Efficient green-colored electrochemiluminescence from cyclometalated iridium(III) complex

The spectroscopy, electrochemistry, and electrochemiluminescence (ECL) of cyclometalated iridium(III) bis(2-(p-tolyl)pyridinato-N, C2′) (picolinate) [(tpy)2Ir(pico)] was investigated. (tpy)2Ir(pico) shows high photoluminescence efficiency (ΦPL = ∼0.31) and quasi-reversible redox behaviors in acetonitrile solution. Intense green ECL was observed from all three modes of ECL generation (annihilation, oxidative-reduction, and reductive-oxidation). Relative ECL efficiencies with or without coreactants from (tpy)2Ir(pico) were estimated using Ru(bpy)32+ (bpy, 2,2′-bipyridine) as a relative standard. Typically, in the reductive-oxidation process with peroxodisulfate (S2O82−), (tpy)2Ir(pico) produces 8-fold more efficient ECL at approximately 531 nm than Ru(bpy)32. This efficient green ECL indicates potential for the development of multicolored ECL analysis in addition to standard Ru(bpy)32+ systems.