Chemistry of Unique Chiral Olefins
--A Light-Powered Chiral Molecular Motor with Monodirectional Rotation--

Nobuyuki HARADA*, Nagatoshi KOUMURA and Ben L. FERINGA

Institute for Chemical Reaction Science, Tohoku University; 2-1-1 Katahira, Aoba, Sendai-shi 980-8577 Japan
Department of Organic and Molecular Inorganic Chemistry, University of Groningen; Nijenborgh 4, 9747 AG Groningen, The Netherlands

One of the ultimate research goals of materials science would be the construction of molecular machines, where one molecule mechanically works as a machine by external energy sources. Recently we have first succeeded in the construction of a light-powered chiral molecular motor, which photochemically rotates only in one-direction reflecting the chirality of the motor molecule. The motor rotation is also controlled by the ``ratchet effect'' due to the irreversible isomerization. In this paper, we account for the unique chemistry of motor molecules, chiral and helical olefins of 1,1', 2,2', 3,3', 4,4'-octahydro-3,3' -dimethyl-4,4'-biphenanthrylidene (E)-(3) and (Z)-isomer (4), and also report the irreversible thermal isomerization of unstable (3R, 3'R)-(M, M)-(E)-3 to stable (3R, 3'R)-(P, P)-(E)-(|)-3, which works as the “ratchet effect” of the motor. The stereochemistry and rotation mechanism of the motor are explained.

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