Synthesis, characterization and interaction of mixed polypyridyl ruthenium(II) complexes with calf thymus DNA

New mixed polypyridyl {HPIP = 2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline, phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline, dmb = 4,4'-dimethyl-2,2'-bipyridine} ruthenium(II) complexes [Ru(phen)(2)(HPIP)](2+), [Ru(dmp)(2)(HPIP)](2+) and [Ru(dmb)(2)(HPIP)](2+) were synthesized and characterized by elemental analyses H-1-n.m.r., u.v.-vis. spectroscopy and cyclic voltammetry. Their DNA-binding properties were demonstrated by absorption, luminescence titrations, steady-state emission quenching and viscosity measurements. The results suggested that all the examined complexes bind with CT-DNA intercalatively. Methyl groups substituted at the 4,4'-positions of bpy has no obvious effect on its DNA binding, whereas substituents at the 2- and 9-positions of phen have an impressive effect on its DNA-binding, as revealed by the decreased binding affinity.