Synthesis, Structure, Spectroscopic Properties, and Photochemistry of Homo- and Heteropolynuclear Copper(I) Complexes Bridged by the 2,5-Bis(2-pyridyl)pyrazine Ligand

Cu(I)−Cu(I) and Cu(I)−Ru(II) dinuclear complexes bridged by the 2,5-bppz (2,5-bis(2-pyridyl)pyrazine) ligand have
been prepared and characterized including the X-ray crystallographic study of the dinuclear [{CuI(PPh3)2}2(μ-2,5-bppz)](PF6)2·2CH3Cl complex:  a = 13.974(2), b = 13.993(2), c = 13.537(2) Å; α = 101.98(1), β = 103.22(1),
γ = 113.90(1)°; triclinic, P1̄, Z = 1. The trinuclear [{(bpy)2RuII(μ-2,5-bppz)}2CuI](PF6)5 complex was also prepared,
and the structure of the complex in solution was studied by spectrometric titration. The dinuclear Cu(I) complex
and [(bpy)2RuII(μ-2,5-bppz)CuI(PPh3)2](PF6)5 show photoluminescence in the solid state, which should arise from
MLCT states. Photochemical oxidation of the trinuclear RuII2CuI complex occurs in the presence of oxygen to give
a RuII2CuII complex. The MLCT states and the redox reaction in the excited state are discussed.