Autonomous flipping of azobenzene assemblies under light irradiation (II)

To create autonomous microrobots which move in the presence of a constant energy source, their mechanical motion must have a capacity for self-control. This is realized when a structural change occurs with conversion of energy facilitated by cofactors, with a self-regulation component to prevent reaching a static state. Here, we present a single crystal structure analysis of azobenene derivatives which reveals a mille-feuille-like layered structure of sparse and dense layers of six independent azobenzene moieties. In this anisotropic structure, a specific azobenzene molecule acts as a reaction center for a light-to-mechanical function process. The other molecules in the crystal act as modulators. Moreover, depending on the photoisomerisation process activated by a polarized light source, different cyclic motions are observed. We clarify the mechanism by which the self-organized mechanical behavior of these azobenzene molecules is achieved at the molecular level. Thus, the present results demonstrate that autonomously driven molecular materials can exhibit information-responsive and self-sustainable motion by incorporating stimulus-responsive sensors.