Rotaxane and Catenane Based Devices

This project is concerned with the syntheses of novel interlocked molecular architectures using anionic species as templating motifs. The resulting threaded rotaxane and catenane molecular systems have the potential, by virtue of their unique topological cavities, to exhibit unprecedented anion recognition, sensing and molecular machine-like properties, whereby anion binding controls molecular movement of the rotaxane/catenane constituent parts.

 

Shown below is our initial pseudo-rotaxane along with the crystal structure. It can be seen that the templation of the pseudo-rotaxane occurs through binding of a chloride anion. Pi stacking interactions between the pyridyl rings and the hydroquinones and hydrogen bonding between the polyether chain and the methyl group of the pyridinium cation also contribute to the molecular assembly. This work has been extended with different macrocycles and threads. More complex structures, such as the catenane shown below, have been synthesized.

This methodology has been extended by the incorporation of a fluorophore into the macrocycle (see scheme and structure below). This allows the formation of the rotaxane to be reported by fluorescence. The larger macrocycle structure, which includes a bipyridyl ring, requires the very large calixarene stoppers to form the rotaxane. The anion may be removed from the rotaxane structure to provide a novel anion receptor that is selective for hydrogen sulfate.

Schematic depiction of the formation of a rotaxane that incorporates a fluorophore

A rotaxane incorporating a fluorophore

References

Curiel, David; Beer, Paul D..  Anion directed synthesis of a hydrogensulfate selective luminescent rotaxane.    Chemical Communications (Cambridge, United Kingdom)  (2005),   (14),  1909-1911.

Sambrook, Mark R.; Beer, Paul D.; Wisner, James A.; Paul, Rowena L.; Cowley, Andrew R.; Szemes, Fridrich; Drew, Michael G. B.  Anion-Templated Assembly of Pseudorotaxanes: Importance of Anion Template, Strength of Ion-Pair Thread Association, and Macrocycle Ring Size.    Journal of the American Chemical Society  (2005),  127 (7),  2292-2302.

Curiel, David; Beer, Paul D.; Paul, Rowena L.; Cowley, Andrew; Sambrook, Mark R.; Szemes, Fridrich. Halide anion directed assembly of luminescent pseudorotaxanes. Chemical Communications (Cambridge, United Kingdom), (2004),  (10), 1162-1163.

Sambrook, Mark R.; Beer, Paul D.; Wisner, James A.; Paul, Rowena L.; Cowley, Andrew R.  Anion-Templated Assembly of a [2]Catenane.    Journal of the American Chemical Society  (2004),  126 (47),  15364-15365.

Wisner, James A.; Beer, Paul D.; Drew, Michael G. B.; Sambrook, Mark R. Anion-Templated Rotaxane Formation. Journal of the American Chemical Society (2002), 124 (42), 12469-12476.

Wisner, James; Beer, Paul D.; Drew Michael G. B.. A Demonstration of Anion Templation and Selectivity in Pseudorotaxane Formation. Angew. Chem., Int. Ed. (2001), 40 (19), 3606-3609.