Phosphorescent Cuprous Complexes with N,O Ligands – Synthesis, Photoluminescence, and Electroluminescence

Abstract

AbstractSix heteroleptic cuprous complexes, [L1Cu(PPh3)2](BF4) (1a), [L1Cu(DPEphos)](BF4) (1b), [L2Cu(PPh3)2](BF4) (2a), [L2Cu(DPEphos)](BF4) (2b), [L3Cu(PPh3)2](BF4) (3a), and [L3Cu(DPEphos)](BF4) (3b) {L1 = diphenyl(2‐pyridyl)phosphane oxide, L2 = diphenyl(8‐quinolyl)phosphane oxide, L3 = diphenyl(2‐pyridylmethyl)phosphane oxide, DPEphos = bis[2‐(diphenylphosphanyl)phenyl] ether}, were prepared and fully characterized. The electronic absorption spectra and quantum chemical calculations indicate that the lowest excited states of these complexes can be assigned to the metal‐to‐ligand charge transfer (MLCT) transition. In poly(methyl methacrylate) (PMMA) films, these complexes exhibit blue‐green to orange emissions with long lifetimes ranging from 7.5 to 28.6 μs. With wide energy‐band gaps of 3.50 and 3.28 eV, complexes 3a and 3b emit efficiently in 20 wt.‐% PMMA films with photoluminescence quantum efficiencies of 0.69 and 0.72, and emission maxima at 477 nm and 495 nm, respectively. Electroluminescent devices were fabricated with these N,O‐based CuI complexes as emitters. The best device performance, with a peak current efficiency of 4.9 cd/A, was obtained for 3b.