Structural Characterization and Photochemical Properties of Mono- and Bimetallic Cu-Mabiq Complexes.

We present a series of monometallic ([Cu(Mabiq)OTf] (1) and [Cu(Mabiq)] (2)) and bimetallic copper-Mabiq complexes ([Cu2(Mabiq)(PPh3)2(OTf)2] (3) and [Cu2(Mabiq)(PPh3)2]PF6 (4)). The latter compounds contain an additional CuI center that binds in a tetrahedral fashion to the external bipyrimidine nitrogens of the macrocyclic ligand. Compounds 3 and 4 represent the first examples of bimetallic transition metal Mabiq complexes, stable both in solution and in the solid state. The structural and electronic properties of compounds 1-4 were analyzed by means of X-ray crystallography, cyclic voltammetry, and spectroscopic methods. One-electron reduced 2 and 4 consist of a CuII ion coordinated by a Mabiq ligand radical, [CuII(Mabiq•)]. Thus, both bimetallic compounds are mixed-valent with respect to the copper oxidation states. Complexes 2 and 4 can be generated photochemically, upon irradiation of 1 or 3 with visible light in the presence of a sacrificial electron donor.