Shifting Merocyanine-Imine Exchange with Visible Light

We show the dynamic covalent exchange between merocyanines and imines and demonstrate how the equilibrium composition can be shifted with visible light. For this purpose, we exploited a negative photochromic T-type merocyanine that engages in a covalent exchange with an aniline nucleophile to provide an imine. Since the merocyanine can quantitatively be converted into its spiropyran isomer that is nonreactive in the exchange, the system can be shifted and trapped in the static spiropyran state. In the dark, however, the system thermally reverts back to the dynamic merocyanine that re-engages in the exchange. The process of shifting/trapping and re-equilibration can be repeated multiple times. The system provides opportunities for designing materials that allow for spatial and temporal control over their dynamic properties.