The binding kinetics properties of three Ru（Ⅱ） complexes of [Ru（bpy） 2（dhipH 3）]（ClO4）2, [（bpy） 2Ru（eipcH）]（ClO4）2 and [（bpy） 2Ru（ebipcH 2）Ru（bpy） 2]（ClO4）4, where bpy2,2′-bipyridine, dhipH 33,4-dihydroxyphenyl-（imidazo[4,5-f][1,10]phenanthroline）, eipcHN-ethyl-4-（imidazolo[4,5-f]-（1,10-phenanthrolin）-2-yl）carbazole, and ebipcH 2N-ethyl-4,7-bis（imidazolo[4,5-f]-（1,10-phenanthrolin）-2-yl）carbazole, with yeast-RNA were investigated by monitoring the decays in absorbance for π-π* absorption peaks at 286 nm with binding time. The decay curves for the complexes were well fitting to biexponential decay functions with half-life times for rapidly-decayed components being 0.006, 0.02 and 0.8 min, and those for slowly-decayed components being 0.7, 4.2 and 103 min, respectively. The rapidly- and slowly-decayed components are probably due to electrostatic interaction and aromatic base stacking of the RNA with the Ru（Ⅱ） complexes, respectively. The results indicate that not only binuclear complexes but also mononuclear complexes can slowly bind to the RNA depending on the molecular structures of the complexes.
