Strongly Luminescent Cyclometalated Gold(III) Complexes Supported by Bidentate Ligands Displaying Intermolecular Interactions and Tunable Emission Energy

A series of charge‐neutral Au III complexes, which comprise a dicarbanionic C‐deprotonated biphenyl ligand and bidentate ancillary ligands ([Au(C^C)(L^X)]; L^X=β‐diketonate and relatives (O^O), quinolinolate and relatives (N^O), and diphosphino (P^P) ligands), were prepared. All the complexes are emissive in degassed CH 2 Cl 2 solutions and in thin‐film samples with Φ em up to 18 and 35 %, respectively, except for 5 and 6 , which bear (N^O)‐type ancillary ligands. Variation of the electronic characteristics of the β‐diketonate ancillary ligand was demonstrated to be a viable route for tuning the emission color from blue‐green (peak λ em at ca. 466 nm for 1 and 2 ; 501 nm for 4 a and 4 b ) to orange (peak λ em at 585 nm for 3 ), in contrast to the common observations that the ancillary ligand has a negligible effect on the excited‐state energy of the Au III complexes reported in the literature. DFT/time‐dependent (TD) DFT calculations revealed that the energies of the 3 ππ*(C^C) and the 3 ILCT(O^O) excited states (ILCT=intraligand charge transfer) switch in order on going from O^O=acetylacetonate (acac) to aryl‐substituted β‐diketonate ligands. Solution‐processed and vacuum‐deposited organic light‐emitting diode (OLED) devices of selected complexes were prepared. The vacuum‐deposited OLED fabricated with 2 displays a sky‐blue emission with a maximum external quantum efficiency (EQE) of 6.71 % and CIE coordinates of (0.22, 0.40). The crystal structures of 7 and 9 reveal short intermolecular Au III ⋅⋅⋅Au III contacts, with intermetal distances of 3.408 and 3.453 Å, respectively. DFT/TDDFT calculations were performed on 7 and 9 to account for the noncovalent interactions. Solid samples of 1 , 3 , and 9 exhibit excimeric emission at room temperature, which is rarely reported in Au III complexes.