Preparation of a DNA-bound [Ru(bpy)₂(mbpibH2)]²+ film and its two-mode luminescence tuning by copper(II) ions and EDTA.

An imidazophenanthroline-containing ruthenium(II) complex [Ru(bpy)(2)(mbpibH2)](2+) (bpy=2,2'-bipyridine, mbpibH2=1,3-bis([1,10]phenanthroline[5,6-d]imidazol-2-yl)benzene) can bind DNA through groove-binding and/or non-classical intercalation modes, revealed by spectrophotometric methods, viscosity measurements and variable ionic strength experiments. On the basis of binding interactions between cationic [Ru(bpy)(2)(mbpibH2)](2+) and anionic DNA at a molar ratio of 1:1, a yellow transparent cast film has been assembled on an indium-tin oxide (ITO) surface using a solution-based self-standing method. The prepared DNA-[Ru(bpy)(2)(mbpibH2)](2+) film shows a bi-exponential luminescence decay with τ(1)=62.1 ns (8.0%) and τ(2)=594.5 ns (92.0%), whose lifetimes become much shorter than those of DNA-bound [Ru(bpy)(2)(mbpibH2)](2+) in buffer solutions. The Ru(II) complex with a free bi-dentate coordination site in the DNA cast film shows tunable luminescence, quenched dynamically by Cu(2+) and restored by using EDTA to eliminate two modes of Cu(2+)-binding. The results from this study provide a significant foundation for better understanding the fabrication and modulation of a DNA-based solid luminescence device using the Ru(II) complexes as DNA-concentrating and signal-sensing agents.