A supercharged molecular motor operating by constitutional alteration and proton transfer.

Light-driven molecular motors undergo directional motions upon the input of external energy and represent archetypical molecular machines. So far, such motors have functioned via light-induced bond rotations, where directionality is dictated by a fixed source of asymmetry. During the operation cycle, no further structural changes occur, other than the rotation itself. Here we disclose a highly effective mechanism for light-driven motor rotation involving constitutional alteration and reversible proton transfer. Associated with this unusual mechanism is a particularly high energy content from the incident light that the motor retains. This feature is further exploited in a low-temperature molecular solar thermal energy storage application, where solar energy can be stored and released in a controlled fashion and tracked step by step with the naked eye. With these findings, unique possibilities emerge for the design and use of molecular motors with hitherto unknown modes of action and power.