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.