The trans-cis photoisomerization behavior of azobenzene-bipyridine ligand (dmpAB) was synchronized with coordination of the bipyridine moiety to copper. The coordination reaction can be reversibly controlled with reversible redox reaction of copper, to afford [Cu(dmpAB)(2)](+) in Cu-I state and free dmpAB in Cu-II state. UV irradiations to Cu-I and Cu-II samples form trans-rich and cis-rich compositions, respectively. The results enable us to control the trans-cis isomerization reversibly through Cu-II/Cu-I redox and a single UV light.