Thermodynamic study of the complexation between Nd3+ and functionalized diacetamide ligands in solution

Abstract

A series of amine functionalized ligands, including 2,2′-(benzylazanediyl)bis(N,N′-dimethylacetamide) (BnABDMA), 2,2′-azanediylbis(N,N′-dimethylacetamide) (ABDMA), and 2,2′-(methylazanediyl)bis(N,N′-dimethylacetamide) (MABDMA), are synthesized for the thermodynamic study of their complexation with Nd³⁺ ions. Their complexation in solution is investigated using potentiometry, spectrophotometry, calorimetry, and electrospray ionization mass spectrometry. The results suggest that these ligands act as tridentate ligands. Furthermore, direct comparison between ABDMA and an analogous ether-functionalized ligand, 2,2′-oxybis(N,N′-dimethylacetamide) (TMDGA), showed that the amine functionalized ligand forms thermodynamically stronger complexes with Nd³⁺ ions than the ether-functionalized ligand. In addition, the amine functionalized ligand can allow the fine-tuning of the binding strength with metal ions via substitution on the central amine N atom with different functional groups, which is not possible for ether functionalized ligands such as TMDGA.