-01

Summary The continuous flow synthesis of a range of organic solutions of N,N-dialkyl-N-chloramines is described using either a bespoke meso-scale tubular reactor with static mixers or a continuous stirred tank reactor. Both reactors promote the efficient mixing of a biphasic solution of N,N-dialkylamine in organic solvent, and aqueous sodium hypochlorite to achieve near quantitative conversions, in 72–100% in situ yields, and useful productivities of around 0.05 mol/h with residence times from 3 to 20 minutes. Initial calorimetric studies have been carried out to inform on reaction exotherms, rates and safe operation. Amines which partition mainly in the organic phase require longer reaction times, provided by the CSTR, to compensate for low mass transfer rates in the biphasic system. The green metrics of the reaction have been assessed and compared to existing procedures and have shown the continuous process is improved over previous procedures. The organic solutions of N,N-dialkyl-N-chloramines produced continuously will enable their use in tandem flow reactions with a range of nucleophilic substrates. PMID:26734089

Continuous formation of N-chloro-N,N-dialkylamine solutions in well-mixed meso-scale flow reactors

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A. John Blacker

2015-12-01

Full Text Available The continuous flow synthesis of a range of organic solutions of N,N-dialkyl-N-chloramines is described using either a bespoke meso-scale tubular reactor with static mixers or a continuous stirred tank reactor. Both reactors promote the efficient mixing of a biphasic solution of N,N-dialkylamine in organic solvent, and aqueous sodium hypochlorite to achieve near quantitative conversions, in 72–100% in situ yields, and useful productivities of around 0.05 mol/h with residence times from 3 to 20 minutes. Initial calorimetric studies have been carried out to inform on reaction exotherms, rates and safe operation. Amines which partition mainly in the organic phase require longer reaction times, provided by the CSTR, to compensate for low mass transfer rates in the biphasic system. The green metrics of the reaction have been assessed and compared to existing procedures and have shown the continuous process is improved over previous procedures. The organic solutions of N,N-dialkyl-N-chloramines produced continuously will enable their use in tandem flow reactions with a range of nucleophilic substrates.

An S-N2-model for proton transfer in hydrogen-bonded systems

DEFF Research Database (Denmark)

Kuznetsov, A.M.; Ulstrup, Jens

2004-01-01

A new mechanism of proton transfer in donor-acceptor complexes with long hydrogen bonds is suggested. The transition is regarded as totally adiabatic. Two closest water molecules that move synchronously by hindered translation to and from the reaction complex are crucial. The water molecules induce...... a shift of the proton from the donor to the acceptor with simultaneous breaking/formation of hydrogen bonds between these molecules and the proton donor and acceptor. Expressions for the activation barrier and kinetic hydrogen isotope effect are derived. The general scheme is illustrated with the use...... of model molecular potentials, and with reference to the excess proton conductivity in aqueous solution....

Effects of carboxylic acids on nC60 aggregate formation

International Nuclear Information System (INIS)

Chang Xiaojun; Vikesland, Peter J.

2009-01-01

The discovery that negatively charged aggregates of C 60 fullerene (nC 60 ) are stable in water has raised concerns regarding the potential environmental and health effects of these aggregates. In this work, we show that nC 60 aggregates produced by extended mixing in the presence of environmentally relevant carboxylic acids (acetic acid, tartaric acid, citric acid) have surface charge and morphologic properties that differ from those produced by extended mixing in water alone. In general, aggregates formed in the presence of these acids have a more negative surface charge and are more homogeneous than those produced in water alone. Carboxylic acid identity, solution pH, and sodium ion concentration, which are all intricately coupled, play an important role in setting the measured surface charge. Comparisons between particle sizes determined by analysis of TEM images and those obtained by dynamic light scattering (DLS) indicate that DLS results require careful evaluation when used to describe nC 60 aggregates. - The effects of carboxylic acids on the formation of nC 60 aggregates are discussed

Studies on (acid + base) equilibria in substituted (phenol + n-butylamine) systems in acetonitrile

Energy Technology Data Exchange (ETDEWEB)

Kozak, A. [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Czaja, M. [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Chmurzynski, L. [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland)]. E-mail: lech@chem.univ.gda.pl

2005-08-15

(Acid + base) equilibria, including molecular heteroconjugation ones, between n-butylamine and one of the following phenols: 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2,5-dinitrophenol, 3-chlorophenol, 4-chlorophenol, 2,3,4,5,6-pentachlorophenol and 2,4,6-tribromophenol have been studied potentiometrically in a protophobic polar aprotic solvent, acetonitrile. Among the phenols studied, 2,5-dinitrophenol exhibited the strongest tendency towards formation of asymmetric hydrogen bonds with n-butylamine, whereas a weakest complex was formed with 2-nitrophenol. In the (n-butylamine + 2,3,4,5,6-pentachlorophenol) and (n-butylamine + 2,4-dinitrophenol) systems proton transfer reactions occurred.

N-(Thiazol-2-ylacetamide

Directory of Open Access Journals (Sweden)

Uzma Yunus

2008-08-01

Full Text Available The title compound, C5H6N2OS, was synthesized from acetyl chloride and 2-aminothiazole in dry acetone. The asymmetric unit contains two molecules. The crystal structure is stabilized by N—H...N and C—H...O hydrogen bonds.

Methylation of ribonucleic acid by the carcinogens dimethyl sulphate, N-methyl-N-nitrosourea and N-methyl-N′-nitro-N-nitrosoguanidine. Comparisons of chemical analyses at the nucleoside and base levels

Science.gov (United States)

Lawley, P. D.; Shah, S. A.

1972-01-01

1. The following methods for hydrolysis of methyl-14C-labelled RNA, and for chromatographic isolation and determination of the products, were investigated: enzymic digestion to nucleosides at pH6 or 8; alkaline hydrolysis and conversion into nucleosides; hydrolysis by acid to pyrimidine nucleotides and purine bases, or completely to bases; chromatography on Dowex 50 (NH4+ form) at pH6 or 8.9, or on Dowex 50 (H+ form), or on Sephadex G-10. 2. The suitability of the various methods for determination of methylation products was assessed. The principal product, 7-methylguanosine, was unstable under the conditions used for determinations of nucleosides. 3- and 7-Methyladenine and 3- and 7-methylguanine are best determined as bases; 1-methyladenine and 3-methylcytosine can be isolated as either nucleosides or bases; O6-methylguanine is unstable under the acid hydrolysis conditions used and can be determined as the nucleoside; 3-methyluracil was detected, but may be derived from methylation of the ionized form of uracil. 3. Differences between the patterns of methylation of RNA and homopolyribonucleotides by the N-methyl-N-nitroso compounds and dimethyl sulphate were found: the nitroso compounds were able to methylate O-6 of guanine, were relatively more reactive at N-7 of adenine and probably at N-3 of guanine, but less reactive at N-1 of adenine, N-3 of cytosine and probably at N-3 of uridine. They probably reacted more with the ribose–phosphate chain, but no products from this were identified. 4. The possible influences of these differences on biological action of the methylating agents is discussed. Nitroso compounds may differ principally in their ability to induce miscoding in the Watson–Crick sense by reaction at O-6 of guanine. Both types of agent may induce miscoding to a lesser extent through methylation at N-3 of guanine; both can methylate N atoms, presumably preventing Watson–Crick hydrogen-bonding. N-Methyl-N-nitrosourea can degrade RNA, possibly

Hydrogen bonding in (substituted benzene)·(water)n clusters with n≤4

International Nuclear Information System (INIS)

Barth, H.-D.; Buchhold, K.; Djafari, S.; Reimann, B.; Lommatzsch, U.; Brutschy, B.

1998-01-01

Infrared ion-depletion spectroscopy, a double resonance method combining vibrational predissociation with resonant two-photon ionization (R2PI) spectroscopy, has been applied to study mixed clusters of the type (substituted benzene)·(H 2 O) n with n≤4. The UV chromophores were p-difluorobenzene, fluorobenzene, benzene, toluene, p-xylene and anisole. From the IR depletion spectra in the region of the OH stretching vibrations it could be shown that the water molecules are attached as subclusters to the chromophores. Size and configuration of the subclusters could be deduced from the IR depletion spectra. In the anisole·(H 2 O) 1 a nd 2 complexes the water clusters form an ordinary hydrogen bond to the oxygen atom of the methoxy group. In all other mixed complexes a π-hydrogen bond is formed between one of the free OH groups of a water subcluster and the π-system of the chromophore. According to the strength of this interaction the frequency of the respective absorption band exhibits a characteristic red-shift which could be related to the total atomic charges in the aromatic ring. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Amide-N-oxide heterosynthon and amide dimer homosynthon in cocrystals of carboxamide drugs and pyridine N-oxides.

Science.gov (United States)

Babu, N Jagadeesh; Reddy, L Sreenivas; Nangia, Ashwini

2007-01-01

The carboxamide-pyridine N-oxide heterosynthon is sustained by syn(amide)N-H...O-(oxide) hydrogen bond and auxiliary (N-oxide)C-H...O(amide) interaction (Reddy, L. S.; Babu, N. J.; Nangia, A. Chem. Commun. 2006, 1369). We evaluate the scope and utility of this heterosynthon in amide-containing molecules and drugs (active pharmaceutical ingredients, APIs) with pyridine N-oxide cocrystal former molecules (CCFs). Out of 10 cocrystals in this study and 7 complexes from previous work, amide-N-oxide heterosynthon is present in 12 structures and amide dimer homosynthon occurs in 5 structures. The amide dimer is favored over amide-N-oxide synthon in cocrystals when there is competition from another H-bonding functional group, e.g., 4-hydroxybenzamide, or because of steric factors, as in carbamazepine API. The molecular organization in carbamazepine.quinoxaline N,N'-dioxide 1:1 cocrystal structure is directed by amide homodimer and anti(amide)N-H...O-(oxide) hydrogen bond. Its X-ray crystal structure matches with the third lowest energy frame calculated in Polymorph Predictor (Cerius(2), COMPASS force field). Apart from generating new and diverse supramolecular structures, hydration is controlled in one substance. 4-Picoline N-oxide deliquesces within a day, but its cocrystal with barbital does not absorb moisture at 50% RH and 30 degrees C up to four weeks. Amide-N-oxide heterosynthon has potential utility in both amide and N-oxide type drug molecules with complementary CCFs. Its occurrence probability in the Cambridge Structural Database is 87% among 27 structures without competing acceptors and 78% in 41 structures containing OH, NH, H(2)O functional groups.

Investigation of microstructure and V-defect formation inInxGa1-xN/GaN MQW grown using temperature-gradient MOCVD

Energy Technology Data Exchange (ETDEWEB)

Johnson, M.C.; Liliental-Weber, Z.; Zakharov, D.N.; McCready,D.E.; Jorgenson, R.J.; Wu, J.; Shan, W.; Bourret-Courchesne, E.D.

2004-11-19

Temperature-gradient Metalorganic Chemical Vapor Deposition was used to deposit In{sub x}Ga{sub 1-x}N/GaN multiple quantum well structures with a concentration gradient of indium across the wafer. These multiple quantum well structures were deposited on low defect density (2 x 10{sup 8} cm{sup -2}) GaN template layers for investigation of microstructural properties and V-defect (pinhole) formation. Room temperature photoluminescence and photomodulated transmission were used for optical characterization which show a systematic decrease in emission energy for a decrease in growth temperature. Triple-axis X-ray diffraction, scanning electron microscopy and cross-section transmission electron microscopy were used to obtain microstructural properties of different regions across the wafer. Results show that there is a decrease in crystal quality and an increase in V-defect formation with increasing indium concentration. A direct correlation was found between V-defect density and growth temperature due to increased strain and indium segregation for increasing indium concentration.

A contribution to the study of the extraction of mineral acids and of actinide (IV) and (VI) cations by N,N-dialkylamides

International Nuclear Information System (INIS)

Condamines, N.

1990-03-01

N,N-dialkylamides are alternate extractants to tributylphosphate, TBP, for the actinides separation in nuclear fuel reprocessing. N,N-di (2-ethyl hexyl) butyramide and N,N-di (2 ethyl hexyl) isobutyramide are selected for their sufficient extraction and partition ability towards actinides (IV) and (VI) without coextracting fission products. Mechanisms of HNO 3 , UO 2 2+ , Pu 4+ , Th 4+ are investigated. Nitric acid extraction is due to the competitive formation of the species (HNO 3 )L 2 , (HNO 3 )L, (HNO 3 ) 2 L (L: DOBA or DOiBA). An hydrogen bond is the driving force of the transfer. For low acidity media, amides are neutral extractants. Physical interactions, between free ligand and metallic complex, arise for high amide concentrations. Taking into account the non-ideality of the organic medium by a hard spheres mixture model, we estimate that such interactions are far from negligible and very specific to the amide group. Unlike TBP, when increasing acidity, amides behave as anionic extractants. DOBA and DOiBA appear to be satisfactory extractants for fuel reprocessing [fr

E/Z-Photoisomerization of N,N'-Bis(4-dimethylaminobenzylidene1,2-diaminoethane and N,N'-Bis(4-dimethylaminobenzylidene1,3-diaminopropane in Chloroform

Directory of Open Access Journals (Sweden)

Asghar Samimi

2011-01-01

Full Text Available The E/Z-Photoisomerization of Schiff bases N,N'-bis(4-dimethylamino benzylidene1,2-diaminoethane (BDAE and N,N'-bis(4-dimethylaminobenzyli-dene1,3-diaminopropane (BDAP were studied by UV-Vis absorption spectroscopy and theoretical chemistry calculations. Photochemical investigations in solution depict the time resolved spectral changes, recorded before and after irradiation. The shift indicates the transformation from E to Z configuration of the C=N bond in solution for BDAE and BDAP. Spectra profiles and kinetic constants were evaluated using multivariate curve resolution and non-linear least squares curve fitting by toolbox of MATLAB program using the corresponding absorption spectra-time data. The experimental results show that BDAP can perform the photochromism easier than BDAE, may be due to the molecular topology difference.

Un-catalyzed peptide bond formation between two monomers of glycine, alanine, serine, threonine, and aspartic acid in gas phase: a density functional theory study

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Bhunia, Snehasis; Singh, Ajeet; Ojha, Animesh K.

2016-05-01

In the present report, un-catalyzed peptide bond formation between two monomers of glycine (Gly), alanine (Ala), serine (Ser), threonine (Thr), and aspartic acid (Asp) has been investigated in gas phase via two steps reaction mechanism and concerted mechanism at B3LYP/6-31G(d,p) and M062X/6-31G(d,p) level of theories. The peptide bond is formed through a nucleophilic reaction via transition states, TS1 and TS2 in stepwise mechanism. The TS1 reveals formation of a new C-N bond while TS2 illustrate the formation of C=O bond. In case of concerted mechanism, C-N bond is formed by a single four-centre transition state (TS3). The energy barrier is used to explain the involvement of energy at each step of the reaction. The energy barrier (20-48 kcal/mol) is required for the transformation of reactant state R1 to TS1 state and intermediate state I1 to TS2 state. The large value of energy barrier is explained in terms of distortion and interaction energies for stepwise mechanism. The energy barrier of TS3 in concerted mechanism is very close to the energy barrier of the first transition state (TS1) of the stepwise mechanism for the formation of Gly-Gly and Ala-Ala di- peptide. However, in case of Ser-Ser, Thr-Thr and Asp-Asp di-peptide, the energy barrier of TS3 is relatively high than that of the energy barrier of TS1 calculated at B3LYP/6-31G(d,p) and M062X/6-31G(d,p) level of theories. In both the mechanisms, the value of energy barrier calculated at B3LYP/6-31G(d,p) level of theory is greater than that of the value calculated at M062X/6-31G(d,p) level of theory.

Erratic Male Meiosis Resulting in 2n Pollen Grain Formation in a 4x Cytotype (2n=28 of Ranunculus laetus Wall. ex Royle

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Puneet Kumar

2012-01-01

Full Text Available Two accessions were studied for male meiosis in Ranunculus laetus from the cold regions of Northwest Himalayas. One accession showed the presence of 14 bivalents at diakinesis and regular segregation of bivalents at anaphase I which lead to normal tetrad formation with four n microspores and consequently n pollen grains and 100% pollen fertility. Second accession from the same locality revealed the erratic meiosis characterized by the presence of all the 28 chromosomes as univalents in meiocytes at metaphase I. Univalent chromosomes failed to segregate during anaphases and produced restitution nuclei at meiosis I and II. These restitution nuclei resulted into dyads and triads which subsequently produced two types of apparently fertile pollen grains. On the basis of size, the two types of pollen grains were categorized as n (normal reduced and 2n (unreduced, 1.5-times larger than the n pollen grains. The estimated frequency of 2n pollen grains from dyads and triads (61.59% was almost the same as that of the observed one (59.90%, which indicated that 2n pollen grains in R. laetus were the result of dyads and triads. The present paper herein may provide an insight into the mechanisms of the formation of various intraspecific polyploids through sexual polyploidization in R. laetus.

Facile Synthesis and Superior Catalytic Activity of Nano-TiN@N-C for Hydrogen Storage in NaAlH4.

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Zhang, Xin; Ren, Zhuanghe; Lu, Yunhao; Yao, Jianhua; Gao, Mingxia; Liu, Yongfeng; Pan, Hongge

2018-05-09

Herein, we synthesize successfully ultrafine TiN nanoparticles (hydrogen storage in NaAlH 4 . Adding 7 wt % nano-TiN@N-C induces more than 100 °C reduction in the onset dehydrogenation temperature of NaAlH 4 . Approximately 4.9 wt % H 2 is rapidly released from the 7 wt % nano-TiN@N-C-containing NaAlH 4 at 140 °C within 60 min, and the dehydrogenation product is completely hydrogenated at 100 °C within 15 min under 100 bar of hydrogen, exhibiting significantly improved desorption/absorption kinetics. No capacity loss is observed for the nano-TiN@N-C-containing sample within 25 de-/hydrogenation cycles because nano-TiN functions as an active catalyst instead of a precursor. A severe structural distortion with extended bond lengths and reduced bond strengths for Al-H bonding when the [AlH 4 ] - group adsorbs on the TiN cluster is demonstrated for the first time by density functional theory calculations, which well-explains the reduced de-/hydrogenation temperatures of the nano-TiN@N-C-containing NaAlH 4 . These findings provide new insights into designing and synthesizing high-performance catalysts for hydrogen storage in complex hydrides.

Characterization of as-grown and adsorbate-covered N-polar InN surfaces using in situ photoelectron spectroscopy

International Nuclear Information System (INIS)

Eisenhardt, Anja; Himmerlich, Marcel; Krischok, Stefan

2012-01-01

The surface electronic properties and adsorption behaviour of as-grown and oxidized N-polar InN films are characterized by photoelectron spectroscopy (XPS, UPS). The epitaxial growth of the InN layers was performed by plasma-assisted molecular beam epitaxy on GaN/6H-SiC(000-1). After growth and in situ characterization the InN surfaces were exposed to molecular oxygen to evaluate the adsorption behaviour of O 2 on N-polar InN and to study its impact on the surface electronic properties of the III-nitride material. The results are compared with studies on In-polar InN on GaN/sapphire templates. The as-grown N-polar InN surface exhibits a pronounced surface state at a binding energy of ∝1.6 eV. The valence band minimum lies about 0.8-1.0 eV below the surface Fermi level. Additionally, the XPS core level binding energies for InN(000-1) are reduced compared to InN(0001) films, indicating different surface band bending for clean N-polar and In-polar InN, respectively. The interaction of molecular oxygen with the InN(000-1) surface leads to a downward band bending by 0.1 eV compared to the initial state. Additional adsorption of species from the residual gas of the UHV chamber increases the surface downward band bending. Furthermore two pronounced oxygen related states with an energy distance of ∝5 eV could be detected in the valence band region. The adsorbed oxygen results in an additional component in the N1s core level spectra, which is interpreted as formation of NO x bonds. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Different Supramolecular Coordination Polymers of [N,N'-di(pyrazin-2-yl-pyridine-2,6-diamine]Ni(II with Anions and Solvent Molecules as a Result of Hydrogen Bonding

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Hsin-Ta Wang

2007-04-01

Full Text Available Ni(II complexes of N,N'–di(pyrazin–2–ylpyridine–2,6–diamine (H2dpzpda with different anions were synthesized and their structures were determined by X-ray diffraction. Hydrogen bonds between the amino groups and anions assembled the mononuclear molecules into different architectures. The perchlorate complex had a 1-D chain structure, whereas switching the anion from perchlorate to nitrate resulted in a corresponding change of the supramolecular structure from 1-D to 3-D. When the nitrate complex packed with the co-crystallized water, a double chain structure was formed through hydrogen bonding. The magnetic studies revealed values of g = 2.14 and D = 3.11 cm-1 for [Ni(H2dpzpda2](ClO42 (1 and g = 2.18 and D = 2.19 cm-1 for [Ni(H2dpzpda2](NO32 (2, respectively.

Improving p-type doping efficiency in Al0.83Ga0.17N alloy substituted by nanoscale (AlN)5/(GaN)1 superlattice with MgGa-ON δ-codoping: Role of O-atom in GaN monolayer

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Zhong, Hong-xia; Shi, Jun-jie; Zhang, Min; Jiang, Xin-he; Huang, Pu; Ding, Yi-min

2015-01-01

We calculate Mg-acceptor activation energy EA and investigate the influence of O-atom, occupied the Mg nearest-neighbor, on EA in nanoscale (AlN)5/(GaN)1 superlattice (SL), a substitution for Al0.83Ga0.17N disorder alloy, using first-principles calculations. We find that the N-atom bonded with Ga-atom is more easily substituted by O-atom and nMgGa-ON (n = 1-3) complexes are favorable and stable in the SL. The O-atom plays a dominant role in reducing EA. The shorter the Mg-O bond is, the smaller the EA is. The Mg-acceptor activation energy can be reduced significantly by nMgGa-ON δ-codoping. Our calculated EA for 2MgGa-ON is 0.21 eV, and can be further reduced to 0.13 eV for 3MgGa-ON, which results in a high hole concentration in the order of 1020 cm-3 at room temperature in (AlN)5/(GaN)1 SL. Our results prove that nMgGa-ON (n = 2,3) δ-codoping in AlN/GaN SL with ultrathin GaN-layer is an effective way to improve p-type doping efficiency in Al-rich AlGaN.

Improving p-type doping efficiency in Al0.83Ga0.17N alloy substituted by nanoscale (AlN5/(GaN1 superlattice with MgGa-ON δ-codoping: Role of O-atom in GaN monolayer

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Hong-xia Zhong

2015-01-01

Full Text Available We calculate Mg-acceptor activation energy EA and investigate the influence of O-atom, occupied the Mg nearest-neighbor, on EA in nanoscale (AlN5/(GaN1 superlattice (SL, a substitution for Al0.83Ga0.17N disorder alloy, using first-principles calculations. We find that the N-atom bonded with Ga-atom is more easily substituted by O-atom and nMgGa-ON (n = 1-3 complexes are favorable and stable in the SL. The O-atom plays a dominant role in reducing EA. The shorter the Mg-O bond is, the smaller the EA is. The Mg-acceptor activation energy can be reduced significantly by nMgGa-ON δ-codoping. Our calculated EA for 2MgGa-ON is 0.21 eV, and can be further reduced to 0.13 eV for 3MgGa-ON, which results in a high hole concentration in the order of 1020 cm−3 at room temperature in (AlN5/(GaN1 SL. Our results prove that nMgGa-ON (n = 2,3 δ-codoping in AlN/GaN SL with ultrathin GaN-layer is an effective way to improve p-type doping efficiency in Al-rich AlGaN.

Investigation on Surface Polarization of Al2O3-capped GaN/AlGaN/GaN Heterostructure by Angle-Resolved X-ray Photoelectron Spectroscopy.

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Duan, Tian Li; Pan, Ji Sheng; Wang, Ning; Cheng, Kai; Yu, Hong Yu

2017-08-17

The surface polarization of Ga-face gallium nitride (GaN) (2 nm)/AlGaN (22 nm)/GaN channel (150 nm)/buffer/Si with Al 2 O 3 capping layer is investigated by angle-resolved X-ray photoelectron spectroscopy (ARXPS). It is found that the energy band varies from upward bending to downward bending in the interface region, which is believed to be corresponding to the polarization variation. An interfacial layer is formed between top GaN and Al 2 O 3 due to the occurrence of Ga-N bond break and Ga-O bond forming during Al 2 O 3 deposition via the atomic layer deposition (ALD). This interfacial layer is believed to eliminate the GaN polarization, thus reducing the polarization-induced negative charges. Furthermore, this interfacial layer plays a key role for the introduction of the positive charges which lead the energy band downward. Finally, a N 2 annealing at 400 °C is observed to enhance the interfacial layer growth thus increasing the density of positive charges.

Pd-catalyzed versus uncatalyzed, PhI(OAc)2-mediated cyclization reactions of N6-([1,1'-biaryl]-2-yl)adenine nucleosides.

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Satishkumar, Sakilam; Poudapally, Suresh; Vuram, Prasanna K; Gurram, Venkateshwarlu; Pottabathini, Narender; Sebastian, Dellamol; Yang, Lijia; Pradhan, Padmanava; Lakshman, Mahesh K

2017-11-09

In this work we have assessed reactions of N 6 -([1,1'-biaryl]-2-yl)adenine nucleosides with Pd(OAc) 2 and PhI(OAc) 2 , via a Pd II /Pd IV redox cycle. The substrates are readily obtained by Pd/Xantphos-catalyzed reaction of adenine nucleosides with 2-bromo-1,1'-biaryls. In PhMe, the N 6 -biarylyl nucleosides gave C6-carbazolyl nucleoside analogues by C-N bond formation with the exocyclic N 6 nitrogen atom. In the solvent screening for the Pd-catalyzed reactions, an uncatalyzed process was found to be operational. It was observed that the carbazolyl products could also be obtained in the absence of a metal catalyst by reaction with PhI(OAc) 2 in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). Thus, under Pd catalysis and in HFIP, reactions proceed to provide carbazolyl nucleoside analogues, with some differences. If reactions of N 6 -biarylyl nucleoside substrates were conducted in MeCN, formation of aryl benzimidazopurinyl nucleoside derivatives was observed in many cases by C-N bond formation with the N 1 ring nitrogen atom of the purine (carbazole and benzimidazole isomers are readily separated by chromatography). Whereas Pd II /Pd IV redox is responsible for carbazole formation under the metal-catalyzed conditions, in HFIP and MeCN radical cations and/or nitrenium ions can be intermediates. An extensive set of radical inhibition experiments was conducted and the data are presented.

EPR study of N+-ion-induced free radical formation in antibiotic-producers

International Nuclear Information System (INIS)

Xie Liqing; Zhang Yinfen; Chen Ruyi; Gao Juncheng; Zhang Peiling; Ying Hengfeng.

1995-01-01

Under the room temperature, electron paramagnetic resonance (EPR) spectrometer was used to study free radical formation in antibiotic-producers in order to investigate antibiotic-producer mutagenic breeding, which were induced by N + ion implanting into antibiotic-producers (e.g., Streptomyces ribosidificus, Streptomyces kanamyceticus and the phage-resistant culture of Streptomyces kanamyceticus). The results show that a lot of free radicals can be induced by N + ion implanting into antibiotic-producers, and the yields of the free radicals increase with implanting dose. The death rate of antibiotic-producers rises due to the increase of N + -ion-induced free radical yields. (author)

Crystal structure of a looped-chain CoII coordination polymer: catena-poly[[bis-(nitrato-κO)cobalt(II)]bis-[μ-bis-(pyridin-3-ylmeth-yl)sulfane-κ2N:N'

Science.gov (United States)

Moon, Suk-Hee; Seo, Joobeom; Park, Ki-Min

2017-11-01

The asymmetric unit of the title compound, [Co(NO 3 ) 2 (C 12 H 12 N 2 S) 2 ] n , contains a bis-(pyridin-3-ylmeth-yl)sulfane ( L ) ligand, an NO 3 - anion and half a Co II cation, which lies on an inversion centre. The Co II cation is six-coordinated, being bound to four pyridine N atoms from four symmetry-related L ligands. The remaining coordination sites are occupied by two O atoms from two symmetry-related nitrate anions in a monodentate manner. Thus, the Co II centre adopts a distorted octa-hedral geometry. Two symmetry-related L ligands are connected by two symmetry-related Co II cations, forming a 20-membered cyclic dimer, in which the Co II atoms are separated by 10.2922 (7) Å. The cyclic dimers are connected to each other by sharing Co II atoms, giving rise to the formation of an infinite looped chain propagating along the [101] direction. Inter-molecular C-H⋯π (H⋯ring centroid = 2.89 Å) inter-actions between one pair of corresponding L ligands and C-H⋯O hydrogen bonds between the L ligands and the nitrate anions occur in the looped chain. In the crystal, adjacent looped chains are connected by inter-molecular π-π stacking inter-actions [centroid-to-centroid distance = 3.8859 (14) Å] and C-H⋯π hydrogen bonds (H⋯ring centroid = 2.65 Å), leading to the formation of layers parallel to (101). These layers are further connected through C-H⋯O hydrogen bonds between the layers, resulting in the formation of a three-dimensional supra-molecular architecture.

Polymorphic one-dimensional (N2H4)2ZnTe: soluble precursors for the formation of hexagonal or cubic zinc telluride.

Science.gov (United States)

Mitzi, David B

2005-10-03

Two hydrazine zinc(II) telluride polymorphs, (N2H4)2ZnTe, have been isolated, using ambient-temperature solution-based techniques, and the crystal structures determined: alpha-(N2H4)2ZnTe (1) [P21, a = 7.2157(4) Angstroms, b = 11.5439(6) Angstroms, c = 7.3909(4) Angstroms, beta = 101.296(1) degrees, Z = 4] and beta-(N2H4)2ZnTe (2) [Pn, a = 8.1301(5) Angstroms, b = 6.9580(5) Angstroms, c = 10.7380(7) Angstroms, beta = 91.703(1) degrees, Z = 4]. The zinc atoms in 1 and 2 are tetrahedrally bonded to two terminal hydrazine molecules and two bridging tellurium atoms, leading to the formation of extended one-dimensional (1-D) zinc telluride chains, with different chain conformations and packings distinguishing the two polymorphs. Thermal decomposition of (N2H4)2ZnTe first yields crystalline wurtzite (hexagonal) ZnTe at temperatures as low as 200 degrees C, followed by the more stable zinc blende (cubic) form at temperatures above 350 degrees C. The 1-D polymorphs are soluble in hydrazine and can be used as convenient precursors for the low-temperature solution processing of p-type ZnTe semiconducting films.

XANES study on Ruddlesdan-Popper phase, Lan+1NinO3n+1 (n = 1, 2 and ∞)

International Nuclear Information System (INIS)

Park, Jung-Chul; Kim, Dong-Kuk; Byeon, Song-Hu; Kim, Don

2001-01-01

Ruddlesden-Popper phase, La n+1 Ni n O 3n+ 1 (n = 1, 2, and ∞) compounds were prepared by citrate sol-gel method. We revealed the origin of the variation of the electrical conductivities in La n+1 Ni n O 3n+1 (n= 1, 2, and ∞) using resistivity measurements, Rietveld analysis, and X-ray absorption spectroscopy. According to the XANES spectra, it is found that the degree of 4pπ - 4pσ energy splitting between 8345 eV and 8350 eV is qualitatively proportional to the elongation of the out-of-plane Ni-O bond length. With the decrease of 4pπ-4pσ splitting, the strong hybridization of the σ-bonding between Ni-3d and O-2p orbitals creates narrow antibonding σ bands, which finally results in the lower electrical resistivity. (au)

Transition Metal Free C-N Bond Forming Dearomatizations and Aryl C-H Aminations by in Situ Release of a Hydroxylamine-Based Aminating Agent.

Science.gov (United States)

Farndon, Joshua J; Ma, Xiaofeng; Bower, John F

2017-10-11

We outline a simple protocol that accesses directly unprotected secondary amines by intramolecular C-N bond forming dearomatization or aryl C-H amination. The method is dependent on the generation of a potent electrophilic aminating agent released by in situ deprotection of O-Ts activated N-Boc hydroxylamines.

Structure of poly(di-n-hexylsilane) in nanoporous materials

International Nuclear Information System (INIS)

Korotkova, I.; Sakhno, T.; Drobit'ko, I.; Sakhno, Yu.; Ostapenko, N.

2010-01-01

Graphical abstract: On the basis of theoretical calculations using TD/CEP-31G method we found and interpreted the complexation mechanism of poly(di-n-hexylsilane) incorporated in nanoporous materials. - Abstract: In this work the effects of solvent polarity and conformation changing on the electronic characteristics of poly(di-n-hexylsilane) incorporated in the nanoporous materials are calculated. The dependence of energy levels of electronic-excited states of investigated compounds is analyzed as a function of the Si-Si-Si-Si twist angle and length of Si-Si and Si-C bonds. The possibility of complex formation between silicon atom of polymer and oxygen ions of nanoporous materials is shown.

Crystal structure of poly[N,N-diethyl-2-hydroxyethan-1-aminium [μ3-cyanido-κ3C:C:N-di-μ-cyanido-κ4C:N-dicuprate(I

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Peter W. R. Corfield

2016-07-01

Full Text Available In the title compound, {(C6H16NO[Cu2(CN3]}n, the cyanide groups link the CuI atoms into an open three-dimensional anionic network, with the molecular formula Cu2(CN3−. One CuI atom is tetrahedrally bound to four CN groups, and the other CuI atom is bonded to three CN groups in an approximate trigonal-planar coordination. The tetrahedrally coordinated CuI atoms are linked into centrosymmetric dimers by the C atoms of two end-on bridging CN groups which bring the CuI atoms into close contact at 2.5171 (7 Å. Two of the cyanide groups bonded to the CuI atoms with trigonal-planar surrounding link the dimeric units into columns along the a axis, and the third links the columns together to form the network. The N,N-diethylethanolamine molecules used in the synthesis have become protonated at the N atoms and are situated in cavities in the network, providing charge neutrality, with no covalent interactions between the cations and the anionic network.

A two-dimensional CdII coordination polymer: poly[diaqua[μ3-5,6-bis(pyridin-2-ylpyrazine-2,3-dicarboxylato-κ5O2:O3:O3,N4,N5]cadmium

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Monserrat Alfonso

2016-09-01

Full Text Available The reaction of 5,6-bis(pyridin-2-ylpyrazine-2,3-dicarboxylic acid with cadmium dichloride leads to the formation of the title two-dimensional coordination polymer, [Cd(C16H8N4O4(H2O2]n. The metal atom is sevenfold coordinated by one pyrazine and one pyridine N atom, two water O atoms, and by two carboxylate O atoms, one of which bridges two CdII atoms to form a Cd2O2 unit situated about a centre of inversion. Hence, the ligand coordinates to the cadmium atom in an N,N′,O-tridentate and an O-monodentate manner. Within the polymer network, there are a number of O—H...O hydrogen bonds present, involving the water molecules and the carboxylate O atoms. There are also C—H...N and C—H...O hydrogen bonds present. In the crystal, the polymer networks lie parallel to the bc plane. They are aligned back-to-back along the a axis with the non-coordinating pyridine rings directed into the space between the networks.

N,N-Dimethyl-N-propyl-propan-1-aminium chloride monohydrate.

Science.gov (United States)

Kärnä, Minna; Lahtinen, Manu; Valkonen, Jussi

2008-10-11

The title compound, C(8)H(20)N(+)·Cl(-)·H(2)O, has been prepared by a simple one-pot synthesis route followed by anion exchange using resin. In the crystal structure, the cations are packed in such a way that channels exist parallel to the b axis. These channels are filled by the anions and water mol-ecules, which inter-act via O-H⋯Cl hydrogen bonds [O⋯Cl = 3.285 (3) and 3.239 (3) Å] to form helical chains. The cations are involved in weak inter-molecular C-H⋯Cl and C-H⋯O hydrogen bonds. The title compound is not isomorphous with the bromo or iodo analogues.

First-principle study of silicon cluster doped with rhodium: Rh{sub 2}Si{sub n} (n = 1–11) clusters

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shuai; Luo, Chang Geng; Li, Hua Yang [Department of Physics, Nanyang Normal University, Nanyang 473061 (China); Lu, Cheng, E-mail: lucheng@calypso.cn [Department of Physics, Nanyang Normal University, Nanyang 473061 (China); State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Li, Gen Quan; Lu, Zhi Wen [Department of Physics, Nanyang Normal University, Nanyang 473061 (China)

2015-06-15

The geometries, stabilities and electronic properties of rhodium-doped silicon clusters Rh{sub 2}Si{sub n} (n = 1–11) have been systematically studied by using density functional calculations at the B3LYP/GENECP level. The optimized results show that the lowest-energy isomers of Rh{sub 2}Si{sub n} clusters favor three-dimensional structures for n = 2–11. Based on the averaged binding energy, fragmentation energy, second-order energy difference and HOMO-LUMO energy gap, the stabilities of Rh{sub 2}Si{sub n} (n = 1–11) clusters have been analyzed. The calculated results suggest that the Rh{sub 2}Si{sub 6} cluster has the strongest relative stability and the doping with rhodium atoms can reduce the chemical stabilities of Si{sub n} clusters. The natural population and natural electron configuration analysis indicate that there is charge transfer from the Si atoms and 5s orbital of the Rh atoms to the 4d and 5p orbitals of Rh atoms. The analysis of electron localization function reveal that the Si–Si bonds are mainly covalent bonds and the Si–Rh bonds are almost ionic bonds. Moreover, the vertical ionization potential, vertical electron affinity, chemical hardness, chemical potential, vibrational spectrum and polarizability are also discussed. - Highlights: • The geometric structures of Rh{sub 2}Si{sub n} (n = 1–11) clusters are determined. • The stabilities and electronic properties of Rh{sub 2}Si{sub n} clusters are discussed. • The Rh{sub 2}Si{sub 6} cluster has the higher stability than other clusters. • The doped rhodium atoms can reduce the chemical stabilities of Si{sub n} clusters.

Architecture of the hydrophobic and hydrophilic layers as found from crystal structure analysis of N-benzyl-N,N-dimethylalkylammonium bromides.

Science.gov (United States)

Hodorowicz, Maciej; Stadnicka, Katarzyna; Czapkiewicz, Jan

2005-10-01

The molecular and crystal structures of N-benzyl-N,N-dimethylalkylammonium bromides monohydrates with chain length n=8-10 have been determined. The crystals are isostructural with the N-benzyl-N,N-dimethyldodecylammonium bromide monohydrate. The structures consist of alternated hydrophobic and hydrophilic layers perpendicular to [001]. The attraction between N+ of the cation head-groups and Br- anions is achieved through weak C_H...Br interactions. The water molecules incorporated into ionic layers are donors for two O_H...Br hydrogen bonds and serve as the acceptors in two weak interactions of C_H...O type. The methylene chains, with the slightly curved general shape, have the extended all-trans conformation. The mutual packing of the chains in the hydrophobic layers is governed by weak C_H...pi interactions.

DYNAMICS OF THE PHYSICAL EDUCATION IN THE AGRONOMY’S ENGINEER PROFESSIONAL FORMATION / DINÁMICA DE LA EDUCACIÓN FÍSICA EN LA FORMACIÓN PROFESIONAL DEL INGENIERO AGRÓNOMO

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José Manuel Benítez García

2013-04-01

Full Text Available For the professional's formation needed by society in this XXI century, we do emphasize in a professional that stands out as person and a reflexive being in his technical, cultural and physical training, hence, in this article, attention is focused in Physical Education as an essential condition to achieve professionals integral formation. In diagnostic studies accomplished in the formation of the Agronomy's Engineer at Las Tunas University, insufficiencies in their integral formation from Physical Education were identified, because its dynamics has not being enough deepened, because it is still conceived from a traditional approach, so as to evidence that potentialities of Physical Education are not enough taken into account in the professionals´ formation process. Thus, it is considered here that it is necessary to continue deepening into the specificities of each professional profile and, specially, in the profile of the Agronomist to be able to introduce the necessary changes in the dynamics of the formation process from Professional Physical Education. RESUMEN: Para la formación del profesional que necesita la sociedad en este siglo XXI, se hace énfasis en un profesional que se distinga como persona y como ser reflexivo en su preparación técnica, cultural y física, es por ello que en este artículo se centra la atención en la Educación Física como condición esencial para lograr la formación integral del profesional de Ingeniería Agrónoma. En estudios diagnósticos realizados en la Universidad de las Tunas, se identificó insuficiencias en la formación integral del profesional desde la Educación Física, al no profundizar en la dinámica de dicho proceso que aún se concibe con un enfoque tradicional, lo que evidencia que no se aprovechan al máximo las potencialidades de la Educación Física en el proceso de formación del Ingeniero Agrónomo. Es por ello que se considera necesario continuar profundizando en las

Diazo compounds and N-tosylhydrazones: novel cross-coupling partners in transition-metal-catalyzed reactions.

Science.gov (United States)

Xiao, Qing; Zhang, Yan; Wang, Jianbo

2013-02-19

Transition-metal-catalyzed carbene transformations and cross-couplings represent two major reaction types in organometallic chemistry and organic synthesis. However, for a long period of time, these two important areas have evolved separately, with essentially no overlap or integration. Thus, an intriguing question has emerged: can cross-coupling and metal carbene transformations be merged into a single reaction cycle? Such a combination could facilitate the development of novel carbon-carbon bond-forming methodologies. Although this concept was first explored about 10 years ago, rapid developments inthis area have been achieved recently. Palladium catalysts can be used to couple diazo compounds with a wide variety of organic halides. Under oxidative coupling conditions, diazo compounds can also react with arylboronic acids and terminal alkynes. Both of these coupling reactions form carbon-carbon double bonds. As the key step in these catalytic processes, Pd carbene migratory insertion plays a vital role in merging the elementary steps of Pd intermediates, leading to novel carbon-carbon bond formations. Because the diazo substrates can be generated in situ from N-tosylhydrazones in the presence of base, the N-tosylhydrazones can be used as reaction partners, making this type of cross-coupling reaction practical in organic synthesis. N-Tosylhydrazones are easily derived from the corresponding aldehydes or ketones. The Pd-catalyzed cross-coupling of N-tosylhydrazones is considered a complementary reaction to the classic Shapiro reaction for converting carbonyl functionalities into carbon-carbon double bonds. It can also serve as an alternative approach for the Pd-catalyzed cross-coupling of carbonyl compounds, which is usually achieved via triflates. The combination of carbene formation and cross-coupling in a single catalytic cycle is not limited to Pd-catalyzed reactions. Recent studies of Cu-, Rh-, Ni-, and Co-catalyzed cross-coupling reactions with diazo

Interaction of amines with native aluminium oxide layers in non-aqueous environment: Application to the understanding of the formation of epoxy-amine/metal interphases

International Nuclear Information System (INIS)

Mercier, D.; Rouchaud, J.-C.; Barthes-Labrousse, M.-G.

2008-01-01

Interaction of propylamine (PA), 1,2-diaminoethane (DAE) or 3-aminomethyl-3,5,5-trimethylcyclohexylamine (isophorone diamine, IPDA) with native aluminium oxide layers in non-aqueous environment has been studied using time-resolved inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS). The formation of several surface complexes has been evidenced. Monodentate and bidentate metal-bond surface complexes (MBSC) result from interactions between the amine terminations of the molecule and aluminium cations by donation of the N lone electron pair to the metal ion (Lewis-like mechanism leading to O-Al...N bonds). Monodentate and bidentate hydrogen-bond surface complexes (HBSC) are due to interaction of the amino group with surface hydroxyl groups by protonation of the amine termination (Bronsted-like mechanism leading to the formation of Al-OH...N bonds) or interaction with carbonaceous contamination (C x O y H z ...N bonds). Diamines can also form mixed complexes with one amino group forming an O-Al...N bond and the other group forming an Al-OH...N or C x O y H z ...N bond. Al-OH...N and C x O y H z ...N bonds are less stable under vacuum than O-Al...N bonds, leading to partial desorption of the DAE molecules in vacuum and modification of the interaction modes. Only DAE and IPDA can lead to partial dissolution of the aluminium native (hydr)oxide films. A detailed mechanism of dissolution has been proposed based on the formation of mononuclear bidentate (chelate) MBSC by ligand exchange between the terminal η 1 -OH and bridged μ 2 -OH surface sites and the amino terminations of the molecule. The detachment of this complex from the surface is likely to be the precursor step to the formation of the interphase in epoxy-amine/metal systems

Trifurcatia flabellata n. gen. n. sp., a putative monocotyledon angiosperm from the Lower Cretaceous Crato Formation (Brazil

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B. Mohr

2002-01-01

Full Text Available The Lower Cretaceous Crato Formation (northeast Brazil contains plant remains, here described as Trifurcatia flabellata n. gen. and n. sp., consisting of shoot fragments with jointed trifurcate axes, each axis bearing a single amplexicaul serrate leaf at the apex. The leaves show a flabellate acrodromous to parallelodromous venation pattern, with several primary, secondary and higher order cross-veins. This very unique fossil taxon shares many characters with monocots. However, this fossil taxon exhibits additional features which point to a partly reduced, and specialized plant, which probably enabled this plant to grow in (seasonally dry, even salty environments. In der unterkretazischen Cratoformation (Nordostbrasilien sind Pflanzenfossilien erhalten, die hier als Trifurcatia flabellata n. gen. n. sp. beschrieben werden. Sie bestehen aus trifurcaten Achsen, mit einem apikalen amplexicaulen fächerförmigen serraten Blatt. Diese Blätter zeigen eine flabellate bis acrodrome-paralellodrome Aderung mit Haupt- und Nebenadern und transversale Adern 3. Ordnung. Diese Merkmale sind typisch für Monocotyledone. Allerdings weist dieses Taxon einige Merkmale auf, die weder bei rezenten noch fossilen Monocotyledonen beobachtet werden. Sie müssen als besondere Anpassungen an einen (saisonal trockenen und vielleicht übersalzenen Lebensraum dieser Pflanze interpretiert werden. doi:10.1002/mmng.20020050121

Characterization of glutamate-induced formation of N- acylphosphatidylethanolamine and N-acylethanolamine in cultured neocortical neurons

DEFF Research Database (Denmark)

Hansen, Harald S.; Lauritzen, L.; Strand, A.M.

1997-01-01

) assay). The increase in NAPE and NAE could be detected earlier than the neuronal death. Neither cyclic AMP, cyclic GMP, nitric oxide, protein kinase C, nor peroxidation appears to be involved in the formation of NAPE and NAE, as assessed by the use of different pharmacological agents. Exposure to 5 m...... receptors as seen by the inhibitory action of the NMDA-selective receptor antagonists D(-)-2-amino-5-phosphonovalerate and N- (1-(2-thienyl)-cyclohexyl)piperidine and the lack of effect of the a-amino- 3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate-receptor antagonist 6-cyano-7-nitro......-quinoxaline-2,3-dione (CNQX). In 6-day-old cultures, exposure to NMDA (100 µM for 24 h) induced a linear increase in the formation of NAPE and NAE as well as a 40-50% neuronal death, as measured by a decrease in cellular formazan formation [3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT...

Preparation of catalytically active, covalent α-polylysine-enzyme conjugates via UV/vis-quantifiable bis-aryl hydrazone bond formation.

Science.gov (United States)

Grotzky, Andrea; Manaka, Yuichi; Kojima, Taisuke; Walde, Peter

2011-01-10

Covalent UV/vis-quantifiable bis-aryl hydrazone bond formation was investigated for the preparation of conjugates between α-poly-d-lysine (PDL) and either α-chymotrypsin (α-CT) or horseradish peroxidase (HRP). PDL and the enzymes were first modified via free amino groups with the linking reagents succinimidyl 6-hydrazinonicotinate acetone hydrazone (S-HyNic, at pH 7.6) and succinimidyl 4-formylbenzoate (S-4FB, at pH 7.2), respectively. The modified PDL and enzymes were then conjugated at pH 4.7, whereby polymer chains carrying several enzymes were obtained. Kinetics of the bis-aryl hydrazone bond formation was investigated spectrophotometrically at 354 nm. Retention of the enzymatic activity after conjugate formation was confirmed by using the substrates N-succinimidyl-l-Ala-l-Ala-l-Pro-l-Phe-p-nitroanilide (for α-CT) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS, for HRP). Thus, not only a mild and efficient preparation and convenient quantification of a conjugate between the polycationic α-polylysine and enzymes could be shown, but also the complete preservation of the enzymatic activity.

properties of Cr(C,N) hard coatings deposited in Ar-C2H2-N2 plasma

International Nuclear Information System (INIS)

Macek, M.; Cekada, M.; Kek, D.; Panjan, P.

2002-01-01

Mechanical properties, microstructure and the average chemical composition of Cr(C,N) hard coatings deposited in Ar-C 2 H 2 -N 2 plasma strongly depends on the partial pressure of the reactive gases (N 2 , C 2 H 2 ) and on the type of the deposition equipment. In this study we report on the properties of Cr(C,N) hard coatings deposited by means of the triode ion plating in the BAI 730 apparatus and those prepared by sputter deposition in Balzers Sputron in the pressure range from 0.12 Pa (pure Ar) up to 0.35 Pa with different ratios (0-100%) between C 2 H 2 and N 2 . At first mechanical properties (microhardness and adhesion) of coatings were analyzed on the common way. Internal stress was measured by the radius of substrate curvature. Chemical composition of coatings was analyzed by means of AES while the Raman and XPS spectroscopy was used to determined the nature of carbon bonding in the Cr(C,N) films. Microstructure was determined by XRD as well as by means of TEM and TED. Chemical state of various elements in the coating has been studied by XPS. The ratio of the carbide bond (C-Cr) against the C-C and C-H bonds was calculated. The existence of the graphite phase in some Cr(C,N) coatings was confirmed by Raman spectroscopy. (Authors)

N,N-Diethylanilinium 2,4-dioxo-5-(2,4,6-trinitrophenyl-1,2,3,4-tetrahydropyrimidin-6-olate

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Manickam Buvaneswari

2011-12-01

Full Text Available In the crystal structure of the title molecular salt, C10H16N+·C10H4N5O9−, the components are linked through a N—H...O hydrogen bonds. R22(8 ring motifs are formed between inversion-related barbiturate residues. Two intramoleculer N—H...O hydrogen bonds are observed in the anion. The dihedral angle between 2,4,6-trinitrophenyl and barbiturate rings is 53.6 (2°. The N,N-diethylamine substituent is disordered and was modeled as two geometrically equivalent conformers with occupancies of 0.737 (2 and 0.273 (2.

Formation and hydrolysis of amide bonds by lipase A from Candida antarctica; exceptional features.

Science.gov (United States)

Liljeblad, Arto; Kallio, Pauli; Vainio, Marita; Niemi, Jarmo; Kanerva, Liisa T

2010-02-21

Various commercial lyophilized and immobilized preparations of lipase A from Candida antarctica (CAL-A) were studied for their ability to catalyze the hydrolysis of amide bonds in N-acylated alpha-amino acids, 3-butanamidobutanoic acid (beta-amino acid) and its ethyl ester. The activity toward amide bonds is highly untypical of lipases, despite the close mechanistic analogy to amidases which normally catalyze the corresponding reactions. Most CAL-A preparations cleaved amide bonds of various substrates with high enantioselectivity, although high variations in substrate selectivity and catalytic rates were detected. The possible role of contaminant protein species on the hydrolytic activity toward these bonds was studied by fractionation and analysis of the commercial lyophilized preparation of CAL-A (Cat#ICR-112, Codexis). In addition to minor impurities, two equally abundant proteins were detected, migrating on SDS-PAGE a few kDa apart around the calculated size of CAL-A. Based on peptide fragment analysis and sequence comparison both bands shared substantial sequence coverage with CAL-A. However, peptides at the C-terminal end constituting a motile domain described as an active-site flap were not identified in the smaller fragment. Separated gel filtration fractions of the two forms of CAL-A both catalyzed the amide bond hydrolysis of ethyl 3-butanamidobutanoate as well as the N-acylation of methyl pipecolinate. Hydrolytic activity towards N-acetylmethionine was, however, solely confined to the fractions containing the truncated form of CAL-A. These fractions were also found to contain a trace enzyme impurity identified in sequence analysis as a serine carboxypeptidase. The possible role of catalytic impurities versus the function of CAL-A in amide bond hydrolysis is further discussed in the paper.

Oxo-group-14-element bond formation in binuclear uranium(V) pacman complexes

International Nuclear Information System (INIS)

Jones, Guy M.; Arnold, Polly L.; Love, Jason B.

2013-01-01

Simple and versatile routes to the functionalization of uranyl-derived U"V-oxo groups are presented. The oxo-lithiated, binuclear uranium(V)-oxo complexes [{(py)_3LiOUO}_2(L)] and [{(py)_3LiOUO}(OUOSiMe_3)(L)] were prepared by the direct combination of the uranyl(VI) silylamide ''ate'' complex [Li(py)_2][(OUO)(N'')_3](N''=N(SiMe_3)_2) with the polypyrrolic macrocycle H_4L or the mononuclear uranyl (VI) Pacman complex [UO_2(py)(H_2L)], respectively. These oxo-metalated complexes display distinct U-O single and multiple bonding patterns and an axial/equatorial arrangement of oxo ligands. Their ready availability allows the direct functionalization of the uranyl oxo group leading to the binuclear uranium(V) oxo-stannylated complexes [{(R_3Sn)OUO}_2(L)] (R=nBu, Ph), which represent rare examples of mixed uranium/tin complexes. Also, uranium-oxo-group exchange occurred in reactions with [TiCl(OiPr)_3] to form U-O-C bonds [{(py)_3LiOUO}(OUOiPr)(L)] and [(iPrOUO)_2(L)]. Overall, these represent the first family of uranium(V) complexes that are oxo-functionalised by Group 14 elements. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Mechanism of CO 2 Fixation by Ir I -X Bonds (X = OH, OR, N, C)

KAUST Repository

Vummaleti, Sai V. C.; Talarico, Giovanni; Nolan, Steven P.; Cavallo, Luigi; Poater, Albert

2015-01-01

Density functional theory calculations have been used to investigate the CO2 fixation mechanism proposed by Nolan et al. for the IrI complex [Ir(cod)(IiPr)(OH)] (1; cod = 1,5-cyclooctadiene; IiPr = 1,3-diisopropylimidazol-2-ylidene) and its derivatives. For 1, our results suggest that CO2 insertion is the rate-limiting step rather than the dimerization step. Additionally, in agreement with the experimental results, our results show that CO2 insertion into the Ir-OR1 (R1 = H, methyl, and phenyl) and Ir-N bonds is kinetically facile, and the calculated activation energies span a range of only 12.0-23.0 kcal/mol. Substantially higher values (35.0-50.0 kcal/mol) are reported for analogous Ir-C bonds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanism of CO 2 Fixation by Ir I -X Bonds (X = OH, OR, N, C)

KAUST Repository

Vummaleti, Sai V. C.

2015-09-08

Density functional theory calculations have been used to investigate the CO2 fixation mechanism proposed by Nolan et al. for the IrI complex [Ir(cod)(IiPr)(OH)] (1; cod = 1,5-cyclooctadiene; IiPr = 1,3-diisopropylimidazol-2-ylidene) and its derivatives. For 1, our results suggest that CO2 insertion is the rate-limiting step rather than the dimerization step. Additionally, in agreement with the experimental results, our results show that CO2 insertion into the Ir-OR1 (R1 = H, methyl, and phenyl) and Ir-N bonds is kinetically facile, and the calculated activation energies span a range of only 12.0-23.0 kcal/mol. Substantially higher values (35.0-50.0 kcal/mol) are reported for analogous Ir-C bonds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dichlorido[N-(N,N-dimethylcarbamimidoyl-N′,N′,4-trimethylbenzohydrazonamide]platinum(II nitromethane hemisolvate

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Dmitrii S. Bolotin

2014-04-01

Full Text Available In the title compound, [PtCl2(C13H21N5]·0.5CH3NO2, the PtII atom is coordinated in a slightly distorted square-planar geometry by two Cl atoms and two N atoms of the bidentate ligand. The (1,3,5-triazapentadienePtII metalla ring is slightly bent and does not conjugate with the aromatic ring. In the crystal, N—H...Cl hydrogen bonds link the complex molecules, forming chains along [001]. The nitromethane solvent molecule shows half-occupancy and is disordered over two sets of sites about an inversion centre.

Stoichiometry behavior of TaN, TaCN and TaC thin films produced by magnetron sputtering

International Nuclear Information System (INIS)

Vargas, M.; Castillo, H.A.; Restrepo-Parra, E.; De La Cruz, W.

2013-01-01

Thin films were synthesized in a magnetron sputtering system using a target of Ta with 99.99% purity and silicon substrates (1 1 1). The gases used for the film growth were (Ar + N 2 ), (Ar + CH 4 + N 2 ) and (Ar + CH 4 ) mixtures for TaN, TaCN and TaC, respectively. The substrate temperature increased from room temperature to 500 °C. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS), revealing Ta-N, Ta-C-N, Ta-C and C-C bonds. Moreover, the crystallographic structure was analyzed using X-ray diffraction (XRD), indicating the presence of (1 1 1) and (2 0 0) planes belonging to a face-centered cubic structure. The stoichiometry variation dependence on the CH 4 and N 2 flow was analyzed, and the influence of the substrate temperature on the coatings was investigated. Finally, scanning electron microscopy (SEM) was used to determine the evolution on the grain formation in the coatings as the substrate temperature increased.

Stoichiometry behavior of TaN, TaCN and TaC thin films produced by magnetron sputtering

Energy Technology Data Exchange (ETDEWEB)

Vargas, M. [Centro de Nanociencia y Nanotecnología, Universidad Nacional Autónoma de México, A.P. 2681, C.P. 22860, Ensenada, B.C. (Mexico); Castillo, H.A. [Centro de Enseñanza Técnica y Superior, CETYS Universidad, Campus Tijuana, Tijuana, B.C. (Mexico); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [Universidad Nacional de Colombia Sede Medellín Colombia, Facultad de Minas, Manizales (Colombia); De La Cruz, W. [Centro de Nanociencia y Nanotecnología, Universidad Nacional Autónoma de México, A.P. 2681, C.P. 22860, Ensenada, B.C. (Mexico)

2013-08-15

Thin films were synthesized in a magnetron sputtering system using a target of Ta with 99.99% purity and silicon substrates (1 1 1). The gases used for the film growth were (Ar + N{sub 2}), (Ar + CH{sub 4} + N{sub 2}) and (Ar + CH{sub 4}) mixtures for TaN, TaCN and TaC, respectively. The substrate temperature increased from room temperature to 500 °C. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS), revealing Ta-N, Ta-C-N, Ta-C and C-C bonds. Moreover, the crystallographic structure was analyzed using X-ray diffraction (XRD), indicating the presence of (1 1 1) and (2 0 0) planes belonging to a face-centered cubic structure. The stoichiometry variation dependence on the CH{sub 4} and N{sub 2} flow was analyzed, and the influence of the substrate temperature on the coatings was investigated. Finally, scanning electron microscopy (SEM) was used to determine the evolution on the grain formation in the coatings as the substrate temperature increased.