Conformational Mobility and Phase Transitions in Alkyloxybenzoate of Cholesterol

Abstract

The structural particularities of polymorphic modifications and cholesterol liquid crystal phase have been investigated by theoretical and experimental IR spectroscopy methods. The spectra were recorded in the interval of temperatures 293–523 K within the range of 600–3600 cm^?1. The frequencies of normal modes and intensities in the IR spectra have been calculated for the alkyloxybenzoate of cholesterol conformers, which may be realized under certain temperatures. Comparison of results of theoretical modelling and recorded spectra confirmed suggestion about conformational mobility basically defined with changing of steroid kennel orientation comparatively stayed part of molecule in the different phase state.     

Intermolecular interactions and the structure of near-surface layers in heterogeneous two-component systems based on nanocystallites of titanium dioxide

This contribution provides the theoretical background for the structure-determining role of hydrogen bonding in the formation of a near-surface layer of titania nanocrystallites, previously revealed by the authors in the investigation of IR experimental spectra of two-component solid mixtures of nanocrystalline titanium dioxide with benzophenone or 4-pentyl-4′-cyanobiphenyl. DFT calculations (B3LYP) in 6-31+G(d) basis set is used to simulate the structure and IR spectra of free molecules of water, 4-pentyl-4′-cyanobiphenyl, benzophenone and their H-complexes formed in the near-surface layers of titania nanocrystallites due to presence of water adsorbed on their surfaces. Using the results of simulation and analysis of IR spectrum bands corresponding to stretching vibrations of polar bonds O-H, C=O, C≡N, the formation mechanism of near-surface layers of titania nanocrystallites in the considered heterogeneous two-component systems is theoretically substantiated: they are formed by hydrogen-bonded complexes involving components of the mixture and water.     

2-Amino- and 2-hydroxymethylbenzimidazolium bromides as protein tyrosine phosphatase 1В (PTP1В) inhibitors and other targets associated with diabetes mellitus

Russian Chemical Bulletin - New 2-amino- and 2-hydroxymethylbenzimidazoles were synthesized and used to prepare the previously unknown 1,2,3-tri- and 1,2,3,5-tetrasubstituted benzimidazolium...     

Phase transitions,conformational lability,and intermolecular interactions in alkoxycyanobiphenyls

Vibrational spectroscopy methods (IR absorption, Raman scattering, calculations) were used to study changes in molecular structures of alkoxycyanobiphenyls during phase transitions. The spectra were measured in the 33–3500 cm⁻¹ region at temperatures of 100–450 K. The temperature dependences of the IR bands that correspond to the noncharacteristic vibrations of molecular fragments between the phenyl rings and the alkyl radicals point to the conformational polymorphism of these molecules. An analysis of the Raman bands corresponding to the characteristic vibrations of the C−H bonds of alkyl radicals [q(CH)], the C−H and C−C bonds of phenyl rings [q(CH) and Q(CC)], and the CN bonds of the cyano groups [Q(CN)] suggests significant intermolecular interactions. The conformational lability and intermolecular interactions are associated with differences in molecular packing in the substances of this homologous series. Saratov State University. Institute of Solid State Physics, Rostov State University. Institute of Physics, Uzbekistan Academy of Sciences. Samarkand State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 5, pp. 814–822, September–October, 1995. Translated by I. Izvekova     

Synthesis and pharmacological activity of 2-(biphenyl-4-yl)imidazo[1,2-a]benzimidazoles

Russian Chemical Bulletin - An efficient method for the synthesis of novel 9H-imidazo[1,2-a]benzimidazole derivatives containing a biphenyl substituent at position 2 was developed. These compounds,...     

Structural-dynamic model of 2-biphenylmethanol in an anharmonic approximation

Using a density functional B3LYP/6-31G(d) method, the geometry, electro-optical parameters, quartic force field, and vibrational spectra (IR and Raman) of 2-biphenylmethanol have been calculated. A vibrational analysis was performed. The resulting IR and Raman spectra were interpreted in detail.     

Vibrational structure of the electron transition to the second excited singlet state of pyridine N-oxide

The vibrational structure of the electron transition to the second singlet excited state of pyridine N-oxide has been studied. The frequency of the 0–0 transition is 34502 cm⁻¹. A computer-aided technique for the assignment of the frequencies of the normal vibrations of polyatomic molecules in the excited electronic states is proposed. The frequencies of the totally symmetric vibrations of pyridine N-oxide in the second singlet electronically excited state are assigned. N. G. Chernyshevskii Saratov State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 350–355, March–April, 1995. Translated by I. Izvekova     

Specific intermolecular interactions in a heterogeneous system benzophenone-titanium dioxide

IR spectroscopy methods (experiment, theoretical simulation) have been applied to study the structural features and intermolecular interactions in a two-component heterogeneous nano-size system benzophenone-titanium dioxide (BPh-TiO₂). IR spectra of the sample were recorded at room temperature within the range 400–4000 cm^?1. The spectra display hydrogen bonding determining the intermolecular interactions between titanium dioxide, BPh molecules, and water in the near-surface layers of nanocrystalline TiO₂ particles. IR spectra of free BPh molecules, water, model H-complexes of BPh with water, and the fragment of hydrated titania surface (BPh…HOH and BPh…Ti≡) have been simulated. Experimental and theoretical spectra were analyzed in the region of stretching vibrations of carbonyl, hydroxyl, and other groups sensitive to a variation of intermolecular interactions. It is found that hydrogen bonding in the near-surface layers of nanocrystalline TiO₂ particles in the two-component heterogeneous nanosystem BPh-TiO₂ gives rise to the formation of complexes BPh-O-Ti(OH)-O-, BPh…HOH, along with complexes of-O-Ti(OH)-O-with water and pure water complexes.