Photon-Only Molecular Motor with Reverse Temperature-Dependent Efficiency

Abstract

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.

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

“…Instead, three consecutive and different photoreactions lead to a directional stepwise rotation of one molecular fragment with respect to the other. Notably, the speed of rotation increased upon lowering the temperature, which was unusual behavior for light‐ or chemically driven molecular motors reported previously…”

Photoefficient 2nd generation molecular motors responsive to visible light

“…[29][30][31] A related photon-only molecular motor was disclosed in 2018. 32 However, in view of future applications it is evident that there is a major need for distinct rotary motors which are able to perform full 360 rotations using low-energy light. We further explored the use of push-pull systems to achieve enhanced red-shiing of the absorption maximum by installing substituents in the stator and rotor halves, in conjugation with the central double-bond serving as the axle of the motor (Fig.…”

Planarization‐Induced Activation Wavelength Red‐Shift and Thermal Half‐Life Acceleration in Hydrazone Photoswitches

“…The development of novel strategies that can help in modulating these properties in known systems, will contribute to the integration of photoswitches into diverse applications, in addition to opening the way for new functions and possibilities. [10] Our interest in hydrazone-based materials [11] recently resulted in the development of a new family of bistable hydrazone photoswitches (τ 1/2 of up to 5,300 years). [12] Structure-property analyses of the hydrazones led us to the observation that they adopt a uniform molecular geometry (based on their crystal structures) in which the rotor ring (red) is twisted out of the plane of the hydrazone core (Scheme 1).…”