[Cu(POP)(N^S)][PF6] and [Cu(xantphos)(N^S)][PF6] compounds with 2-(thiophen-2-yl)pyridines

摘要

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.