The binding behavior of a helical column supramolecule formed by 6-deoxy-6-(2-pyrimidinethio)-β-cyclodextrin in both solution and the solid state

The mono-modified β-cyclodextrin, 6-deoxy-6-(2-pyrimidinethio)-β-cyclodextrin, was synthesized and characterized. Its self-assembly behavior was measured in both solution and the solid state. The crystal structure shows that the pyrimidine group penetrates deeply into the hydrophobic cavity of the adjacent β-cyclodextrin from the second side, and the molecules are stacked along the twofold screw axis to form a head-to-tail helical columnar superstructure. Furthermore, the effective binding constant K and the aggregation number n were calculated to be 354 M−1 and 2.1, respectively, by means of 1H NMR spectroscopy titration. The results indicate that the intramolecular/intermolecular interactions are a critical factor in determining the self-assembly behavior.