Novel Cyanide-Bridged Three-Dimensional Coordination Polymer Derived from an Octahedral Rhenium Cluster [Re6Te8(CN)6]4?: Synthesis and Crystal Structure of [{Mn(H2O)2(DMF)} 2Re6Te8(CN)6]·2H2O

The reaction of a water solution of K₄Re₆Te₈(CN)₆ with a solution of Mn(NO₃)₂ in 0.02M hydrochloric acid in the presence of DMF gave crystals of a cluster rhenium complex [{ Mn(H₂O)₂(DMF)}₂Re₆Te₈(CN)₆]·2H₂O. The structure of the compound was determined by single crystal X-ray diffraction (a = 12.6679(9) Å, b = 17.4524(12) Å, c = 9.7882(6) Å, β = 105.570(6)°, V = 2084.6(3) ų, Z = 2, space group P2₁/n, R = 0. 0389). In the complex, the [Re₆Te₈(CN)₆]⁴⁻ cluster anions are linked to Mn²⁺ cations by the cyanide bridges, the manganese cations being additionally coordinated by the DMF molecule and two water molecules. The neighboring clusters are joined by Re-C-N-Mn bridges into a three-dimensional framework possessing cavities filled with doubly disordered water molecules.Original Russian Text Copyright © 2004 by Yu. V. Mironov, S. F. Solodovnikov, V. E. Fedorov, and Yu. V. Gatilov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 918–922, September–October, 2004.     

Factors affecting physicochemical properties of liposomes prepared with hydrogenated purified egg yolk lecithins by the microencapsulation vesicle method

We examined hydrogenated purified egg yolk lecithins, having practical advantages over non-hydrogenated ones, as liposomal membrane materials. Liposomes were prepared by the microencapsulation vesicle (MCV) method in which liposomes are formed through two-step emulsification and dispersion. Three types of purified egg yolk lecithins with different iodine values were examined after being dissolved in one of three lipid solvents. The liposome size increased as the temperature during the second emulsification increased, being closer to the boiling temperature of the solvent. The preparation temperature in relation to the transition temperature of each lecithin was also a factor affecting liposome sizes. As for the encapsulation efficiencies of the model compound calcein in liposomes, they differed mainly depending on the solubility of each lecithin in a lipid solvent and it was more obvious in hydrogenated lecithins. A high preparation temperature resulted in lower encapsulation efficiencies, suggesting that leakage of encapsulated calcein was facilitated at high temperature in the MCV methods. There was a significant correlation between liposome sizes and encapsulation efficiencies in non-hydrogenated purified egg yolk lecithin but not in hydrogenated ones. When using hydrogenated purified egg yolk lecithins as liposomal membrane materials, it was suggested that a lipid solvent should be chosen so that a lecithin completely dissolves under the preparation condition in order to achieve a higher encapsulation efficiency. Smaller liposome particles were obtained when the second emulsification was performed at a lower temperature compared with the boiling point of the lipid solvent. These findings can be applied to control encapsulation efficiencies and particle sizes in each particular liposome preparation enclosing therapeutic agents.     

Nonlinear Optical Properties of Tri—nuclear Transition Metal Clusters M—（μ—S）s—M′（M=Mo,W;M′=Cu,Ag,Au）

The static polarizabilities and the second-order hyperpolarizabilities of a series of tri-nuclear metal cluster models MS4(M′PPh3)2(M′PPh3)(M=Mo,W;M′=Cu,Ag,Au)have been calculated within the first-principle theoretical framework. The model clusters have two fragments of rhombic units and it is the charge ransfer from one of these moieties to the other that is responsible for nonlinear optical property. This kind of electronic delocaization, differentiated from that of planar π-system, is very interesting and is worthy for further investigation.     

Supersonic jet spectroscopy of naphthalene–fluorene bichromophoric cluster

We have investigated the supersonic jet spectroscopy and photophysics of 1-methylnaphthalene–fluorene (1MN–FL) cluster, and looked for indications of intramolecular electronic energy transfer (Intra-EET) from the FL (donor, D) to 1MN (acceptor, A). The clusters were identified by their time of flight (TOF) mass spectra. We observed clusters bands in the LIF spectrum near the region of 1MN origin. We have also observed cluster TOF–resonance enhanced multi-photon ionization (REMPI) spectrum near the electronic origin of the fluorene moiety. However, this spectrum was almost independent of the excitation wavelength, and was not observed in the LIF spectrum. This is probably due to fast Intra-EET resulting in lifetime broadening of the donor chromophore cluster spectrum, similar to that observed previously for the naphthalene–anthracene bichromophoric system.     

Mesoscopic structure and properties of liquid crystalline mesophase pitch and its transformation into carbon fiber

The history and present state of the art in the chemistry of mesophase pitch, which is an important precursor for carbon fiber and other high-performance industrial carbons, are reviewed relative to their structural properties. The structural concepts in both microscopic and macroscopic views are summarized in terms of the sp(2) carbon hexagonal plane as a basic unit common to graphitic materials, its planar stacking in clusters, and cluster assembly into microdomains and domains, the latter of which reflect the isochromatic unit of optical anisotropy. Such a series of structural units is described in a semiquantitative manner corresponding to the same units of graphitic materials, although the size and stacking height of the hexagonal planes (graphitic sheets) are very different. Mesophase pitch is a liquid crystal material whose basic structural concepts are maintained in the temperature range of 250 to 350 degrees C. The melt flow and thermal properties are related to its micro- and mesoscopic structure. The structure of mesophase-pitch-based carbon fiber of high tensile strength, modulus, and thermal conductivity has been formed through spinning, and has inherited the same structural concepts of mesophase pitch. Stabilization settles the structure in successive heat treatments up to 3000 degrees C. Carbonization and graphitization enable growth of the hexagonal planes and their stacking into units of graphite. Such growth is governed and controlled by the alignment of micro- and mesoscopic structures in the mesophase pitch, which define the derived carbon materials as nanostructural materials. Their properties are controlled by the nanoscopic units that are expected to behave as nanomaterials when appropriately isolated or handled.     

Pt-V2O5/HM催化剂积炭机理的TPO研究

Ｐｔ┐Ｖ２Ｏ５／ＨＭ催化剂积炭机理的ＴＰＯ研究蔡炳新（湖南大学化学化工系，长沙４１００１２）周烈华郑小明（杭州大学催化研究所，杭州３１００２８）关键词铂，五氧化二钒，氢型丝光沸石，程序升温氧化酸性载体Ｐｔ系贵金属双功能催化剂表面积炭是导致其催化性能衰...     

色谱技术在中药指纹图谱研究中的应用

 介绍了气相色谱、高效液相色谱、超临界流体色谱和高速逆流色谱等几种色谱技术在中药指纹图谱研究中的应用现状,以及使用模糊聚类分析和人工神经网络分析指纹图谱对中药进行模式识别和质量鉴定的方法。