Manganese(II) complexes of substituted salicylaldehydes and α-diimines: Synthesis, characterization and biological activity

The interaction of Mn+2 with substituted salicylaldehydes (X-saloH) led to the formation of five manganese(II) complexes formulated as [Μn(X-salo)2(MeOH)2]. When the reactions took place in the presence of an α-diimine such as 2,2′-bipyridine, 1,10-phenanthroline or 2,2′-bipyridylamine, five manganese(II) complexes of the formula [Mn(X-salo)2(α-diimine)] were isolated. The characterization of the complexes was accomplished by various spectroscopic techniques and single-crystal X-ray crystallography. The antioxidant activity of the compounds was evaluated via the scavenging of 1,1-diphenyl-picrylhydrazyl, 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl free radicals. The antibacterial activity of the complexes was tested in vitro against Staphylococcus aureus and Xanthomonas campestris bacterial strains and was found moderate. Diverse techniques were employed to examine the interaction of the complexes with calf-thymus DNA which showed intercalation as the most possible interaction mode. The affinity of the complexes for bovine serum albumin was investigated by fluorescence emission spectroscopy and the binding constants were determined. Ten manganese(II) complexes bearing diverse salicylaldehydes as ligands and α-diimines as co-ligands were isolated and their structures were characterized. In vitro monitoring of the biological activity showed that the compounds intercalate to calf-thymus DNA, bind tightly to bovine serum albumin, possess antimicrobial activity and present effective antioxidant activity. [Display omitted] •Ten manganese(II) complexes with salicylaldehydes (and α-diimines) were characterized.•Intercalation is the most possible interaction mode of complexes with calf-thymus DNA.•The antimicrobial activity of the complexes was also examined.•The complexes show significant radical scavenging activity.•The complexes may bind tightly and reversibly to bovine serum albumin.