1,2,3-Triazolyl-pyridine derivatives as chelating ligands for blue iridium(iii) complexes. Photophysics and electroluminescent devices

Abstract

We report on the study of a new family of neutral heteroleptic Ir(F₂ppy)₂L (F₂ppy = 2-(2,4-difluorophenyl)pyridine) complexes bearing different triazole derivatives (L = 2-(1,2,3-triazol-5-yl)pyridine) as the third ligand. Two of these ligands were used for the first time as ancillary ligands in iridium(III) complexes. A full photophysical and electrochemical study of these complexes is reported here, together with theoretical investigations at the density functional theory (DFT) level. The complexes were also obtained as single crystals and their structures were determined by X-ray crystallography. The newly reported complexes exhibit blue emission with high quantum yields in solution. Photophysical results are also compared to those reported for their 1,2,4-triazole isomer analogues. The emitting state is a mixture between the triplet metal-to-ligand charge transfer (³MLCT) and triplet inter-ligand charge transfer (³ILCT) states, and it is more localized on the F₂ppy ligand as supported by DFT calculations. In addition, this paper reports some preliminary tests of polymer light-emitting diodes (PLEDs) doped with these iridium complexes. The results indicate that such molecules are good candidates as blue- and green-emitting dopants in LED devices.