Vanadium complexes with 2-pyridineformamide thiosemicarbazones: In vitro studies of insulin-like activity

Reaction of VOCl2 with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives in ethanol gave as products [VO(H2Am4DH)Cl2] (1), [VO(H2Am4Me)Cl2] · 1/2HCl (2), [VO(H2Am4Et)Cl2] · HCl (3) and [VO(2Am4Ph)Cl] (4). Upon the dissolution of 1–4 in water, oxidation immediately occurs with the formation of [VO2(2Am4DH)] (5), [VO2(2Am4Me)] (6), [VO2(2Am4Et)] (7) and [VO2(2Am4Ph)] (8). The crystal and molecular structures of 5 and 6 were determined. Complexes 5–8 inhibited glycerol release in a similar way to that observed with insulin but showed a low enhancing effect on glucose uptake by rat adipocytes.