V. L. Sorokin

Reactions of Arylamine and Aminophenol Derivatives, and Riboflavin with Organic Radicals

Based on product yield data on radiolysis of hexane, ethanol and 3 M aqueous ethylene glycol solutions, the ability of a number of arylamine, aminophenol and quinonimine derivatives to affect processes involving peroxyl, alkyl or α-hydroxyalkyl radicals was assessed. It has been shown that the introduction of a hydroxyl group into aromatic amine structure enhances its antioxidant performance and makes it significantly more reactive with respect to carbon-centered organic radicals. Replacement of the hydrogen atom of a hydroxyl group by a methyl group decreases the anti-radical activity of aminophenols drastically. Compounds containing (or capable of forming) a quinonimine moiety interact with alkyl or α-hydroxyalkyl radicals most effectively, suppressing recombination and fragmentation reactions of the latter. In the sequence: aromatic amines--aminophenols--quinonimines, a trend towards enhancement of the ability of the compounds studied to react with carbon-centered radicals was noted. Also, this study presents for the first time evidence of riboflavin reactivity with respect to organic radicals.

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.

Copper (II) complexes of sterically hindered o-diphenol derivatives: synthesis, characterization and microbiological studies

Cu (II) complexes with the sterically hindered diphenol derivatives 3,5-di(tert-butyl)-1,2-benzenediol (I), 4,6-di(tert-butyl)-1,2,3-benzenetriol (II) and the sulfur-containing 4,6-di(tert-butyl)-3-(2-hydroxyethylsulfanyl)-1,2-benzenediol (III) and 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]acetic acid (IV) have been synthesized and characterized by elemental analysis, TG/DTA, FT-IR, ESR, XPS, XPD and conductivity measurements. Compounds I–III can coordinate in their singly deprotonated forms and act as bidentate ligands. These compounds yield Cu (II) complexes of the stoichiometry Cu(L)2, which have square planar geometry (g| > g⊥ > ge). Unlike them, compound IV behaves as a terdentate ligand, and its complex Cu(LIV)2 has distorted octahedral geometry. According to ESR data, only the Cu(LII)2 complex contains a very small amount of phenoxyl radicals. Antimicrobial activities of these ligands and their respective Cu (II) complexes have been determined with respect to Gram-positive and Gram-negative bacteria, as well as on yeasts. Their phytotoxic properties against Chlorella vulgaris 157 were also examined.

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.

Synthesis and Antiviral Activity of Hydroxy-Substituted Benzaldehydes and Related Compounds

A series of hydroxy-substituted benzaldehydes and related compounds were synthesized and studied in cell culture against herpes simplex type I (HSV-1) and influenza A (H7N1) viruses. It was found that salicylaldehyde, 2,3-dihydroxybenzaldehyde, and gossypol could suppress HSV-1 replication. The structure–activity relationship of the series of hydroxylated benzaldehydes was analyzed.

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.