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981.
Sergiy O. Nikitin Rostyslav D. Lampeka Yulian M. Volovenko Gennady V. Palamarchuk Oleg V. Shishkin 《Polyhedron》2010
A series of new 3d-metal complexes have been prepared by the reaction of M(CH3COO)2 (M = Zn(II), Co(II), Ni(II)) and 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-ketopyrrole (HL) in a methanol (3) or a methanol/dmf (1, 2) medium. All the complexes have been studied by elemental analyses, electronic and IR spectroscopies. The zinc(II) complex 1 and the ligand HL have been investigated using the method of 1H NMR-spectroscopy at various temperatures. The disappearance of the signal from one proton of the amino group H(5) in the spectrum of complex 1 confirmed the existence of the ligand in the deprotonated form. According to the data of the 1H NMR-spectroscopy, the ligand HL is coordinated to zinc(II) through the nitrogen atom of the deprotonated amino group and the nitrogen atom of the benzothiazole substituent. These data are in agreement with X-ray structural studies for the ligand HL and the zinc(II) complex 1. 相似文献
982.
We devise a nonlocal correlation energy functional that describes the entire range of dispersion interactions in a seamless fashion using only the electron density as input. The new functional is considerably simpler than its predecessors of a similar type. The functional has a tractable and robust analytic form that lends itself to efficient self-consistent implementation. When paired with an appropriate exchange functional, our nonlocal correlation model yields accurate interaction energies of weakly-bound complexes, not only near the energy minima but also far from equilibrium. Our model exhibits an outstanding precision at predicting equilibrium intermonomer separations in van der Waals complexes. It also gives accurate covalent bond lengths and atomization energies. Hence the functional proposed in this work is a computationally inexpensive electronic structure tool of broad applicability. 相似文献
983.
984.
Sigal-Batikoff I Konovalov O Singh A Berman A 《Langmuir : the ACS journal of surfaces and colloids》2010,26(21):16424-16433
A two-dimensional bio/synthetic hybrid system at the air-solution interface made of a polymerized diacetylene Langmuir film with nucleobase modified headgroups is presented. The polymerized film presents a crystalline array of nucleobases, capable of specific binding of complementary mononucleoside or oligonucleotide sequences. Mixed monolayers of the linear polyconjugated polydiacetylene (PDA) films derivatized with cytosine (10,12-pentacosadiyne-cytidyl, PDC) monomers and alcohol-terminated diacetylene lipid (10,12-pentacosadiynol, PDOH) at a 3:1 ratio (PDC 75%) were compressed and polymerized at the air-water interface with circular polarized light (CPL) or nonpolarized UV light. Here we report a grazing incidence X-ray diffraction (GIXD) investigation of PDC films polymerized to different chirality and hybridized with complementary ssDNA strands. We have demonstrated enantioselective interactions on synthetic structured interfaces produced by Langmuir surface compression followed by polymerization with circular polarized UV light (CPL). The left- and right-CPL polymerized light exhibit the same well-defined crystalline structure. The observed difference between left- and right-CPL polymerized PDC 75% Langmuir films compressed over the complementary mononucleotide guanosine or hybridized with fully complementary ssG(12)T(5) oligonucleotide in the subphase suggests that they are indeed enantiomeric structures, capable of enantioselective binding of their natural ligand, guanosine, solely as a result of surface induced asymmetry in "left" but not in "right" form. This observation may also be related to the intriguing question of chiral selection during the early period of "Origin of Life". We show that achiral compounds, as a result of irradiation with circular polarized light, can organize in chiral surface structures capable of amplification of biopolymer binding of particular handedness. 相似文献
985.
Prof. Dr. Danil N. Dybtsev Maxim P. Yutkin Dr. Denis G. Samsonenko Prof. Dr. Vladimir P. Fedin Dr. Alexey L. Nuzhdin Andrey A. Bezrukov Prof. Konstantin P. Bryliakov Prof. Evgeniy P. Talsi Prof. Rodion V. Belosludov Prof. Hiroshi Mizuseki Prof. Yoshiyuki Kawazoe Dr. Oleg S. Subbotin Vladimir R. Belosludov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(34):10348-10356
Two new, homochiral, porous metal–organic coordination polymers [Zn2(ndc){(R)‐man}(dmf)]?3DMF and [Zn2(bpdc){(R)‐man}(dmf)]?2DMF (ndc=2,6‐naphthalenedicarboxylate; bpdc=4,4′‐biphenyldicarboxylate; man=mandelate; dmf=N,N′‐dimethylformamide) have been synthesized by heating ZnII nitrate, H2ndc or H2bpdc and chiral (R)‐mandelic acid (H2man) in DMF. The colorless crystals were obtained and their structures were established by single‐crystal X‐ray diffraction. These isoreticular structures share the same topological features as the previously reported zinc(II) terephthalate lactate [Zn2(bdc){(S)‐lac}(dmf)]?DMF framework, but have larger pores and opposite absolute configuration of the chiral centers. The enhanced pores size results in differing stereoselective sorption properties: the new metal–organic frameworks effectively and stereoselectively (ee up to 62 %) accommodate bulkier guest molecules (alkyl aryl sulfoxides) than the parent [Zn2(bdc){(S)‐lac}(dmf)]?DMF, while the latter demonstrates decent enantioselectivity toward precursor of chiral anticancer drug sulforaphane, CH3SO(CH2)4OH. The new homochiral porous metal–organic coordination polymers are capable of catalyzing a highly selective oxidation of bulkier sulfides (2‐NaphSMe (2‐C10H7SMe) and PhSCH2Ph) that could not be achieved by the smaller‐pore [Zn2(bdc){(S)‐lac}(dmf)]?DMF. The sorption of different guest molecules (both R and S isomers) into the chiral pores of [Zn2(bdc){(S)‐lac}(dmf)]?DMF was modeled by using ab initio calculations that provided a qualitative explanation for the observed sorption enantioselectivity. The high stereo‐preference is accounted for by the presence of coordinated inner‐pore DMF molecule that forms a weak C? H???O bond between the DMF methyl group and the (S)‐PhSOCH3 sulfinyl group. 相似文献
986.
Lin K Lebedev OI Van Tendeloo G Jacobs PA Pescarmona PP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(45):13509-13518
Porous titanosilicate beads with a diameter of 0.5-1.5 mm (TiSil-HPB-60) were synthesized from a preformed titanosilicate solution with a porous anion-exchange resin as template. The bead format of this material enables its straightforward separation from the reaction mixture in its application as a liquid-phase heterogeneous catalyst. The material displays hierarchical porosity (micro/mesopores) and incipient TS-1 structure building units. The titanium species are predominantly located in tetrahedral framework positions. TiSil-HPB-60 is a highly active catalyst for the epoxidation of cyclohexene with t-butyl hydroperoxide (TBHP) and aqueous H(2)O(2). With both oxidants, TiSil-HPB-60 gave higher epoxide yields than Ti-MCM-41 and TS-1. The improved catalytic performance of TiSil-HPB-60 is mainly ascribed to the large mesopores favoring the diffusion of reagents and products to and from the titanium active sites. The epoxide yield and selectivity could be further improved by silylation of the titanosilicate beads. Importantly, TiSil-HPB-60 is a stable catalyst immune to titanium leaching, and can be easily recovered and reused in successive catalytic cycles without significant loss of activity. Moreover, TiSil-HPB-60 is active and selective in the epoxidation of a wide range of bulky alkenes. 相似文献
987.
The reaction of a peptide featuring a bis(2-sulfanylethyl)amino (SEA) group on its C-terminus with a cysteinyl peptide in water at pH 7 and 37 °C leads to the chemoselective and regioselective formation of a native peptide bond. This method called SEA ligation enriches the native peptide ligation repertoire available to the peptide chemist. Preparation of an innovative solid support which allows the straightforward synthesis of peptide SEA fragments using standard Fmoc/tert-butyl solid phase peptide synthesis procedures is also described. 相似文献
988.
Jonathan Tennyson Peter F. Bernath Alain Campargue Ludovic Daumont Joseph T. Hodges Oleg L. Polyansky Laurence S. Rothman Ann Carine Vandaele Sophie Fally Tibor Furtenbacher Shui-Ming Hu Boris A. Voronin 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(15):2160-1106
This is the second of a series of articles reporting critically evaluated rotational-vibrational line positions, transition intensities, pressure dependences, and energy levels, with associated critically reviewed assignments and uncertainties, for all the main isotopologues of water. This article presents energy levels and line positions of the following singly deuterated isotopologues of water: HD16O, HD17O, and HD18O. The MARVEL (measured active rotational-vibrational energy levels) procedure is used to determine the levels, the lines, and their self-consistent uncertainties for the spectral regions 0-22 708, 0-1674, and 0-12 105 cm−1 for HD16O, HD17O, and HD18O, respectively. For HD16O, 54 740 transitions were analyzed from 76 sources, the lines come from spectra recorded both at room temperature and from hot samples. These lines correspond to 36 690 distinct assignments and 8818 energy levels. For HD17O, only 485 transitions could be analyzed from three sources; the lines correspond to 162 MARVEL energy levels. For HD18O, 8729 transitions were analyzed from 11 sources and these lines correspond to 1864 energy levels. The energy levels are checked against ones determined from accurate variational nuclear motion computations employing exact kinetic energy operators. This comparison shows that the measured transitions account for about 86% of the anticipated absorbance of HD16O at 296 K and that the transitions predicted by the MARVEL energy levels account for essentially all the remaining absorbance. The extensive list of MARVEL lines and levels obtained are given in the Supplementary Material of this article, as well as in a distributed information system applied to water, W@DIS, where they can easily be retrieved. In addition, the transition and energy level information for H217O and H218O, given in the first paper of this series [Tennyson, et al. J Quant Spectr Rad Transfer 2009;110:573-96], has been updated. 相似文献
989.
Alexander P. Kozachenko Oleg V. Shablykin Andrei A. Gakh Eduard B. Rusanov Vladimir S. Brovarets 《Heteroatom Chemistry》2010,21(7):492-498
Easily accessible 2‐aroylamino‐3,3‐dichloroacrylonitriles, when treated successively with ethylenediamine, phosphorus pentasulfide, water, and methyl and benzyl halides, furnish the corresponding derivatives of 4,5,7,8‐tetrahydroimidazo[1,2‐c][1,3]thiazolo[4,5‐e][1,3,2]diazaphosphinine, a novel‐fused heterocycle. The structure of the compounds obtained is unequivocally confirmed by the spectroscopic method and X‐ray diffraction analysis. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:492–498, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20638 相似文献
990.
Conformational flexibility of pyrimidine rings of nucleic acid bases in polar environment: PCM study
The results of calculations of molecular structures of nucleic acid bases in polar environment using Polarized Continuum Model
of solvent combined with the MP2/cc-pvdz level of ab initio theory demonstrate considerable polarization of thymine, cytosine,
and guanine. This phenomenon can be related to considerable contribution of zwitter-ionic resonant forms into total structure
of the studied species. It leads to significant increase (about 30%) of frequencies of the out-of-plane pyrimidine ring vibrations
and is related to considerable decrease of conformational flexibility of heterocycle due to smaller out-of-plane deformability
of pyrimidine ring in zwitter-ionic resonant forms. In the case of adenine, the presence of a polar environment results in
an increase of conformational flexibility of pyrimidine ring. 相似文献