Controlling Photophysical Properties in Bis-Cyclometalated Ir(III)-Terpyridine Complexes through Photoinduced Intraligand Charge Transfer

This work is the study of the role of a remote amine substituent on the terpyridine ligand in controlling the photophysical and electroluminescent behavior of complexes [Ir(Ph-btz) 2 (R-C 6 H 4 -terpy-κ 2 N)]PF 6 . Introduction of the amine group into the Ph-terpy framework induced perturbations in the absorption and luminescent characteristics of [Ir(Ph-btz) 2 (R-C 6 H 4 -terpy-κ 2 N)]PF 6 relative to the parent chromophores [Ir(Ph-btz) 2 (terpy-κ 2 N)]PF 6 and [Ir(Ph-btz) 2 (C 6 H 5 -terpy-κ 2 N)]PF 6 . Consistent with the presence of vibronic structure, negligible emission solvatochromism, weak rigidochromic behavior, and substantial overlap with the phosphorescence of 2-phenylbenzothiazole, the emissive triplet excited state of the model complexes was assigned to 3 IL Ph-btz with a minor 3 MLCT contribution. The amine-substituted Ir(III) complexes were found to exhibit altered emission characteristics, manifested by a structureless emission band impacted by the amine group and solvent polarity. It was rationalized by a switch from the 3 IL Ph-btz /MLCT excited state in model chromophores to a configurationally mixed 3 ILCT/IL/MLCT R-terpy in [Ir(Ph-btz) 2 (R-C 6 H 4 -terpy-κ 2 N)]PF 6 . With respect to the preliminary electroluminescence investigations, it was found that the introduction of the triphenylamine moiety enhances the stability of O/PEDOT/PSS/complex/Al devices. A deep insight into ground- and excited-state characters and photophysical properties of [Ir(Ph-btz) 2 (R-C 6 H 4 -terpy-κ 2 N)]PF 6 was obtained by applying a wide range of experimental techniques, including cyclic voltammetry, UV–vis spectroscopy, photoluminescence spectroscopy, and transient absorption, complemented by DFT and TD-DFT calculations.