Luminescent color control and electroluminescent characteristics of iridium(III) complexes containing a four-membered chelating ring from ancillary ligand

Six dpppy (P,P-diphenyl-N-(pyridin-2-yl)phosphinic amide)- and dppq (P,P-diphenyl-N-(quinolin-2-yl)phosphinic amide)-based iridium(III) complexes 1a, 1b, 2a, 2b, 3a and 3b containing four-membered chelate architecture were synthetized. Their crystal structure and photophysical properties were investigated. The crystal structure shows that two coordinating N atoms from the ancillary ligand dpppy and dppq form a four-membered chelate architecture with the centered iridium(III). By changing the substituent groups and conjugation of the cyclometalated ligand, the control of the luminescent color of the complexes was achieved. In CH2Cl2 solution, complexes 1a, 1b, 2a, 2b, 3a and 3b emitted phosphorescence peaked at 509, 506, 479, 478, 620 and 618 nm with CIE color coordinates of (0.29, 0.60), (0.27, 0.61), (0.13, 0.37), (0.14, 0.35), (0.67, 0.33) and (0.67, 0.33), respectively. The quantum chemical calculation shows that their emitting light is primarily from 3LC π−π* states of the cyclometalated ligand. Electroluminescent devices with dual light-emitting layers were fabricated and exhibited mild efficiency roll-off.