Is a Crystal Engineering Approach Useful in Designing Metallogels? A Case Study

A crystal engineering based design strategy for metallogels has been demonstrated in a series of mixed ligand based Cu<sup>II</sup>/Co<sup>II</sup> coordination polymers derived from two bis-pyridyl-bis-amide ligands namely <i>N</i>,<i>N</i>′-bis-(3-pyridyl)isophthalamide (<b>L1</b>) and <i>N</i>,<i>N</i>′-bis-(3-pyridyl)terephthalamide (<b>L2</b>) and various dicarboxylates. These mixed ligand coordination polymers are shown to form gels as well as X-ray quality crystals under different conditions. The crystal structures of the gel fibers in the xerogels have been determined by using powder and single-crystal X-ray diffraction data. The results support the proof of the concept based on which the metallogels are designed.