Thermally activated delayed fluorescence in luminescent cationic copper(i) complexes

In this work, the photophysical characteristics of [Cu(N boolean AND N)(2)](+) and [Cu(N boolean AND N)(P boolean AND P)](+) complexes were described. The concept of thermally activated delayed fluorescence (TADF) and its development throughout the years was also explained. The importance of Delta E-(S1-T-1) and spin-orbital coupling (SOC) values on the TADF behavior of [Cu(N boolean AND N)(2)](+) and [Cu(N boolean AND N)(P boolean AND P)](+) complexes is discussed. Examples of Delta E-(S1-T-1) values reported in the literature were collected and some trends were proposed (e.g. the effect of the substituents at the 2,9 positions of the phenanthroline ligand). Besides, the techniques (or calculation methods) used for determining Delta E-(S1-T-1) values were described. The effect of SOC in TADF was also discussed, and examples of the determination of SOC values by DFT and TD-DFT calculations are provided. The last chapter covers the applications of [Cu(N boolean AND N)(2)](+) and [Cu(N boolean AND N)(P boolean AND P)](+) TADF complexes and the challenges that are still needed to be addressed to ensure the industrial applications of these compounds.