Heteroleptic platinum(II) NHC complexes with a C^C* cyclometalated ligand – synthesis, structure and photophysics

摘要: Platinum(II) complexes [(NHC)Pt(L)] with various β-diketonate based auxiliary ligands (L: 3-meacac = 3-methylacetylacetonato, dpm dipivaloylmethanato, dbm dibenzoylmethanato, mesacac dimesitoylmethanato, duratron bis(2,3,5,6-tetramethylbenzoyl)methanato) and a C^C* cyclometalated N-heterocyclic carbene ligand (NHC: dpbic 1,3-diphenylbenzo[d]imidazol-2-ylidene, dpnac 1,3-diphenylnaphtho[2,3-d]imidazol-2-ylidene or bnbic 1-phenyl-3-benzylbenzo[d]imidazol-2-ylidene) were found to show different aggregation photophysical properties depending on the ligand. Eight prepared from silver(I)–NHC intermediate by transmetalation, cyclometalation subsequent treatment potassium-tert-butanolate β-diketone. They fully characterized standard techniques including 195Pt NMR. Five additionally 2D NMR spectroscopy (COSY, HSQC, HMBC NOESY). Solid-state structures of five could be obtained tendency square-planar compounds form pairs Pt–Pt distances bulkiness substituents at The result measurements in amorphous PMMA films reveals quantum yields up 85% an emission maximum blue region comparatively short decay lifetimes (3.6 μs). Density functional theory (DFT/TD-DFT) calculations performed elucidate process revealed predominant 3ILCT/3MLCT character. Organic light-emitting devices (OLEDs) comprising one achieved 12.6% EQE, 11.9 lm W−1 luminous efficacy 25.2 cd A−1 current efficiency 300 m−2. influence additional hole-transporter emissive layer was investigated improve device lifetime factor seven.