Rate Acceleration of Light-Driven Rotary Molecular Motors

• Published in: Advanced functional materials 2007-03, Vol.17 (5), p.718-729
• Main Authors: Pollard, M. M., Klok, M., Pijper, D., Feringa, B. L.
• Format: Article
• Language: English
• Subjects: Chirality; Molecular machines; Molecular motors; Nanotechnology; Photochemistry
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200601025

One of the key challenges in taking light‐driven unidirectional rotary motors from discovery to application is to increase the rate of rotation. Herein, we review our ongoing efforts to address this issue by meticulous improvement to the molecular design. To accelerate the rotary cycle, we have focused primarily on the rate‐limiting thermal isomerization step. This has been a fascinating and formidable objective, given that the first system we reported had a half‐life of over one week at room temperature! Our research has ultimately led to the construction of a unidirectional rotary molecular motor with a cycle 108 times faster than the original; that is, it can in principle function at 44 rotations per second. Control over the rotary speed of, and, in particular, the means to accelerate, light‐driven unidirectional rotary motor systems is the key to their future application. Here, the structural features that influence the rate of rotation of molecular motors that are based on overcrowded alkenes are reviewed. This intriguing and instructive line of research ultimately leads to a motor that is capable of 44 rotations per second—5 × 108 times faster than the original design (see figure).