Synthesis, structure and biological evaluation of mixed ligand oxidovanadium(iv) complexes incorporating 2-(arylazo)phenolates

Abstract

[VO(acac)₂] was used as a metal precursor to synthesize a series of mixed ligand oxidovanadium(IV) complexes [V^IVO(L^1–4)(L^NN)] (1–5) with tridentate ONO donor arylazo ligands (H₂L^1–4) (where H₂L¹ = 1-(2-hydroxyphenyl)diazenyl)naphthane-2-ol, H₂L² = 1-(2-hydroxy-4-methylphenyl)diazenyl)naphthane-2-ol, H₂L³ = 1-(2-hydroxy-4-nitrophenyl)diazenyl)naphthane-2-ol and H₂L⁴ = 1-(2-hydroxy-4-bromophenyl)diazenyl)naphthane-2-ol) along with an ancillary ligand (L^NN), namely 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) as a co-ligand. All complexes were characterized by spectroscopic, ESI-MS and X-ray crystallographic techniques, which show their distorted octahedral geometry. The molecular structure shows the presence of a vanadyl group in six-coordinated V^IVN₃O₃ geometry. The species exhibit quasi-reversible one-electron transfer of E^c_1/2 value between −1.29 and −1.37 V, while irreversible one-electron oxidation peaks lie in the range 0.37–0.67 V versus SCE in acetonitrile solution. All the complexes show DNA binding activity with CT-DNA having binding constant values in the range 7.1 × 10³–2.03 × 10⁴ M⁻¹. The interaction of synthesized mixed ligand oxidovanadium(IV) species with bovine serum albumin (BSA) was also studied experimentally, which revealed moderate binding affinity. Further, the antiproliferative activity of 1–5 was examined against A549 (lung cancer) cancer cell lines by MTT assay. The cytotoxicity of the complexes is affected by the various functional groups attached to the arylazo derivative as well as the presence of two different co-ligands and 2 showed considerable antiproliferative activity compared to other chemotherapeutic drugs.