Vanadium complexes with salicylaldehyde-based Schiff base ligands—structure, properties and biological activity

Schiff base ligands based on 5-bromosalicylaldehyde and 4-tertbutylbenzhydrazide or benzhydrazide were used in syntheses of eight vanadium complexes with VOSO4(aq), [VO(acac)2] and [V(acac)3] in ethanolic solution. In selected syntheses 1,10-phenanthroline (phen), 2,2’-bipyridine (bpy) or 2,5-pyridinedicarboxylic acid (dpy) were used as co-ligands to fill the coordination sphere and to increase complex stability. The complexes were characterized by elemental analyses, IR, UV-Vis, EPR spectroscopy, cyclic voltammetry, magnetic susceptibility and for one complex two single crystal X-ray structures were determined for complexes with two different solvent molecules (H2O and MeCN). Three complexes were found to be active in inhibition of human recombinant PTP1B, one of them is twice more active than suramin.