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A Cyclic Alkyl(amino)carbene as Two‐Atom π‐Chromophore Leading to the First Phosphorescent Linear Cu I Complexes
Author(s) -
Gernert Markus,
Müller Ulrich,
Haehnel Martin,
Pflaum Jens,
Steffen Andreas
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201605412
Subject(s) - phosphorescence , carbene , chromophore , oled , excited state , chemistry , ligand (biochemistry) , alkyl , photochemistry , fluorescence , triplet state , acceptor , crystallography , molecule , physics , organic chemistry , catalysis , atomic physics , biochemistry , receptor , layer (electronics) , quantum mechanics , condensed matter physics
The members of a series of linear and trigonal copper(I) complexes bearing a cyclic alkyl(amino)carbene (CAAC) ligand show surprising photophysical properties compared to those of the corresponding N‐heterocyclic carbene (NHC) complexes. Whereas the linear NHC complexes [CuX(NHC)] are almost non‐emissive, [CuX(CAAC)] (X=Cl, Br, I) and [Cu(CAAC) 2 ]PF 6 show very bright emissions from their triplet excited states in the blue to green region, displaying quantum yields of up to 65 % in the solid state, even though the π‐acceptor comprises only the carbene C and N atoms with no other π conjugation. [Cu(CAAC) 2 ]PF 6 is the fastest Cu I ‐based triplet state emitter characterized to date, not displaying thermally activated delayed fluorescence (TADF), with an intrinsic lifetime of only 10.6 μs, that is, k r =9.4×10 4 s −1 , competitive with many Pt II ‐ and Ir III ‐based emitters. In order to test the stability of such linear copper CAAC complexes in devices, some of our compounds have been applied in proof‐of‐principle organic light‐emitting diodes (OLEDs). This case study thus demonstrates for the first time the use of CAACs as suitable π‐chromophores for Cu I ‐based phosphorescent emitters, and their implementation in OLEDs underlines the general applicability of this class of ligands in materials science.