A highly selective and multisignaling optical-electrochemical sensor for Hg2+ based on a phosphorescent iridium(III) complex

A highly selective phosphorescent chemosensor for Hg2+ based on the iridium(III) complex Ir(btp)(2)(acac) was realized. Multisignaling changes were observed through UV-vis absorption, phosphorescent emission, and electrochemical measurements. Upon addition of Hg2+, the obvious spectral blue-shifts in absorption and phosphorescent emission bands were measured for Ir(btp)(2)(acac), which could be observed by the naked eye. Further investigation indicated that the interaction between Hg2+ and the sulfur of cyclometalated ligands is responsible for the significant variation in optical and electrochemical signals, which was also confirmed by density functional theory (DFT) calculation. It is the charge transfer from the iridium center to cyclometalated ligands that increases the electron density of cyclometalated ligands, which makes the coordination of sulfur to Hg2+ easier.