Slipping synthesis of cucurbit[7]uril-based [2]rotaxane in organic environment

A dumbbell molecule with one naphthalimide and one isophthalic acid stoppers was synthesized and could fold into the cavity of cucurbit[7]uril (CB[7]) in formic acid to form a 1:1 complex. Once the solution of the complex was heated, the CB[7] ring would slip over the isophthalic acid unit, producing a stable [2]rotaxane. The energy barrier (△H‡) of this slippage was estimated as 109 kJ mol−1.