Carbene–Metal Complexes As Molecular Scaffolds for Construction of through-Space Thermally Activated Delayed Fluorescence Emitters

• Published in: Inorganic chemistry 2022-01, Vol.61 (4), p.2174-2185
• Main Authors: Ruduss, Armands, Turovska, Baiba, Belyakov, Sergey, Stucere, Kitija A, Vembris, Aivars, Traskovskis, Kaspars
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c03371

The through-space charge transfer (CT) process is observed in Cu­(I) carbene–metal–amide complexes, where conventional imidazole or imidazoline N-heterocyclic (NHC) carbene fragments act as inert linkers and CT proceeds between a metal-bound carbazole donor and a distantly situated carbene-bound phenylsulfonyl acceptor. The resulting electron transfer gives a rise to efficient thermally activated delayed fluorescence (TADF), characterized with high photoluminescence quantum yields (ΦPL up to 90%) and radiative rates (k r) up to 3.32 × 105 s–1. The TADF process is aided by fast reverse intersystem crossing (rISC) rates of up to 2.56 × 107 s–1. Such emitters can be considered as hybrids of two existing TADF emitter design strategies, combining low singlet–triplet energy gaps (ΔE ST) met in all-organic exciplex-like emitters (0.0062–0.0075 eV) and small, but non-negligible spin–orbital coupling (SOC) provided by a Cu atom, like in TADF-active organometallic complexes.