Excited-state Properties in Gold(I) N-Heterocyclic Carbene Complexes

Due to their tailorable excited-state properties, gold(I) complexes are exciting options for OLEDs and non-linear optical materials. In collaboration with the Air Force Research Lab and Case Western Reserve University, the photophysical properties of multiple gold(I) complexes bearing electron-releasing (diphenylamino) and electron-withdrawing (benzothiazolyl) ligands were studied. The observed phosphorescence, intersystem crossing quantum yields above 50%, and long triplet lifetimes ranging from 300-1000 ms, indicate an excited state with promising optical properties. This led to additional interest in the excited-state dynamics of these molecules, specifically the presence of triplet-triplet annihilation (TTA). To further investigate the excited-state dynamics and triplet decay pathways of these gold(I) complexes, the presence of TTA was studied through delayed fluorescence and energy-dependent triplet decay kinetics. Even though the presence of TTA appears to be an efficient and competing decay pathway for excited triplet states in these molecules, the aforementioned favorable photophysical properties still lend promise for the use of these compounds in novel solid optical materials.