IR spectroscopic study of molecular associates of mesogenic cyanophenyls

Molecular association greathy affects the physicochemical properties of mesogenic cyanophenyls, which are currently widely used as molecular materials for optoelectronics. This paper reports on a polythermal IR spectroscopic study of molecular association for mesogenic alkyl/alkoxycyanobiphenyls and their hydrated and heteroaromatic analogs in nonpolar solutions, low-temperature inert matrices, and molecular condensate layers in the temperature ranges of 5–10 and 80–330 K. Correlation of the thermodynamic parameters of association with molecular structure of cyanophenyls is established. M. V. Lomonosov Moscow State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 3, pp. 395–400, May–June, 1998. This work was carried out in the framework of the Federal Program “Universities of Russia” and the International Scientific Collaboration Program OMMEL.     

Effect of repulsive interaction on the structural and dynamic features of liquid water. The role of molecular polarizability

The effect of variation of the potential function on the structural and dynamic properties of model water when the surface of pair interactions is invariant is studied by the molecular dynamics method. Variations for the rigid and polarizable models are compared. Translated fromZhurnal Strukturnoi Khimii, Vol.40, No. 2, pp. 296–303, March–April, 1999.     

NMR methods for molecular structure studies of paramagnetic lanthanide complexes in solutions. Applications to crown ether complexes

The literature data on NMR spectroscopic methods for investigation of the spatial structure and molecular dynamics of lanthanide complexes with macrocyclic potyethers in solutions are reviewed. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 714–730, July–August, 1998.     

Asymptotic formulas for Coulomb and hybrid integrals with slater type functions

Asymptotic expressions are obtained for two-center Coulomb and hybrid integrals with Slater functions. Results of numerical test of these expressions are presented. The use of asymptotic formulas in LCAO-MO calculations of electronic molecular structure substantially reduces the computation time. V.I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 2, pp. 12–15, March–April, 1994. Translated by L. Chernomorskaya     

MNDO study of the electronic structure and potential energy surface of fluorinated singlet cyclopentadienyl and methylcyclopentadienyl cations

The electronic structure and geometry of some symmetric fluorinated singlet cyclopentadienyl and methylcyclopentadienyl cations are studied by the MNDO method. The structure of the potential energy surface (PES), which is a pseudorotation surface, is investigated. Extreme points of the PES, determining the PES barrier, correspond to structures with inverted frontier molecular orbitals. (Anti)aromaticity of fluorinated methylcyclopentadienyl cations is estimated using the Dewar-Breslow criterion. Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 6, pp. 1023–1030, November–December, 1996. Translated by L. Smolina     

Data selection for structure generation in structure elucidation systems using molecular spectroscopy databases

Data selection techniques are considered for structure generation in structure elucidation systems using molecular spectroscopy databases. The starting data are sets of microfragments and connected structural fragments obtained from computer-aided analysis of mass, IR, and NMR spectra. Selection of fragments that do not isomorphically fit in larger fragments mostly leads to correct results with fewer output structures anddemands less computer time. Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 2, pp. 46–53, March–April, 1994. Translated by L. Smolina     

“Perfect” structure regions in amorphous argon

The structure of molecular dynamic models of amorphous argon is investigated by the Voronoi-Delaunay method. It is shown that the majority of Delaunay simplices (determined by quadruplets of the nearest atoms) are “perfect,” i.e., close in their shape either to the ideal tetrahedron or to the ideal quartoctahedron. These two types of structural elements are positioned in a correlated manner relative to each other, forming regions of a “perfect” structure which, however, is not crystalline. The regions themselves are separated by sections of an “imperfect” structure in which the shape of simplicial atomic configurations differs from the mentioned ideal forms. Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences. Novosibirsk State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 1, pp. 53–63, January–February, 1994. Translated by L. Chernomorskaya     

Ab initio study of the ground state and conformational stability of peroxyacetyl nitrate in internal rotation about the peroxide bond

The molecular and electronic structure of the ground state of peroxyacetyl nitrate (PAN) was calculated by the unrestricted Hartree-Fock-Roothaan method with the use of the standard 3–21G and 6–31G basis set. The potential curve of the internal rotation about the peroxide bond of PAN was calculated with the 6–31G basis set. The curve contains two maxima. The ground state of PAN is characterized by a structure in which groups of atoms adjacent to the peroxide bond lie in planes that are perpendicular to each other (the dihedral angle ϱ(COON) is 89.9°). The calculated barriers to rotation are 19.6 and 66.8 kJ mol⁻¹. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 600–604, April, 1998.     

Secondary structure of crystals

Published experimental data on the dependence of the properties of crystal substances on crystal size are discussed. The dependence is of the same form for different properties and different crystal substances. When the crystal diminishes in size, its properties remain constant until the size decreases to 10⁻⁵–10⁻⁶ cm; smaller crystals considerably change their properties. It is shown that the currently available experimental data are sufficient to substantiate the notion of an “elementary unit of a solid crystal” (“crystal quantum”). The elementary unit of a crystal is regarded as a basis for the secondary structure (macrostructure) of a solid and an elementary carrier of its “crystal” properties. Due to this notion, we can interpret the vast experimental material on the real structures and properties of solids from a single viewpoint. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 4, pp. 724–730, July–August, 1995. Translated by L. Smolina     

Role of water structure in thermodynamics of nonpolar solvation

The SSOZ (site-site Ornstein-Zernike) equation with an original closure condition for liquid molecular systems is used to calculate thermodynamic functions of noble gas solvation in water. Water is modeled by two close sets of atom-atomic potential functions. The calculations indicate that the chemical solvation potential is strongly sensitive to water structure. A comparison with experiment is given. Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 4, pp. 736–741, July–August, 1996. Translated by L. Smolina     

Calculation of the vibronic spectra of adenine

The vibrational structure of the absorption spectra of the first two π-π* singlet transitions of adenine is calculated in the Franck-Condon approximation including Herzberg-Teller interactions. The effect of excitation-induced changes in molecular angles on the intensities of the vibrational components is estimated. Structural models of the adenine molecule in the excited states are constructed. The theoretical and absorption spectra of the first π-π* transition are compared. The results of the electronic structure calculations of adenine by different CNDO/S methods are discussed. Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 2, pp. 334–344, March–April, 1997.     

Crystal and Molecular Structure of the Isoflavones Irilin B and Betavulgarin

The molecular structures of the isoflavones irilin B and betavulgarin, which were isolated for the first time from the aerial part of Iris tenuiflorita, were solved by x-ray structure analyses. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 319–321, July–August, 2005.     

Algorithm for determination of the local similarity of molecules

An algorithm for seeking common structural fragments in compounds of different classes is developed. The algorithm allows for the molecular geometry and atomic characteristics, It may be used for recognition of compounds with properties associated with the local similarity of molecules such as ligand complementarity to a receptor. An example of seeking common structural elements for nondrug analgesics (para-acetamidophenol, acetylsalicylic acid, and amidopyrine) is given. I. I. Polzunov Altai State Technical University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 6, pp. 1083–1087, November–December, 1995. Translated by L. Smolina     

Structural and electronic properties of aln and bn wide-gap semiconductors and their B<Subscript>x</Subscript>Al<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>N solid solutions

The structural and electronic properties of B_xAl_1−x N solid solutions (x = 0.25, 0.5, 0.75) were examined by calculating the electronic energy structure by the local coherent potential method within the framework of multiple scattering theory. The charge is transferred from aluminum to nitrogen atoms and increases with the content of boron atoms. The concentration dependences of the structural and electronic properties of these solutions are discussed. __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 5, pp. 822–829, September–October, 2005.     

Determination of molecular constants of yttrium triiodide from electron diffraction data

Among the molecular constants needed for calculating the thermodynamic properties of yttrium triiodide, onlyR(Y- I) measured in the 1950s by electron diffractometry with a high error are available in the literature [1]. It was assumed that the geometrical configuration of YI₃ has D_3h symmetry. In [2] it was attempted to estimate the vibration frequencies of yttrium triiodide (the errors are not given and are thought to be more than 15%). To refine the available data in the framework of our program of molecular constant determination for transition metal iodides, we investigated the structure of yttrium triiodide by gas phase electron diffractometry. This paper deals with the results of this study. Translated fromZhurnal Strukturnoi Khimii Vol. 38, No. 1, pp. 203–206, January–February, 1997.     

Supramolecular organic photochemistry of crown-ether-containing styryl dyes

The data on the molecular design, spectral properties, photochemistry and complexation of photochromic crown ethers containing a C=C bond are described systematically and generalized. Prospects for the practical application of these compounds are considered. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp 641–665, April, 1997.     

Combining X-ray scattering and exafs experiments for studying amorphous alloys of 3d transition metals with zirconium

The atomic structure of the amorphous alloys of several transition metals (Fe, Co, Ni, and Cu) with zirconium is studied in terms of partial paired correlation functions. The short-range order parameters, namely, the shortest interatomic distances, coordination numbers, and the form of distribution functions, are compared and a correlation between the atomic structure and the interaction between atoms of different sorts is established. The study offers the possibility to model the spatial distribution of atoms and the physical properties of the analyzed alloys and predict the properties of new systems. Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 6, pp. 1025–1030, November–December, 1998.     

Matrix method of conformational optimization. Application to cyclic and polyhedral water clusters

A matrix method for conformational optimization of quasi-one-dimensional molecular structures is suggested. The method is used to determine cyclic and polyhedral configurations of water clusters with the maximal number of stable trans-conformations of molecular pairs forming hydrogen bonds. Institute of Earth Cryosphere, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 1, pp. 107–115, January–February, 1996 Translated by L. Smolina     

Synthesis and crystal structure of cytisino-<Emphasis Type="Italic">N</Emphasis>-(2-hydroxyethyl)-thiocarbamide

A thiourea derivative of the alkaloid cytisine was synthesized by reacting it with 1-propargyloxyethoxyethylisothiocyanate. It was shown that the synthesized acetal thiourea derivative underwent hydrolysis in acidic medium to cytisino-N-(2-hydroxyethyl)-thiocarbamide, the molecular structure of which was confirmed by an x-ray structure analysis. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 56–58, January–February, 2009.