钒邻苯二酚双齿配合物从头算研究

运用Gaussian 94W量子化学程序包,采用LanL2DZ基组,对钒邻苯二酚双齿配合物结构单元V(cat)₃^n-(n=1,2)进行从头算研究。探讨这些配合物的稳定性、分子轨道能量、原子净电荷布居规律以及处于前沿的一些分子轨道的组成特征,为过渡金属双齿配合物的合成、分子组装及其在酶和蛋白质中的活性部位研究提供理论参考。     

钒(Ⅴ)巯基苯酚双齿配合物从头算研究

运用Ｇ９４Ｗ量子化学程序包,采用ＬＡＮＬ２ＤＺ基组,对钒与Ｈ２ｍｐ（ｏ－巯基苯酚）形成的双齿配合物结构单元Ｖ（ｍｐ）３ｎ－（ｍｐ＝ＯＣ６Ｈ４Ｓ２－,ｎ＝１,２）进行从头算研究．探讨这些配合物结构单元的稳定性、分子轨道能量、原子净电荷布居规律以及一些前沿分子轨道的组成特征等,为过渡金属双齿配合物的合成、分子组装分析及其在酶和蛋白质中的活性部位研究提供理论参考．     

Fe、Co、Ni双齿巯基配合物从头算研究

运用Gaussian94量子化学程序包，采用LanL2DZ基组，对Fe（Ⅲ）、Co（Ⅲ）、Ni（Ⅱ）与Hmpo（2-巯基氧化吡啶）的双齿配合物Fe（mpo）3、Co（mpo）3、Ni（mpo）2进行从头算研究。讨论这些配合物的稳定性、分子轨道能量、原子电荷分布以及最高占据轨道的特征等，为过渡金属双齿配合物的合成、结构分析及其在酶与蛋白质中的活性部位研究提供一些理论参考．     

草酰胺衍生物桥联双核镍配合物从头算研究

采用LanL2DZ基组 ,对N,N′ 双(2 苯甲酸根)草酰胺桥联双核镍配合物Ni(obbz)Ni(H2O)4 进行从头计算研究 ,探讨该配合物单、三重态的电子组态的稳定性、电子结构特征及电子自旋布居规律等。计算结果表明 ,该配合物分子的三重态比单重态稳定 ,因此 ,该配合物择型于三重态的电子组态。电子自旋主要布居于八面体环境的Ni(1)中心上 ,而处于四方配位环境的Ni(2)中心则没有发现电子自旋布居。同时 ,Ni(2)中心主要参与的分子轨道都处于低能区 ,表明Ni(2)中心的配位是相当稳定的 ,这与实验规律相符。     

Au(Ⅰ)电荷转移配合物光谱性质的从头算研究

过渡金属电荷转移配合物的电荷分离是光能转化为电能的光物理过程,与配合物的电子结构密切相关.采用从头算方法探索了双核Au(Ⅰ)配合物,cis-[Au2(SHCH2PH2)2]2 (1),cis-[Au2(SHCH2S)2](2)和cis-[Au2(PH2CH2S)2](3)的电荷转移性质.采用MP2计算得到基态的Au(Ⅰ)—Au(Ⅰ)距离分别为0.2972,0.2888和0.2903 nm,表明Au(Ⅰ)之间存在弱吸引作用;电子激发使得配合物2和3的金属间的距离缩短了约0.016 nm,而配合物1仅增长了0.002 nm.CIS方法预测配合物1~3的3A激发态分别产生383,463和422 nm最低能发射,具有金属中心(Metal-centered,MC)跃迁和分子内电荷转移(Intramolecular Charge Transfer,ICT)的混合性质.     

Au(Ⅰ)电荷转移配合物光谱性质的从头算研究

过渡金属电荷转移配合物的电荷分离是光能转化为电能的光物理过程, 与配合物的电子结构密切相关. 采用从头算方法探索了双核Au(Ⅰ)配合物, cis-[Au2(SHCH2PH2)2]2+(1), cis-[Au2(SHCH2S)2](2) 和cis-[Au2(PH2CH2S)2](3)的电荷转移性质. 采用MP2计算得到基态的Au(Ⅰ)—Au(Ⅰ)距离分别为0.2972, 0.2888和0.2903 nm, 表明Au(Ⅰ)之间存在弱吸引作用; 电子激发使得配合物2和3的金属间的距离缩短了约0.016 nm, 而配合物1仅增长了0.002 nm. CIS方法预测配合物1~3的3A激发态分别产生383, 463和422 nm最低能发射, 具有金属中心(Metal-centered, MC)跃迁和分子内电荷转移(Intramolecular Charge Transfer, ICT)的混合性质.     

草酰胺桥联双核铜配合物结构单元的从头算

运用Gaussian 94W量子化学程序包 ,采用LanL2DZ基组 ,对草酰胺桥联双核铜配 (聚 )合物结构单元Cu2 (oxen) (OH) 2 [H2 oxen =N ,N' 二 ( 2 胺乙基 )草酰胺 ](包括顺、反构型及其单、三重态电子组态 )进行从头算研究 ,探讨该配合物结构单元的稳定性 ,并从电荷布居及分子轨道组成等电子结构特征分析这种配合物反式三重态比较稳定的原因 .计算结果与实验规律相符合 .     

平面四方金属苯配合物的非线性光学性质的从头算研究

反位平面四方型过渡金属有机配合物[XM(PEt₃)₂-C₆H₄-R] (M＝Pd, Pt; X＝Br, I; R＝NO₂, CHO), 已被测定有较高的非线性光学系数. 本工作采用从头算方法对该配合物的结构和非线性光学性质进行研究. 构型在MP2/Lanl2DZ水平优化. 对基组进行慎重选择后, 认为应该在赝势价分裂基Lanl2DZ的基础上添加弥散函数和极化函数. 弥散函数按几何级数规则增加, 极化函数的指数应取低一个角量子数的基函数中最弥散的两个函数的指数的比例中项. 本工作的SCF水平计算表明苯的对位取代基R的吸电子能力越强, 金属对位配体X的电负性越强, 则配合物的超极化率越大.     

锕系双原子分子的从头算研究

用相对论有效原子实势(RECP)和密度泛函方法(B3LYP),采用U和Pu原子的紧缩价基集合[5s4p3d4f]/[3s3p2d2f],优化了U2和Pu2分子的平衡结构,得到它们的长键长(LBL)和短键长(SBL)分别为:U2分子是0.38965和0.29927 nm,Pu2分子是0.45375和0.35202 nm;导出了基态和最低激发态的势能函数,计算出它们的力常数、光谱数据和离解能.     

含双齿膦配体的铜配合物的合成和结构的初步研究

利用双齿膦配体１，１－双（二苯基膦）甲烷和１，２－双（二苯基膦）乙烷的还原性以及硝酸配体的易变特性，通过配体还原反应和配体取代反应，于甲醇溶剂中，在ｄｐｐｍ和ｄｂｂｅ的存在下，合成了两个双核铜（Ｉ）配合物［Ｃｕ（ｄｐｐｍ）（Ｌ）］］２（Ｌ分别为ＢＨ４和ＣＩＯ４）和两个单核铜（Ｉ）配合物［Ｃｕ（ｄｐｐｅ）（Ｌ）］（Ｌ分别为ＢＨ４和ＣＩＯ４）。本文又采用两种不同方法合成了两个合成了两个混配铜Ⅱ）配合物     

STUDY ON THE STRUCTURES OF COMPLEXES OF LANTHANIDE WITH BIDENTATE HETEROCYCLIC AMINE——THE STRUCTURE OF BIS[TRI(TRICHLOROACETATO)-1,10-PHENANTHROLINE-BTHANOL-GADOLINIUM]

<正> (GdC12H8N2(CCl3CO2)3C2H5OH)2,Mr=870.60,monoclinic,space group P21/n, a= 12.489(1), b= 18.5194(1),c=13.399(1)A,β=92.9(1)°,V=3095.2A3,Dc=1.868g/cm3 and Z=2. The structure was solved by Patterson and Fourier methods,and refined by full matrix least squares method to R=0.078 for 1619 observed reflections with I>3σ(I).The molecule of the complex is a dimer located at the crystallographic center and each Gd(Ⅲ) atom is eight-coordinated with the coordination polyhedron being a distorted square antiprism.     

聚苯基单醚喹噁啉和铂铑络合物的研究

<正> 芳杂环高分子是一种耐高温高分子,诸如聚酰亚胺、聚苯基单醚喹噁啉等,都是耐高温优良的高分子,而后者还具有突出的耐高温水解性。鉴于芳杂环高分子主链结构上含N、S或O原子,它们都有未成键的电子,可以作为电子给体,而金属化合物中的金属有空轨道,可以作为电子受体,在合适条件发生电荷转移形成络合物。实验结果表明,聚苯     

Ab initio studies of

Ab initio calculations of the [1,5]-H shift in (3Z)-penta-1,3-diene and other substituted pentadienes and heteroanalogues using the hybrid density functional Becke3LYP with the 6-31G basis set are presented. Electron-donating substituents, such as methoxy in (3Z)-3-methoxypenta-1,3-diene 1, or heteroatoms such as a nitrogen atom in (Z)-ethylidenevinylamine 2, (1Z)-buta-1,3-dienylamine 3, (2Z)-but-2-enylideneamine 4, (Z)-allylidenemethylamine 5, and methylene-(Z)-propenylamine 6 are introduced. The electron-withdrawing fluoride is substituted for the hydrogen atoms in (3Z)-3-fluoropenta-1,3-diene 7, (3Z)-2,4-difluoropenta-1,3-diene 8, (3Z)-1,1',2,3,4,5,5'-heptafluoropenta- 1,3-diene 10, (1E,3E)-1,3,5-trifluoropenta-1,3-diene 11, and (1Z,3E)-1,3,5- trifluoropenta-1,3-diene 13. A detailed analysis of the geometries, energies, and electronic characteristics of the sigmatropic transposition compared to those of the unsubstituted case provides insights into substituent effects of this prototype of pericyclic reaction. The inductive and mesomeric effects of heteroatoms or heterosubstituents are of a great importance and in a continuous balance in the energetics of the transformation. Sterics can also play an important role due to the geometrical constraints of the reaction. As a general trend, decreasing the electron density of the phi system destabilizes the aromatic transition structure and increases the activation energy, and vice versa.     

Ab initio Ehrenfest dynamics

We present an ab initio direct Ehrenfest dynamics scheme using a three time-step integrator. The three different time steps are implemented with nuclear velocity Verlet, nuclear-position-coupled midpoint Fock integrator, and time-dependent Hartree-Fock with a modified midpoint and unitary transformation algorithm. The computational cost of the ab initio direct Ehrenfest dynamics presented here is found to be only a factor of 2-4 larger than that of Born-Oppenheimer (BO) dynamics. As an example, we compute the vibration of the NaCl molecule and the intramolecular torsional motion of H2C=NH2+ by Ehrenfest dynamics compared with BO dynamics. For the vibration of NaCl with an initial kinetic energy of 1.16 eV, Ehrenfest dynamics converges to BO dynamics with the same vibrational frequency. The intramolecular rotation of H2C=NH2+ produces significant electronic excitation in the Ehrenfest trajectory. The amount of nonadiabaticity, suggested by the amplitude of the coherent progression of the excited and ground electronic states, is observed to be directly related to the strength of the electron-nuclear coupling. Such nonadiabaticity is seen to have a significant effect on the dynamics compared with the adiabatic approximation.     

SYNTHESIS OF MONOSUBSTITUTED PENTAKIS(2,6-DIETHYLPHENYLISO-CYANIDE)COBALT(I) COMPLEXES WITH BIDENTATE TERTIARY PHOSPHINE LIGANDS. II. BIMETALLIC COMPLEXES

Abstract

Reaction of bidentate tertiary phosphines with excess [Co(CNR)₅]BF₄, or reaction of [Co(CNR)₄L-L]BF₄ with excess [Co(CNR)₅]BF₄, leads to bimetallic complexes of the form, [(RNC)₄CoL-LCo(CNR)₄](BF₄)₂, R = 2,6-Et₂C₆H₃, L-L = p-Ph₂PC₆H₄PPh₂, Ph₂PC═CPPh₂, Me₂PCH₂CH₂PMe₂, Ph₂PCH₂CH₂PPh₂, Ph₂PCH₂CH₂CH₂PPh₂. Comparison of the v(? N═C) IR patterns, electronic spectra, and molar conductivity values of these bimetallic complexes with data for other Co(I)-organoisocyanide complexes indicates that the two -Co(CNR)₄ moieties are almost totally independent of each other. Recorded λ_max values are the same as for the [Co(CNR)₄L-L]BF₄ complexes, but the ε values, although very large, are less than double. Λ_M values in acetone, and probably also in CH₂Cl₂, are better interpreted as twice the normal conductivity for 1:1 electrolytes than conductivity for 2:1 electrolytes.     

VANADIUM(III) AND VANADIUM(IV) COMPLEXES WITH PYRAZINE IN ALCOHOL SOLUTION

Abstract

The V(III)-pyrazine system was examined spectroscopically in the isoamyl alcohol solution. An unstable, violet-red, binuclear vanadium(III) complex [V₂(pyraz)Cl₄]²⁺ was found to be formed. On exposure to air it was slowly converted into a sparingly soluble green vanadium(IV) compound, [VO(pyraz)OH]Cl.H₂O. This compound was examined by the analytical, spectroscopic (electronic and infra-red spectra) and magnetic methods.     

Ab initio polypeptide structure prediction

The biological activity of a polypeptide strongly depends on its 3D structure. Ab initio prediction of the native structure from the sequence of amino acids has long motivated the development of an optimum energy model such that interactions present in the native conformation are stronger than those present in nonnative conformations and of algorithms capable of finding the basin of lowest free energy among an astronomically large number of possible conformations. Despite recent progress in our understanding of the factors responsible for both polypeptide stability and formation, computer simulations of polypeptide models are still far from being practical software tools for biologists. In this work, state-of-the-art computer simulations aimed at ab initio structure prediction in aqueous solution are reviewed and their strengths and weaknesses are highlighted. Received: 23 June 1999 / Accepted: 20 September 1999 / Published online: 15 December 1999     

Benzooxirene. Ab initio calculations

Ab initio calculations have been performed on benzooxirene, the corresponding oxo carbene (“ketocarbene”), and the transition state linking the two. At the highest level used, QCISD(T)/6-31G^*//MP2(FULL)/6-1G^* with MP2(FULL)/ 6-31G^* zero point energy corrections, the relative energies of the oxirene, the transition state and the carbene are 0, 24.6, and −17.8 kJ mol⁻¹. Correlation energy effects are very important in this system: at the QCISD(T) level the oxirene lies above the carbene, as at the MP4 and HF levels, but at the MP2 level the ordering is reversed. Benzooxirene is probably slightly nonplanar: the HF/6-31G^* geometry is C_2v but the MP2(Fermi contact)/6-31G^* geometry is C_s with a 6-/3-ring coplanarity deviation of about 6.9 °, although in the MP2(FULL)/6-31G^* geometry this is reduced to about 3.1 °.