Syntheses and structural investigation of some alkali metal ion-mediated LVVO2− (L2− = tridentate ONO ligands) species: DNA binding, photo-induced DNA cleavage and cytotoxic activities

Abstract

Eight alkali metal ion-mediated dioxidovanadium(V), [{V^VO₂L¹⁻⁶}A(H₂O)_n]_∝, complexes for A = Li⁺, Na⁺, K⁺ and Cs⁺, containing tridentate aroylhydrazonate ligands coordinating via ONO donor atoms, are described. All the synthesised ligands and the metal complexes were successfully characterised by elemental analysis, IR, UV-Vis and NMR spectroscopy. X-ray crystallographic investigation of 3, 5–7 shows the presence of distorted NO₄ coordination geometries for LVO₂⁻ in each case, and varying μ-oxido and/or μ-aqua bridging with interesting variations correlated with the size of the alkali metal ions: with small Li⁺, no bridging-O is found but four ion aggregates are found with Na⁺, chains for K⁺ and finally, layers for Cs⁺. Two (5) or three-dimensional (3, 6 and 7) architectures are consolidated by hydrogen bonding. The dioxidovanadium(V) complexes were found to exhibit DNA binding activity due to their interaction with CT-DNA by the groove binding mode, with binding constants ranging from 10³ to 10⁴ M⁻¹. Complexes 1–8 were also tested for DNA nuclease activity against pUC19 plasmid DNA which showed that 6 and 7 had the best DNA binding and photonuclease activity; these results support their good protein binding and cleavage activity with binding constants ranging from 10⁴ to 10⁵ M⁻¹. Finally, the in vitro antiproliferative activity of all complexes was assayed against the HeLa cell line. Some of the complexes (2, 5, 6 and 7) show considerable activity compared to commonly used chemotherapeutic drugs. The variation in cytotoxicity of the complexes is influenced by the various functional groups attached to the aroylhydrazone derivative.