Abstract
The synthesis of a novel imidazolidine type N-heterocyclic carbene (NHC) Cu (I) complex with asymmetrically attached phenylsulfonyl- acceptor group is presented. The asymmetrical ligand was used for the preparation two Cu(I) carbene-metal-amide (CMA) complexes with carbazolide (complex 1) or 1,8-dimethylcarbazolide (complex 2) as the amide donors. Obtained complexes exhibit efficient thermally activated delayed fluorescence (TADF) with luminescence quantum yields (QY) reaching 0.80 in PMMA matrix. Metal promoted through-space charge transfer approach in the emitter design lowers the ΔΕ<sub>ST</sub> gap and the small spin-orbit coupling (SOC) provided by metal atom enables high radiative rates (k<sub>r</sub> = 2.21×10<sup>5</sup> s<sup>-1</sup> for complex 2). The photophysical properties of the asymmetrical (1-2) and previously reported symmetrical (3-6) molecular designs are compared. Obtained results suggest a closely similar photophysical behavior for both the asymmetrical and symmetrical CMA complexes.
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