Photoisomerization of an Azobenzene on the Bi(111) Surface

Modifying surface-bound molecular switches by adding side groups is an established concept for restoration of functionality which a molecule possesses in solution and which is often quenched upon adsorption. Instead of decoupling the photochromic unit from the substrate, we follow a different approach, namely treating the complete molecule–substrate system. We use photoelectron spectroscopies to determine the energetic positions of the frontier orbitals of di- m -cyanoazobenzene on Bi(111) and to elucidate the isomerization mechanism which is stimulated by a substrate-mediated electron transfer process.