[Cu(POP)(N^S)][PF 6 ] and [Cu(xantphos)(N^S)][PF 6 ] compounds with 2-(thiophen-2-yl)pyridines.

A series of [Cu(POP)(N^S)][PF 6 ] and [Cu(xantphos)(N^S)][PF 6 ] compounds (POP = bis(2-(diphenylphosphino)phenyl)ether, xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) in which the N^S ligand is a 2-(thiophen-2-yl)pyridine (1), 2-(thiophen-2-yl)-6-methylpyridine (2), 2-(5-methylthiophen-2-yl)pyridine (3) or 2-(5-methylthiophen-2-yl)-6-methylpyridine (4) have been prepared and characterized in solution and the solid state. Single crystal structures of [Cu(POP)(1)][PF 6 ], [Cu(xantphos)(1)][PF 6 ], [Cu(xantphos)(2)][PF 6 ], [Cu(POP)(3)][PF 6 ]·CH 2 Cl 2 , and [Cu(xantphos)(4)][PF 6 ] confirm chelating N^S and P^P ligands, and distorted tetrahedral copper(i) centres. There is close cation⋯anion association, particularly in [Cu(xantphos)(1)][PF 6 ]. Although the compounds are stable over days in CH 2 Cl 2 solution, they are susceptible to the effects of competing ligands such as chloride ion and MeCN. Analysis of the NMR spectroscopic data of a solution of [Cu(POP)(3)][PF 6 ] with added Cl - , gives a K d value of 0.14 ± 0.03 mM, indicative of ion-pairing. [Cu(POP)(N^S)][PF 6 ] and [Cu(xantphos)(N^S)][PF 6 ] exhibit quasi-reversible or irreversible Cu + /Cu 2+ oxidations. They are blue emitters in solution, and the presence of the 5-methyl group in the thiophene ring in 3 and 4 leads to a red-shift in the emission. The highest photoluminescence quantum yields are for [Cu(POP)(2)][PF 6 ] (30.8%) and [Cu(POP)(4)][PF 6 ] (33.2%), both of which have a 6-methyl-substituted pyridine ring in the N^S ligand. Excited-state lifetimes are <5 ns. On going from solution to powder samples, red-shifts of 133 to 163 nm are observed leading to yellow emitters. The brightest emitter, [Cu(xantphos)(1)][PF 6 ], was tested in a LEC device but showed poor electroluminescence and poor charge transporting characteristics.