Temperature-induced large amplitude conformational change in the complex of oxatub[4]arene revealed via rotaxane synthesis

Elevated temperature usually plays a destructive role in supramolecular complexes. At higher temperature, folded proteins tend to unfold and supramolecular assemblies tend to disassemble. In contrast, histidine kinases are able to perform a different function at higher temperature. This results from temperature-induced large amplitude conformational changes. However, similar phenomena have rarely been reported for synthetic receptors. Herein, we report that the conformationally adaptive oxatub[4]arene is able to show a conformational response to temperature change in the presence of an appropriate guest. By employing rotaxane synthesis, the host's conformation in the complex at different temperatures can be fixed. The resulting rotaxanes with different host conformations have been carefully characterized by using 2D NMR spectroscopy, mass spectrometry, and X-ray single crystallography.