A study of DNA/BSA interaction and catalytic potential of oxidovanadium(v) complexes with ONO donor ligands

Abstract

The study of DNA/BSA interaction and the catalytic potential of four mononuclear oxidoalkoxido vanadium(v) [VVO(L1-4)OEt] (1-4) and one dinuclear oxidoalkoxido mixed-ligand vanadium(v) [{VO(L2)OEt}2(Q)]{Q = 4,4?-bipyridine}(5) complexes, with tridentate binegative aroylazine ligands are reported [where H2L1 = anthranylhydrazone of 2-hydroxy-1-napthaldehyde, H2L2 = salicylhydrazone of 2-hydroxy-1-napthaldehyde, H2L3 = benzoylhydrazone of 2-hydroxy-1-acetonaphthone, H2L4 = anthranylhydrazone of 2-hydroxy-1-acetonaphthone]. All the complexes are characterized by elemental analysis as well as various spectroscopic techniques. Single crystal X-ray diffraction crystallography of 2 reveals that the metal centre is in distorted square pyramidal geometry with O4N coordination spheres, whereas 5 exhibits a distorted octahedral geometry around the metal center. In addition, all the complexes (1-5) show moderate DNA binding propensity which is investigated using UV-vis absorption titration, circular dichroism, thermal denaturation and fluorescence spectral studies. The experimental results show that the complexes effectively interact with CT-DNA through both minor and major groove binding modes, with binding constants ranging from 104105 M1. Among 1-5, complexes 3 and 4 show higher binding affinity towards CT-DNA than others and at the same time also exhibit negative ?Tm values of about ?1.5 and 1.0 �C which resembles the properties shown by cisplatin. All complexes show moderate photo-induced cleavage of pUC19 supercoiled plasmid DNA with complex 3 showing the highest photo induced DNA cleavage activity of ?48%. In coherence with the DNA interaction studies, 3 and 4 also exhibit good binding affinity towards BSA in the range of 10101011 M1, which is also supported by their ability to quench the tryptophan fluorescence emission spectra of BSA. All the complexes show remarkable photo-induced BSA cleavage activity (>90%) at a complex concentration of 50 ?M. The catalytic potential of 1-5 is also tested for the oxidative bromination of styrene, salicylaldehyde and oxidation of methyl phenyl sulphide. All the reactions show a high percentage of conversion (>90%) with a high turnover frequency (TOF). Particularly, in the oxidative bromination of styrene the percentage of conversion and TOF vary from 96-98% and 8000-19600 (h1) respectively, which signifies the potential of these oxidovanadium(v) complexes to stimulate research for the synthesis of a better catalyst. � The Royal Society of Chemistry.