Synthesis, Characterization and DNA-Binding Affinity of a New Zinc(II) Bis(5-methoxy-indol-3-yl)propane-1,3-dione Complex.

The novel zinc(II) µ-oxo-bridged-dimeric complex [Zn(µ-O)(BMIP)] (BMIP = 1,3-bis(5-methoxy-1-methyl-1-indol-3-yl)propane-1,3-dione), , was synthetized and fully characterized. The spectral data indicate a zincoxane molecular structure, with the BMIP ligand coordinating in its neutral form via its oxygen atoms. Structural changes in in dimethylsulfoxide (DMSO) were evidenced by means of spectroscopic techniques including infrared absorption and nuclear magnetic resonance, showing DMSO entrance in the coordination sphere of the metal ion. The resulting complex [Zn(µ-O)(BMIP)(DMSO)], , readily reacts in the presence of -methyl-imidazole (NMI), a liquid-phase nucleoside mimic, to form [Zn(µ-O)(BMIP)(NMI)], , through DMSO displacement. The three complexes show high thermal stability, demonstrating that has high affinity for hard nucleophiles. Finally, with the aim of probing the suitability of this system as model scaffold for new potential anticancer metallodrugs, the interactions of with calf thymus DNA were investigated in vitro in pseudo-physiological environment through UV-Vis absorption and fluorescence emission spectroscopy, as well as time-resolved fluorescence studies. The latter analyses revealed that [Zn(µ-O)(BMIP)(DMSO)] binds to DNA with high affinity upon DMSO displacement, opening new perspectives for the development of optimized drug substances.