Chemistry |
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1995, Special Issue
L.A. Onuchak, S.P. Kotova, E.V. Kotov
The character of the orientation of nematic liquid crystals (LC) of p,p'-alkoxiazoxibenzenes and p,p'-alkoxicyanobiphenyls homologs molecules at the free surface was determined on the basis of measurements of the temperature dependances of surface tension»7 g»0 (by the pendant drop technique) and relative anisotrophy of the reflectivity coefficients for a polarized He-Ne laser beam. It has been determined, that the molecules long axes of the p,p'-alkoxicyanobiphenyls homologs were perpendicular relative to surface for all mesophase temperatures. The temperature depen-dance of the orientation for the LC of the p,p'-azoxyalkoxybenzenes homologs is individual for every homolog. The parallel or almost parallel orientation of molecules of the LC of that homologs relative to free surface takes place at lower temperatures of mesophase.
V.N. Serezhkin, L.B. Serezhkin
Using phosphate-containing compounds of uranyl as an example the abilities of the model of interatomic interaction basing on the considering crystal structure as Voronoi-Dirichlet (VD) tes-selation were analysed. In proposing model the presence of the common face of VD polyhedra corresponding to atoms U and 0 responds to the existence of chemical interaction between them and a bipyramid with the common face of VD polyhedra in equatorial plane and with these atoms in two axial positions is a 3-dimentional geometric image of a chemical bond U-O. It was shown that the solid angle between the faces of this bipyramid crossing at the point corresponding to the position of an atom can be used for the quantitive evaluation of electron donor ability of oxygen-coutaining ligands being coordinated by uranium atoms in approximation that the U-0 interaction is stipulated by the tendency of uranium atoms to form the 18 electrons configuration of valent shell. On the basis of the mentioned model a number of experimental facts are interpeted and the correlation between electron donor characteristics of ligands, composition and structure of the resalting coordination uranyl compounds is demonstrated.