Belt-Shaped [20]Collarene 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 [20]collarene and a series of fullerenes. [20]Collarene is capable of complexing both C₆₀ and C₇₀ 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 (K_a up to 10⁵ M^-1) lead to host-guest complexes that display ultrafast charge separation and a stable charge-separated state. Moreover, [20]collarene possesses a shape-adaptable cavity when complexing with two fullerene derivatives, PC61BM and DPC61Py, via different complexation modes. Specifically, [20]collarene exhibits fully encapsulated host-guest complexation with PC61BM, whereas it engages in solvent-synergistic complexation with DPC61Py. This work systematically establishes the host-guest chemistry of [20]collarene 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.