C∧C Cyclometalated Platinum(II) Complexes with Dibenzofuranyl-1,2,4-triazol-5-ylidene Ligands: Synthesis, Characterization, and Photoluminescent Properties

Two series of new platinum­(II) NHC complexes with C∧C* cyclometalating 1-(dibenzo­[b,d]­furan-4-yl)-4-methyl-1H-1,2,4-triazole and 1-(dibenzo­[b,d]­furan-2-yl)-4-methyl-1H-1,2,4-triazole ligands and several β-diketonato auxiliary ligands (acetylacetonato, dibenzoylmethanato, and dimesitoylmethanato) were synthesized, characterized (NMR spectroscopy, elemental analysis, and X-ray crystallography for two complexes) and investigated in terms of their photoluminescence properties. All complexes are strongly emissive at room temperature in a 2 wt % complex doped poly­(methyl methacrylate) film at room temperature. Using dibenzoylmethanato as auxiliary ligand leads to a broad emssion band with a maximum in the green region of the spectrum, whereas the complexes with acetylacetonato and dimesitoylmethanato ligands reveal structured blue emissions with wavelengths that strongly depend on the arrangement of the dibenzo­[b,d]­furan (DBF) unit.