The coordination chemistry of N-heterocyclic carboxylic acid: A comparison of the coordination polymers constructed by 4,5-imidazoledicarboxylic acid and 1H-1,2,3-triazole-4,5-dicarboxylic acid

In recent decades, coordination polymers (CPs) constructed by metal ions/clusters as nodes and organic linkers through coordination interactions, have expanded rapidly in both academic and industrial realms. Understanding the coordination chemistry of the organic linkers can greatly help the rational design and synthesis of targeted CPs because a minor change in the organic linker can greatly induce a structural variation of the final coordination structures. 4,5-imidazoledicarboxylic acid (H3imda) and 1H-1,2,3-triazole-4,5-dicarboxylic acid (H3tda) are two analogue N-heterocyclic carboxylic ligands except for the difference of 2-site N or C, which have the advantages from both imidazole/triazole and carboxylic groups and have been widely used as multifunctional linkers to construct numerous CPs with various architectures and interesting properties such as gas storage and separation, luminescence, catalysis, and magnetism in the past two decades. When the 2-site N donor of H3tda is not coordinated with metal center, they can present similar architectures; however, when the 2-site N donor is deprotonated and binds to metal centers, they generally exhibit distinct differences in the structures and accessorial properties. In this context, these two ligands provide a valuable model for understanding the key role of donor position to the influence of structures of CPs. This review provides an overview on the coordination chemistry of H3imda and H3tda, which are organized as follows: (i) the coordination modes of H3imda and H3tda influenced by the various acidity-dependent systems; (ii) the coordination chemistry of homometallic CPs (HOCPs) with H3imda and H3tda; (iii) the coordination chemistry of heterometallic CPs (HECPs) with H3imda and H3tda. Representative examples are shown in each section that highlights the relationships between the two ligands and targeted structures. Besides, the readers will also be directed to the relevant articles and reviews on N-heterocyclic derivatives, which will guide further investigations into a particular aspect of coordination chemistry with N-heterocyclic derivatives.