Emergent Behavior of a Photoswitchable Solute in a Biphasic Solvent System.

Due to thermal E/Z isomerization, hydrazones in solution typically exist in thermodynamic equilibria between their isomers. Irradiation of such solutions leads to photostationary states that may differ from the equilibrium distribution. Operating such switchable hydrazones in a biphasic system of two immiscible solvents introduces three new degrees of freedom: the E/Z equilibrium in the second solvent and two equilibria for distribution of each of the isomers between the solvents. Irradiation of such a system can be performed in three different ways - the first solvent only, the second solvent only, and both solvents at once - all yielding distinct outcomes. Depending on the choice of materials and the mode of irradiation, such setup may lead to different emergent behaviors that are not immediately intuitive, including net cyclic transport or the accumulation of one photoswitched product in one of the phases, beyond what is reachable by irradiating a simple solution of the same photoswitch.