Triptycene‐Derived Calix[6]arenes: Synthesis, Structures, and Their Complexation with Fullerenes C 60 and C 70

Two pairs of novel triptycene‐derived calix[6]arenes 4 a , b and 5 a , b have been efficiently synthesized through both one‐pot and two‐step fragment‐coupling strategies starting from 2,7‐bis(hydroxymethyl)‐1,8‐dimethoxytriptycene 1 . Subsequent demethylation of 4 a , b and 5 a , b with BBr 3 in dry dichloromethane gave the macrocyclic compounds 6 a , b and 7 a , b . Treatment of either 4 a or 6 a with AlCl 3 resulted in the same debutylated product 8 , while 9 was similarly obtained from either 5 a or 7 a . Structural studies revealed that all of the macrocycles have well‐defined structures with fixed conformations both in solution and in the solid state owing to the introduction of the triptycene moiety with a rigid three‐dimensional (3D) structure, making them very different from their classical calix[6]arene counterparts. As a consequence, it was found that all of these the triptycene‐derived calix[6]arenes could encapsulate small neutral molecules in their cavities in the solid state. Moreover, it was also found that the macrocycles 4 b and 5 b showed highly efficient complexation abilities toward fullerenes C 60 and C 70 , forming 1:1 complexes with association constants ranging from (5.22±0.20)×10 4 to (8.68±0.30)×10 4   M −1 .