Thermodynamic, Structural, and Computational Investigation on the Complexation between UO22+ and Amine-Functionalized Diacetamide Ligands in Aqueous Solution

Phuong V Dau; Zhicheng Zhang; Yang Gao; Bernard F Parker; Phuong D Dau; John K Gibson; John Arnold; Marilena Tolazzi; Andrea Melchior; Linfeng Rao

doi:10.1021/acs.inorgchem.7b02971

Thermodynamic, Structural, and Computational Investigation on the Complexation between UO₂²⁺ and Amine-Functionalized Diacetamide Ligands in Aqueous Solution

Inorg Chem. 2018 Feb 19;57(4):2122-2131. doi: 10.1021/acs.inorgchem.7b02971. Epub 2018 Feb 2.

Authors

Phuong V Dau¹, Zhicheng Zhang¹, Yang Gao^{1

2}, Bernard F Parker^{1

3}, Phuong D Dau¹, John K Gibson¹, John Arnold^{1

3}, Marilena Tolazzi⁴, Andrea Melchior⁴, Linfeng Rao¹

Affiliations

¹ Chemical Science Division, Lawrence Berkeley National Laboratory , One Cyclotron Road, Berkeley, California 94720, United States.
² College of Nuclear Science and Technology, Harbin Engineering University , Harbin 150001, China.
³ Department of Chemistry, University of California-Berkeley , Berkeley, California 94720, United States.
⁴ Laboratori di Chimica, Università di Udine , via delle Scienze 99, 33100 Udine, Italy.

PMID: 29394057
DOI: 10.1021/acs.inorgchem.7b02971

Abstract

The stability constants (log β), enthalpies of complexation (ΔH), and entropies of complexation (ΔS) for the complexes of uranium(VI) with a series of amine-functionalized diaetamide ligands, 2,2'-benzylazanediylbis(N,N'-dimethylacetamide) (BnABDMA), 2,2'-azanediylbis(N,N'-dimethylacetamide) (ABDMA), and 2,2'-methylazanediylbis(N,N'-dimethylacetamide) (MABDMA), in aqueous solution were determined by potentiometry and calorimetry. Electronspray ionization mass spectrometry was used to verify the presence of uranium(VI) complexes in solution. The thermodynamic data indicate that the binding strengths of the three ligands with UO₂²⁺ follow the order BnABDMA < ABDMA < MABDMA, parallel to the order of the protonation constants as well as the order of the stability of the Nd³⁺ complexes, suggesting that the complexation of UO₂²⁺ with the ligands consist predominantly of electrostatic interactions. Denisty functional theory calculations were conducted to reveal the structures, electronic charge distribution, and energetics of the uranium(VI) complexes, providing insight into the thermodynamic trends of the complexation. Extended X-ray absorption fine structure spectroscopy was used to identify the structures of the uranium(VI) complexes in aqueous solution.