Thiosemicarbazone-based Dioxomolybdenum (VI) complexes as inorganic nucleases

This study focuses on the design of alkyl-substituted thiosemicarbazones from 5-bromosalicylaldehyde and substituted thiosemicarbazides and the corresponding dioxomolybdenum(VI) complexes, hitherto unreported. In addition to elemental analyses, the synthesized ligands and the corresponding complexes are further analyzed by physico-chemical and spectroscopic techniques. The DNA interaction studies are based on UV absorption titration and gel electrophoretic methods. The binding constants (K_b) for the ligands (L1-L4) are found to be 1.20 ± 0.1 × 10⁴ M⁻¹; 1.32 ± 0.2 × 10⁴ M⁻¹; 1.27 ± 0.3 × 10⁴ M⁻¹ and 1.25 ± 0.3 × 10⁴ M⁻¹ respectively and that of the complexes (C1–C4) are 1.45 ± 0.2 × 10⁴ M⁻¹; 2.10 ± 0.4 × 10⁴ M⁻¹; 1.54 ± 0.2 × 10⁴ M⁻¹ and 2.13 ± 0.2 × 10⁴ M⁻¹, respectively. The complexes have shown relatively higher binding propensity as compared to that of the ligands. Further, as the outcome of gel electrophoresis studies, the ligands show a cleavage pattern of nicked circular (Form I). However, the complexes show cleavage patterns of both nicked circular and supercoiled, Forms I & II respectively. This implies that both the ligands and complexes possess varying binding efficacy with DNA and accordingly the cleavage patterns also differ.