Intra-Cation versus Inter-Cation π-Contacts in Cu (PP) (NN) PF6 Complexes

A series of Cu (POP) (NNPF6 and Cu (xantphos) (NNPF6 compounds has been prepared and characterized in which POP = bis2- (diphenylphosphanyl) phenylether (IUPAC PIN oxydi (2, 1-phenylene) bis (diphenylphosphane), xantphos = 4, 5-bis (diphenylphosphanyl) -9, 9-dimethyl-9H-xanthene (IUPAC PIN (9, 9-dimethyl-9H-xanthene- 4, 5-diyl) bis (diphenylphosphane) ) and the NN ligands are 4- (4-bromophenyl) -6, 6′-dimethyl-2, 2′- bipyridine (1), 5, 5′-bis (3-methoxyphenyl) -6-methyl-2, 2′-bipyridine (2), and 6-benzyl-2, 2′-bipyridine (3). The single crystal structures of Cu (xantphos) (1) PF6·CH2Cl2, Cu (xantphos) (2) PF6·CH2Cl2 and Cu (POP) (3) PF6·0. 5H2O were determined by X-ray diffraction. Each complex contains a copper (I) ion in a distorted tetrahedral environment with chelating NN and PP ligands. In the Cu (xantphos) (1) + and Cu (xantphos) (2) + cations, there are face-to-face π-stackings of bpy and PPh2 phenyl rings (i. e. , between the ligands) ; in addition in Cu (xantphos) (2) PF6·CH2Cl2, inter-cation π-embraces lead to the formation of infinite chains as a primary packing motif. In Cu (POP) (3) PF6·0. 5H2O, centrosymmetric pairs of Cu (POP) (3) + cations engage in C–H…π (phenyl to bpy) and offset face-to-face (bpy…bpy) contacts. The electrochemical and photophysical properties of the compounds containing ligands 1 and 2 are reported. They are green or yellow emitters in the solid-state (λem in the range 535–577 nm) with values for the photoluminescence quantum yield (PLQY) in the range 19%–41%.