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-imidazo4,5-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.