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Coordination of Tetravalent Actinides (An=Th IV , U IV , Np IV , Pu IV ) with DOTA: From Dimers to Hexamers
Author(s) -
Tamain Christelle,
Dumas Thomas,
Hennig Christoph,
Guilbaud Philippe
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201700493
Subject(s) - chemistry , aqueous solution , actinide , protonation , dota , crystallography , octahedron , extended x ray absorption fine structure , dimer , thorium , crystal structure , absorption spectroscopy , inorganic chemistry , nuclear chemistry , chelation , uranium , ion , materials science , physics , organic chemistry , quantum mechanics , metallurgy
Three tetravalent actinide (An IV ) hexanuclear clusters with the octahedral core [An 6 (OH) 4 O 4 ] 12+ (An IV =U IV , Np IV , Pu IV ) were structurally characterized in the solid state and in aqueous solution by using single‐crystal X‐ray diffraction, X‐ray absorption, IR, Raman, and UV/Vis spectroscopy. The observed structure, [An 6 (OH) 4 O 4 (H 2 O) 8 (HDOTA) 4 ] ⋅ HCl/HNO 3 ⋅ n H 2 O (An=U( I ), Np( II ), Pu( III )), consists of a An IV hexanuclear pseudo‐octahedral cluster stabilized by DOTA (1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid) ligands. The six actinide atoms are connected through alternate μ 3 ‐O 2− and μ 3 ‐OH − groups. Extended X‐ray absorption fine structure (EXAFS) investigations combined with UV/Vis spectroscopy provide evidence for the same local structure in moderate acidic and neutral aqueous solutions. The synthesis mechanism was partially elucidated and the main physicochemical properties (pH range stability, solubility, and protonation constant) of the cluster were determined. The results underline the importance of: 1) considering such polynuclear species in thermodynamic models, and 2) competing reactions between hydrolysis and complexation. It is interesting to note that the same synthesis route with thorium(IV) led to the formation of a dimer, Th 2 (H 2 O) 10 (H 2 DOTA) 2 ⋅ 4 NO 3 ⋅ x H 2 O ( IV ), which contrasts to the structure of the other An IV hexamers.