Phosphorescent Platinum(II) Complexes with C not equal to Cyclometalated NHC Dibenzofuranyl Ligands: Impact of Different Binding Modes on the Decay Time of the Excited State

Two C not equal to * cyclometalated platinum(II) N-heterocyclic carbene (NHC) complexes with the general formula [(C not equal to *)Pt(O omicron )] (C not equal to *=1-dibenzofuranyl-3-methylbenzimidazolylidene; O omicron =dimesitoylmethane) have been synthesized and extensively characterized, including solid-state structure determination, super(195)PtNMR spectroscopy, and 2D NMR (COSY, HSQC, HMBC, NOESY) spectroscopy to elucidate the impact of their structural differences. The two regioisomers differ in the way the dibenzofuranyl (DBF) moiety of the NHC ligand is bound to the metal center, which induces significant changes in their physicochemical properties, especially on the decay time of the excited state. Quantum yields of over 80% and blue emission colors were measured. The dibenzofuranyl ligand fragment has shown interesting and promising properties in the past. Different ways of attaching the cyclometalating unit to the metal center led to regioisomeric platinum(II) complexes, which were found to exhibit significantly changed physicochemical properties. Thus, it might be worthwhile to investigate the binding modes of other functional ligands to yield improved materials.