Neutral and Dianionic Ru(II) Bathophenanthrolinedisulfonate Complexes: A Route To Enhance Electrochemiluminescence Performance in Aqueous Media

We report the strong enhancement of ECL intensity and duration in neutral and dianionic Ru(II) complexes hearing mixed 2,2'-bipyridine (bpy) and bathophenanthrolinedisulfonate (BPS) ligands. In aqueous conditions, using the tripropylamine-assisted method and applying a constant potential, we observed for Ru(BPS)(bpy)(2) a remarkable 26-fold ECL integrated intensity increase with respect to Ru(bpy)(3)(2+). The results herein obtained reveal that the cause of reduced ECL intensity of [Ru(BPS)(3)](4-) and [Ru(BPS)(2)(bpy)](2-) can be ascribed to surface effects related to the interaction of the oxidized complex with the electrode. The expected reduction or absence of electrostatic interactions with biomolecules, together with the strongly enhanced performance, makes the zwitterionic Ru(BPS)(bpy)(2) complex a highly promising candidate for the development of very efficient ECL labels For ultrasensitive bioassays and functional imaging applications.