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; [M₂(bpy)₄L](ClO₄)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 [Cu₂(bpy)₂(OH₂)₂L](BF₄)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 (IC₅₀ = 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 IC₅₀ 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.