CH2XH→CH3X (X＝O, S, Se)异构化的量子拓扑研究

利用从头算和量子拓扑方法讨论了CH₂XH→CH₃X (X＝O, S, Se)异构化过程的反应机理. 着重从电子密度拓扑分析计算了反应进程中的各点, 讨论了反应进程中键的断裂和生成, 上述反应都经历了三元环过渡结构, 找到了这类反应的"能量过渡态"和"结构过渡态", 且结构过渡态均在能量过渡态之后出现. 三元结构过渡态结构出现的范围与反应热成正比.     

Topological polymer chemistry by dynamic selection from electrostatic polymer self-assembly

A collection of recent developments in topological polymer chemistry is presented. First, topological isomerism occurring on randomly coiled, flexible polymer molecules having cyclic and linear structures is discussed. Second, an electrostatic self-assembly and covalent fixation strategy has been developed for the synthesis of polymeric topological isomers. These isomers have double cyclic, manacle-, and theta-shaped constructions, and are prepared by using either linear or star telechelic polymer precursors having moderately strained cyclic ammonium salt groups, which carry multifunctional carboxylate counteranions. A technique of reversed-phase chromatography (RPC) is demonstrated as an effective means to separate polymers with different topologies, especially polymeric topological isomers. A further extension of topological polymer chemistry has been observed by dynamic selection from electrostatic polymer self-assembly to enable the effective formation of tadpole-shaped, cyclic-linear hybrid topologies.     

Experimental and theoretical study of the structure of N,N-dimethyl-4-nitroaniline derivatives as model compounds for non-linear optical organic materials

Molecular and crystal structure of a series of derivatives of N,N-dimethyl-4-nitroaniline has been studied by both X-ray diffraction method and high-level ab initio calculations. According to these data, the dimethylamino groups were found to have a trigonal-pyramidal configuration and are considerably turned with respect to the ring plane in all molecules having a substituent in the ortho-position; on the contrary, this group is planar in the meta-substituted molecules. Topological analysis of the electron density function for all molecules studied within the framework of Bader's ‘atoms in molecules’ (AIM) theory revealed that introduction of a substituent into the ortho- or meta-position of the ring results in increasing of the contribution of the resonance forms different from the quinoid one. Contribution of the latter form is predominant for the structure of N,N-dimethyl-4-nitroaniline (1). Topological analysis of the electron density distribution was used to explain a decreasing of the molecular hyperpolarisabilites of the ortho- and meta-substituted compounds as compared with those for 1.     

Three-dimensional aromaticity in deltahedral boranes and carboranes

Methods derived from topology and graph theory indicate that the deltahedral boranes B _n H _n ^2– and the corresponding carboranes C₂B_n–2H _n (6 n 12) may be regarded as three-dimensional delocalized aromatic systems in which surface bonding and core bonding correspond to -bonding and -bonding, respectively, in planar polygonal two-dimensional hydrocarbons CinnH _n ^(n–6)+ (n=5/7). The two extreme types of topologies which may be used to model core bonding in deltahedral boranes and carboranes are the deltahedral (D _n ) topology based on the skeleton of the underlying deltahedron and the complete (K _n ) topology based on the corresponding complete graph. Analyses of the Hoffmann-Lipscomb LCAO extended Hückel computations, the Armstrong—Perkins—Stewart self-consistent molecular orbital computations, and SCF MOab initio GAUSSIAN-82 computations on B₆H₆ ^2– indicate that the approximation of the atomic orbitals by the sum of the molecular orbitals, as is typical in modernab initio computations, leads to significantly weaker apparent core bonding approximated more closely by deltahedral (D _n ) topology than by complete (K _n ) topology.This work was presented at the Workshop The Modern Problems of Heteroorganic Chemistry sponsored by the A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences (May 8–13, 1993).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1353–1360, August, 1993.     

化合物结构／性质相关的研究／拓扑指数法（Ⅰ）

本文提出一种新的拓扑指数－ＥＡ系列指数，它是从表示分子图形的邻接矩阵出发，结合图形中顶点的度构造成ＥＡ矩阵，计算ＥＡ矩阵的本征值，求出本征值绝对值和指数ＥＡΣ及本征值绝对值最大值指数ＥＡｍａｘ，实验表明，ＥＡ系列指数具有良好的唯一性和相关性。     

Molecular Volume of Phosphates, Arsenates and Vanadates

The present paper discusses some characteristics of the molecular volumes of phosphates, arsenates and vanadates. In the salts, the volumes of per acid radical ((?)) quantitatively depend on the radii, charges, numbers of cations and anions. The functional relations between the (?) values of phosphates, arsenates, vanadates and the factors mentioned above are obtained. The molecular volumes of these salts are equal to the sum of the topological volumes of cations and anions. The authors have got a series of universally united topological volume values of cations and anions. It confirms that the topological molecular volume of the crystal water (H_2O) in the hydrates of the salts approximates to a constant, 244 (?)~3 with σ_(n-1)= 2.1. The topological volume of the hydroxide ion (OH~-) approximates to a constant too. The average value is 16.89 (?)~3 with σ_(n-1)=1.68.     

Energetic and topological analyses of the oxidation reaction between Mo(n) (n = 1, 2) and N2O

The interaction between molybdenum, atom, and dimer, with nitrous oxide has been investigated using density functional theory. The analysis of the potential energy surfaces for both reactions has revealed that a single molybdenum atom can activate the N--O bond of N2O requiring a small activation energy. However, the presence of several intersystem crossings between three different spin states, namely, septet, quintet and triplet states, seems to be the major constraint to the Mo + N2O reaction. Contrarily, the low-lying excited states (triplet and quintet) do not participate in the reaction between the molybdenum dimer and N2O. The latter reaction fully evolves on the singlet spin surface. Three different regions have been distinguished along the pathway: formation of an adduct complex, formation of an inserted compound, and the N2 detachment. The connection between the two first regions has been characterized by the formation of a special complex in which the N--O bond is so weakened that it could be considered as a first step in the insertion process. It has been shown that the topological changes along the pathways provide a clear explanation for the geometrical changes that occur along the reaction pathway. In summary, the detachment of the N2 molecule is found to be kinetically an effective process for both reactions, owing to the high exothermicity and consequently to the high internal energy of the insertion intermediates. However, in the case of Mo atom, the reaction should be a slow process due to the presence of spin-forbidden transitions. These results fully agree with previous experimental works.     

3D Uranyl Organic Frameworks Supported by Rigid Octadentate Carboxylate Ligand: Synthesis,Structure Diversity,and Luminescence Properties

Seven three dimensional (3D) uranyl organic frameworks (UOFs), formulated as [NH₄][(UO₂)₃(HTTDS)(H₂O)] ( 1 ), [(UO₂)₄(HTTDS)₂](HIM)₆ ( 2 , IM=imidazole), [(UO₂)₄(TTDS)(H₂O)₂(Phen)₂] ( 3 , Phen=1,10-phenanthroline), [Zn(H₂O)₄]_0.5[(UO₂)₃(HTTDS)(H₂O)₄] ( 4 ), and {(UO₂)₂[Zn(H₂O)₃]₂(TTDS)} ( 5 ), {Zn(UO₂)₂(H₂O)(Dib)_0.5(HDib)(HTTDS)} ( 6 , Dib=1,4-di(1H-imidazol-1-yl)benzene) and [Na]{(UO₂)₄[Cu₃(u₃-OH)(H₂O)₇](TTDS)₂} ( 7 ) have been hydrothermally prepared using a rigid octadentate carboxylate ligand, tetrakis(3,5-dicarboxyphenyl)silicon(H₈TTDS). These UOFs have different 3D self-assembled structures as a function of co-ligands, structure-directing agents and transition metals. The structure of 1 has an infinite ribbon formed by the UO₇ pentagonal bipyramid bridged by carboxylate groups. With further introduction of auxiliary N-donor ligands, different structure of 2 and 3 are formed, in 2 the imidazole serves as space filler, while in 3 the Phen are bound to [UO₂]²⁺ units as co-ligands. The second metal centers were introduced in the syntheses of 4–7 , and in all cases, they are part of the final structures, either as a counterion ( 4 ) or as a component of framework ( 5 − 7 ). Interesting, in 7 , a rare polyoxometalate [Cu₃(μ₃-OH)O₇(O₂CR)₄] cluster was found in the structure. It acts as an inorganic building unit together with the dimer [(UO₂)₂(O₂CR)₄] unit. Those uranyl carboxylates were sufficiently determined by single crystal X-ray diffraction, and their topological structures and luminescence properties were analyzed in detail.     

Locally s-distance transitive graphs and pairwise transitive designs

The study of locally s-distance transitive graphs initiated by the authors in previous work, identified that graphs with a star quotient are of particular interest. This paper shows that the study of locally s-distance transitive graphs with a star quotient is equivalent to the study of a particular family of designs with strong symmetry properties that we call nicely affine and pairwise transitive. We show that a group acting regularly on the points of such a design must be abelian and give general construction for this case.