Research about constructing a [2] r otaxane type molecular ratchet

1. Research about constructing a [2] rotaxane type molecular ratchet M1 Ryo Takabayashi, Tobelaboratory Division of Frontier Materials Science, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University

2. Contents Introduction 1. What is Molecular Ratchet Examples of Molecular Ratchets 1. First Example (Rotary Motion) 2. Second Example (Rotary Motion) 3. Third Example (Linear Motion) 3. Fourth Example My Work

3. Definition Ratchet : A ratchet is a mechanical device that allows linear or rotary motion in only one direction while preventing motion in the opposite direction. Forward motion What is Rotaxane Backward motion Molecular Ratchet : A molecular ratchet is a ratchet on a molecular level. (However, it’s not always necessary that a molecular ratchet allows liner or rotary motion in only one direction. )

4. First Example of Molecular Ratchet (Rotary Motion) The authors expected that this molecule would work as a molecular ratchet, which means the triptycene unit would rotate in only one direction. It was because the helicene group had a helical conformation (as right figure shows), so rotation in one direction looked easier. This direction looks easier to rotate. Rotation axis Kelly, T. R.; Sestelo, J. P.; Tellitu, I. J. Org. Chem. 1998, 63 (11), 3655-3665.

5. First Example of Molecular Ratchets (Rotary Motion) A disproportionate share of the polarization that had moved was transferred equally to the remaining two resonances. The triptycene unit didn’t rotate in one direction but rotated in both direction. This result was because rotation in only one direction without an input of energy would require the violation of the Second Law of Thermodynamics. Kelly, T. R.; Sestelo, J. P.; Tellitu, I. J. Org. Chem. 1998, 63 (11), 3655-3665.

6. Second Example of Molecular Ratchets (Rotary Motion) Kuwahara, S.; Fujita, T.; Harada, N. Eur. J. Org. Chem. 2005, 4544-4556.

7. Second Example of Molecular Ratchets (Rotary Motion) 2b 2d 2a 2a 2c Rotation in one direction occurred. For one rotation, three different steps were done. This speed of one rotation was relatively high, 90 seconds. This rotation could be done continuously. Kuwahara, S.; Fujita, T.; Harada, N. Eur. J. Org. Chem. 2005, 4544-4556.

8. What is Rotaxane

9. Third Example of Molecular Ratchet (Linear Motion) Serreli, V.; Lee, C.-F.; Kay, E. R.; Leigh, D. A. Nature 2007, 445 (7127), 523-527

10. Third Example of Molecular Ratchet (Linear Motion) Initial State dba : mba = 65 : 35 ↓ Final State dba : mba = 45 : 55 (65-45) / 65 = 31% of ring, which was originally in stable state, were pumped to unstable state by this oepration. Serreli, V.; Lee, C.-F.; Kay, E. R.; Leigh, D. A. Nature 2007, 445 (7127), 523-527

11. Fourth Example of Molecular Ratchet This system can be useful to make a molecular ratchet because this reaction was controlled kinetically, Oshikiri, T.; Takashima, Y.; Yamaguchi, H.; Harada, A. Eur. J. Org. Chem. 2007, 7091-7098.

12. My Work Creation of dynamic potential change system toward a molecular ratchet Dynamic potential change system Molecular ratchet can be described with energy diagrams. Activation energy is dependent on direction. Molecular design To make that system, I designed this [2] rotaxane. That system will be achieved by combination of chemical reaction.