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

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 (Φ PL up to 90%) and radiative rates ( k r ) up to 3.32 × 10 5 s -1 . The TADF process is aided by fast reverse intersystem crossing (rISC) rates of up to 2.56 × 10 7 s -1 . Such emitters can be considered as hybrids of two existing TADF emitter design strategies, combining low singlet-triplet energy gaps (Δ E 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.