I. V. Skornyakov

Manifestation of intramolecular hydrogen bonds in the IR spectra of bioactive aminophenols

The intermolecular interactions in solutions of aminophenols in CCl4 are studied by the methods of IR Fourier spectroscopy. If the hydroxyl groups of aminophenol molecules occupy the ortho positions with respect to the amino groups of the molecules, the hydroxyl and amino groups are involved in intramolecular interactions with the formation of hydrogen bonds O-H...N and N-H...O. The introduction of two additional tert-butyl groups into the structure of the aminophenol molecule facilitates the formation of O-H...N bonds and impedes the formation of N-H...O bonds. The occurrence of the carbonyl group in the structure of aminophenols leads to the formation of intramolecular hydrogen bonds O-H...O=C. The introduction of the methyl groups into carbonyl-containing aminophenols transforms the O-H...O=C bond into the hydrogen bond N-H...O=C.

Analysis of Transformer Oil Using IR Analyzers

Spectral characteristics of samples of transformer oil that differ in technical grade, service life, and content of an antioxidant additive and dissolved water are investigated. It is suggested to determine service deterioration of insulating oils from absorption in the region 1710 cm−1 using IR filter analyzers.

Electronic structure, spectral-luminescent, and proton acceptor properties of biologically active aminophenols

The absorption and fluorescence spectra and fluorescence quantum yields of a number of biologically active derivatives of o-aminophenol are measured in an inert solvent, hexane. The IR spectrum of a solution of 2-amino-4,6-di-tert-butylphenol is studied in CCI4 and IR bands are found that indicate the presence of two conformers in this solution with intramolecular hydrogen bonds O-H…N and N-H…O. Using methods of IR Fourier transform spectroscopy, the structural features of a number of biologically active o-aminophenols with different substituents are considered. The absorption and fluorescence spectra of o-aminophenols are calculated and interpreted by the method of intermediate neglect of differential overlap with spectroscopic parameterization. Calculation data are compared with the results of the experiment. Proton acceptor properties of o-aminophenol molecules are theoretically evaluated using the method of molecular electrostatic potential. The role played by various substituents in the formation of the proton acceptor properties of o-aminophenols is experimentally studied.

Electronic structure and spectroscopic properties of anti-HIV active aminophenols

We have measured the absorption and fluorescence spectra and fluorescence quantum yields of sulphone-containing anti-HIV active o-aminophenol molecules in an inert solvent, hexane, and in a polar solvent, acetonitrile. We have studied IR Fourier-transform spectra and examined structural features of o-aminophenols with different substituents in solutions and crystals. Functional groups of molecules that are involved in the formation of hydrogen bonds have been revealed. Proton acceptor properties of o-aminophenol molecules have been theoretically evaluated using the method of molecular electrostatic potential. Using quantum chemistry methods, we have calculated and interpreted absorption and fluorescence spectra of o-aminophenols. Calculation data are compared with experimental results. We have determined the main channels and mechanisms of photophysical relaxation processes in o-aminophenols.

Spectroscopic properties of pharmacologically active phenols

The IR Fourier-transform spectra of pharmacologically active phenol molecules in solutions in CCl4 and in the crystalline state have been studied. Phenol derivatives with different directivities and different levels of pharmacological efficiency have been examined. Based on analysis of the IR spectra of screened phenols, the antimicrobial activity of phenols with free hydroxyl groups has been shown to be highest. The high antimicrobial activity of aminophenols is related to the formation of intramolecular hydrogen bonds. For aminophenols that are active against herpesviruses, O-H...N hydrogen bonds are formed in molecules. The main characteristic of the high antiviral activity against A-type influenza is predominance of intramolecular hydrogen bonds of the O-H...O=C type in molecules. Sulfur-containing aminophenols, which manifest activity against HIV infection, are characterized by the occurrence of hydrogen bonds that involve the participation of the OH, NH, and SO2 groups.

Spectroscopic and proton-acceptor properties of biologically active molecules of benzoic acid and its derivatives

We have measured the absorption, fluorescence, fluorescence excitation spectra, fluorescence quantum yields, and IR Fourier-transform spectra of aromatic acids in solutions. We have considered spectroscopic particular features of benzoic acid, its hydroxylated and methoxylated derivatives. Using quantumchemistry methods, we have calculated and interpreted electronic spectra. Data of calculations have been compared with experimental results. We have ascertained the main channels and mechanisms of photophysical relaxation processes in the molecules under study. Proton-acceptor properties of molecules of aromatic acids have been evaluated. We have analyzed in detail mechanisms by which hydrogen bonds are formed, intramolecular charge redistribution is realized, and the electron density of oxygen atoms changes. Spectroscopic indications of participation of oxygen-containing groups in intramolecular interactions and in intermolecular interactions with the formation of cyclic dimers have been revealed.

Intermolecular interactions of immunoactive 8-azasteroid

Intermolecular interactions in 2,3-dimethoxy-8-azagone-1,3,5(10),13-tetraene-12,17-dione and the molecular and crystal structure of this compound were studied by IR spectroscopy and x-ray diffraction analysis. Shortened intermolecular contacts related to the C-H⋯O, C-H⋯π, and π⋯π interactions were revealed in crystals of this 8-azasteroid. These contacts manifest themselves in changes in the characteristic frequencies of C-H, C=O, and C=C vibrations in the IR spectra. A relationship between the intermolecular interactions occurring in the crystalline and noncrystalline solid phases and the changes in the IR spectra of this compound was established.

IR spectra of benzaldehyde and its derivatives in different aggregate states

We have measured the IR Fourier-transform spectra of biologically active benzaldehyde and its derivatives in the gas and liquid phases. For compounds of this class, the role played by C=O, OH, and CH groups in intra- and intermolecular has been analyzed. We have revealed spectral features that characterize the participation of C=O groups of unsubstituted benzaldehyde molecules in the occurrence of intermolecular hydrogen bonds C=O...H-C with the formation of molecular dimers of different types. For 2-hydroxybenzaldehyde molecules, spectral data have been obtained that are indicative of the occurrence of intramolecular hydrogen bonds of the C=O...H-C type in solutions. In 2-methoxybenzaldehyde molecules, no intramolecular hydrogen bonds have been observed.

INFRARED FILTERS AND ANALYZERS OF THE COMPOSITION OF SUBSTANCES BASED ON THEM

Results of investigations on designing band dispersion and dispersion-interference filters for the 4–30 μm IR range and cutoff filters for the 50–300 μm region are presented. Analyzers of the composition of a substance that are designed on the basis of band IR filters and analysis procedures are described.

Intramolecular hydrogen bonds in the phenylazomethine biomolecules

The FTIR spectra of the solutions of biologically active molecules (screened phenylazomethines) in CCl4 are studied. The role of the OH- and N=C groups in the formation of the intramolecular H bonds is analyzed. The analysis of the FTIR spectra shows that three types of H bonds (O-H…O-H, O-H…N=C, and O-H…O-H…N=C) are possible in the molecules under study. A correlation of the H-bond formation in the phenylazomethine molecules and the antivirus properties of such molecules is revealed. The antivirus activity is observed for molecules that exhibit intramolecular O-H…O-H…N=C bonds in the absence of free hydroxyls. The antivirus activity decreases when the molecule contains additional OH groups that are not involved in H bonds.