Trapping an Ester Hydrate Intermediate in a -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 [CH3OSO2(OH)(2)](-), serving as the template for the self-assembly of a pi-stacked boat-shaped macrocycle (CH3OSO2(OH)(2))(0.67)(CH3OSO3)(1.33)@{[ClLCoII](6)}center dot Cl-4 center dot 13CH(3)OH center dot 9H(2)O (1) (L = tris(2-benzimidazolylmethyl) amine), can be trapped in the host by multiple NH center dot center dot center dot O hydrogen bonds. In the solution of CoCl2, L, and H2SO4 in MeOH, HSO4- reacts with MeOH, producing [CH3OSO3](-) via the ester hydrate intermediate of [CH3OSO3(OH)(2)](-). Both the product and the intermediate serve as the template directing the self-assembly of the p-stacked macrocycle, in which the short-lived ester hydrate is firmly trapped and stabilized, as revealed by single-crystal analysis.