Development of a heterobimetallic Ru(II)–Cu(II) complex for highly selective and sensitive luminescence sensing of sulfide anions

A heterobimetallic ruthenium(II)–copper(II) complex-based luminescent chemosensor, [Ru(bpy)2(bpy-DPA)Cu]4+ (bpy: 2,2′-bipyridine; bpy-DAP: 4-methyl-4′-[N,N-bis(2-picolyl)amino-methylene]-2,2′-bipydine), has been designed and synthesized for the highly selective and sensitive recognition and detection of sulfide anions in 100% aqueous solutions. Owing to the high affinity of sulfide to Cu(II), the non-luminescent chemosensor can specifically and rapidly react with sulfide to yield the corresponding ruthenium(II) complex, [Ru(bpy)2(bpy-DPA)]2+, accompanied by the remarkable luminescence enhancement. The dose-dependent luminescence enhancement of the sensor shows a good linearity with a detection limit of 20.7 nM for sulfide anions. The novel luminescence sensor has a widely available pH range from 4.5 to 10 and an excellent response selectivity to sulfide only even in the presence of various other anions. Based on this chemosensor, a rapid, selective and sensitive luminescence method for the detection of sulfide anions in wastewater samples was established. The coefficient variations (CVs) of the method are less than 3.1%, and the recoveries are in the range of 90.9–108.5%.