Diaryl‐1,2,3‐Triazolylidene Platinum(II) Complexes

Control of the excited state geometry by rational ligand design leads to a new class of phosphorescent emitters with extraordinary photophysical properties. Extension of the π‐system in the triplet state leading to a significant bathochromic shift of the emission was avoided by introduction of additional steric demand. We report the synthesis, characterization and photophysical properties of novel platinum(II) complexes bearing C^C* cyclometalated mesoionic carbene (MIC) with different β‐diketonate ligands. The MIC ligand precursors were prepared from 1‐phenyl‐1,2,3‐triazole using arylation protocols, introducing phenyl or mesityl functionalities. A solid state structure confirming the NMR assignments is presented. The emission properties were investigated in detail at room temperature and 77 K and are supported by DFT calculations and cyclic voltammetry. All complexes, with emission maxima between 502–534 nm, emit with quantum efficiencies ranging from 70–84 % in PMMA films.