[VIVO]2+ complexes: Structure, unusual magnetic properties and cytotoxic effect

The present investigation was carried out with the aim of synthesizing and characterizing five vanadium coordination compounds (6-10) with different Schiff bases (1 = N, N'-bis(salicylidene)-o-phenylenediamine, 2 = N, N'-bis(4-hydroxysalicylidene)-o-phenylenediamine, 3 = N, N'-bis(4-methoxysalicylidene)-o-phenylenediamine, 4 = N, N'-bis(3-hydroxysalicylidene)-o-phenylenediamine, 5 = N, N'-bis(3-methoxysalicylidene)-ophenylenediamine) and studying their cytotoxic properties. Based on their physical (magnetic susceptibility), spectral (X-ray, electronic, IR, H-1 NMR, C-13 NMR, EPR and mass) and analytical (elemental analysis) results, the structures of these Schiff bases and their respective oxidovanadium(IV) complexes were established. Crystal structures of compounds 6 (Monoclinic, C 2/c, Z = 16) and 7-8 (Triclinic, P-1, Z = 2) had been determined by X-ray diffraction and confirmed pentacoordination of vanadium(IV) with a slightly distorted square-pyramidal geometry. Vanadium coordination compounds displayed low effective magnetic moments (0.85-0.89 BM) that maybe due to the intermolecular hydrogen bonding and pi-stacking interactions in the crystal arrangements. Cytotoxic activity was evaluated on human tumor cell lines: 6-9 (HeLa= 0.443-1.502 mu M) and 6-10 (HCT15 = 0.373-1.415 mu M), with exception of 7. Cell growth inhibition revealed that regardless of the cancer cell line type compounds 6 and 8 showed similar activity -possible effect due to the complex per se-giving new insights into the structure-activity relationship for these complexes.