Coordination chemistry of lanthanide ions with X-(CH2-COO-)2 (X = O, NH, S) ligands: The leading role of X as carboxylate-connecting group

Oxydiacetate, iminodiacetate, and thiodiacetate are flexible dicarboxilates which have been used as chelating agents towards d-metal ions for decades. They differ among each other only in the central connecting group X: O, NH, or S. The interaction of these ligands with lanthanide ions has also received significant attention in recent years. This review deals with various aspects of the coordination chemistry of Ln ions with these three ligands. It includes a critical analysis of the stability studies carried out in solution, shedding light on the influence of X in the thermodynamic stability of the resulting complexes. In the solid state, the discovery of new materials by combination of the diverse coordination modes offered by the two carboxylate groups (or the protonated forms of them) with the fluxional geometry of the central hinge X, is explored. Luminescent properties both in solution and in the solid state are also discussed, again with regard to the coordination abilities of these ligands. Finally, the most relevant applications are discussed, including the design of white-light emitters and other optic materials and the preparation of MOFs with one-dimensional channels that are currently assayed as catalysts in several organic processes.