Nikolai P. Osipovich

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.

Bioactive Silver(I) Complexes with Phenolic Derivatives of Thioglycolic and Thiopropionic Acids

Ag(I) complexes formed by polydentate phenolic derivatives of thioglycolic and thiopropionic acids with Ag(I) ions could be a promising field of search for potential chemotherapeutic agents. Convenient synthetic methods to prepare these ligands have been developed on the basis of addition reactions occurring between S-nucleophiles and o- benzoquinones. The results are presented of physicochemical investigation of Ag(I) ions complexation with phenolic ligands, which made it possible to determine ionic and redox ligand forms with high nucleophilicity of metal-ion binding sites, the peculiarities of the structural organization of the coordination cores of the newly synthesized complexes. The in- vestigation of the molecular and electronic structure of Ag(I) complexes has been performed within the density functional theory framework. On the basis of the pharmacological screening results the selection is justified of a lead compound pos- sessing antibacterial, antifungal and antiherpetic activity comparable to those of some standard drugs to develop effective pharmaceuticals for combination therapy of mixed infections. Data have been obtained on the ability of some phenolic de- rivatives of thioglycolic and thiopropionic acids as well as their Ag(I) complexes to reduce bovine cytochrome c.

ELECTROCHEMICAL STUDY OF PHOTOCHEMICALLY TREATED THIOL-CAPPED ZnSe(S) NANOCRYSTALS

Electrochemical studies of thiol-capped ZnSe and ZnSe(S) semiconductor nanocrystals (NCs) in an aqueous solution have demonstrated several distinct oxidation peaks in the voltammograms, with the peak positions being nanocrystal size dependent. The evolution of these peaks as a function of the photochemical treatment is studied. The interpretation of the results is found to be in good correlation with the proposed mechanism of the ZnSe NCs phototreatment, i.e. the formation of a sulfur-enriched surface shell.