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

Abstract

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