Reversible photoelectronic signal conversion based on photoisomerization-controlled coordination change of azobenzene-bipyridine ligands to copper

A new "molecular photoelectronic transducer", working in a cyclic manner totally powered with light irradiation, has been constructed. The UV/blue-controlled repetitive motion of azobenzene moieties in 6,6'-bis(4' '-tolylazo)-4,4'-bis(4-tertbutylphenyl)-2,2'-bipyridine causes reciprocal CuI translocation between two coordination environments, resulting in pumping of the redox potential of CuI. Therefore, UV/blue light information can be successfully transformed into an electrode potential change and positive/negative current response, which is closely related to natural visual transduction both functionally and mechanically. This result demonstrates a new strategy for artificial molecular machine assembly, i.e. forming a path with multistep chemical reactions between input/output couples at choice.