Reversible 1:1 Inclusion Complexes of C${}_{60}$ Derivatives in $\alpha$- and $\beta$-Cyclodextrins Implications for Molecular Recognition-Based Sensing and Supramolecular Assembly

Abstract

We developed a novel pathway to highly efficiently synthesize the [60]Fullerene (C${}_{60}$)-Cyclodextrin (CD) complex, which is termed as solvent-induced reversible recognition. Three kinds of typical complexes, namely, C${}_{60}$-2GUA${}^{+}$-$\alpha$-CD, C${}_{60}$-2GUA${}^{+}$-$\beta$-CD and C${}_{60}$-4OH-$\beta$-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 the solubility test. Furthermore, 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 C${}_{60}$ derivatives with CD. The pathway overcame the preparation limitation of traditional complex, and was extended to the prepare $\alpha$-CD containing complex. To the best of our knowledge, it is the first time to report $\alpha$-CD related complex. The geometric relation between C${}_{60}$ and CD for all the three kinds of complexes were analyzed. We can achieve high efficiency to obtain solid-state complex products, which lays the foundation for the widely practical application of complex and provides enough experimental basis for the advanced application of C${}_{60}$ and CD in supramolecular assembly. Notably, the solvent-induced reversibility and ionic instability of the complex provides a new possibility for the molecular recognition-based sensing.