Wade规则在稠合型硼烷等中的应用

本文把Ｗａｄｅ规则推广应用于稠合型硼烷和稠合型金属碳硼烷中,导出计算它们价电子数（ＮＶＥ）的公式。对于稠合型硼烷,本文公式与唐敖庆等的拓扑结构规则的计算结果相同。但本文公式的适用范围比上述两个规则广。     

硼烷簇合物的结构规则

从超额电子数出发，提出了1种稠合型硼烷的结构规则，讨论了各种规则间的关系。     

硼烷及杂硼烷簇合物的结构规则

硼烷及杂硼烷簇合物的结构规则张晓辉，陈利平，由业诚，王国栋（大连大学师范学院化学系大连１１６０３５）关键词原子簇化合物，稠合硼烷，杂硼烷，结构规则本文在研究前人工作的基础上［１－１２］，利用徐光宪提出的超额电子数概念，将硼烷分成多个分子片，以讨论它们...     

四层过渡金属夹心化合物的电子构型

本文利用共点稠合型硼烷的拓扑结构规则和EHMO量子化学计算方法, 讨论了四层过渡金属夹心化合物的电子构型, 以及它与几何结构之间的关系. 用于解释实际化合物的电子构型. 继而, 对四层、三层和双层夹心化合物的电子构型与几何结构之间的关系进行了比较和讨论.     

Mo(W)-Cu(Ag)-S簇合物的拓扑学研究

本文给出了一种由Mo(W)-Cu(Ag)-S簇合物分子式导出可能结构的拓扑方法。作为例子，文中利用该方法导出了四核单Mo(W)簇合物的各种可能结构，并预测了簇合物［Mo₂O₂S₆Cu₄(PPh₃)₄］的各种可能结构。本文介绍的拓扑方法，为Mo(W)-Cu(Ag)-S簇合物的结构提供了一个组织框架，也为预测簇合物的新结构提供了一个合理的基础和途径。     

应用有机结构数据库系统研究钼簇合物的键价规律

本文基于有机结构数据库CSD中簇合物的大量信息, 依靠计算机检索、图形显示和运算功能, 系统分析了449个钼簇合物的价电子总数和Mo-Mo键的键价, 键长, 提出钼簇合物的价电子Counting规则和Mo-Mo键的总键价计算修正公式, 总结出Mo-Mo键的键价、健长等。     

[B20H18]n-(n=0,2,4,6)离子异构体的结构、稳定性与电子计数规则

对单个多面体硼烷(Polyhedral boranes)已有较多的理论研究，由多个多面体通过共用一个或多个顶点而构成的稠合型硼烷(Macropolyhedral borones)，具有多种多样的结构类型，并已被大量合成出来，目前对稠合型硼烷结构及成键特性的理论研究尚不充分，它们不能再以简单的closo，nido和arachno分类，Wade规则也不再适于解释其结构，理论上各种电子计数规则已有不少报道，对预言和发现新的分子十分重要。     

「VS_4-Cu_n」簇合物的固相合成、结构规律和成簇机理的研究

以(NH_4)_3VS_4为起始原料与CuCl在低温团相不同反应条件下,得到了不同簇骼的[VS_4-CU_n]的簇合物,并总结了CuCl/(NH_4)_3VS_4不同摩尔比、不同反应温度和时间对簇合物生成的影响和[VS_4-Cu_n]簇合物的结构规律.同时探索了V-Cu-S簇合物固相合成的成簇机理.     

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     

原子簇化合物的结构规则与化学键性质

本文从形成双中心键,三中心键和四中心键时,成键与相应的反键之间数目关系的三个基本假定出发,推导出封闭型、巢型和网型硼烷的Wade规则及其分子中双中心键、三中心键和四中心键的具体数目。进而将Wade规则推广,使之适用于包括具有戴帽结构的杂硼烷和推广到用B原子稠合成的稠合型硼烷。最后用于讨论过渡金属羰基化合物和具有密堆积型过渡金属羰基化合物的结构规则。     

ELECTRONIC CONFIGURATIONS OF TRANSITION METAL SANDWICH COMPLEXES

In this paper the electronic configurations of n+1-decker transition metal sandwich com-plexes have been generally discussed by means of the structural rule of transition metalheterocarborans and the numbers of their valence bonding orbitals have been obtained as fol-lows: VBO = 6n + 3-6n + 5,which are not dependent on the properties of transition metal atoms and coordination rings.Then the results of EHMO quantum chemistry calculations of the model skeletons and cor-responding analyses on electronic configurations of actual molecules for double-, triple- andtetra-decker sandwich complexes have been discussed to verify the above formula.     

Magnetism in Simple Metal and 4<Emphasis Type="Italic">d</Emphasis> Transition Metal Clusters

In this review article I discuss two aspects of magnetism in small metal clusters. The first question discussed is whether simple metal clusters, that obey electronic shell models and mimic properties of elemental atoms, also obey Hund’s rule of maximum spin multiplicity. The second question is whether small clusters of 4d transition metal atoms, that are non-magnetic in the bulk, have magnetic ground states. The question arises because calculations showed that small V clusters are magnetic although the bulk metal is not. We discuss known results on Rh clusters in detail to show that small clusters are generally magnetic, but it is difficult to unequivocally identify the ground state due to the presence of many isomers and spin states that are very close in energy.     

Condensed Metal Clusters

The chemistry of metals in low valence states is marked by the frequent occurrence of metal clusters, which are easily recognizable when they occur as molecular units. Many metal-rich compounds of transition metals with p-elements (3rd to the 6th main groups) are closely related to the corresponding halides, since they are built up from metal clusters of the same type. The clusters are however, linked together (condensed) by metal-metal bonds. This principle of construction holds particularly well in the case of the novel reduced halides of the lanthanoids.     

Formation,growth mechanism and packing sequences of binary alloy cluster anions from laser ablation of mixtures of lead and transition metals

By using laser ablation of the mixtures of a transition metal (M: Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag) plus lead, M/Pb binary cluster anions were observed except for Zn, and the number of transition metal atoms contained in the binary clusters is at most 4. This behavior is different from that reported previously for M/Ge binary clusters. The experiments indicate that it is also very difficult to form Al/Pb clusters. The distribution patterns of M/Pb binary alloy cluster anions are remarkably similar to those of pure Pb clusters, consistent with a formation mechanism in which transition metal atoms are sequentially attached to [M(x-1)Pb(y)](-) clusters and thus form [M(x)Pb(y)](-) clusters by a simple condensation process. As the number of transition metal atoms increases, the intensities of binary clusters gradually decrease. It is proposed that [MPb(4)](-) and [MPb(5)](-) cluster anions might be the unit building blocks of M/Pb binary cluster anions, and the layer packing sequences for magic clusters are predicted on this basis. The [M(x)Pb(y)](-) binary clusters containing 13 atoms (x + y = 13; x not equal 0) are proposed to have an icosahedral structure.     

FORMATION STUDY OF TOROIDAL CONDENSATION OF DNA

A detailed study of the formation of toroidal condensation produced from the 2700 base pair fragments of plasmid PUCI3 DNA, induced by metal ions, is introduced. We have extracted several typical intermediate structures based on investigation by electron microscopy, and compared their size distributions. The observations suggest that the formation process of DNA condensation is the process of folding and arranging DNA chains and that of disorderorder transition. The result also indicates that the condensed particles are polymeric, but not randomly aggregative, further proving thetoroidal structures are formed in certain regularities.     

Formation study of toroidal condensation of DNA.

A detailed study of the formation of toroidal condensation produced from the 2700 base pair fragments of plasmid PUC13 DNA, induced by metal ions, is introduced. We have extracted several typical intermediate structures based on investigation by electron microscopy, and compared their size distributions. The observations suggest that the formation process of DNA condensation is the process of folding and arranging DNA chains and that of disorder-order transition. The result also indicates that the condensed particles are polymeric, but not randomly aggregative, further proving the toroidal structures are formed in certain regularities.     

Kinetics of supersaturated vapor nucleation on molecular condensation nuclei

The kinetics of nucleation is calculated for a supersaturated vapor containing molecular condensation nuclei, that is, foreign molecules able to induce the formation of viable nuclei of a condensed phase by themselves. In contrast to the previous calculation, the possibility of the escape of molecular condensation nuclei from very small clusters containing a few condensed vapor molecules is taken into account. More exact equations are derived for the rate of steady-state nucleation and the concentration of aerosol particles in a quasisteady-state regime of nucleation. The calculation demonstrates that, at a high probability of the escape of a molecular condensation nucleus, the predominating mechanism of cluster formation is the attachment of a molecular condensation nucleus to a cluster formed from vapor molecules rather than their condensation on the nucleus. At the same time, allowances for the possible escape of molecular condensation nuclei from clusters slightly affect the rate of nucleation and the concentration of aerosol particles being formed.     

Infrared Spectra,Structures and Bonding of Binuclear Transition Metal Carbonyl Cluster Ions

Binuclear transition metal carbonyl clusters serve as the simplest models in understanding metal-metal and ligand bonding that are important organometallic chemistry catalysis. Binuclear first row transition metal carbonyl ions are produced via a pulsed laser vaporization/supersonic expansion cluster ion source in the gas phase. These ions are studied by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Density functional theory calculations have been performed on the geometric structures and vibrational spectra of the carbonyl ions. Their geometric and electronic structures are determined by comparison of the experimental IR spectra with the simulated spectra. The structure and the metal-metal and metal-CO bonding of both saturated and unsaturated homonuclear as well as heteronuclear carbonyl cluster cations and anions are discussed.     

Structures and stabilities of 3d-transition metal-benzene organometallic clusters

In the gas phase, we have successfully synthesized organometallic clusters, M_n(benzene)_m (M=3d transition metal atoms), by using a laser vaporization method. The measurements of mass spectra and ionization energies (E_i) have revealed that the organometallic clusters can take two types of structures; layered sandwich structures (m = n + 1) and metal clusters saturatedly covered with benzenes. For early transition metals of Sc, Ti, and V, only the multiple decker sandwich structure clusters were preferentially produced, in which benzene and metal atoms are alternately piled up. For late transition metals of Co and Ni, the metal clusters saturatedly surrounded by benzenes were also produced as well as the sandwich clusters. Furthermore, the E_is of M₁(benzene)₂ (M = Sc-Ni) were systematically measured and their electronic properties will be discussed.     

DNA condensation and its thermal stability influenced by phospholipid bilayer and divalent cations

We studied the effect of divalent alkaline earth metal cations Ca2?, Mg2? and transition metals Co2?, Ni2?, Cu2? and Zn2? on DNA condensation and its protection against thermal denaturation in presence of dioleoylphosphatidylcholine liposomes (DOPC). Experimental results have shown that Ca2? and Mg2? as well as Zn2? mediate DNA condensation. Cu2? causes DNA double helix destabilization, and does not mediate binding between DNA and DOPC liposomes. Co2? and Ni2? can interact with DNA on both ways mentioned above. Static light scattering was use to follow the size of aggregates in DNA condensation process. Phospholipid bilayer and divalent cations protect condensed DNA against thermal destabilization. The highest stabilization effect was found in aggregates with Ca2? and Zn2?, whereas in presence of either Co2? or Ni2? some volume fraction of DNA is denatured.