Rationally Designed Blue Triplet Emitting Gold(III) Complexes Based on a Phenylpyridine-Derived Framework

A series of blue-emitting phosphorescent mono-cyclometalated Au^III complexes have been successfully synthesized. Tailoring the substitutions on the phenylpyridine (ppy) ligand scaffold with electron-withdrawing fluorine groups on the phenyl ring to achieve stabilization of the HOMO and an electron-donating dimethylamino group on the pyridine ring to destabilize the LUMO resulted in a large energy gap and bestowed on the gold(III) complexes high-energy emission and high quantum efficiencies. The results of cyclic voltammetry studies suggested a predominantly redox event localized on the cyclometalated ligand. Thermogravimetric analysis of selected complexes revealed a high stability up to 280 °C, thus the complexes are suitable for device fabrication through vacuum-deposition. Photophysical investigations performed on all the derivatives revealed phosphorescence emission in neat solid, solution, doped in poly(methyl methacrylate) (PMMA) films at room temperature as well as in rigidified glass media (2-MeTHF) at 77 K. A high photoluminescent quantum efficiency of 28 % was obtained for a complex in PMMA, the highest quantum yield reported for a blue-emitting gold(III) complex.