Dynamic Switching between Single- and Double-Axial Rotaxanes Manipulated by Charge and Bulkiness of Axle Termini Cheng Yang, † Young Ho Ko, ‡ Narayanan Selvapalam, ‡ Yumi Origane, † Tadashi Mori, § Takehiko Wada, § Kimoon Kim,* ,‡ and Yoshihisa Inoue* ,†,§ ICORP Entropy Control Project, JST, 4-6-3 Kamishinden, Toyonaka 560-0085, Japan, Department of Chemistry, Pohang UniVersity of Science and Technology, Pohang, 790-784, Republic of Korea, and Department of Applied Chemistry, Osaka UniVersity, 2-1 Yamada-oka, Suita 565-0871, Japan inoue@chem.eng.osaka-u.ac.jp Received August 31, 2007 ABSTRACT Twin-axial [3]pseudorotaxanes, in which two multicharged axles simultaneously thread through the γ-CD cavity, were formed for the first time in solution. The twin-axial [3]pseudorotaxane was converted exclusively to a CB [6]-stoppered [4]pseudorotaxane by the addition of CB[6] but regenerated from the [4]pseudorotaxane by the addition of spermine, implementing an unprecedented switching of single/twin-axial rotaxanation. The design and construction of functional rotaxanes have received much attention in recent years. 1 Shuttling of the wheel component along the axle, controlled by external stimuli such as temperature, pH, ion, photon, and electron, 2 renders rotaxanes a promising element of molecular devices and machines. 3 Here we demonstrate that one of the axles in a twin-axial [3]pseudorotaxane can be moved in and out of the wheel by changing the electronic and steric nature of † ICORP Entropy Control Project, JST. ‡ Pohang University of Science and Technology. § Osaka University. (1) (a) Sauvage, J.-P.; Dietrich-Buchecker, C. Molecular Catenanes, Rotaxanes and Knots; Wiley-VCH: Weinheim, Germany, 1999. (b) Yoon, I.; Narita, M.; Shimizu, T.; Asakawa, M. J. Am. Chem. Soc. 2004, 126, 16740. (c) Aucagne, V.; Hanni, K. D.; Leigh, D. A.; Lusby, P. J.; Walker, D. B. J. Am. Chem. Soc. 2006, 128, 2186. (d) Swager, T. Nat. Mater. 2002, 1, 151. (e) Gaeta, C.; Vysotsky, M. O.; Bogdan, A.; Bohmer, V. J. Am. Chem. Soc. 2005, 127, 13136. (f) Badjic, J. D.; Balzani, V.; Credi, A.; Silvi, S.; Stoddart, J. F. Science 2004, 303, 1845. (g) Lee, J. W.; Ko, Y. H.; Park, S.-H.; Yamaguchi, K.; Kim, K. Angew. Chem., Int. Ed. 2001, 40, 399. (2) (a) Bissell, R. A.; Cordova, E.; Kaifer, A. E.; Stoddart, J. F. Nature 1994, 369, 133. (b) Wang, Q. C.; Qu, D. H.; Ren, J.; Chen, K.; Tian, H. Angew. Chem., Int. Ed. 2004, 43, 1661. (c) Jiang, L.; Okuno, J.; Orita, A.; Otera, J. Angew. Chem., Int. Ed. 2004, 43, 2121. (d) Murakami, H.; Kawabuchi, A.; Kotoo, K.; Kunitake, M.; Nakashima, N. J. Am. Chem. Soc. 1997, 119, 7605. (e) Kihara, N.; Hashimoto, M.; Takata, T. Org. Lett. 2004, 6, 1693. (3) (a) Balzani, V. V.; Credi, A.; Raymo, F. M.; Stoddart, J. F. Angew. Chem., Int. Ed. 2000, 39, 3348. (b) Collin, J. P.; Dietrich-Buchecker, C.; Gavina, P.; Jimenez-Molero, M. C.; Sauvage, J. P. Acc. Chem. Res. 2001, 34, 477. (c) Schalley, C. A.; Beizai, K.; Vogtle, F. Acc. Chem. Res. 2001, 34, 465. (d) Ballardini, R.; Balzani, V.; Credi, A.; Gandolfi, M. T.; Venturi, M. Acc. Chem. Res. 2001, 34, 445. (e) Harada, A. Acc. Chem. Res. 2001, 34, 456. (f) Feringa, B. L. Acc. Chem. Res. 2001, 34, 504. (g) Pease, A. R.; Jeppesen, J. O.; Stoddart, J. F.; Luo, Y.; Collier, C. P.; Heath, J. R. Acc. Chem. Res. 2001, 34, 433. ORGANIC LETTERS 2007 Vol. 9, No. 23 4789-4792 10.1021/ol702142j CCC: $37.00 © 2007 American Chemical Society Published on Web 10/20/2007