Synthesis, Crystal Structure and Electrochemical Properties of [Ni(phen)3]·(m-nitrobenzoic acid)2·(H2O)

A new nickel(Ⅱ) coordination complex [Ni(phen)3]·(m-nitrobenzoic acid)2·(H2O) was synthesized by self-assembly of m-nitrobenzoic acid, 1,10-phenanthroline and nickelous perchlorate. It crystallizes in the monoclinic system, space group C2/c, with a = 2.4596(6), b = 1.2124(3), c = 1.9824(5) nm, β = 97.088(5)°, V = 5.866(3) nm3, Dc = 1.474 g/cm3, Z = 4, Mr = 1301.82, μ(MoKα) = 0.417 mm-1 F(000) = 2688, R = 0.0493 and wR = 0.1025. Structural determination indicates that the nickel(Ⅱ) ion is coordinated with six nitrogen atoms from three phens, giving a distorted octahedral coordination geometry. The cyclic voltametric analysis shows that the electron transfer in the electrode reaction is irreversible.     

La6Mo8O33: a new ordered defect scheelite superstructure

The structure of La₆Mo₈O₃₃ has been determined from a triple pattern powder diffraction analysis. Two high-resolution neutron diffraction patterns collected at 1.594 and 2.398 Å and one X-rays were used. This molybdate crystallizes in a non-centrosymmetric monoclinic space group P2₁(N°4), Z=2,a=10.7411(3) Å, b=11.9678(3) Å, c=11.7722(3) Å, β=116.062 (1)°. La₆Mo₈O₃₃ is an unusual ordered defect Scheelite. Hence, it should be described with cation vacancies and an extra oxygen atom following the formula: La₆□₂Mo₈O₃₂₊₁. This extra oxygen atom leads to a pyramidal environment, whereas the other molybdenum atoms present tetrahedral environment. A molybdenum tetrahedral is connecting to the pyramid, forming an [Mo₂O₉] unit.     

疏水性微孔中水的结构和扩散性质的分子模拟

用分子动力学（MD）方法模拟了受限在疏水性微孔中的水的结构与动力学行为.分别考察了孔径、温度和压力对水在孔道方向的密度分布和自扩散系数的影响,计算了不同温度下水的径向分布函数.发现在小孔径的微孔中,随着温度的降低,水分子沿孔道的分布逐渐变得不均匀,最终导致气-液相分离,微孔孔道内有明显的分段现象.受限在小孔径微孔中水的自扩散系数大约为体相流体水的20％～30％,并且随着孔径的减小,自扩散系数也减小.同时还发现沿孔道方向的自扩散系数分量大约为孔径方向的4～5倍.提出了微孔中水自扩散系数的关联模型.     

A theoretical study of substituent effects on the structure of isolated and condensed three-membered rings. A comparison between radicals and parent hydrocarbons

Substituent effects on the structure of radicals and parent hydrocarbons formed by isolated or condensed three-membered rings have been investigated by Hartree-Fock, post-Hartree-Fock and density functional methods. The trends of structural parameters computed for the hydrocarbon systems are in agreement with available experimental data. Substituent effects can be rationalized in terms of interactions between localized orbitals obtained by natural bond analysis. The effects are even larger in free radicals and can be analyzed using the same model. Received: 13 March 1998 / Accepted: 13 July 1998 / Published online: 9 October 1998     

部份层无序铝交联蒙脱土结构的研究

应用非完整晶体的XRD衍射及阳离子交换量的测定等实验数据, 得出了铝交联蒙脱土的三维结构模型. 结构中Al(III)多数以十三聚体形式进入层间, 层间距为1.97 nm, 几率为0.65, 少数以六聚体形式进入层间, 层间距为1.5 nm, 几率为0.25, 其余10%的层间仅为水分子. 并给出了交联柱子在层间的分布与层单元之间的连接方式. 目前通用的以Bragg公式计算所得的d_(001)值来表征交联浆脱土的层间距是不确切的.     

丝氨酸在蔗糖水溶液中的稀释焓

利用LKB 2277生物活性检测仪分别测定了298.15 K时丝氨酸在不同组成的蔗糖水溶液中的稀释焓, 利用McMillan-Mayer理论,计算了丝氨酸在不同组成的蔗糖水溶液中的焓对相互作用系数,并与其在葡萄糖水溶液中的焓对相互作用系数h2进行了比较.结果表明,丝氨酸在蔗糖和葡萄糖水溶液中的焓对相互作用系数h2都是负值,并且随着糖浓度的增加,h2系数的绝对值逐渐减少.根据溶质-溶质相互作用和溶质-溶剂相互作用对结果进行了解释.     

Structural and energetic consequences of the formation of intramolecular hydrogen bonds

Formation of intramolecular hydrogen bonds leads to structural modifications in the whole molecule, which are discussed on the basis of B3LYP/6-31G(d,p) calculations. The energy and the structure of various hydrogen-bonded and open conformers are considered for two groups of ortho-substituted phenols–N-dimethylaminomethylphenols (Mannich bases) and N-methylbenzylideneamines (Schiff bases). The energy of intramolecular hydrogen bond formation in Mannich bases was corrected for non-bonded interactions within the molecules, based on a thermodynamic cycle. Structural data were used to estimate the fraction of the ortho-quinoid (keto) form in particular tautomers. It is shown that proton transfer in Schiff bases leads to an increase of this fraction to about 40%, while opening of the hydrogen bond in the proton transferred form increases the keto fraction to 70%.     

Zur Kristallchemie der Oxoplatinate

On the Crystal Chemistry of Oxoplatinates Referring to the coordination of Pt²⁺ and Pt⁴⁺ by oxygen the crystal structures of oxoplatinates will be systemized. Pt²⁺ exclusively shows in solids a square and planar coordination well known and typical for Cu²⁺, Pd²⁺ and Ni²⁺ too. Often mixed valences (Pt²⁺/Pt⁴⁺) are observed in square planar oxygen surrounding. Some exceptionally rare coordination is the dumbbell like O—Pt²⁺—O. The crystal chemistry of Pt⁴⁺ resembles the countless metal ions showing octahedral coordination by oxygen. Despite different compositions the compounds BaLn₂PtO₅, Ba₃Cu₂Ln₂PtO₁₀, Ba₅Ln₈Zn₄O₂₁, Ba₁₃Ln₈Zn₄Pt₄O₃₇ and Ba₁₇Ln₁₆Zn₈Pt₄O₅₇ show amazing relationships of polyhedra connections. Additionally will be shown that Ba₄Sm₄Zn₃PtO₁₅ is isotypic to Ba₆Nd₂Al₄O₁₅ and Ba₄NaCu_{0, 5}Pt_{1, 5}O₈ to Ba₁₅Pt₆O₂₇. Oxoplatinates containing lone pair active elements show one side open polyhedra. The positions of the free (s²) electrons are calculated using the Coulomb terms of lattice energy.     

Consequence of assuming gamma-type distribution for characterizing structural heterogeneity of microporous solids

Extensive model studies were carried out for the gamma-type distribution, which was used to characterize structural heterogeneity of microporous solids. This distribution lead to a simple equation, which gave a good representation of many adsorption isotherms measured on microporous activated carbons. Assuming physically realistic values of the adsorption parameters, the gamma-type distribution curves were calculated together with curves of the adsorption isotherm, micropore distribution, adsorption potential distribution, enthalpy and entropy of adsorption.

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Die Konsequenz der Annahme einer Gamma-Typ-Verteilung bei der Charakterisierung der strukturellen Heterogenität von mikroporösen Feststoffen

Zusammenfassung Es wurden für die Gamma-Typ-Verteilung, die zur Charakterisierung der strukturellen Heterogenität von mikroporösen Feststoffen genutzt wurde, ausgedchnte Modellrechnungen durchgeführt. Diese Verteilung führte zu einer einfachen Gleichung, die eine gute Darstellung vieler Adsorptionsisothermen an mikroporös-aktiviertem Kohlenstoff erlaubt. Unter der Annahme von physikalisch realistischen Werten für die Adsorptionsparameter wurden die Gamma-Typ-Verteilungskurven zusammen mit Kurven für die Adsorptionsisothermen, der Mikroporenverteilung, der Adsorptionspotentialverteilung und der Enthalphie und Entropie der Adsorption berechnet.