A chelating diisocyanide ligand for cyclometalated Ir(III) complexes with strong and tunable luminescence

We report the synthesis, the structural characterisation and a detailed pho-tophysical description of three cationic cyclometalated iridium(III) com-plexes (2-4) bearing a chelating diisocyanide as ancillary ligand (1 = 2,2"-diisocyano-1,1':3',1"-terphenyl). All compounds display irreversible reduc-tion and oxidation potentials and emit from a triplet excited state centred on the cyclometalating ligands with lifetimes of several dozens microseconds, as commonly observed for other iridium(III) isocyanide complexes and fur-ther confirmed by DFT calculations. Room-temperature photoluminescence can be tuned from blue to orange upon variation of the cyclometalating lig-ands and related quantum yields range from around 30% in acetonitrile so-lution to nearly 80% in solid-state, as for complex 3 embedded in a 1% w/w poly(methyl methacrylate) matrix.