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Reactions of vanadium(III) with thiosemicarbazones

Thiosemicarbazones found wide application in industry and analytical chemistry, while some of their derivatives show antiparasital and antiviral properties. In many cases biological activity of thiosemicarbazones is related to their chelating properties, since they can be in vivo coordinated to metal ions. In the solid state thiosemicarbazones exist in the thione form. In solution, however, they tautomerize into the thiol form. Complexation usually takes place via sulfur atom and imino nitrogen atom, resulting in the formation of a five-membered chelate ring. When an additional donor site D is present in ortho position in such ligands D, N, S tricoordination usually takes place. In our recent work we have performed reactions of vanadium(III) acetylacetonate with salicyaldehyde-4-phenylthiosemicarbazone (H2L1) and o-vaniline-4-phenylthiosemicarbazone (H2L2). All reactions were carried under inert atmosphere. Reactions afforded thiosemicarbazonato complexes of vanadium(V) of general formula [VO(L)(OCH3)] (A), as well as unexpected products of intermolecular cyclization of thiosemicarbazone ligands and acetylacetone (B). All compounds were characterised by means of IR spectroscopy, X-ray powder diffraction and single crystal X-ray diffraction methods.

Thiosemicarbazones; vanadium(III) acetylacetonate; IR spectroscopy; X-ray powder diffraction; single crystal X-ray diffraction

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