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Reversing the direction in a light-driven rotary molecular motor.

Research paper by Nopporn N Ruangsupapichat, Michael M MM Pollard, Syuzanna R SR Harutyunyan, Ben L BL Feringa

Published on: 17 Dec '10Published in: Nature Chemistry

Abstract

Biological rotary motors can alter their mechanical function by changing the direction of rotary motion. Achieving a similar reversal of direction of rotation in artificial molecular motors presents a fundamental stereochemical challenge: how to change from clockwise to anticlockwise motion without compromising the autonomous unidirectional rotary behaviour of the system. A new molecular motor with multilevel control of rotary motion is reported here, in which the direction of light-powered rotation can be reversed by base-catalysed epimerization. The key steps are deprotonation and reprotonation of the photochemically generated less-stable isomers during the 360° unidirectional rotary cycle, with complete inversion of the configuration at the stereogenic centre. The ability to change directionality is an essential step towards mechanical molecular systems with adaptive functional behaviour.