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 (K-b) of (3.52 +/- 0.1) x 10(3) M-1 and (4.49 +/- 0.1) x 10(3) 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. According to our results both complexes bind to DNA via a non-intercalative mode, presumably through groove binding. (C) 2013 Elsevier B. V. All rights reserved.