Trapping an Ester Hydrate Intermediate in a π-Stacked Macrocycle with Multiple Hydrogen Bonds

Ester hydrates, as the intermediates of the esterification between acid and alcohol, are very short-lived and challenging to be trapped. Therefore, the crystal structures of ester hydrates have rarely been characterized. Herein, we present that the mono-deprotonated ester hydrates [CH(3)OSO(2)(OH)(2)](−), serving as the template for the self-assembly of a π-stacked boat-shaped macrocycle (CH(3)OSO(2)(OH)(2))(0.67)(CH(3)OSO(3))(1.33)@{[ClLCo(II)](6)}·Cl(4)·13CH(3)OH·9H(2)O (1) (L = tris(2-benzimidazolylmethyl) amine), can be trapped in the host by multiple NH···O hydrogen bonds. In the solution of CoCl(2), L, and H(2)SO(4) in MeOH, HSO(4)(−) reacts with MeOH, producing [CH(3)OSO(3)](−) via the ester hydrate intermediate of [CH(3)OSO(3)(OH)(2)](−). Both the product and the intermediate serve as the template directing the self-assembly of the π-stacked macrocycle, in which the short-lived ester hydrate is firmly trapped and stabilized, as revealed by single-crystal analysis.