Open AccessUranium(VI) Complexes with a Calix[4]arene‐Based 8‐Hydroxyquinoline Ligand: Thermodynamic and Structural Characterization Based on Calorimetry, Spectroscopy, and Liquid–Liquid Extraction
Author(s) -
Bauer Anne,
Jäschke Astrid,
Schöne Sebastian,
Barthen Robert,
März Juliane,
Schmeide Katja,
Patzschke Michael,
Kersting Berthold,
Fahmy Karim,
Oertel Jana,
Brendler Vinzenz,
Stumpf Thorsten
Publication year - 2018
Publication title -
chemistryopen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 29
ISSN - 2191-1363
DOI - 10.1002/open.201800085
Subject(s) - chemistry , enthalpy , endothermic process , calorimetry , ligand (biochemistry) , solvent , chemical stability , crystallography , organic chemistry , thermodynamics , adsorption , biochemistry , physics , receptor
The environmental aspects of ore processing and waste treatment call for an optimization of applied technologies. There, understanding of the structure and complexation mechanism on a molecular scale is indispensable. Here, the complexation of U VI with a calix[4]arene‐based 8‐hydroxyquinoline ligand was investigated by applying a wide range of complementary methods. In solution, the formation of two complex species was proven with stability constants of log ß 1:1 =5.94±0.02 and log ß 2:1 =6.33±0.01, respectively. The formation of the 1:1 complex was found to be enthalpy driven [Δ H 1:1 =(−71.5±10.0) kJ mol −1 ; T Δ S 1:1 =(−37.57±10.0) kJ mol −1 ], whereas the second complexation step was found to be endothermic and entropy driven [Δ H 2:1 =(32.8±4.0) kJ mol −1 ; T Δ S 2:1 =(68.97±4.0) kJ mol −1 ]. Moreover, the molecular structure of [UO 2 (H 6 L)(NO 3 )](NO 3 ) ( 1 ) was determined by single‐crystal X‐ray diffraction. Concluding, radiotoxic U VI was separated from a Eu III ‐containing solution by the calix[4]arene‐based ligand in solvent extractions.