Remote Modification of Bidentate Phosphane Ligands Controlling the Photonic Properties in Their Complexes: Enhanced Performance of [Cu(RN‐xantphos)(N ^ N)][PF 6 ] in Light‐Emitting Electrochemical Cells

A series of copper(I) complexes of the type [Cu(HN‐xantphos)(N ^ N)][PF 6 ] and [Cu(BnN‐xantphos)(N ^ N)][PF 6 ], in which N ^ N = bpy, Mebpy, and Me 2 bpy, HN‐xantphos = 4,6‐bis(diphenylphosphanyl)‐10H‐phenoxazine and BnN‐xantphos = 10‐benzyl‐4,6‐bis(diphenylphosphanyl)‐10H‐phenoxazine is described. The single crystal structures of [Cu(HN‐xantphos)(Mebpy)][PF 6 ] and [Cu(BnN‐xantphos)(Me 2 bpy)][PF 6 ] confirm the presence of N ^ N and P ^ P chelating ligands with the copper(I) atoms in distorted coordination environments. Solution electrochemical and photophysical properties of the BnN‐xantphos‐containing compounds (for which the highest‐occupied molecular orbital is located on the phenoxazine moiety) are reported. The first oxidation of [Cu(BnN‐xantphos)(N ^ N)][PF 6 ] occurs on the BnN‐xantphos ligand. Time‐dependent density functional theory (TD‐DFT) calculations have been used to analyze the solution absorption spectra of the [Cu(BnN‐xantphos)(N ^ N)][PF 6 ] compounds. In the solid‐state, the compounds show photoluminescence in the range 518–555 nm for [Cu(HN‐xantphos)(N ^ N)][PF 6 ] and 520–575 nm for [Cu(BnN‐xantphos)(N ^ N)][PF 6 ] with a blue‐shift on going from bpy to Mebpy to Me 2 bpy. [Cu(BnN‐xantphos)(Me 2 bpy)][PF 6 ] exhibits a solid‐state photoluminescence quantum yield of 55% with an excited state lifetime of 17.4 µs. Bright light‐emitting electrochemical cells are obtained using this complex, and it is shown that the electroluminescence quantum yield can be enhanced by using less conducting hole injection layers.