Luminescent bis-cyclometallated iridium(III) complexes containing phosphine-based ligands: Influence of the P^N bridge

Abstract

Three cationic bis-cyclometallated iridium complexes [Ir(C^N-ppyMe)2(P^N)][PF6](1–3) with 4-methyl-2-phenylpyridine (ppyMe) as the C^N-cyclometallated ligands and 8-(diphenylphosphino)quinoline (Ph2Pqn, L1), 2-(diphenylphosphinoamino)pyridine (Ph2PNHpy, L2) or 2-(diphenylphosphinoamino) pyrimidine (Ph2PNHpym, L3) as P^N-ligands, were prepared, and their crystal structures and photoluminescence were investigated. The substitution of an “aromatic CAr” (of a quinolyl group) by an “NH” bridge between the phosphine and imine ligating units of the P^N ligand dramatically changes the luminescence characteristics of the resulting complexes. The complexes 2–3 featuring the P–NH–N ligand emit in the blue region, whereas complex 1 incorporating the P–CAr–N unit displays orange photoluminescence.