A new model of light-powered chiral molecular motor with higher speed of rotation, part 2 - Dynamics of motor rotation

To clarify the mechanism and dynamics of the new model of light-powered chiral molecular motor (2) of five-membered ring type, the second motor rotation isomer, the unstable cis-olefin 2b, was isolated and its stereostructure was determined. Similarly, the fourth motor rotation isomer, the unstable trans-olefin 2d, was detected by H-1 NMR at low temperature, and its stereostructure was also determined. With the aid of this knowledge of the stereo structures of the motor rotation isomers and their spectroscopic data, the dynamics of the motor rotation 2a -> 2b 2c -> 2d -> 2a were studied by H-1 NMR and CD, revealing that the fourth rotation step 2d -> 2a was much accelerated, as expected from the design of the new motor. Continuous rotation of this motor was achieved by repetition of the operations of photoirradiation and heating. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).