Identifying the Missing Protonated Complex Species and Revisiting the Overestimated Stability Constants of Two Known Complexes of Uranyl(VI) with Dipicolinic Acid

Qi Yang; Tingting Liu; Jiwen Tan; Liyang Zhu; Qian Liu; Suliang Yang; Guoxin Tian

doi:10.1021/acs.inorgchem.2c00808

Identifying the Missing Protonated Complex Species and Revisiting the Overestimated Stability Constants of Two Known Complexes of Uranyl(VI) with Dipicolinic Acid

Inorg Chem. 2022 Jun 27;61(25):9381-9384. doi: 10.1021/acs.inorgchem.2c00808. Epub 2022 May 31.

Authors

Qi Yang¹, Tingting Liu², Jiwen Tan¹, Liyang Zhu¹, Qian Liu¹, Suliang Yang¹, Guoxin Tian^{1

3}

Affiliations

¹ Department of Radiochemistry, China Institute of Atomic Energy, Beijing 102413, China.
² Nuclear Chemical Engineering Department, Harbin Engineering University, Harbin 150001, China.
³ Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China.

PMID: 35639092
DOI: 10.1021/acs.inorgchem.2c00808

Abstract

The complexation of uranium(VI) [U(VI)] with dipicolinic acid was revisited with respect to the missing protonated complex species existing in acidic solutions. For the first time, the presence of the protonated complex, UO₂HL⁺, in aqueous solutions was confirmed and the stability constant was determined by fluorescence spectroscopy. Considering the protonated species, which was missing in previous investigations, the overestimated stability constants of the two known complexes, UO₂L and UO₂L₂^2-, were carefully reevaluated with potentiometry using N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid as a competing ligand. While a single crystal of the solid compound UO₂(HL)₂(H₂O)₄ with two monoprotonated HL^- bonding UO₂²⁺ in a tridentate mode was successfully grown from aqueous solutions, the corresponding complex species UO₂(HL)₂(aq) could not yet be clearly identified and characterized.