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Koumura N, Geertsema EM, van Gelder MB, et al. Second generation light-driven molecular motors. Unidirectional rotation controlled by a single stereogenic center with near-perfect photoequilibria and acceleration of the speed of rotation by structural modification. J Am Chem Soc. 2002;124(18):5037-51doi: 10.1021/ja012499i.
Koumura, N., Geertsema, E. M., van Gelder, M. B., Meetsma, A., & Feringa, B. L. (2002). Second generation light-driven molecular motors. Unidirectional rotation controlled by a single stereogenic center with near-perfect photoequilibria and acceleration of the speed of rotation by structural modification. Journal of the American Chemical Society, 124(18), 5037-51. https://doi.org/10.1021/ja012499i
Koumura, Nagatoshi, et al. "Second generation light-driven molecular motors. Unidirectional rotation controlled by a single stereogenic center with near-perfect photoequilibria and acceleration of the speed of rotation by structural modification." Journal of the American Chemical Society vol. 124,18 (2002): 5037-51. doi: https://doi.org/10.1021/ja012499i
Koumura N, Geertsema EM, van Gelder MB, Meetsma A, Feringa BL. Second generation light-driven molecular motors. Unidirectional rotation controlled by a single stereogenic center with near-perfect photoequilibria and acceleration of the speed of rotation by structural modification. J Am Chem Soc. 2002 May 08;124(18):5037-51. doi: 10.1021/ja012499i. PMID: 11982368.
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J Am Chem Soc. 2002 May 08;124(18):5037-51. doi: 10.1021/ja012499i.

Second generation light-driven molecular motors. Unidirectional rotation controlled by a single stereogenic center with near-perfect photoequilibria and acceleration of the speed of rotation by structural modification.

Journal of the American Chemical Society

Nagatoshi Koumura, Edzard M Geertsema, Marc B van Gelder, Auke Meetsma, Ben L Feringa

Affiliations

  1. Department of Organic and Molecular Inorganic Chemistry, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.

PMID: 11982368 DOI: 10.1021/ja012499i

Abstract

Nine new molecular motors, consisting of a 2,3-dihydro-2-methylnaphtho[2,1-b]thiopyran or 2,3-dihydro-3-methylphenanthrene upper part and a (thio)xanthene, 10,10-dimethylanthracene, or dibenzocycloheptene lower part, connected by a central double bond, were synthesized. A single stereogenic center, bearing a methyl substituent, is present in each of the motors. MOPAC93-AM1 calculations, NMR studies, and X-ray analysis revealed that these compounds have stable isomers with pseudoaxial orientation of the methyl substituent and less-stable isomers with pseudoequatorial orientation of the methyl substituent. The photochemical and thermal isomerization processes of the motors were studied by NMR and CD spectroscopy. The new molecular motors all show two cis-trans isomerizations upon irradiation, each followed by a thermal helix inversion, resulting in a 360 degrees rotation around the central double bond of the upper part with respect to the lower part. The direction of rotation is controlled by a single stereogenic center created by the methyl substituent at the upper part. The speed of rotation, governed by the two thermal steps, was adjusted to a great extent by structural modifications, with half-lives for the thermal isomerization steps ranging from t(1/2)(theta) 233-0.67 h. The photochemical conversions of two new motors proceeded with near-perfect photoequilibria of 1:99.

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