Long-lived and oxygen-responsive photoluminescence in the solid state of copper(I) complexes bearing fluorinated diphosphine and bipyridine ligands

Luminescence properties of a family of newly synthesized copper(I) complexes bearing 2,2'-bipyridine derivatives and 1,2-bis[bis(pentafluorophenyl)phosphino]ethane (dfppe), [Cu(diimine)(dfppe)]PF6, were investigated. The quantum yield and the lifetime of the emission of [Cu(6dmbpy)(dfppe)]PF6 (6dmbpy = 6,6'-dimethyl-2,2'-bipyridine) in the solid state under argon (Phi = 9%, tau = 16, 180 mu s), which is one of the longest lifetimes among all copper(I) complexes bearing diimine and diphosphine, are much larger than those under air (Phi < 0.5%, tau = 1.5, 8.0 mu s). Crystal packing, structural rearrangement in the excited state, and nature of the transitions are important for the photophysics of dfppe complexes. The voids in the crystals as well as the very long lifetimes of the excited states play a key role for oxygen responsive photoluminescence in the solid state.