Structure and Stability of Endohedral Complexes X @（HAlNH）12 （X = He, Ne, Ar, Kr）

1 INTRODUCTION The structure and property of endohedral com- plexes X@An have been well represented, including Fullerene structures with bigger volume, such as Ln3 @C60[1], Sc3N@C80[2] and Sc3N@C78[3], or metal cluster complexes of Al(Al13-)[4] and Ga(Ga13-)[5] with relatively smaller volume. These studies have revealed much structure and property information, for example, the impact of building-in atom X on the cage structure, the interaction character of X-An in the cage, and the…     

Synthesis and structure of linear hexanuclear manganese (Ⅱ)benzoate cluster

From a reaction system including benzoic acid and Mn(NO3)2 in alkali medium, two hexanuclear manganese benzoate cluster compounds have been synthesized. A compound [Et4N]2[Mn6(PhCOO)14] has been structurally characterized, which contains hexanuclear Mn11 moieties extending unlimitedly to form one-dimensional linear structure. Carboxyl oxygen atoms are bridged in variety of modes to the Mn atoms, forming an arrangement like a sinusoid for the Mn atoms. The structural parameters of these compounds were compared with the data obtained from EXAFS determination for the Mn cluster in the OEC of PS11, supporting that the coordination sphere of the Mn site in the OEC may contain carboxyl bridges. The possible combination modes between the carboxyl group and the Mn atoms have been suggested. The NMR signals exhibit widening and shift produced by the influence of the paramagnetic Mn" sites. The red-shift of the absorption in IR spectrum was observed to be attributed to the coordination of the carboxyl group to the Mn     

Catalytic activity of phosphorus and steam modified HZSM-5 and the theoretical selection of phosphorus grafting model

The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phosphorus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic properties of 1% phosphorus and steam modified HZSM-5 zeolites have been investigated. The X-ray diffraction （XRD） results exhibit that there is considerable variation in the relative intensity of the individual diffraction peaks. The acidity of the samples decreases with an increase in the steaming temperature, which is determined by the IR of adsorbed pyridine and temperature programmed desorption （TPD） of ammonia. The oxidation state of phosphorus shown by XPS is ＋5, and a model for surface structure modification is proposed. The nitrogen adsorption isotherm for all samples is a combination of type I and type IV, all hysteresis loops resemble the H4-type. The density functional and cluster model methods have been invoked to select the phosphorus grafting model, and it was found that the phosphorus grafting model were more probable in the form of the terminal oxygen coordinating with aluminum.     

An undecanuclear iron (Ⅲ) oxo-hydroxo aggregate with near nanometer size:Synthesis and crystal structure of[Fe_(11)O_6(OH)_6(O_2CPh)_3(O_2CPhMe-p)_(12)]

The tide compound is formed by controlled hydrolytic polymerization in nonaqueous solution of simple oxo-bridged binuclear ferric salts under the presence of carboxylate ligands. The rhombohedral crystalline form of the cluster with six imidazole molecules, which has crystallographically required C3v symmetry, will be reported. The largest Fe-Fe distance in the undecairon oxo-hydroxo cluster is about 0.68 nm and the cluster has a diameter near 2 nm, which implies that this cluster reaches a nanometer-sized dimension.     

Theoretical Study of Geometric Structures for Ground-state Al_nC（n=2-7） Clusters

With the aid of the molecular orbital DMol3 program,the energetics and electronic structures of several AlnC(n = 2-7) configurations have been searched and calculated by improved minimum energy paths(MEPs) by setting "imaging product".A new high symmetry,supervalence isomer of Al5C cluster,i.e.,D5h-Al5C,at the local minimum in the MEPs is detected.Several parameters,such as binding energy,HOMO-LUMO energy gap,vertical electron detachment energy and electron affinity energy,are calculated to characterize and evaluate the stability of three Al5C configurations,i.e.,D5h-Al5C,Cs-Al5C and C1-Al5C.The results show that the D5h-Al5C cluster is the ground state structure instead of Cs-Al5C.Due to the formation of many central σ bonds after polymerizing for D5h-Al5C,the decrease of the energy for HOMO orbit results in more territory for HOMO electrons of dislocation effect,then the energy difference between HOMO and LUMO is increasing to enhance the stability of molecules to produce such supervalence structure of Al5C cluster.The configuration evolution between D5h-Al5C,Cs-Al5C and C1-Al5C and the synthesis preference in the mode of Al5 + C → Al5C reveals that the Cs-Al5C and C1-Al5C con-figurations are permissive to coexist with D5h-Al5C structure in energetics.     

Hartree-Fock-Roothaan Calculations for Ground States of Some Atoms Using Minimal Basis Sets of Integer and Noninteger n-STOs

Hartree-Fock-Roothaan (HFR) calculations for ground states of some atoms, i.e. He, Be, Ne, Ar, and Kr have been performed using minimal basis sets of Slater type orbitals (STOs) with integer and noninteger principal quantum numbers (integer n-STOs and noninteger n-STOs). The obtained total energies for these atoms using minimal basis sets of integer n-STOs are in good agreement with those in the previous literature. On the other hand, for the case of minimal basis sets of noninteger n-STOs, although the calculated total energies of these atoms agree well with the results in literature, some striking results have been obtained for atoms Ar and Kr. Our computational resuits for the energies of atoms Ar and Kr are slightly better than those in literature, by amount of 0.00222 and 0.000054 a.u., respectively. The improvement in the energies of atoms Ar and Kr may result from the efficient calculations of one-center two-electron integrals over noninteger n-STOs. For some atomic ions in their ground state, HFR calculations have been carried out using minimal basis sets of noninteger n-STOs. The obtained total energies for these atomic ions are substantially lower than those available in literature.     

Theory Study of the Adsorption of Hydrocyanic Acid onto Small Silver Clusters

Density functional theory calculations have been performed to study the interaction of small silver clusters, Ag2 ~Ag9, with HCN. The adsorption of HCN on-top site of the silver cluster, among various possible sites, is energetically preferred. The adsorption energies of HCN on the silver clusters reach a local maximum at n = 4, which is only about 0.450 eV, indicating that the adsorbed HCN molecule is weakly perturbed. The adsorbed C–N and C–H stretching frequencies are blue- and red-shifted compared with the values of free HCN, respectively.     

A SERIES OF TRINUCLEAR MOLYBDENUM CLUSTERS WITH LOOSE COORDINATION SITES

<正> The cluster compound Mo3S4[S2P(OEt)2]4(H2O) with a comparatively stable cluster core [Mo3(μ3-S)(μ-S)3]4+ and some labile ligands or loosely coordination sites has been already prepared successfully by a self-assembly reaction. Its surprising chemical reactivity in the reactions of substitution, addition, and oxidation has been noted and used widely for the syntheses of a series of new, trinuclear Mo cluster compounds, of which the structures of the 12 selected compounds characterized by X-ray diffraction analysis are exhibited in diagrams. Meanwhile, those compounds with the same cluster core [Mo3(μ3-S)(μ-S)2]4+ show two groups of characteristic IR bands at ~480 cm-1 for the Mo-(μ-S) vibration and -450cm-1. for the Mo- (μ3-S), and their selected bond distances are tabulated as well.In a cluster-catalyzed homogeneous process, it is important that clusters have loose coordination sites or are coordination unsaturated. In our further research on the medium-valence molybdenum clusters[1], we have foun     

Investigation on Oxidation-Reduction Properties of Some Fe-S and Mo-Fe-S Clusters

Oxidation-reduction properties of some Fe-S and Mo-Fe-S clusters have been studied by cyclic voltammetric measurement. It is indicated that there are some factors which affect the oxidation- reduction properties of clusters, of which are charge density of metal atom in cluster core, electron effect of ligands, charge and geometric configurations of the reactant particle, etc.     

Studies in cluster ion formation. Part I. Fast atom bombardment mass spectrometry of tetraalkylammonium halides: Factors influencing cluster ion size and stability

Positive and negative ion fast atom bombardment mass spectra of tetraalkylammonium halide salts (NR₄X, where X = Cl, Br, I and NR₄ = NMe₄, NEt₄) have been studied and intense cluster ion formation has been observed. The cluster ion intensity distributions were found to show enhancements at certain cluster numbers (n). The negative cluster ions of NMe₄X salts showed anomalous ion intensity regions, which differed from both the positive cluster ions of all NR₄X salts and also the corresponding negative clusters of NEt₄X salts. The influence of anion and cation size on cluster ion formation and abundances has been studied and it has been established that smaller anion and cation size favours the formation of larger cluster ions. The possible structures of the cluster ions exhibiting relative increased stabilities are discussed.     

Rotational diffusivity of fractal clusters

The rotational diffusion behavior of fractal clusters generated through an off-lattice cluster-cluster aggregation algorithm in both diffusion-limited cluster aggregation and reaction-limited cluster aggregation conditions is investigated. The extended Kirkwood-Riseman theory (Garcia de la Torre et al., Macromolecules, 1987) is used to estimate the cluster rotational diffusion tensor. The three eigenvalues of this tensor, which correspond to the three main rotational diffusivity values of the cluster, have been computed for each generated cluster. Once the eigenvalues have been sorted in ascending order, each of them has been averaged over several thousands of clusters. It is found that one of the three main average rotational diffusivities is substantially larger than the other two, indicating significant anisotropy of fractal clusters. Moreover, a rotational hydrodynamic radius Rh,r has been determined on the basis of the mean value of the three average rotational diffusivities, which is about 25% larger than the mean translational hydrodynamic radius Rh calculated through the same Kirkwood-Riseman theory. Finally, the obtained Rh,r values have been applied to interpret dynamic light scattering data from aggregating colloidal systems and to investigate the reliability of the assumption, Rh = Rh,r, typically made in the literature.     

An improved clusterion-photoelectron coincidence technique for the investigation of the ionisation dynamics of clusters

The introduction of photoion-photoelectron coincidence techniques has made it possible to investigate photoionisation properties of heavy clusters, which are not accessible by conventional mass spectrometry. This technique has been further developed in combination with a zero-volt electron energy analyser and greatly improved in performance. The method has been applied to the investigation of different homogeneous and heterogeneous clusters. This type of cluster experiment requires both a very high resolution and a large dynamic range in order to identify also clusters present in low abundance. As an example, a series of coincidence mass spectra of Xe clusters has been recorded at different wavelengths. Below a photon energy of 11.1 eV, the range of observable clusters shifts to higher cluster sizes with decreasing energy. Appearance potentials and the binding energy of different cluster ions were obtained. Intensity fluctuations, already observed in spectra with electron bombardment ionisation (magic numbers), have also been detected in the coincidence spectra and become most pronounced near the ionisation threshold. This indicates that these fluctuations are caused by the size-dependent stability of the ionic and not the neutral cluster. Furthermore, the threshold size does not change linearly with cluster size. The binding energy per particle seems to change drastically aroundn=13 which indicates the existence of a shell structure in the cluster ion.     

A large indium sulfide supertetrahedral cluster built from integration of ZnS-like tetrahedral shell with NaCl-like octahedral core

An entirely new type of chalcogenide cluster and a new structural mechanism for the formation of large semiconducting tetrahedral clusters have been revealed as a result of crystallization of a templated indium sulfide consisting of an unprecedented cluster, In(38)S(65), which is the largest supertetrahedral cluster based on trivalent metal ions. At the core of this cluster is In(10)S(13), which can be considered as a fragment of the NaCl-type lattice. The In(10)S(13) cluster is coupled to four In(4)S(10) supertetrahedral T2 clusters and four In(3)S(3) hexagonal rings to give In(38)S(65), which is also the largest inorganic chalcogenide supertetrahedral cluster, superseding a supertetrahedral T5 cluster with only 35 metal sites.     

The Drift Velocity of a Fractal Cluster

The drift velocity of a fractal cluster has been analyzed as depending on a parameter that characterizes its permeability. Equations have been derived that determine the range in which the conditions of the Stokes regime of cluster motion are met. Calculation results represented as the plots of the studied dependences have been discussed.     

Some structural systematics in metal carbonyl cluster chemistry

The recently developed electron-counting rules for condensed polyhedral metal carbonyl clusters have been utilised to develop a systematic approach for enumerating the structural alternatives for metal cluster compounds which are isoelectronic. The more usual cluster degradation and aggregation processes are represented in a matrix form which relates the change in electron count to the number of new bonds formed (or broken). The matrices for cluster degradation and aggregation are represented in a complementary fashion so that the search for isoelectronic clusters greatly simplified. The utility of the approach is illustrated by reference to some recent examples from metal carbonyl cluster chemistry.     

The formation and kinetics of Ionized Cluster Beams

The formation and kinetics of large vapourized-material cluster beams (large size metal clusters) are discussed. The clusters are formed by injecting the vapour of solid state materials into a high vacuum region through a nozzle of a heated crucible. The conditions under which metal clusters form are analysed using nucleation theory. Computer simulation by combining the nucleation and flow equations has also been made. The results show that the theory can be useful in predicting qualitative dependences of metal cluster formation on operation conditions. Several experimental results are also presented, which support the finding that a large size metal cluster is formed by homogeneous nucleation and growth. The advantageous characteristics of ionized cluster beam for thin film formation are also discussed.     

Fluorescence of rare gas clusters excited with synchrotron radiation

A cluster beam experiment for fluorescence measurements on rare gas clusters has been built up. First results on the evolution of energy levels of neutral krypton clusters with a cluster size between 200–8500 atoms/cluster are reported. The well known bulk excitons of solid krypton do not merge into the first atomic lines and appear only in clusters larger than 300 atoms/cluster. Smaller clusters absorb only at energies which fit well with surface excitons of the solid.     

Mo（W）－Co（Ni，Fe）簇合物的加氢脱硫催化活性

对线型、立方烷型和笼状３种不同构型的Ｍｏ（Ｗ）－Ｃｏ（Ｎｉ，Ｆｅ）－Ｓ（Ｏ）簇共１２种化合物进行了噻吩加氢脱硫和环己烯加氢的催化活性研究．讨论了簇合物的组成，金属原子的配比、价态与催化活性的关系．探讨了不同构型对活性的影响．     

激光产生的钒硫簇离子的统计分布与结构探讨

以脉冲激光在高真空中溅射钒粉和硫粉的混合物，产生了一系列钒硫原子簇正负离子。根据对其实验记录的激光等离子体质谱进行分析，发现钒硫原子簇的化学键基本上是共价型的，对应于相同钒原子数目的正负离子的相对丰度分别符合于不同形式的对数正态分布。正离子的相对丰度随硫原子数的增加呈对数衰减，由此可以确定各种大小簇合物的簇骼与几何构型；负离子的相对丰度则基本上呈正常的正态分布，说明在簇骼上结合了不同数量硫原子的负离子之结构稳定性大致相近。在实验中还观察到一类硫原子含量较高的簇离子，其中的部分硫原子可能在本身成键形成环状的硫集团后，又与原来的簇骼结合，因而在硫原子数较多时它们的相对丰度符合另一条对数正态分布曲线。