C^C cyclometalated platinum(ii) N-heterocyclic carbene complexes with a sterically demanding β-diketonato ligand - synthesis, characterization and photophysical propertiesElectronic supplementary information (ESI) available: Structure determination, NMR spectra as well as xyz-coordinates and calculated geometries of the DFT-calculations. CCDC 1026181 and 1026238. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4dt03613a

Neutral cyclometalated platinum( ii ) N-heterocyclic carbene complexes [Pt(C^C*)(O^O)] with C^C* ligands based on 1-phenyl-1,2,4-triazol-5-ylidene and 4-phenyl-1,2,4-triazol-5-ylidene, as well as acetylacetonato (O^O = acac) and 1,3-bis(2,4,6-trimethylphenyl)propan-1,3-dionato (O^O = mesacac) ancillary ligands were synthesized and characterized. All complexes are emissive at room temperature in a poly(methyl methacrylate) (PMMA) matrix with emission maxima in the blue region of the spectrum. High quantum efficiencies and short decay times were observed for all complexes with mesacac ancillary ligands. The sterically demanding mesityl groups of the mesacac ligand effectively prevent molecular stacking. The emission behavior of these emitters is in general independent of the position of the nitrogen in the backbone of the N-heterocyclic carbene (NHC) unit and a variety of substituents in 4-position of the phenyl unit, meta to the cyclometalating bond. New platinum( ii ) triazolylidene complexes were prepared to investigate the influence of the 1,3-bis(2,4,6-trimethyl)-phenylpropan-1,3-dionato ligand on the photoluminescence properties.