Metal-induced gelation in dipyridyl ureas

A series of pyridyl-appended bis(urea) ligands form supramolecular gels in the presence of metal ions (metallogels), particularly copper(II) and silver(I). The gels have been characterised by rheometry and SEM, and the effect of the metal ions on gel strength and morphology examined. The metal-induced gelation is linked to the competition between urea-urea and urea-pyridyl hydrogen bonding interactions. Crystals grown from these gels reveal a wealth of structural information about these systems that can be related to gel structure using powder X-ray diffraction data of their xerogels.