The dimerization of a well-known DNA light-switch [Ru(phen)2dppz]2+(phen=1,10-phenanthroline, dppz=dipyrido[3,2-a:2′,3′-c]phenazine), and its effect on calf thymus binding properties were studied by UV-Vis and emission spectroscopy in Tris-HCl buffered 50 mmol/L NaCl(pH=7.1). The results show that the complex has a strong tendency to dimerize with a dimerization constant of (1.8±0.3)×106 L/mol at the same order of magnitude as the DNA binding constant of (6.0±1.2)×106 L/mol for the Ru(Ⅱ) complex dimer, but one order of magnitude less than (4.9±1.5)×107 L/mol for the Ru(Ⅱ) complex monomer. This study has provided insight into a fundamental but important issue that should be taken into account for the DNA binding studies.
