Hydrogen-bonded networks of 2,2′-substituted 4,4′-biimidazoles: New ligands for the assembled metal complexes

4,4′-Biimidazole derivatives having alkyl-substituents at 2- and 2′-positions were synthesized as new component molecules of supramolecular assemblies based on hydrogen-bonding interaction. The crystal structure analyses of methyl and ethyl derivatives revealed intriguing three-dimensional structures constructed by hydrogen-bonded networks. Furthermore, the methyl derivative formed a six-membered cyclic motif of hydrogen-bonded network to build up a channel structure. The ethyl derivative gave the two polymorphous, anhydrate and dihydrate, depending on conditions of the crystallization. The anhydrate constructed three-dimensional hydrogen-bonded networks by direct N–H⋯N hydrogen-bondings. In the crystal structure of the dihydrate of ethyl derivative, three-dimensional hydrogen-bonding interaction through water molecules formed a channel structure.

Graphical abstractThe crystal structures of methyl- and ethyl-substituted 4,4′-biimidazole derivatives (Me-4,4′-Bim and Et-4,4′-Bim) were investigated. A simple modification on 4,4′-biimidazole skeleton changes the hydrogen-bonded structures to construct a variety of three-dimensional structures by hydrogen-bonded networks.Figure optionsDownload full-size imageDownload as PowerPoint slide