Ring-shaped rhenium(I) multinuclear complexes: improved synthesis and photoinduced multielectron accumulation.

We successfully developed selective synthesis of strongly emissive ring-shaped Re(I) multinuclear complexes (RnP(x)(n+) in Chart 1) with much higher yields compared with the previously reported method. This improved method could also be employed to prepare a novel ring-shaped multinuclear complex composed of structurally different Re(I) units. Each Re unit in RnP(x)(n+) could electrochemically accept one electron, and the multielectron reduced states of RnP(x)(n+) were stable. In the presence of triethanolamine, the ring-shaped tetranuclear and hexanuclear complexes can be photochemically reduced and accumulate 2.9-3.6 and 4.4 electrons in one molecule, respectively.