Through-Space Transmission of Unidirectional Rotary Motion in a Molecular Photogear

The construction of molecular photogears that can achieve through-space transmission of the unidirectional double-bond rotary motion of light-driven molecular motors onto a single-bond axis is a formidable challenge in the field of artificial molecular machines. Here, we present a new design of such photogears that is based on the possibility to use stereogenic substituents to control both the relative stabilities of the two helical forms of the photogear and the double-bond photoisomerization that connects them. The potential of the design is verified by quantum-chemical modeling through which photogearing is found to be a favorable process compared to free-standing single-bond rotation (“slippage”). Overall, our study unveils a surprisingly simple approach to realizing unidirectional photogearing.