Andrey I. Poddel’sky

Heteroligand o-Semiquinonato-Formazanato Cobalt Complexes

Two novel heteroligand o-semiquinonato-formazanato cobalt complexes [Co(3,6-SQ)(Form)] (1) and [Co(3,6-SQ)2(Form)] (2) (3,6-SQ is 3,6-di-tert-butyl-o-benzosemiquinonate radical anion; Form is 1,3,5-triphenylformazanate anion) were synthesized and characterized in detail. The molecular structures of [Co(3,6-SQ)(Form)] and [Co(3,6-SQ)2(Form)] were determined by X-ray analysis. Magnetic susceptibility measurements and spectroscopic studies have shown that square-planar complex 1 is diamagnetic with a residual paramagnetism due to antiferromagnetic exchange metal-ligand. Complex 2 includes cobalt(III) in the low-spin state and two anionic-radical o-semiquinonato and one formazanate ligand.

Optically controlled distribution of o -quinonemethacrylate metal complexes in polymer materials

The complexation ability of photoreduction products of 2-(2,5-di-tert-butyl-3,4-dioxycyclohexa-1,5-dienyl)ethyl methacrylate in tetrahydrofuran (THF) solution and in its copolymer films with dimethacrylate and ethylene glycol monomethacrylate was studied. The product of photochemical reduction – catechol – reacts with (NH4)6Mo7O24·4H2O, NH4VO3 and (NH4)2Fe(SO4)2 with the formation of corresponding metal complexes in solution and in the polymer bulk. The concentration of the molybdenum complexes in the polymer matrix was proportional to the exposure and holding time in solution of molybdate salt. Polymer film with optically controlled distribution of o-quinonemethacrylate molybdenum complexes was prepared. A film containing antimony and molybdenum complexes together in the polymer structure in predetermined ratio was obtained by sequential treatment of irradiated copolymer film (50% conversion) by THF solution of SbPh3, and water solution of (NH4)6Mo7O24·4H2O.

Electrochemical behavior and anti/prooxidant activity of thioethers with redox-active catechol moiety

A number of asymmetrical thioethers combining sterically hindered catechol moiety and different groups (polar, non-polar, or redox active) at sulfur atom have been synthesized. Redox transformations of sulfides were studied by cyclic voltammetry. The electrooxidation of thioethers at the first stage leads to the formation of o-benzoquinones. The presence of a redox-active thioether linker and additional phenolic fragment favors to an extension of the range of redox properties for such functionalized catechols. The introduction of the thioether fragment into catechol ring affects not only the electrochemical behavior of the compounds, but also the antioxidant activity. The antioxidant activities of the compounds were evaluated using 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH) assay, the oxidative damage of the DNA, the reaction of 2,2′-azobis(2-amidinopropane dihydrochloride) (AAPH)-induced glutathione depletion, and the process of lipid peroxidation of rat liver (Wistar) homogenates in vitro. The compounds have greater antiradical effect than 3,5-di-tert-butylcatechol (CatH2) in DPPH assay. In the course of the AAPH-induced oxidative DNA damage, all tested compounds exhibit inhibitory activity unlike CatH2. Among the compounds under investigation, three catechol thioethers reveal mostly antioxidant properties. Several compounds with polar groups possess dual anti/prooxidant activity. The thiolation of catechol ring can change properties of target thiothers by a variation of different organic fragments at sulfur atom.Graphical abstract