Adaptive Cyclooctatetrathiophene-Tetrazine Macrocycles: Efficient Synthesis, Structures, and Fullerene Recognition

A novel class of cyclooctatetrathiophene-tetrazine macrocycles was synthesized efficiently from COTh derivatives and 3,6-dichlorotetrazine, with structures confirmed by single-crystal X-ray analysis. Macrocycles 1 and 2 with large cavities could be efficient for encapsulating C60 and C70, forming a 1:1 complex with association constants exceeding 103 M-1. These host-guest behaviors demonstrate that COTh-based macrocycles serve as adaptive macrocyclic hosts, generating shape complementarity cavities and optimal size to enable effective π-π interactions with the fullerenes.