Belt-Shaped <b>[20]Collarene</b> with a Rigid Yet Adaptable Cavity for Multimodal Fullerene Complexation

Collarenes, in which alternating benzenoid and 1,4-cyclohexadiene rings are fused to form belt-shaped hydrocarbons, show exceptional promise as molecular containers in supramolecular chemistry. However, the experimental investigation of their host-guest chemistry remains largely untapped. Herein, we report multimodal complexation behaviors between <b>[20]collarene</b> and a series of fullerenes. <b>[20]Collarene</b> is capable of complexing both <b>C</b>_<b>60</b> and <b>C</b>_<b>70</b> to form inclusion complexes, as confirmed by proton nuclear magnetic resonance spectroscopy, isothermal titration calorimetry, high-resolution mass spectrometry, and single-crystal X-ray crystallography. The strong binding affinities for fullerenes (<i>K</i>_a up to 10⁵ M^-1) lead to host-guest complexes that display ultrafast charge separation and a stable charge-separated state. Moreover, <b>[20]collarene</b> possesses a shape-adaptable cavity when complexing with two fullerene derivatives, <b>PC61BM</b> and <b>DPC61Py</b>, via different complexation modes. Specifically, <b>[20]collarene</b> exhibits fully encapsulated host-guest complexation with <b>PC61BM</b>, whereas it engages in solvent-synergistic complexation with <b>DPC61Py</b>. This work systematically establishes the host-guest chemistry of <b>[20]collarene</b> with a rigid yet adaptive cavity, thereby laying a crucial foundation in the field of collarene-based supramolecular chemistry and guiding its future development toward functional materials.