DNA-binding studies of two dioxomolybdenum(VI) complexes of salicylaldehyde benzoylhydrazone ligands

The reaction of [MoO2(acac)2] with salicylaldehyde benzoylhydrazone (H2L1) and with one of its derivatives (H2L2) resulted in the production of two neutral mononuclear dioxomolybdenum complexes; MoO2L1(MeOH) 1 and MoO2L2(MeOH) 2, respectively. (H2L1) was derived from the reaction of benzhydrazide and 2-hydroxybenzaldehyde (salicylaldehyde) and (H2L2) was derived from the reaction of benzhydrazide and 2-hyroxy-3-methoxybenzaldehyde. Interactions of the complexes were investigated with calf thymus DNA by UV–Vis, fluorescence and circular dichroism spectroscopies to determine their biological effects. Results evaluated the binding affinity of complexes 1 and 2 to CT-DNA by UV and presented binding constants (Kb) of (3.52 ± 0.1) × 103 M−1 and (4.49 ± 0.1) × 103 M−1, respectively. Evaluations of fluorescence approved the binding of the fluorescent complex 2, to DNA. Competitive studies with ethidium bromide (EB) showed that none of the complexes displaced the DNA–EB binding efficiency effectively while they changed the polarity of the environment by occupying the previous place of water molecules around the helix. CD spectral studies revealed that as a result of interaction with both complexes, calf thymus B-DNA turned into A-like structure. ing to our results both complexes bind to DNA via a non-intercalative mode, presumably through groove binding.