Sn(Ⅱ)-X和Sn(Ⅳ)-X (X=O,S,N,C,P,As,Se,Te,F,Cl,Br,I)键价参数

基于剑桥晶体数据库中同配配合物的Sn(Ⅱ)-X和Sn(Ⅳ)-X (X=O,S,N,C,P,As,Se,Te,F,Cl,Br,I)键长数据,采用键价参数B=0.037 nm拟合得到Sn(Ⅱ)-X和Sn(Ⅳ)-X的键价参数R0,这样拟合的经验参数R0中有一些是首次推出.本文所报道的Sn(Ⅱ)-O键基于B=0.037 nm的R0值(0.1956 nm)可适用于多数Sn(Ⅱ)呈各种配位数时的氧化态指定,而文献报道的B=0.055 nm和R0=0.1859 nm主要对于低配位的情况能取得Sn(Ⅱ)原子价态指定的较好结果.本研究证明,进一步研究键价参数对键价和(BVS)计算至关重要的那些可能的因素实乃当务之急.     

Sn(II)―X和Sn(IV)―X (X=O,S, N,C, P,As, Se,Te, F,Cl, Br,I)键价参数

基于剑桥晶体数据库中同配配合物的Sn(Ⅱ)―X和Sn(Ⅳ)―X(X=O,S,N,C,P,As,Se,Te,F,Cl,Br,I)键长数据,采用键价参数B=0.037nm拟合得到Sn(Ⅱ)―X和Sn(Ⅳ)―X的键价参数R0,这样拟合的经验参数R0中有一些是首次推出.本文所报道的Sn(Ⅱ)―O键基于B=0.037nm的R0值(0.1956nm)可适用于多数Sn(Ⅱ)呈各种配位数时的氧化态指定,而文献报道的B=0.055nm和R0=0.1859nm主要对于低配位的情况能取得Sn(Ⅱ)原子价态指定的较好结果.本研究证明,进一步研究键价参数对键价和(BVS)计算至关重要的那些可能的因素实乃当务之急.     

导出铅(Ⅱ)-卤素键价参数的一条新途径

基于精确的晶体结构数据并设定B=0.037nm以拟合经验参数R0是通常采用的键价参数推导方法.与此相反,作者提出从分子气相电子衍射的键长设定经验参数R0,然后从晶体结构数据拟合经验参数B.以Pb(Ⅱ)—卤素键为例,PbX_2气相电子衍射Pb—X(X=F,Cl,Br,I)键长分别为0.2036,0.2447,0.2598和0.2804nm,经拟合到最佳B值分别为0.0382,0.040,0.040,0.0386nm,与普适参数B值0.037nm有一定的差距.所提出的键价参数不仅得到比较理想的键价值和计算结果,而且保留了键价参数R_0作为单价键长明确的物理意义.     

导出铅(II)—卤素键价参数的一条新途径

基于精确的晶体结构数据并设定B=0．037nm以拟合经验参数R0是通常采用的键价参数推导方法．与此相反，作者提出从分子气相电子衍射的键长设定经验参数如然后从晶体结构数据拟合经验参数B．以Pb（II）-卤素键为例，PbX2气相电子衍射Pb—x（X=F，Cl，Br，I）键长分别为0．2036，0．2447，0．2598和0．2804nm，经拟合到最佳B值分别为0．0382，0．040，0．040，0．0386nm，与普适参数B值0．037nm有一定的差距．所提出的键价参数不仅得到比较理想的键价值和计算结果，而且保留了键价参数风作为单价键长明确的物理意义．     

镧系元素相关的键价参数研究

根据镧系元素络合物的晶体结构数据确定了单价键长R0的镧系收缩效应，并对已有的键价参数进行了系统的修订.建立了Ln-O键的R0对原子序数N在普适参数B=0.037 nm下的线性方程R0(nm)=0.2879－0.00132N.用不同参数进行键价和的计算并对结果进行了对比和讨论，最后展望了相关研究的前景.     

胺草磷的晶体结构

胺草磷晶体,属三斜晶系,空间群为C_i¹-P1,晶胞中含两个分子,晶体学数据为:a=8.636(1),b=10.483(2),c=10.694(2)Å;α=110.92(1)°,β=111.27(1)°,γ=98.97(1)°;V=796.2(3)ų,D_c=1.33g/cm³,F(000)=336;μ(MoK_α)=3.2cm^-1。此结构用直接法解出,最后的R因子为:R₁=O.055,R₂=0.047。胺草磷分子中的磷原子形成四个四面体向的化学键,其中P-S键含有相当高的双键成分,这意味着磷原子的3d轨函参与成键。     

范德华复合物Kr-C2H2的势能面和振转光谱的理论研究

采用[CCSD（T）]-F12方法和aug-cc-pVTZ基组,同时引入中心键函数（3s3p2d1f1g）构建了Kr-C₂H₂体系的高精度四维势能面.在构建势能面时考虑了分子间的振动方式及C₂H₂单体内的ν₁对称伸缩和ν₃反对称伸缩振动.将计算得到的四维势能面在Q₁方向和Q₃方向分别做积分得到C₂H₂单体分别处于振动基态和（ν₁,ν₃）=（1,1）激发态的平均势能面.计算结果表明,这2个平均势能面均存在2个等价的T型全局极小值和2个等价线性极小值.全局极小值的几何构型位于R=0.41 nm,θ=65.6°/114.4°,势阱深度为151.88 cm^-1.对径向部分采用离散变量表象法（DVR）,角度部分采用有限基组表象法（FBR）,并结合Lanczos循环算法计算了Kr-C₂H₂的振转能级和束缚态.计算结果表明,复合物在（ν₁,ν₃）=（1,1）区域的带心位移为-1.48 cm^-1,表现为红移,与实验值-1.38 cm^-1很接近;计算得到的红外跃迁频率也与实验值相吻合,说明得到的从头算势能面具有高精度.     

三环已基锡L-扁桃酸酯配合物的合成、结构及性质

三环己基氢氧化锡与L-扁桃酸(物质的量比1:1)在苯和乙醇混合溶剂中反应合成了三环己基锡L-扁桃酸酯。 经X射线衍射方法测定了其晶体结构,配合物属斜方晶系,空间群为P2₁2₁2₁,晶体学参数a=0.80825(4) nm,b=1.77151(8) nm,c=1.8385(2) nm,α=β=γ=90°,V=2.6324(2) nm³,Z=4,D_c=1.310 g/nm³,μ(MoKα)=9.92 cm^-1,F(000)=1080,R₁=0.0472,wR₂=0.1341。 中心锡原子与环己基碳原子和氧原子构成畸型四面体。 对其结构进行量子化学从头计算,探讨了配合物的稳定性、分子轨道能量以及一些前沿分子轨道的组成特征。 研究了配合物的热稳定性、电化学性能、圆二色谱和体外抗癌活性。     

2,4-二羟基苯乙酮缩异烟酰腙的实验和DFT理论研究:合成、晶体结构和性质及量化计算

合成了一种酰腙类Schiff碱2,4-二羟基苯乙酮缩异烟酰腙(C₁₄H₁₃N₃O₃,H₂L),经元素分析、红外光谱、紫外光谱、荧光光谱和热重分析等技术手段进行了表征。 用X射线单晶衍射测定了它的晶体结构,该晶体属单斜晶系,C2/c空间群,晶胞参数a=2.0102(2) nm,b=0.75891(8) nm,c=1.9530(2) nm,α= 90°,β=111.481(12)°,γ=90°,V=2.7725(5) nm³,Z=4,D_c=1.4292 g/cm³,R₁=0.0422,wR₂=0.1113,F(000)=1256。 同时进行了量子化学计算研究。 使用Gaussian09量子化学程序包, 在密度泛函理论(DFT)的B3LYP/6-31G(d)水平,对化合物的分子结构进行全参数优化计算,获得了热力学参数和几何结构参数,对分子的总能量及前线分子轨道、Mulliken电荷分布进行了分析讨论;同时,用TD-DEF方法计算了化合物的电子吸收光谱和荧光发射光谱。     

混合配体配合物镉(Ⅱ)-邻菲罗啉-丙二酸根异构体的结构特征研究

由硝酸镉、邻菲罗啉和丙二酸混合反应,得到无色透明单晶.经X射线单晶衍射法测定了该晶体的分子结构,在1个晶胞中存在两个混合配体配合物异构体,其组成为C₂₇H₁₈O₄N₄Cd.晶体学数据为:三斜晶系,P-1空间群.a=0.14432(5)m,b=0.15517(5)nm,c=0.16098(6)nm,α=107.048(6)°,β=98.989(6)°,γ=116.481(6)°,Z=2,F(000)=1287,D_c=1.453g/cm3,μ=0.802mm^-1,R₁=0.0645,wR₂=0.1756.该异构体的差别在于丙二酸根中2个羧基中各1个氧原子配位(1)或1个羧基中2个氧原子同时配位(2).1和2之间靠氢键和π-π堆积等弱相互作用形成超分子结构.     

Stoichiometric Valence and Structural Valence—Two Different Sides of the Same Coin: “Bonding Power”

Two valencies instead of one! Stoichiometric valence and structural valence are two distinct properties of atoms. The former, ^stoichV, is derived from the composition of a compound and has integer values; the latter, ^structV, depends on the structure of a compound and has non‐integer values. The scheme shows a representation of valence states of antimony and oxidation of Sb^III to Sb^V, as a function of the eccentricity parameter Φ _i.

     

XMVB: a program for ab initio nonorthogonal valence bond computations

An ab initio nonorthogonal valence bond program, called XMVB, is described in this article. The XMVB package uses Heitler-London-Slater-Pauling (HLSP) functions as state functions, and calculations can be performed with either all independent state functions for a molecule or preferably a few selected important state functions. Both our proposed paired-permanent-determinant approach and conventional Slater determinant expansion algorithm are implemented for the evaluation of the Hamiltonian and overlap matrix elements among VB functions. XMVB contains the capabilities of valence bond self-consistent field (VBSCF), breathing orbital valence bond (BOVB), and valence bond configuration interaction (VBCI) computations. The VB orbitals, used to construct VB functions, can be defined flexibly in the calculations depending on particular applications and focused problems, and they may be strictly localized, delocalized, or bonded-distorted (semidelocalized). The parallel version of XMVB based on MPI (Message Passing Interface) is also available.     

Charge transfer and dispersion interaction stabilization of the D2h isomer of O4

The results of some minimal basis set valence bond calculations, with an antibonding midbond molecular orbital (π_m*) included, are reported for the D_2h isomer of O₄. The in-plane π_m*←π* excitations describe the charge transfer from each monomer, while the π*←π excitations on each monomer partially describe the intermolecular dispersive attractions. It is found that the charge-transfer interactions by themselves are insufficient to stabilize the S=0 spin D_2h dimer of O₄ relative to two O₂ monomers when a correction is included for basis set superposition error. The inclusion of both the charge transfer and dispersion terms yields an estimate of 14 cm⁻¹ for the binding energy (D_e) at an equilibrium separation (R_e) of 3.29 Å. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 129–134, 1998     

过渡金属羰基簇合物的键价计算和分析

本文运用原子簇化合物键价计算公式 ,对过渡金属羰基簇合物成键情况进行了分析 ,利用金属键轨道数 ,价非键轨道数和金属配体成键轨道数计算簇合物价轨道总数 .计算结果表明 :簇合物价轨道总数与金属键轨道数成线性关系 ,BT=9N -Bn.对于一般簇合物其价轨道总数与Lauher的EHMO计算结果 ,与唐敖庆的结构拓扑规则一致 ,对于反常的高核簇合物其价轨道总数与按化学式计算的 1/ 2VE相吻合     

On the rapid evaluation of cofactors in the calculation of nonorthogonal matrix elements

The calculation of matrix elements involving nonorthogonal orbitals is speeded up by recognizing the orthogonalities between orbitals, leading to generalized Slater rules. The block structure present in the overlap matrix makes an efficient evaluation of its cofactors possible. These cofactors are calculated per subblock, each with its own parity sign. An adjustment parity sign has to be evaluated, which is added to the combined local signs, to give the correct total sign for the matrix element. An algorithm for the evaluation of this adjustment sign has been developed, making an easy and correct evaluation possible. The current scheme is shown to be very efficient, but possibilities for further improvement remain. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 77–83, 1998     

Bonding of the chain structure for novel boranes B_(3k+)H_(5k+p+3)~-

The molecular orbitals obtained from conventional quantum chemistry calculations, are expressed in terms of symmetrized valence bond functions of fragment, and a direct picture of chemical bonding can be drawn easily. This method is utilized, together with extended Huckel calculations, to interpret the bonding properties of a centipede-like chain structure for novel laser-producing boranes B3k+pH5k+p+3- which is constructed from the repeated unit B3H5 linked to each other by three B-H-B bonds.     

Ⅱ conjugation in the butadiene

The π electronic delocalization in trans-C4H6 and cis-C4H6 has been investigated in the frame of ab initio valence bond theory with 6-31G basis set. The result shows that the Csp2-Csp2 single bond length (1.506 A) is only about 0.024 A shorter than the Csp3-Csp3 bond, thus the central bond length shortening would be mainly due to π conjugation. The theoretical resonance energies of the trans-C4H6 and cis-C4H6 are 8.48 and 7.44 kcal/mol, respectively.     

Ab initio Valence Bond Study on AB-type Molecules,A Description for XH(X=L,Be,B,C,N,O,F) and XF(X=Li,Be,B)

Ab initio valence bond method is employed to quantitatively study the concepts of ionic resonance energy and ionicity of a chemical bond in the cases of hydrides XH(X=Li,Be,B,C,N,O,F) and fluorides XF(X=Li,Be,B),By establishing the relationship between resonance and stability,and comparing the calculated ionicities with Pauling‘s earlier estimations in the above diatomic molecules,the merits of Pauling‘s classical resonance theory were demonstrated at the ab initio level.