Crystallographic, Theoretical, and Spectroscopic Studies of the Luminescent d¹⁰−d¹⁰ Binuclear Copper Acetate Complex Cu₂(dppm)₂(O₂CCH₃)⁺

The new d10−d10 dimer Cu2(dppm)2(O2CCH3)+ (as a BF4- salt) has been prepared and characterized by X-ray crystallography and by 1H and 31P NMR, vibrational, and electronic spectroscopy. The compound is luminescent at 77 K but not at room temperature. MO calculations and geometry optimizations have been performed using the EHMO and DFT models, respectively. In the solid state the Cu2 separation is 2.788(1) Å where ν(Cu2) = 87.7 cm-1, indicating the presence of weak Cu···Cu interactions. The MO calculations predict that the lowest energy excited states are MLCT from Cu to phenylphosphine/acetate. These predictions have been confirmed by electronic spectroscopy via a comparison between Cu2(dppm)2(O2CCH3)+ and Cu2(dppm)2(O2CC6H5)+. In solutions, both NMR (1H and 31P) and luminescence spectroscopies (time-resolved spectra and τe analysis) demonstrate the presence of two metal species in solutions: Cu2(dppm)2(O2CCH3)+ and Cu2(dppm)(O2CCH3)+. The dimer crystallizes in the triclinic space group P1̄ with a = 11.572(2) Å, b = 12.552(2) Å, c = 19.543(3) Å, α = 85.274(12)°, β = 82.108(11)°, γ = 68.950(12)°, and Z = 2.