The influence of numbers and ligation positions of the triphenylamine unit on the photophysical and electroluminescent properties of homoleptic iridium(iii) complexes: a theoretical perspective

Abstract

A DFT/TDDFT investigation was carried out on a series of homoleptic triphenylamine-featured Ir(III) complexes 1a–1c [1a: (fac-tris[2-phenyl-4-(2-(N,N-diphenylamino)phenyl)pyridine]iridium(III)); 1b: (fac-tris[2-phenyl-4-(3-(N,N-diphenylamino)phenyl)pyridine]iridium(III)); 1c: (fac-tris[2-phenyl-4-(4-(N,N-diphenylamino)phenyl)pyridine]iridium(III))] with one triphenylamine unit in the 2-phenylpyridine (ppy) ligand and 2a–2c [2a: (fac-tris[2,4-bis(2-(N,N-diphenylamino)phenyl)pyridine]iridium(III)); 2b: (fac-tris[2,4-bis(3-(N,N-diphenylamino)phenyl)pyridine]iridium(III)); 2c: (fac-tris[2,4-bis(4-(N,N-diphenylamino)phenyl)pyridine]iridium(III))] with two triphenylamine units in the ppy ligand, respectively, aiming to gain insight into the influence of number and ligation position of triphenylamine units on the photophysical and electronic properties of the studied complexes. Complexes 2a–2c have been synthesized recently. For comparison, the parent complex Ir(ppy)₃ was also investigated. The calculated results reveal that the introduction of the triphenylamine unit leads to enhanced charge-injection abilities and a balanced charge-transfer process compared with Ir(ppy)₃. The different ligation positions of triphenylamine unit have an obvious effect on the absorption intensities for these complexes. The emissions of 1a–1c and 2a–2c undergo significant red shift with the introduced triphenylamine unit in ppy ligands compared with that of Ir(ppy)₃, while the extent of red shift shows an apparent dependence on the number of triphenylamine units. The factors that might affect the quantum yield have been discussed.