Oxidovanadium(v) complexes of aroylhydrazones incorporating heterocycles: synthesis, characterization and study of DNA binding, photo-induced DNA cleavage and cytotoxic activities†
Four neutral oxidovanadium(V) complexes VO2L1 (1), VO2L2 (2), VOL3(OEt) (3) and VOL4(OEt)EtOH (4) [where HL1 = 2-thiophenoylhydrazone of 2-acetylpyridine, HL2 = 2-amino benzoylhydrazone of 2-benzoyl pyridine, H2L3 = isonicotinoylhydrazone of 2-hydroxy acetophenone, H2L4 = 2-furoylhydrazone of 2-hydroxy-1-napthaldehyde] with a hydrazone scaffold containing either furan, thiophene and pyridine residues have been synthesised. All complexes were thoroughly characterized by various spectroscopic (IR, UV-Vis, NMR and ESI-MS) and single crystal X-ray diffraction techniques. Crystallography establishes five-coordinate geometries, distorted toward square pyramidal for each of 1 and 2, based on a tridentate-O,N,N coordinating anion and two oxido-O atoms. The dianion in 3 is tetradentate, coordinating one V atom as for 1 and 2, and bridging another via the pyridyl-N atom, and the N2O4 octahedral coordination geometry is completed by oxido- and ethanolate-O atoms. The result of the V–N bridging is a helical coordination polymer. An NO5 octahedral geometry is found in 4 defined by a tridentate-O,N,O anion, as well as oxido-, ethanolate- and ethanol-O atoms. Biological studies reveal that 1–4 have DNA binding propensity and show these to interact with CT-DNA through the minor groove binding mode, with binding constants ranging from 103 to 105 M−1. All complexes show good photo-induced cleavage of pUC19 supercoiled plasmid DNA with 3 showing the highest photo-induced DNA cleavage activity of ∼65%. Additionally, 1–4 are cytotoxic against the human cervical cancer cell line (HeLa) with IC50 values ranging from 10 to 20 μM.