<i>N</i>-heterocyclic carbenes (NHC) with a cyclometalated fragment (C^C*) are exceptionally strong σ-donor ligands, which allow the synthesis of platinum complexes with outstanding photophysical properties. The electronic and steric properties of these emitters can be conveniently predicted and fine-tuned using DFT calculations. The square planar geometry of platinum(II) complexes allows for intermolecular interactions which result in unique photophysics. Unfortunately, these interactions frequently have negative effects, for example on the quantum yield. We reported that certain C^C* ligands could invert this trend: through aggregation, they allow for higher quantum yields together with a simultaneous decrease of the phosphorescence lifetimes. We show that the electronic properties of the aggregated species can conveniently be investigated via an emission excitation matrix analysis (EEM). Hence we were able to obtain different emission colours from a single complex only by selective excitation of the monomer or the aggregate. We show that C^C* ligands can also be exploited to obtain bimetallic platinum complexes with approximately unitary phosphorescent quantum yields and unprecedented short decay times.

Chemistry and photophysics of cyclometalated carbene platinum complexes: from theory to efficient phosphorescent emitters for OLED applications

2019 Spring National Meeting

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