Luminescence properties of [Ru(bpy)2MDHIP]2+ modulated by the introduction of DNA, copper(II) ion and EDTA

The luminescence properties of [Ru(bpy)2MDHIP]2+ (bpy = 2,2′-bipyridine, MDHIP = 2,4-dihydrophenyl-imidazo[4,5-f][1,10]phenanthroline) in the absence and presence of DNA modulated by the introduction of Cu2+ ion and EDTA have been investigated. It is found that the ruthenium(II) complex can insert and stack between the base pairs of calf thymus DNA with MDHIP ligand, and the intramolecular hydrogen bond is located inside of the DNA. The presence of DNA can enhance the luminescence intensities of [Ru(bpy)2MDHIP]2+ both in buffer solution and on an ITO surface. Moreover, the luminescence intensities of [Ru(bpy)2MDHIP]2+ and DNA-bound [Ru(bpy)2MDHIP]2+ are quenched by Cu2+, and next recovered by the addition of EDTA. The repetitive luminescence-modulations have been achieved through the introduction of equimolar Cu2+ and EDTA, respectively. In addition, it becomes evident that the number of luminescence-modulation cycles for [Ru(bpy)2MDHIP]2+ in the absence and presence of DNA is influenced by the cumulative concentrations of CuEDTA, generated successively by the strong coordination of Cu2+ to EDTA.