Synthesis, DNA-binding and photocleavage studies of ruthenium(II) complex with 2-(3′-phenoxyphenyl)imidazo[4,5-f][1,10]phenanthroline

A new polypyridyl ligand MPPIP {MPPIP = 2-(3′-phenoxyphenyl)imidazo[4,5-f]-[1,10]phenanthroline} and its ruthenium(II) complexes, [Ru(bpy)2MPPIP]2+ (1) (bpy = 2,2′-bipyridine) and [Ru(phen)2MPPIP]2+ (2) (phen = 1,10-phenanthroline) have been synthesized and characterized. The binding of the two complexes to calf thymus DNA (CT-DNA) has been investigated with spectrophotometric methods, viscosity measurements, as well as equilibrium dialysis and circular dichroism spectroscopy. The results suggest that both complexes bind to CT-DNA through intercalation, and enantioselectively interact with CT-DNA in a way. However, complex 2 is a much better candidate as an enantioselective binder to CT-DNA than complex 1. When irradiated at 365 nm, both complexes have also been found to promote the photocleavage of plasmid pBR322 DNA.