A novel dinuclear ruthenium(ii)–copper(ii) complex-based luminescent probe for hydrogen sulfide

A novel dinuclear ruthenium(II)-copper(II) complex, [Ru(bpy)2(phen-cyc)Cu](PF6)4 (bpy: 2,2'-bipyridine; cyc: 1,4,7,10-tetraazacyclododecane; phen: 1,10-phenanthroline), has been designed and synthesized by conjugating a ruthenium(II) complex with a cyclen-Cu(2+) complex. This has almost no luminescence due to the efficient quenching by Cu(2+) of the luminescence of the ruthenium(II) complex. In aqueous media, the reaction of [Ru(bpy)2(phen-cyc)Cu](PF6)4 with hydrogen sulfide results in the release of the Cu(2+) from the azamacrocyclic ring, accompanied by a ~130-fold increase in the luminescence intensity at 605 nm with a 159 nm Stokes shift. The dose-dependent luminescence enhancement shows a good linearity in a concentration range of 2.0 to 20 μM, with a detection limit of 21.6 nM for hydrogen sulfide. In addition, the luminescence response of [Ru(bpy)2(phen-cyc)Cu](PF6)4 to hydrogen sulfide is very rapid and widely available in the pH range of 3.0-9.5. It also has excellent selectivity so it can distinguish hydrogen sulfide with no interference by other anions and amino acids. On the basis of these features, a rapid, highly selective and sensitive luminescence method for the detection of hydrogen sulfide under physiological conditions was established, using [Ru(bpy)2(phen-cyc)Cu](PF6)4 as a probe.