10.1021/ol2023888 r 2011 American Chemical Society Published on Web 11/08/2011 ORGANIC LETTERS 2011 Vol. 13, No. 23 6148–6151 Supramolecular Shuttle Based on Inclusion Complex between Cucurbit[6]uril and Bispyridinium Ethylene Viktor Kolman, † Muhammad S. A. Khan, † Martin Babinsk  y, ‡ Radek Marek, †,‡ and Vladimir Sindelar* ,†,§ Department of Chemistry, National Center for Biomolecular Research and Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic, and Research Centre for Toxic Compounds in the Environment, Masaryk University, Kamenice 3, 625 00 Brno, Czech Republic sindelar@chemi.muni.cz Received September 4, 2011 ABSTRACT Cucurbit[6]uril (CB6) and bispyridinium ethylene form a stable inclusion complex. A rotaxane derived from this complex was prepared in which a CB6 wheel shuttles along an axle in an NMR time-resolved regime. Cucurbiturils (CBn) are macrocyclic compounds which are utilized as supramolecular hosts for positively charged and neutral guests. 1 1,1 0 -Dimethyl-4,4 0 -bipyridi- nium (methylviologen, 1) and its extended analog, trans-N, N 0 -dimethyldipyridyliumylethylene (bispyridinium ethyl- ene, 2) (for structures, see Figure 1), represent common guests in the supramolecular chemistry of cucurbituril. These hostguest complexes are used for the construction of various advanced supramolecular systems. Despite several advantages of bispyridinium ethylene derivatives compared to the viologen derivatives, interaction of the former group of guests with CBn is significantly less explored. For instance, both 1 and 2 form charge transfer complexes with hydro- xynaphthalenes, which are stabilized inside the CB8 cavity. The ternary complexes based on 2 are, however, more stable in comparison with those in which 1 is used. 2 Similarly to 1 , two molecules of 2 (or its diamine analog) are able to be simulta- neously included in the CB8 cavity, but in the latter case, selective photodimerization takes place. 3 CB7 forms 1:1 complexes with viologen as well as with bispyridinium ethylene derivatives (or its diamine analogs), although only in the latter case the irradiation of the complexes is followed by the transformation of the trans to cis isomer, which is † Department of Chemistry, Masaryk University. ‡ National Center for Biomolecular Research. § Research Centre for Toxic Compounds in the Environment. (1) (a) Lee, J. W.; Samal, S.; Selvapalam, N.; Kim, H.-J.; Kim, K. Acc. Chem. Res. 2003, 36, 621. (b) Lagona, J.; Mukhopadhyay, P.; Chakrabarti, S.; Isaacs, L. Angew. Chem., Int. Ed. 2005, 44, 4844. (c) Kim, K.; Kim, H.-J. In Encyclopedia of Supramolecular Chemistry; Steed, A., Ed.; Marcel Dekker Inc.: New York, 2004; p 390. (d) Huang, W.-H.; Liu, S.; Isaacs, L. Modern Supramolecular Chemistry: Strategies for Macrocycle Synthesis; Diederich, F., Stang, P., Tykwinski, R. R., Eds.; Wiley-VCH: Weinheim, 2008; p 113. (2) (a) Kim, H.-J.; Heo, J.; Jeon, W. S.; Lee, E.; Kim, J.; Sakamoto, S.; Yamaguchi, K.; Kim, K. Angew. Chem., Int. Ed. 2001, 40, 1526. (b) Lee, J. W.; Kim, K.; Choi, S. W.; Ko, Y. H.; Sakamoto, S.; Yamaguchi, K.; Kim, K. Chem. Commun. 2002, 2692. (c) Kim, K.; Kim, D.; Lee, J. W.; Ko, Y. H.; Kim, K. Chem. Commun. 2004, 848. (e) Ko, Y. H.; Kim, E.; Hwang, I.; Kim, K. Chem. Commun. 2007, 1305. (3) (a) Pattabiraman, M.; Kaanumalle, L. S.; Natarajan, A.; Ramamurthy, V. Langmuir 2006, 22, 7605. (b) Jon, S. Y.; Ko, Y. H.; Park, S. H.; Kim, H. J.; Kim, K. Chem. Commun. 2001, 1938. (c) Pattabiraman, M.; Natarajan, A.; Kaliappan, R.; Mague, J. T.; Ramamurthy, V. Chem. Commun. 2005, 4542.