A supramolecular 2:1 guanidinium-carboxylate-based building block for generation of extensive water channels and tetrameric water clusters in an organic material

Abstract

A bicyclic guanidine derivative is used here to form a hydrogen-bonded 2:1 complex with bipyridine dicarboxylic acid (1). The linear, rigid and charge assisted supramolecular building block has numerous additional hydrogen bond acceptors on the anti lone pairs of carboxylate O atoms and hence could be expected to display high propensity for inclusion of water molecules in the solid state [1]. We here show that, depending on the initial crystallization, it is in fact possible to utilize this property not only to build layered structures with clusters of water tetramers [2], [3], but also structures with extensive, unidirectional water channels [4] with a solvent accessible volume close to 20 % of the unit cell volume.