Reversible 1:1 Inclusion Complexes of C₆₀ Derivatives in α- and β-Cyclodextrins: Implications for Molecular Recognition-Based Sensing and Supramolecular Assembly

We developed a novel pathway to highly efficiently synthesize the [60]fullerene (C60)–cyclodextrin (CD) complex, which is termed solvent-induced reversible recognition. Three kinds of typical complexes, namely, C60-2GUA+-α-CD, C60-2GUA+-β-CD, and C60-4OH-β-CD, were synthesized. The chemical structure of all complexes was fully confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance (NMR), UV–vis spectroscopy, and a solubility test. Furthermore, the crystalline status and thermal degradation were recorded by X-ray diffraction and thermogravimetric analysis, respectively. Both the NMR and ESI-MS results clearly confirmed the 1:1 complex of C60 derivatives with CD. The pathway overcame the preparation limitation of traditional complexes and was extended to prepare an α-CD-containing complex. To the best of our knowledge, this is the first time that an α-CD-related complex is reported. The geometric relation between C60 and CD for all three kinds of complexes was analyzed. We can achieve high efficiency to obtain solid-state complex products, which lays the foundation for the widely practical application of the complex and provides enough experimental basis for the advanced application of C60 and CD in supramolecular assembly. Notably, the solvent-induced reversibility and ionic instability of the complex provides a new possibility for molecular recognition-based sensing.