Structural consequences of competing noncovalent forces: the out–out conformation of the doubly protonated [2.2.2]cryptand

Abstract

The reaction of [2.2.2]cryptand 1 with 2,6-dihydroxybenzoic acid (dhbH) in toluene affords the complex [1-2H]- [(2,6-dhb) ₂ ]; its crystal structure exhibits the first solid state evidence of the out–out form of the doubly protonated macrobicycle and illustrates the role of C–H···O hydrogen bonds in providing additional stability to the cavity of the ligand.