Luminescence properties of a di-ruthenium(II) complex with an intramolecular hydrogen bond modulated by DNA and copper(II) ion

Modulation of the luminescence properties of a di-ruthenium(II) complex [(bpy)(2)Ru(BL)Ru(bpy)(2)](4+) (bpy = 2,2'-bipyridine, BL = 2-hydroxyl-5-methyl-1,3-bis([1,10]phenanthroline-[5,6-d]imidazol-2-yl)benzene) by DNA and/or Cu2+ ion has been investigated. It is found that the ruthenium(II) complex can coordinate to the Cu2+ ion in both the absence and presence of DNA. Binding to DNA is through electrostatic interactions and the intramolecular hydrogen bond in the complex is located outside of the DNA. The binding constant is 1.6 x 10(4) M-1. Moreover, it is demonstrated that DNA has the ability to enhance the luminescence intensities of both the di-ruthenium(II) complex and the tri-metallic system generated by chelating with Cu2+. Conversely, Cu2+ ion can quench the luminescence of both the free ruthenium(II) complex and the DNA-bound ruthenium(II) complex.