Light transmission by polymer-dispersed liquid crystals

Light transmission of nematic liquid crystals dispersed in a polymeric matrix is investigated. The paper gives a theoretical analysis of light transmission by the liquid crystal-polymer and liquid crystaldye-polymer systems based on determination of the total cross section of extinction. The mathematical model is considered in the anomalous diffraction approximation. The theoretical calculations are in good agreement with experimental data obtained for films based on cyanodiphenyl dispersed into a polyvinyl acetate matrix.Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 6, pp. 118–122, November–December, 1993.Translated by L. Chernomorskaya     

Synthesis, properties, and structure of dimethylgold(III) complexes [(CH3)2AuI]2 and (CH3)2AuS2CN(C2H5)2

Volatile diethyldithiocarbamate of dimethylgold(III) was prepared by the interaction of dimethylgold(III) iodide with sodium diethyldithiocarbamate. The complex is examined by the elemental analysis, DTA, IR and electronic spectroscopy. The starting dimeric complex [(CH₃)₂AuI]₂ and a novel monomeric volatile gold(III) complex (CH₃)₂AuS₂CN(C₂H₅)₂ with the AuC₂S₂ coordination core were investigated by single crystal X-ray diffraction for the first time.     

X-ray study of volatile Ni(II), Cu(II), and Pd(II) complexes of β-ketoimine pivalyltrifluoroacetone

Synthesis of volatile complexes based on -ketoimine pivalyltrifluoroacetone, C(CH₃)₃C(NH)CH₂COCF₃, is described. The general formula of the complexes is M(L)₂, where M = Cu, Ni, Pd. Complexes of this kind with Ni and Pd were obtained for the first time. The Cu and Pd complexes were found to be isostructural. A comprehensive crystal-chemical study showed that all structures are molecular and built of trans-complexes. The central atom has a square plane environment. The average M-O and M-N distances are nearly equal in all compounds: 1.84 , 1.92 , and 1.98 for Ni, Cu, and Pd complexes, respectively; the mean values of the O-M-N chelate angles are 93.4°, 91.9°, and 92.7°, respectively.Original Russian Text Copyright © 2004 by I. A. Baidina, G. I. Zharkova, N. V. Pervukhina, S. A. Gromilov, and I. K. IgumenovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 713–722, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Packing of complexes and intermolecular interactions in the crystals of volatile palladium(II) β-diketonates. crystal structure of palladium(II) benzoyltrifluoroacetonate

This paper reports on the synthesis and crystal structure analysis of palladium(II) bis-(trans-benzoyltrifluoroacetonate). Crystal data for PdO₄C₂₀F₆H₁₂:a= 4.748, b = 22.237, c = 9.410 Å, P = 105.44° Z = 2, space group P2₁/c, d_calc. = 1.86 g/cm . CAD-4 diffmctometer(MoKa), heavy atom method, R = 0.041 for 986 reflections. The structure is molecular; the planar molecules are stacked. The Pd atom is surrounded by a square of four O atoms (Pd?O = 1.97 Å, chelate angle 94.4°); Pd is involved in additional intemctions with the C_γ atoms of two neighboring molecules (Pd...C_γ= 3.44 Å). The molecular structure of palladium β-diketonate complexes, molecular packing in crystal, and intermolecular intemctions are considered. The van der Waals energies of the crystal lattice are calculated. The results are compared with the experimental values. In the structures of palladium( 11) β-diketonates, three groups of crystals are isolated: one group with 2 nearest-neighbor interactions (stacks), the second with 4 nearest-neighbor interactions (two-dimensional nets), and the third with 1 nearest-neighbor interaction (dimers). The latter are characteristic of the cis-complexes. The intemctions with 10–12 nearest neighbor molecules determine the energetics of the whole crystal. The high volatility of Pd(hfa)₂ is explained by the weaker intermolecular contacts between stacks in crystal.     

Properties and structure of new volatile phenyl-containing β-diketonates of trimethylplatinum(IV): (CH3)3Pt(btfa)H2O, (CH3)3Pt(bac)Py, and initial complex [(CH3)3PtI]4

By interaction of trimethylplatinum(IV) iodide with phenyl-containing β-diketonates, the volatile monomeric complexes of trimethylplatinum(IV) based on benzoyltrifluoroacetone (Hbtfa) and benzoylacetone (Hbac) of the composition (CH₃)₃Pt(btfa)H₂O (I) and (CH₃)₃Pt(bac)Py (II) are obtained. Synthesis of the complexes is described; data of elemental analysis and IR spectra are reported; thermal characteristics are studied by thermogravimetry. For the first time, a single crystal X-ray diffraction study of complexes (I), (II), and the initial tetrameric complex [(CH₃)₃PtI]₄ (III) is performed.     

Computer-aided design and discovery of protein–protein interaction inhibitors as agents for anti-HIV therapy

Protein–protein interactions (PPI) are involved in most of the essential processes that occur in organisms. In recent years, PPI have become the object of increasing attention in drug discovery, particularly for anti-HIV drugs. Although the use of combinations of existing drugs, termed highly active antiretroviral therapy (HAART), has revolutionized the treatment of HIV/AIDS, problems with these agents, such as the rapid emergence of drug-resistant HIV-1 mutants and serious adverse effects, have highlighted the need for further discovery of new drugs and new targets. Numerous investigations have shown that PPI play a key role in the virus’s life cycle and that blocking or modulating them has a significant therapeutic potential. Here we summarize the recent progress in computer-aided design of PPI inhibitors, mainly focusing on the selection of the drug targets (HIV enzymes and virus entry machinery) and the utilization of peptides and small molecules to prevent a variety of protein–protein interactions (viral–viral or viral–host) that play a vital role in the progression of HIV infection.     

Experimental study of subsonic flows by liquid‐crystal thermogfraphy

The physical basis of liquidcrystal thermography, which allows visualization and measurement of temperature and heatflux fields, are expounded. An experimental technique and methods of obtaining quantitative results are described. Two approaches (monochromatic and chromatic) to interpretation of visualization data are considered. Results illustrating the possibilities of the method in an aerophysical experiment are given.     

Crystal structure of volatile pyridine adducts of trimethylplatinum(IV) β-diketonates

The structures of volatile pyridine adducts of trimethylplatinum(IV) β-diketonates derived from acetylacetone (Hacac) and dipivaloylmethane (Hdpm) are studied for the first time. Their preparation is reported and the data of thermal studies obtained by the DTA technique are presented. The structures of the compounds in question comprise monomeric complexes. The platinum atom is coordinated to three carbon atoms of methyl groups, two oxygen atoms of β-diketone, and the nitrogen atom of the pyridine molecule. The (PtC₃O₂N) coordination core has the shape of a slightly distorted octahedron. The geometrical characteristics of the coordination cores are the following: in all complexes, the values of Pt-O, Pt-C_Me, Pt-N bond lengths and O-Pt-O chelate angles fall within 2.122–2.146 Å, 1.986–2.079 Å, 2.131–2.186 Å and 89.3–90.6° respectively.