Interactions between Methyl Branched-Chain Asymmetric Diglycolamides and Ln3+ Extraction and Spectroscopic and Theoretical Investigations
来源：ACS Publications
Diglycolamides show good selectivity for trivalent lanthanides and actinides and have good application prospects in the treatment of high level liquid waste (HLLW). In this study, two asymmetric diglycolamides with methyl groups at the α-position and β-position of the branched chains were synthesized through a microwave-assisted silane-mediated method: N,N′-dimethyl-N,N′-di(1-methylheptyl) diglycolamide (DMDMHDGA, L1) and N,N′-dimethyl-N,N′-di(2-methylheptyl) diglycolamide (DMD2MHDGA, L2). The extraction performance of these two ligands for Ln3+ was tested in the HNO3 system. The coordination properties of the ligands with Ln3+ were studied by spectroscopy, and the coordination properties of the complexes were analyzed by density functional theory (DFT). Both ligands have better extraction performance for heavy Ln3+ over light Ln3+, while the extraction ability of L2 to light Ln3+ is relatively stronger than that of L1. The ligands form 2:1 complexes with Ln3+, which has a noncentrosymmetric octahedral structure. The ligands primarily form complexes with Ln3+ through electrostatic interactions with covalent characteristics. Differences in the positions of the branched chains lead to steric hindrance and electron-donating effects, thereby influencing their extraction and coordination behaviors toward Ln3+.