Thermally Activated Delayed Fluorescence in Neutral and Cationic Copper(I) Complexes with the 2‑(4-Thiazolyl)benzimidazole Ligand

Cationic [Cu­(P^P)­(Htbz)]­PF6 [P^P = xantphos, dpephos; Htbz = 2-(4-thiazolyl)­benzimidazole] and the corresponding neutral complexes [Cu­(P^P)­(tbz)], obtained through deprotonation of the diimine ligand, have been synthesized with the aim of analyzing the role of the diphosphane and Htbz deprotonation in the emissive properties of these complexes. For the study of the diphosphane effect, the luminescence properties of these compounds have been compared with those of the reported analogous derivatives with Htbz and carborane diphosphanes. Complexes [Cu­(P^P)­(Htbz)]­PF6 (P^P = xantphos, dpephos) and [Cu­(dpephos)­(tbz)] display thermally activated delayed fluorescence, which has been studied, revealing a ΔE(S1–T1) between 658 and 455 cm–1. Theoretical calculations indicate different origins for the absorptions, leading to the observed emissions.