A novel phosphorogenic rhenium(I) polypyridine complex bearing a dinitrobenzosulfonamide moiety for intracellular glutathione sensing

Abstract

In this project, the synthesis and characterization of a novel phosphorogenic rhenium(I) polypyridine complex containing 2,4-dinitrobenzenesulfonyl (DNBS) unit as phosphorescent probe for glutathione (GSH) are reported. The rhenium(I) complex [Re(2,9-Me2-4,7-Ph2-phen)(CO)3(py-DBNS)] (2,9-Me2-4,7-Ph2-phen = 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; py-DBNS = 3-((2,4-dinitrobenzenesulfonyl)aminomethyl)pyridine (1a)) was designed, synthesized and characterized. Its DNBS free counterpart [Re(2,9-Me2-4,7-Ph2-phen)(CO)3(py)] (py = pyridine (1b)) was also synthesized for comparison studies. Upon photoirradiation, the DNBS-appended complex 1a exhibited very weak emission intensity and short lifetime, which is attributed to the photoinduced electron transfer (PET) from the excited rhenium(I) polypyridine unit to the DNBS unit. After treatment with GSH, the emission intensity of a solution of complex 1a showed significant enhancement (I/Io = 8.2). Additionally, after incubation of HeLa cells with complex 1a, potent emission signal was observed, which was achieved to the departure of the DNBS unit after reaction with intracellular GSH.