Efficient electrochemiluminescent cyclometalated iridium(III) complexes: Synthesis, photophysical and electrochemiluminescent properties

A series of new cyclometalated iridium(III) complexes for electrochemiluminescence (ECL) system were synthesized and fully characterized. Using tri-n-propylamine (TPA) as an oxidative–reductive co-reactant, their ECL properties were studied in acetonitrile (CH3CN) and mixed CH3CN/H2O (50:50, v/v) solutions, respectively. Meanwhile, the influencing factors of ECL efficiencies, including working electrode, pH, and surfactant were investigated. A remarkable ECL enhancement (up to about 13.5 times), in comparison with the commonly used Ru(bpy)32+ (2,2′-bipyridyl) ruthenium(II), is observed from Ir(FPP)2(acac) (where FPP is 2-(4-fluorophenyl)-4-phenylpyridine, acac = acetylacetone) at Pt disk electrode. At the same time, an increase in ECL efficiency is also observed in surfactant media. This study provided a new method for further improving and tuning the ECL efficiency by designing new iridium complexes with the appropriate cyclometalated or ancillary ligands.