Theoretical studies on excited‐state properties and luminescence mechanism of a Carbene–Metal–Amide Au(I) complex with thermally activated delayed fluorescence.

Two‐coordinate Carbene−Metal−Amide (CMA) complexes with thermally activated delayed fluorescence (TADF) have attracted much attention owing to their excellent luminescence properties and potential applications in organic light‐emitting devices. However, the luminescence mechanism remains unclear. Herein, we took one CMA Au(I) complex as an example and investigate its relevant photophysics using both density functional theory (DFT) and time‐dependent DFT methods with a polarizable continuum model. The calculated absorption and emission spectra agree with the experimental data and the S1 and T1 states show mixed ligand to ligand charge transfer (CT) and ligand to metal CT characters. Small spatial overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) minimizes the energy difference between the S1 and T1 states (ΔEST). Properly large spin‐orbit coupling promotes the reverse intersystem crossing (rISC) process. At 300 K, the rISC process is much more efficient than the T1 phosphorescent emission, which leads to the TADF emission. [ABSTRACT FROM AUTHOR]