四唑及其衍生物的理论研究 2: 氯代四唑负离子的从头算

用从头计算法, 取6-21G基组, 在MP2水平上, 计算研究了1H-和2H-四唑一氯取代物三种负离子的全优化几何构型和电子结构, 比较讨论了它们的芳香性和稳定性。发现三者均取平面构型, 其芳香性和稳定性次序为: 5-氯四唑负离子>2-氯四唑负离子>1-氯四唑负离子。预示了形成金属配合物时5-氯四唑作为配体的重要性和配位方式。     

四唑及其衍生物的理论研究：II.一氯代四唑负离子的从头算

用从头计算法，取６－３１Ｇ基组，在ＭＰ２水平上，计算研究了１Ｈ－和２Ｈ－四唑一氯取代物三种负离子的全优化几何构型和电子结构，比较讨论了它们的芳香性和稳定性，发现三者均取平面构型，其芳香性和稳定性次序为５－氯四唑负离子〉２－氯四唑负离子〉１－氯四唑负离子，预示了形成金属配俣物时５－氯四唑作为配体的重要性和配位方式。     

四唑及其衍生物的理论研究Ⅷ: 硝氨四唑衍生物的从头算

运用从头计算法,在HF/6-31G^*水平下,全优化计算了7种硝氨四唑衍生物的分子几何和电子结构。结果表明,标题物的四唑环近似为平面构型;2H式中性分子的芳香性大于相应的1H式异构体。5-硝氨-1H四唑分子内氢键使硝氨基与环共面;其余标题物中硝氨基与环垂直。不同水平下的总能量计算表明,标题物中电子相关效应显著;1H式中性分子较2H式的能量高,5-硝氨四唑负离子在三个负离子中最稳定。根据电荷分布阐明了四唑环质子化位置和标题物与金属的配位方式。此外还计算了各标题物的红外光谱及热力学性质。     

四唑及其衍生物的理论研究Ⅷ: 硝氨四唑衍生物的从头算

运用从头计算法,在HF/6-31G^*水平下,全优化计算了7种硝氨四唑衍生物的分子几何和电子结构。结果表明,标题物的四唑环近似为平面构型;2H式中性分子的芳香性大于相应的1H式异构体。5-硝氨-1H四唑分子内氢键使硝氨基与环共面;其余标题物中硝氨基与环垂直。不同水平下的总能量计算表明,标题物中电子相关效应显著;1H式中性分子较2H式的能量高,5-硝氨四唑负离子在三个负离子中最稳定。根据电荷分布阐明了四唑环质子化位置和标题物与金属的配位方式。此外还计算了各标题物的红外光谱及热力学性质。     

四氰基乙烯-四甲基乙烯体系光诱导电子转移双势阱的从头算研 究

以两态模型为基础,用从头算方法,在DZP[所有原子带极化函数的Dunning(9s,5p)/(3s,2p)]基组水平上对四氰基乙烯与四甲基乙烯间的电子转移进行理论计算。通过孤立给体和受体的几何构型优化,计算了给体的电离能和受体的电子亲和能。计算表明,在光诱导电荷分离之后的返回电子转移处于高放热的Marcus反转区。通过碰撞配合物的结构优化和电荷分离处理,在线性反应坐标近似下得到四甲基乙烯-四氰基乙烯配合物电荷分离反应的双势阱,进而获得反应热,键重组能,以及跃迁能。     

密度泛函理论和从头算方法对四唑负离子的比较研究

运用多种密度泛函理论(DFT)方法和从头算(abinitio)方法研究了四唑负离子的分子几何、电子结构、红外光谱和热力学性质.结果表明,B3LYP-DFT法与MP2-abinitio法计算结果较吻合,故可用于对四唑衍生物及其配合物的系统研究.     

三硝基苯-对位取代苯酚负离子荷移复合物从头算研究

运用G94W量子化学程序,在HF/3-21G基组水平上对三硝基苯-对位取代苯酚(取代基:CH~3O-,CH~3-,Cl-)负离子的电荷转移复合物进行从头计算。把电荷转移复合物看成一个超分子,研究该系列复合物的稳定性、电荷转移及几何构型等规律。计算结果表明,苯酚负离子供电中心O沿一倾角指向三硝基苯中的任意相邻两个硝基之间的C位置上,复合物的稳定性按对位取代苯酚取代基CH~3O-,CH~3-,Cl-的次序减小,与实验规律相一致。计算结果还表明,形成该系列复合物具有明显的电荷转移,其稳定性与电荷转移量有关等。     

Si~2Cl~6分子的内旋转能垒和振动基频的理论研究

用从头算方法HF/6-31G^*^*和密度函方法B3LYP/6-31G^*^*,对Si~2Cl~6分子的平衡几何构型进行优化,优化的结果与实验结果吻合得较好.并用上述两种不同的方法计算Si~2Cl~6分子的内旋转能垒,结果分别为8.786和6.694kJ/mol,其中DFT方法的计算结果与实验结果4.18kJ/mol吻合得较好.对Si~2Cl~6分子的振动基频进行计算.用HF/6-31G^*^*SQM力场所计算的频率理论值与实验值的平均误差为7.3cm^-^1,用B3LYP/6-31G^*^*未标度的力场所计算的频率理论值与实验值的平均误差为6.0cm^-^1.该密度泛函方法(B3LYP/~6-31G^*^*)的理论计算值比用HF/6-31G^*^*标度后的SQM力场计算的频率与实验值(除Si--Si键扭转振动基频之外的11条振动基频)吻合得更好.并给出了Si--Si键扭转振动基频的预测值。     

银硫二元团簇[Ag.(Ag~2S)~n]^+(n=3,4)的从头算研究

用abinitio分子轨道限制性Hartree-Fock(RHF)和密度泛函(DFT)方法对银硫二元团簇[Ag.(AgS)~n]^+(n=3,4)的结构进行研究.结果表明,具有环状结构的团簇最为稳定.得到了相应的几何构型和电子结构,并且对这两种团簇可为硫敏化中心自由电子深陷阱的存在形式作出合理解释。     

TinC2n(n=1-6)分子簇的量子化学从头算研究

用量子化学从头计算方法研究了TinC2n(n=1-6)分子簇的几何构型和电子结构。这些TinC2n分子簇以TiC2为结构单元, 通过C-C或Ti-C键进一步连接而逐渐长大。研究结果可以较好地解释实验现象, 并说明Metcars的形成机理。     

Theoretical study on tetrazole and its derivatives (3) MP2 and thermodynamic calculations of amino derivatives of tetrazole

Fully optimized geometries and electronic structures of amino derivatives of tetrazole are obtained at MP2/6-31G* level. The tetrazole rings are planar and aromatic for all the amino derivatives of tetrazole. The amino group is not co-planar with the ring and its conformation is mainly determined by the lone pair electronic repulsion between the substituent and the ring. N(4) atom is more negatively charged and is the most probable coordination site. The energy gaps between LUMOs and HOMOs of 2H-aminotetrazoles and C-aminotetrazole neutrals are smaller than those of the corresponding 1H-isomers and N-aminotetrazole neutrals respectively. The IR frequencies, thermodynamic properties and temperature-dependent functions for heat capacities in the form (a bT cT2) in the 300-1000K range are reported.     

Theoretical Study on Tetrazole and its Derivatives (5) Ab Initio Study on Nitro Derivatives of Tetrazole

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Ab initio study of the transition-metal carbene cations

The geometries and bonding characteristics of the first-row transition-metal carbene cations MCH_2~ were investigated by ab initio molecular orbital theory (HF/LANL2DZ). All of MCH_2~ are coplanar. In the closed shell structures the C bonds to M with double bonds; while in the open shell structures the partial double bonds are formed, because one of the σ and π orbitals is singly occupied. It is mainly the π-type overlap between the 2p_x orbital of C and 4p_x, 3d_(xz), orbitals of M~ that forms the π orbitals. The dissociation energies of C—M bond appear in periodic trend from Sc to Cu. Most of the calculated bond dissociation energies are close to the experimental ones.     

2-苯基苯并咪唑衍生物非线性光学性质的从头算研究

采用HF／6-31G^*方法优化分子构型，在此基础上用CPHF方法系统地研究了多种基团取代的2-苯基苯并咪唑衍生物的二阶非线性光学系数βvec，并对βvdc的影响因素进行了探讨，为进一步设计综合性能优良的有机非线性光学材料提供理论指导．     

Geometrical consequences of resonance-assisted intramolecular hydrogen-bond formation from Ab initio MO calculations on 2-nitroresorcinol

Ab initio orbital calculations on phenol, nitrobenzene, and 2-nitroresorcinol have been performed with the GAUSSIAN 92 series of programs. Initial RHF/6-31G^* and RHF/6-31G^** optimizations were followed by second-order MØller-Plesset MP2(FC)/6-31G^* optimizations. The general geometrical features of these molecules, and, in particular, the characteristic changes as going from phenol to 2-nitroresorcinol and from nitrobenzene to 2-nitroresorcinol are in good agreement with recent gas-phase electron diffraction studies and with the notion of resonance-assisted intramolecular hydrogen-bond formation in 2-nitroresorcinol.     

Ab initio study on structures and stabilities of OLi n hyperlithiated compounds

The geometries of hyperlithiated compounds OLi_n were optimized by means of HF, MP2 and DFT methods with 6-31G basis set. The dissociation energies of those optimized stable geometries of OLi_n were calculated, the results are in good agreement with experimental values; and moreover, the dissociation energy of OLi_6 is predicted. In addition, the fundamental vibrational frequencies were also predicted.     

4-甲醛-1-甲基-1-苯基环己硅烷的从头算研究

运用从头计算法，在HF／6－31G水平上，求得4-甲醛-1-甲基-1-苯基环己硅烷的全优化几何构型和电子结构。将从头算结果与经典电子理论以及AM1和PM3半经验计算结果进行了比较和评估。     

Theoretical study of XCN− (XF,Cl) anions

Geometrical parameters, vibrational frequencies, zero‐point energy, dipole moment, NBO atomic charges of FCN^?, ClCN^? and their isomers, and the isomerization energy of FCN^? and ClCN^? are studied in detail using the ab initio MP2, CCSD, CCSD(T), and density functional B3LYP methods. The results are compared with the existing data reported using various theoretical methods in conjunction with different basis sets. The effect of electron correlation on the structural properties of these molecular anions is discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Ab initio study of the unimolecular decomposition of 2‐butenenitrile: Molecular elimination channels

Ab initio molecular orbital calculations have been performed for the unimolecular decomposition of 2‐butenenitrile (CH₃CH?CHCN), especially for HCN and H₂ molecular elimination channels. Structures and energies of the reactants, products, and relevant species in the individual reaction pathways were determined by MP2 gradient optimization and MP4 CCSD(T) single‐point energy calculations. Direct 1,1 and 1,2 molecular eliminations and H or CN migration followed by elimination channels were identified. Dissociation rates for the individual reaction pathways were calculated from vibrational frequencies at the ab initio transition state geometries by employing Rice–Ramsperger–Kassel–Marcus theory, from which channel branching ratios were determined. It was concluded that the most important reaction channel should be the direct 1,1 three‐center molecular elimination of HCN. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007