Electrochemical Characterization of Spiropyran Structures

Spiropyran (SP) is a type of photochromic molecules widely studied because of their interesting physical and chemical properties. Irradiation of spiropyrans with near UV-light induces heterolytic cleavage of the spiro bond, resulting in the possibility of their application in electro-optical molecular devices and electronic data storage. Although some reports conclude that the opening process also occurs upon electrochemical oxidation of the indolic nitrogen, a complete description of both oxidation and reduction processes, is yet unavailable. In this work, cyclic voltammetry was employed for characterizing nitrospiropyran structures. After oxidation of SP, a reduction signal at a potential value less negative than the original closed compound appeared when successive voltammetric cycles were performed. Based on the results obtained, possible mechanistic pathways are discussed.