Discrete cage form of water hexamer in the hydrophilic channels assembled by heterocyclic azopyrrole

•A heterocyclic azopyrrole compound was synthesized and characterized.•Two pseudo-polymorphisms were characterized by X-ray crystallography.•A discrete cage form hexameric water cluster was accommodated in the 1-D hydrophilic channels of the host.•The cage hexamer was held together by eight O–H…O hydrogen bonds as calculation predicted.•The dehydration/rehydration processes of the host are irreversible.

A heterocyclic azopyrrole compound, meso-diethyl-5,5′-bis(thiazolyldiazo)-dipyrromethane (1), has been synthesized and its two crystals have been characterized by X-ray crystallography. The molecules of compound 1 self-assembled into channel structure in the crystal of 1·3H2O, whereas interlocked type dimer in the crystal of 1·CHCl3. In the 1-D hydrophilic channels of 1·3H2O, six water molecules were held together by eight O–H…O hydrogen bonds and formed discrete cage hexameric clusters. The dehydration/rehydration processes of the compound 1 are also studied.

Graphical abstractThe discrete cage form hexameric water clusters, held together by eight O–H…O hydrogen bonds and with C2 symmetry, were characterized inside the 1-D hydrophilic channels generated by the self-assemble of heterocyclic azopyrrole compound.Figure optionsDownload full-size imageDownload as PowerPoint slide