A comparative quantum-chemical analysis of electronic structures and spectroscopic parameters of cycloalkanes and cyclopolysilanes

A comparative quantum-chemical analysis of the electronic structures and spectroscopic parameters of the cycloalkanes C₃H₆, C₄H₈, C₅H₁₀, and C₆H₁₂ and their silicon analogs Si₃H₆, Si₄H₈, Si₅H₁₀ and Si₆H₁₂ was performed in the framework of the SCF MO LCAO method in the INDO approximation. Qualitative interpretation of “abnormal” ionization potentials and energies of electronic absorption spectra of cyclopolysilanes has been given. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1105–1108, June, 1997.     

Analysis of the effect of the electronic structure of the Cl atom in complexes of chlorides of group IV elements on Cl NQR frequency and asymmetry parameter

Analysis of changes in ³⁵Cl NQR frequency of complexes MCl₄.L and MCl₄.2L for M = Si, Ge, Sn and Ti was performed. The population of the atomic orbitals was calculated by the quantum chemistry methods PM3 and INDO. The results provided an explanation of the changes in ³⁵Cl NQR frequency and the asymmetry parameter upon complex formation. In the complexes of non-transition elements, a decrease in ³⁵Cl NQR frequency is first of all related to increasing population of p_z orbitals on Cl atoms. In the complexes of Ti, the increase in ³⁵Cl NQR frequency depends on a decrease in the p_π to d_π electron density transfer.     

A Green's function approach to the photoelectron spectrum of bis(π-allyl)nickel[1]

The vertical ionization potentials of bis(-allyl)nickel (see (1) in Fig. 1) are calculated by means of the Green's function approach within a semiempirical INDO extension to the first transition metal series. The computed ionization potentials are in good agreement with an experimentally deduced assignment. In contrast to earlier theoretical and experimental studies, the 7a _u () level is predicted on top of the levels corresponding to the Ni 3d orbitals. Our approach leads to a complete assignment of the PE spectrum of (1) in the outer valence region.     

A theoretical study of electronic excited states of photosynthetic reaction center in Rhodopseudomonas viridis

The electronic singlet vertical excited states of photosynthetic reaction center (PSRC) in Rhodopseudomonas (Rps.) viridis were investigated by ZINDO and INDO/S methods. The effects of the interactions of pigment-pigment and pigment-protein on the electronic excitations were examined. The calculation results showed that the interactions of pigment-pigment and pigment-protein play an important role in reasonably assigning the experimental absorption and circular dichroism (CD) spectra of PSRC in Rps. virids. By comparing the theoretically computed excited states with the experimental absorption and CD spectra, satisfactory assignments of the experimental spectroscopic peaks were achieved.     

双核铁原子簇体系的CI计算

用ＩＮＤＯ／ＣＩ方法研究了含有Ｆｅ－Ｆｅ键的原子簇体系［Ｆｅ２Ｓ２Ｘ４］＾２－（Ｘ＝Ｃｌ，Ｂｒ，Ｉ）的电子光谱及电子结构，对于这些多谱带体系，谱带波数计算值与实验值符合，在谱带的指认分析中，发现了πｄ＾１→πｄ等新的跃迁方式，对跃迁方式作了解释和分类，并讨论了谱带的电荷转移性质，此外，还对体系的化学键等性质进行了分析。     

Waugh-型镍钼杂多酸的量子化学计算

采用半经验INDO法，完成了Waugh-型镍钼杂多酸（NH44）6〔NIMO9O32〕·6H2O的量子化学计算，得到146个成键轨道和78个反键轨道，轨道能级，电荷和键序等数据。通过对这些数据的分析，表明杂多酸分子中端氧和Ni都可能为化学活性中心，各原子轨道在分子轨道中都占有一定比例，其HOMO和LUMO能级皆为负值，其体系具有进一步接受电子的能力。这些结论与实验事实一致。     

二铬四醋酸基簇合物的定域分子轨道研究

利用ＩＮＤＯ自洽场半经验量子化学计算方法和Ｅｄｍｉｓｔｏｎ－Ｒｕｅｄｅｎｂｅｒｇ定域化方法，分别计算了没Ｃｒ－Ｃｒ键长的气相、固相Ｃｒ２（Ｏ２ＣＣＨ３）４分子和沿Ｃｒ－Ｃｒ方向有Ｈ２Ｏ配体的「Ｃｒ２（ＣＯ３）４（Ｈ２Ｏ２）２」＾４－离子的化学键性质，结果表明，Ｃｒ２（Ｏ２ＣＣＨ３）４在气相中存在ｄ四重键，而在固相中则不存在，揭示了四重键长之间的联系，直接给出Ｃｒ－Ｃｒｄ四重键的量子化学图象，并阐明     

On the electronic states of macrocycles of the extended porphyrin family and their coordination compounds

The electronic absorption spectra of Ni, Zn and Mg hemiporphyrazine derivatives are presented and discussed together with theoretical results obtained by INDO/S computations. The absorption spectra of all the metal derivatives show marked red shifts of the lowest energy absorption bands with respect to those of the metal free hemiporphyrazine. The possible explanation that in metal derivatives low lying excited states with a fully conjugated π electron system are present is supported by theoretical computations.     

Theoretical study of the unimolecular decomposition mechanisms of energetic TNAD and TNAZ explosives

Calculation methods based on hybrid Density Functional Theory (DFT) with the basis sets of the B3LYP/6‐31+G(d)//B3LYP/4‐31G(d) method and the differential overlap (INDO) program were used to derive reasonable decomposition mechanisms of 1,4,5,8‐tetranitro‐1,4,5,8‐tetraazadecalin (TNAD) and 1,3,3‐trinitroazetidine (TNAZ) explosives. All possible decomposition species and transition states, including intermediates and products, were identified and their corresponding enthalpy of formation and Gibbs free energy of formation were obtained using polyparametric modification equations. INDO bond energy calculation results reveal the weakest bonding site for reference and determine where cleavage can occur easily. This work is concerned mainly with eliminating HONO (cis or trans form). The activation energy for trans‐form HONO elimination is lower than that of cis‐form HONO elimination in the initial steps of both TNAD and TNAZ decomposition, being 18.5 kJ/mol and 33.3 kJ/mol, respectively. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

四苯基卟啉镍的电子结构及光谱研究

本文用INDO/CI方法计算了中位取代四苯基镍卟啉的电子结构与光谱。分子轨道能级表明平面型和垂直型的基态最高占有π轨道(a_(1w)和a_(2w))与次高占有轨道间有较大的能隙。计算的低激发态跃迁光谱表明,最低能量跃迁Q带和B带计算值与实验值符合较好,但N带与L带计算值偏高。算出的最低(nπ~*)跃迁出现在37000 cm~(-1)左右。