The quenching and recovery kinetics of photoluminescence of [Ru(bpy)2(tatp)]2+ (Ru1) and [Ru(bpy)2(dmtatp)]2+ (Ru2) intercalated within DNA (where bpy=2,2′-bipyridine, tatp=1,4,8,9-tetra-aza-triphenylene and dmtatp=2,3-dimethyl-1,4,8,9-tetra-aza-triphenylene) have been investigated by steady-state and time-resolved methods performed at various temperatures (293–333K). Two complexes Ru1 and Ru2 show a single-exponential luminescence decay with τRu1=246.0ns and τRu2=513.5ns, whose luminescence upon intercalating into DNA exhibits very consistent bi-exponential decay changes. The addition of Cu2+ ions is found to dynamically quench the luminescence of both DNA-bound Ru(II) complexes, involving a spontaneous exothermic process. The sequential addition of EDTA can partially recover the luminescence quenched by Cu2+, however depending on methyl substituents of the intercalative ligand. The chemical conversion and luminescence control mechanism of the two DNA-bound Ru(II) complexes is discussed in detail. The present results should be of value for better understanding chemical modulation of DNA-bound Ru(II) complexes as luminescence probes.
Read full abstract