Photon-Only Molecular Motor with Reverse Temperature-Dependent Efficiency

Light-driven
molecular motors are archetypal molecular machines
and enable fast and efficient unidirectional motions under photoirradiation.
Their common working mechanism contains thermal ratcheting steps leading
to slowed-down and even halted directional movement at lower temperatures.
In this work, an alternative type of molecular motor is presented,
which operates without thermal ratcheting in the ground state. Instead,
three consecutive and different photoreactions lead to a directional
stepwise rotation of one molecular fragment with respect to the other.
This motion is increased in speed and directionality at lower temperatures
and at the same time allows a considerably larger fraction of the
supplied photon energy to be used for performing work.