Dinuclear Cu(I) Halides with Terphenyl Phosphines: Synthesis, Photophysical Studies, and Catalytic Applications in...

Several dinuclear terphenyl phosphine copper(I) halide complexes of composition [CuX(PR₂Ar')]₂ (X = Cl, Br, I; R = hydrocarbyl, Ar' = 2,6-diarylterphenyl radical), 1-5, have been isolated from the reaction of CuX with 1 equiv of the phosphine ligand. Most of them have been characterized by X-ray diffraction studies in the solid state, thus allowing comparative discussions of different structural parameters, namely, Cu···Cu and Cu···Aryl separations, conformations adopted by coordinated phosphines, and planarity of the Cu₂X₂ cores. Centrosymmetric complexes [CuI(PMe₂Ar^Xyl2)]₂, 1c, and [CuI(PEt₂Ar^Mes2)]₂, 3c, despite their similar structures, show very distinct photoluminescence (PL) in powder form at room temperature. The photophysical behavior of these compounds in liquid solution, solid-solid Zeonex solution and powder samples at room temperature and 77 K have been investigated and supported by DFT calculation. Identification of vibronic coupling modes, done by group theory calculations and the technique of projection operators, shows that the manifestation of these modes is conditioned by crystal packing. Complexes [CuI(PMe₂Ar^Xyl2)]₂, 1c, and [CuI(PEt₂Ar^Mes2)]₂, 3c, display remarkable activity in copper-catalyzed azide-alkyne cycloaddition reactions involving preformed and in situ-made azides. Reactions are performed in H₂O, under aerobic conditions, with low catalyst loadings and tolerate the use of iodoalkynes as substrates.