Stable and Tunable Phosphorescent Neutral Cyclometalated Au(III) Diaryl Complexes

A series of novel luminescent cyclometalated Au(III) neutral complexes of the type cis-[(N∧C)AuL] [N∧C = 2-phenylpyridine (ppy), L = 1,1′-biphenyl (1)] and cis-[(N∧C)AuL2] [N∧C = 2-phenylpyridine (ppy), L = C6H5 (2), C6F5 (3), C6H4-CF3-p (4), 2-C4H3S (5)]; [N∧C = 2-(2-thienyl)pyridine (thpy), L = C6H5 (6), C6F5 (7)]; [N∧C = 2-(5-methyl-2-thienyl)pyridine (5 m-thpy), L = C6F5 (8)] were successfully synthesized. The X-ray crystal structures of all compounds except 3 have been determined. These complexes were found to show long-lived emission in solution at room temperature. The emission origins of the complexes have been tentatively assigned to be derived from triplet states predominantly bearing intraligand (IL) character with some perturbation from the metal center. Density functional theory (DFT) calculations were performed to evaluate the stability associated with the complexes and TD-DFT calculations to ascertain the nature of the excited state. Variation of the cyclometalated ligands in the complexes readily leads to the tuning of the nature of the lower energy emissive states.