Acceleration of a nanomotor: Electronic control of the rotary speed of a light-driven molecular rotor

Journal of the American Chemical Society

Volumn 127, Issue 50, 2005, Pages 17612-17613

  Pijper, Dirk ^a   Van Delden, Richard A ^a   Meetsma, Auke ^a   Feringa, Ben L ^a  

^a UNIVERSITY OF GRONINGEN   (Netherlands)

Author keywords

[No Author keywords available]

Indexed keywords

NANOPARTICLE;

ARTICLE; CIRCULAR DICHROISM; ELECTRONICS; ENERGY; ISOMERIZATION; KINETICS; LIGHT; MACHINE; STEREOCHEMISTRY; THERMODYNAMICS;

EID: 29344440480     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja054499e     Document Type: Article

References (33)

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22. See Supporting Information.
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24. Assignment of the absolute configuration was based on comparison of CD data with those of related compounds (see ref 7).
25. The positive solvatochromism of the long-wavelength band of the unstable isomer indicates intramolecular charge transfer nature for the corresponding transition. Related push-pull stilbene systems show similar CT bands. See: Meier, H.; Gerald, J.; Kolshorn, H.; Baumann, W.; Bletz, M. Angew. Chem., Int. Ed. 2002, 41, 292-295.
26. Quantum yield = 0.12 (determined in the 5-10% range of photoisomerization).
27. For previous systems, the photoequilibria favor the unstable isomer. Whereas the rate of rotation is almost solely determined by the thermal steps, the "photon-efficiency" is affected, as it is governed by a combination of quantum yield and photostationary state equilibrium.
28. At low temperature, all signals of all isomers of 3 are split up, due to the fact that the rotation in the carbamate moiety is frozen out.
29. 1/2(20 °C) = 50 s for the (2′R) (P)-2 to (2′R)-(M)-2 conversion via the "forward" helix inversion.
30. Hansch, C.; Leo, A.; Unger, S. H.; Kim, K. H.; Nikaitani, D.; Lien, E. J. J. Med. Chem. 1973, 16, 1207-1216.
31. Remarkably, the thermal barrier is significantly increased by the introduction of the methoxy substituent. A reasonable explanation for this observation is that the methoxy group is in conjugation with the carbonyl, thereby lowering its electron-withdrawing capabilities.
32. 3OD, 58% of the unstable trans isomer was converted back to stable cis.
33. The thermal helix inversion of stable (2′R)-(M)-cis-3 to unstable (2′A)-(P)-cis-3 and stable (2′R)-(M)-trans-3 to unstable (2′R)-(P)-trans-3 has never been observed (by NMR or CD).