Antibacterial, DNA interaction and cytotoxic activities of pendant-armed polyamine macrocyclic dinuclear nickel(II) and copper(II) complexes

• Six pendant-armed complexes with benzoyl substituents have been synthesized.
• Antibacterial activity against Gram +ve and Gram −ve bacteria has been studied.
• DNA binding studies suggest the intercalative mode of binding.
• The synthesized complexes act as potent metallonucleases.
• Complexes can enter the nuclei of HepG2 cells and induce cell apoptosis.

A series of dinuclear nickel(II) and copper(II) complexes (1–6) of hexaaza macrocycles of 2,6-diformyl-4-methylphenol with three different benzoyl pendant-arms, 2,2′-benzoyliminodi(ethylamine) trihydrochloride (L), 2,2′-4-nitrobenzoyliminodi(ethylamine) trihydrochloride (L′) and 2,2′-3,5-dinitrobenzoyliminodi(ethylamine) trihydrochloride (L″) have been synthesized and characterized by spectral methods. The electrochemical studies of these complexes depict two irreversible one electron reduction processes around E1pc = −0.62 to −0.76 V and E2pc = −1.21 to −1.31, and nickel(II) complexes (1–3) exhibit two irreversible one electron oxidation processes around E1pa = 1.08 to 1.14 V and E2pa = 1.71 to 1.74 V. The room temperature magnetic moment values (μeff, 1.52–1.54 BM) indicate the presence of an antiferromagnetic interaction in the binuclear copper(II) complexes (4–6) which is also observed from the broad ESR spectra with a g value of 2.14–2.15. The synthesized complexes (1–6) were screened for their antibacterial activity. The results of DNA interaction studies indicate that the dinuclear complexes can bind to calf thymus DNA by intercalative mode and display efficient cleavage of plasmid DNA. Further, the cytotoxic activity of complexes 2, 5 and 6 on human liver adenocarcinoma (HepG2) cell line has been examined. Nuclear-chromatin cleavage has also been observed with PI staining and comet assays.

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