Copper and Gold Cyclic (Alkyl)(amino)carbene Complexes with Sub-Microsecond Photoemissions: Structure and Substituent Effects on Redox and Luminescent Properties.
Copper and gold halide and pseudo-halide complexes stabilised by methyl-, ethyl- and adamantyl-substituted cyclic (alkyl)(amino)carbene (CAAC) ligands are mostly linear monomers in the solid state, without aurophilic Au⋅⋅⋅Au interactions. (Et2L)CuCl shows the highest photoluminescence quantum yield (PLQY) in the series, 70 %. The photoemissions ofMe2L andEt2L copper halide complexes show S1→S0fluorescence on the ns time scale, in agreement with theory, as well as a long-lived emission. Monomeric (Me2L)CuNCS is a white emitter, whereas dimeric [(Et2L)Cu(μ-NCS)]2shows intense yellow emission with a photoluminescence (PL) quantum yield of 49 %. The reaction of (AdL)MCl (M=Cu or Au) with phenols ArOH (Ar=Ph, 2,6-F2C6H3, 2,6-Me2C6H3, 3,5-tBu2C6H3, 2-tBu-5-MeC6H3, 2-pyridyl), thiophenol, or aromatic amines H2NAr'' (Ar'=Ph, 3,5-(CF3)2C6H3, C6F5, 2-py) afforded the corresponding phenolato, thiophenolato and amido complexes. Although the emission wavelengths are only marginally affected by the ring substitution pattern, the PL intensities respond sensitively to the presence of substituents in the ortho or meta positions. In gold aryloxides, PL is controlled by steric factors, with strong luminescence in compounds with Au-O-C-C torsion angles <50°. Calculations confirm the dependence of oscillator strength on the torsion angle, as well as the inter-ligand charge transfer nature of the emission. The HOMO/LUMO energy levels were estimated based on first reduction and oxidation potentials.
School of Chemistry, University of East Anglia, Earlham Road, Norwich, NR4 7TJ, UK.
Alexander S
http://orcid.org/0000-0003-2617-6402
AS
Romanov
School of Chemistry, University of East Anglia, Earlham Road, Norwich, NR4 7TJ, UK.
Ciaran R
CR
Becker
School of Chemistry, University of East Anglia, Earlham Road, Norwich, NR4 7TJ, UK.
Charlotte E
CE
James
Department of Physics, Cavendish Laboratory, Cambridge University, Cambridge, CB3 0HF, UK.
Dawei
D
Di
Department of Physics, Cavendish Laboratory, Cambridge University, Cambridge, CB3 0HF, UK.
Dan
http://orcid.org/0000-0003-4246-2118
D
Credgington
Department of Chemistry, University of Eastern Finland, Joensuu Campus, 80101, Joensuu, Finland.
Mikko
M
Linnolahti
School of Chemistry, University of East Anglia, Earlham Road, Norwich, NR4 7TJ, UK.
Manfred
http://orcid.org/0000-0001-7736-5428
M
Bochmann
copper complex; electrochemistry; fluorescence; photoluminescence; structure determination