Synthesis, DNA Binding, DNA Photocleavage and Antimicrobial Activity of [Co(bpy)₂DMHBT]³⁺, [Co(dmb)₂DMHBT]³⁺ and [Co(phen)₂DMHBT]³⁺ Complexes

ABSTRACT

Cobalt(III) polypyridyl complexes of the type [Co(bpy)₂DMHBT]³⁺, [Co(dmb)₂DMHBT]³⁺ and [Co(phen)₂DMHBT]³⁺ (where DMHBT = 11,13-dimethyl-13H-4,5,9,11,14-hexa aza-benzo[b] triphenylene-10,12-dione; bpy = 2,2′-bipyridine; dmb = 4,4′-dimethyl-2,2′-bipyridine; phen = 1,10-phenanthroline) have been synthesized and fully characterized by elemental analysis, IR, UV-Visible spectra, ¹H, ¹³C-NMR and Mass spectra. The results of absorption and emission titrations as well as thermal temperature and Viscosity measurement studies reveal that [Co(bpy)₂DMHBT]³⁺, [Co(dmb)₂DMHBT]³⁺, and [Co(phen)₂DMHBT]³⁺ are moderate to strong binders of Calf Thymus DNA. An experimental result indicates that the three complexes can intercalate in to DNA base pairs. Under the identical conditions the super-coiled pBR 322 DNA photo-cleavage activities of these three cobalt(III) complexes follow the order:[Co(phen)₂DMHBT]³⁺ > [Co(bpy)₂DMHBT]³⁺ > [Co(dmb)₂DMHBT]³⁺. These complexes are also found to have good antimicrobial activity.

KEYWORDS:

• biological activity
• cobalt(III) complexes
• DNA-binding
• intercalation
• photo-cleavage
• polypyridyl ligands