DNA/lysozyme binding propensity and nuclease properties of benzimidazole/2,2′-bipyridine based binuclear ternary transition metal complexes

In the present contribution, new binuclear ternary complexes; [M(2)(bpy)(4)L](ClO(4))(4) (M = Co(ii) (1) and Ni(ii) (2); bpy = 2,2′-bipyridine; L = 1,1′-(hexane-1,6-diyl)bis[2-(pyridin-2-yl)1H-benzimidazole] and [Cu(2)(bpy)(2)(OH(2))(2)L](BF(4))(4) (3) were synthesized, characterized and screened for their antimicrobial activity and cytotoxicity against human liver carcinoma cells (HepG-2) as well as non-malignant human embryonic kidney cells (HEK-293). The structural studies were complemented by density functional theory (DFT) calculations. DNA binding of 1–3 was spectrophotometrically studied. The DNA cleavage ability of 1–3 towards the supercoiled plasmid DNA (pBR322 DNA) was examined through gel electrophoresis. Compound 3 has the highest cytotoxic activity (IC(50) = 3.5 μg mL(−1)) against HepG-2 among the investigated complexes and is non cytotoxic to noncancerous HEK-293. Complexes (1 and 2) exhibited toxicity to HEK-293 with IC(50) values of 30.3 and 23.5 μg mL(−1) in that order. While compound 1 showed antifungal activity against Cryptococcus neoformans, complex 2 exhibited its toxicity against Candida albicans.