A Dithienylethene that gates a spontaneous reaction and photolyzes with visible light and synthetic progress towards a corresponding hexatriene

1,2-Dithienylethenes (DTEs) and the related ‘hexatriene’ derivative are a robust family of P-Type photochromes whose isomers may exhibit different degrees of reactivity due to the changes in structure and electronics that accompany the re-arrangement of their bonding frameworks. One approach to changing the reactivity is to control the precise localization of electrons in the π systems of the two isomers, which has previously been demonstrated to exert binary,“on/off” control over equilibria and endothermic reactions. In this work, a DTE derivative was shown to exert binary control over a spontaneous fragmentation reaction: after forming the active isomer using UV light, the desired fragmentation occurred. Contrary to expectations, the active isomer of the DTE did not revert to its inactive isomer but instead underwent the same fragmentation by photolysis with UV or visible light. A number of synthetic routes were attempted to form a ‘hexatriene’ counterpart activated by visible light directly, but none were ultimately successful. The reported DTE is thus a cage compound activated by visible light.