Binding of Heterocycles by Cyclohexanohemicucurbiturils and Solid-Phase Extraction of Sulfur-Containing Heterocycles from Water

Here we report a study on cyclohexanohemicucurbit[8]uril (cycHC[8]) binding of sulfur-, oxygen- and nitrogen-containing heterocycles in both solid state and solution, which is investigated by single crystal X-ray diffraction, NMR spectroscopy, isothermal titration calorimetry, and thermogravimetry. Potential guests include environmental pollutants, hazardous compounds, and bioactive substances. We found that cycHC[8] encapsulates five- and six-membered sulfur- and oxygen-containing unsubstituted heterocycles and can be used as a selective sorption material for the extraction of sulfur-heterocycles from water. Both cycHC[6] and cycHC[8] can remove a substituted heterocycle, α-lipoic acid, from an aqueous solution via the formation of an external complex. The results show that cycHC[n] is a promising reusable sorbent material with the potential to be employed in molecular recognition and highly specific solid-phase extraction of sulfur-heterocycles.