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O. A. Ivashkevich Vadim E. Matulis Vitalii E. Matulis P. N. Gaponik 《Chemistry of Heterocyclic Compounds》2005,41(4):456-465
Calculations have been carried out of the total Mulliken charges on carbon and nitrogen atoms, the relative stability, and equilibrium populations of the s-cis(R) and s-trans(R) conformers of a series of 1-vinyl-5R-tetrazoles (R = H, Me, n-Bu, tert-Bu, Ph, NH2, I, CF3, NO2) by the ab initio MP2/6-31G** method. Out-of-plane structures correspond to the stable s-cis(R) conformer, and the deviation from planarity grows regularly with an increase in the bulk of the substituent. The proportion of s-trans(R) conformation increases in the same series and reaches 100% for R = tert-C4H9. The data of quantum-chemical calculations are in agreement with the results of investigations of the spatial structure of 1-vinyl-5R-tetrazoles by 1H and 13C NMR methods. Values of the total energies of the corresponding homodesmotic reactions were calculated to assess the effect of the nature of the substituent in position 5 of the tetrazole ring on the size of the conjugation energy in planar s-trans(R) conformations of the compounds investigated. The quantum-chemical calculations carried out show that the conjugation energy decreases regularly according to the increase in electron-withdrawing properties of the substituent in position 5 of the ring.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 537–548, April, 2005. 相似文献
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The potential functions of internal rotation around the Csp2-Se bond in selenoanisole were ob- tained by quantum-chemical calculations in the approximations HF/3-21G(d), HF/6-31G(d), MP2(f)/6-31G(d), and B3LYP/6-31G(d). The calculations were performed in the range of variation of the torsion angle (between the planes of the benzene ring and Csp2-Se-Csp3 bonds) from 0° to 90° with 15° step. The energy minimum is in the region of the orthogonal conformation ( 90°), and the energy maximum, in the region of the planar form ( 0°). The rotation barriers (kJ mol-
1) are as follows: HF/3-21G(d), 9.20; HF/6-31G(d), 13.13; MP2(f)/6-31G(d), 10.25; and B3LYP/6-31G(d), 6.41. The geometric parameters, Koopmans ionization potentials, and dipole moments are given. The energies, degrees of hybridization, populations of the lone electron pairs of Se, energies of their interaction with the antibonding * orbitals of the benzene ring, and electron density distributions were determined in terms of the natural bond orbital approach. 相似文献
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Abstract Quantum-chemical calculations of the electronic structure of 1,3-, 1,4- and 2,3-diphospha-1,3-butadienes (DPB) and their derivatives with different substituents were performed. The MNDO method was used to describe the electronic structure of phosphaalkenes. The frontier orbitals of all unsubstituted DPB are of π-type. The highest occupied molecular orbital (HOMO) is delocalized through both double phosphorus-carbon bonds; the next occupied MO is a combination of two phosphorus lone pairs (n-MO). The HOMO of 2,3-DPB differs markedly from those of 1,3- and 1,4-isomers: the contributions of phosphorus and carbon p-orbitals are nearly equal, and the energy gap between HOMO and n-MO is very small (0.008 eV). The introduction of the electron-withdrawing substituents results in the reverse order of these MO's. In contrast with 1,3- and 1,4-isomers, the double bonds of 2,3-DPB are almost non-polar. Effect of substituents upon the electron density distribution are considered. The results indicate that orbitally controlled 1,4-additions should be characteristic for the derivatives of 1,3- and 1,4-DPB, similar to 1,3-butadiene. In case of 2,3-DPB, tendency to 1,4-addition should be lower; for its derivatives the reaction type depends greatly upon the electronic effects of substituents. In particular, reactions involving phosphorus lone pairs should be typical for the derivatives of 2,3-DPB with electron-withdrawing substituents. 相似文献
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Quantum-Chemical Study of the Equilibrium Geometry and Electronic Structure of the Defensin Molecule
Rogachevskii I. V. Shchegolev B. F. MacKey M. L. Krylov B. V. Baranovskii V. I. 《Russian Journal of General Chemistry》2002,72(6):976-978
The molecular geometry of rabbit NP-1 defensin is fully optimized by means of molecular mechanics and MNDO methods. Atomic charges are calculated, and an estimate for the dipole moment of the molecule is obtained ( 4.0 D). The possible mechanism of defensin-receptor interactions is discussed. 相似文献
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本文通过酯交换反应合成了一系列脂肪族聚丁二酸酯,对他们的结构和性能作了表征。发现聚酯存在多晶现象,其熔点有奇偶性变化规律。探索了由此系列聚酯与高氯酸锂形成的固体电解质的结构和离子导电性。无机盐的加入提高了电解质的玻璃化温度但降低了聚酯的熔点及结晶度。聚酯电解质的晶体类似于聚酯,其无机盐主要溶解于聚酯的无定形区域。聚酯系列电解质的导电率也有偶奇效应,与熔点变化相反;熔点高的电解质导电率低,熔点低的电解质导电率高。电解质的导电率随温度改变而变化,在室温下电解质的导电率可达10~(-6)s/cm。高分子链上侧基的引入将大大降低电解质的导电性。 相似文献
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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
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Ivashkevich O. A. Matulis Vad. E. Matulis Vit. E. Gaponik P. N. 《Russian Journal of General Chemistry》2004,74(3):409-413
The total Mulliken charges on the C and N atoms, populations of the S-trans-(N1) conformers, and rotation barriers in the molecules of 2-vinyl-5-R-tetrazoles (R = H, CH3, CH = CH2, C6H5, CH2Cl, CF3) were calculated ab initio (HF/6-31G**, MP2/6-31G**). The results were compared with the 1H and 13C NMR data for these compounds. 相似文献
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Enyashin A. N. Makurin Yu. N. Ivanovskii A. L. 《Theoretical and Experimental Chemistry》2004,40(2):71-76
Atomic models are proposed and quantum-chemical modelling is undertaken for hypothetical graphyne-like fullerenes of boron nitride. The electronic structure and interatomic interactions are discussed for the case of the B16N16 and B48N48 molecules. The proposed polyhedral boron–nitrogen molecules, having stable dielectric characteristics and highly porous structure, may be of interest for the creation a family of new intercalated nanomaterials based on these nanoparticles. 相似文献
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通过对LixAlx-1Ge3-x(PO4)3(x=1.1~1.9)锂离子导电玻璃的差示量热扫描(DSC)数据,结合XRD及其Rietveld精修、FESEM和交流阻抗等测试方法,研究了该系微晶玻璃的物相组成、主晶相晶胞参数变化情况、微观结构形貌、锂离子电导率和电化学窗口等。结果表明:LixAlx-1Ge3-x(PO4)3(x=1.1~1.9)锂离子导电微晶玻璃析出导电主晶相为LiGe2(PO4)3。当x=1.5时,由于导电主晶相LiGe2(PO4)3晶粒充分长大、分布均匀,晶界清晰,LAGP导电微晶玻璃的室温电导率最高(可达5.3×10-4 S.cm-1),电化学窗口为7.2V,可以满足全固态锂离子电池对电解质高室温电导率和宽电化学窗口的应用要求。 相似文献
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M. V. Ryzhkov T. A. Denisova V. G. Zubkov L. G. Maksimova 《Journal of Structural Chemistry》2000,41(6):927-933
This paper presents a cluster–DV study of the electronic structure of a large fragment of the crystal lattice of a new compound Pb2Fe(CN)6 having a trigonal structure. The electronic energy spectrum and electron density distribution between Fe–C, C–N, and Pb–N are discussed. 相似文献
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Ivanovskaya V. V. Enyashin A. N. Sofronov A. A. Makurin Yu. N. Medvedeva N. I. Ivanovskii A. L. 《Theoretical and Experimental Chemistry》2003,39(1):1-8
A quantum-chemical model of multiwalled nanotubes of magnesium diboride was produced. The electronic structure and the nature of the interatomic bonds in the multiwalled nanotubes were studied in relation to the diameter and the number of Mg-B2 layers: (6,6) (3,3)@(6,6) (6,6)@(12,12) (3,3)@(6,6)@(12,12). Possible methods for the production of diboride nanotubes are discussed. Features of the electronic states in composite nanotubular structures based on the diborides of s and p metals are examined for the first time as illustrated by the (6,6)AlB2(12,12)MgB2 multiwalled nanotube. 相似文献
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V. M. Tapilin 《Journal of Structural Chemistry》2003,44(4):531-537
A numerical integration method is suggested for calculating Hamiltonian matrix elements in a basis of functions with polynomial tails with allowance for discontinuities of higher-order derivatives of the basis function within the domain of integration. The method is tested by calculating matrix elements for a copper crystal. The results for the overlap matrix elements are presented demonstrating efficiency of the method. 相似文献
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O. A. Ivashkevich Vad. E. Matulis Vit. E. Matulis P. N. Gaponik 《Russian Journal of General Chemistry》2004,74(1):134-140
The total Mulliken charges on the carbon atoms of the vinyl group, populations of S-trans-(N1)conformers, and internal rotation energies were calculated ab initio (HF/6-31G**, MP2/6-31G**, and MP2/6-31G**//AM1) for a series of 2R-5-vinyltetrazoles (R = CH3, C2H5, i-C3H7, t-C4H9, C6H5). The calculation results were compared to the available experimental data. 相似文献
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采用密度泛函(DFT)方法在6-31g(d)水平下研究了聚吡咯和聚吡咯并[3,4-c]吡咯, 以及它们的单体和低聚物的电子结构. 对中心键的键长、电荷密度以及Weberg键级的研究表明, 随着主链聚合度的增加, 其共轭性增强. 对聚合物还进行了能带结构和态密度分析. 结果发现, 在3位聚合的并环化合物具有最优的导电性能, 其能隙仅有0.25 eV, 可以作为潜在的导电聚合物材料. 相似文献
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有机共轭分子电子结构的计算 总被引:1,自引:0,他引:1
根据分子结构的共振理论,为PPP方法选择了一套合理的经验参数。应用CNDO/2方法和PPP方法计算了有机共轭分子的电子能级、最低三重态激发能及增感染料分子的半波电位。 相似文献