A series of [Cu(P^P)(N^N)][PF6] compounds are reported in which N^N is 2,9-dibromo-1,10-phenanthroline (2,9-Br2phen), 3,8-dibromo-1,10-phenanthroline (3,8-Br2phen) or 4,7-dibromo-1,10-phenanthroline (4,7-Br2phen) and P^P is bis(2-(diphenylphosphano)phenyl)ether (POP) or 4,5-bis(diphenylphosphano)-9,9-dimethylxanthene (xantphos). The compounds were characterized by solution multinuclear NMR spectroscopy, mass spectrometry and a single-crystal X-ray analysis. Each compound underwent a partially reversible or irreversible copper-centred oxidation, the highest potential being for 2,9-Br2phen-containing compounds. In solution, the compounds are weak yellow or orange emitters, whereas powdered samples exhibit yellow emissions with photoluminescence quantum yields of up to 45% for [Cu(xantphos)(2,9-Br2phen)][PF6] with an excited state lifetime τ1/2 = 9.9 μs. Values of λemmax for [Cu(POP)(2,9-Br2phen)][PF6] and [Cu(xantphos)(2,9-Br2phen)][PF6] are blue-shifted with respect to compounds with the 3,8-and 4,7-isomers, both in solution and in the solid state.

[Cu(P^P)(N^S)][PF6] with N^S = 2-(thiophen-2-yl)pyridines show close cation⋯anion association in the solid-state; complex cation association with Cl− occurs in solution. The compounds are blue-emitters in solution with a red-shift of the emission on going to the solid.

We report the synthesis and characterization of [Cu(P^P)(N^S)][PF6] complexes with P^P = bis(2-(diphenylphosphino)phenyl) ether (POP) or 4,5-bis(diphenylphosphino)-9,9- dimethylxanthene (xantphos) and N^S = 2-(iso-propylthio)pyridine (iPrSpy) or 2-(tert-butylthio)pyridine (tBuSpy). The single crystal structures of [Cu(POP)(iPrSPy)][PF6] and [Cu(POP)(tBuSPy)][PF6] have been determined and confirm a distorted tetrahedral copper(I) centre and chelating P^P and N^S ligands in each complex. Variable temperature (VT) 1H and 31P{1H} NMR spectroscopy reveals dynamic behavior with motion of the POP backbone in [Cu(POP)(iPrSPy)][PF6] and [Cu(POP)(tBuSPy)][PF6] frozen out at 238 K. VT NMR spectroscopic data including EXSY peaks in the ROESY spectrum of [Cu(xantphos)(tBuSPy)][PF6] at 198 K reveal that two conformers exist in an approximate ratio of 5:1. Replacing bpy by the N^S ligands shifts the Cu+/Cu2+ oxidation to a higher potential. The copper(I) compounds are weak emitters in the solid state with PLQY values of <2%. These values are similar to those for [Cu(POP)(bpy)][PF6] and [Cu(xantphos)(bpy)][PF6] in the solid state.

Heteroleptic copper(I) complexes have attracted much attention during the last few decades as potential earth-abundant materials for solar energy conversion. While overall good photophysical properties have been obtained, the copper(I)...