Synthesis and properties of molecular switches based on the opening and closing of oxazine rings

We designed and synthesized a family of molecular switches each pairing an oxazine ring to a chromophoric fragment. Under the influence of either chemical or optical stimulations, the oxazine ring opens to bring the chromophoric appendage in conjugation with either a 3H-indolium cation or a phenolate anion. These structural transformations alter the electronic structure of the chromophore and, as a result, its electrochemical and spectroscopic signatures. Specifically, we demonstrated that the absorption of triphenylamine and thiophene fragments, the fluorescence of a coumarin appendage and the oxidation potential of a ferrocene center can all be switched with acid, base or ultraviolet inputs. Thus, these operating principles and structural designs for switching properties at the molecular level with the aid of external stimulations might eventually lead to a general strategy for the realization of chemo- and photo-responsive materials.