Binding modes of oxalate in UO(2)(oxalate) in aqueous solution studied with first-principles molecular dynamics simulations. Implications for the chelate effect
2011 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 42, 11192-11199 p.Article in journal (Refereed) Published
Car-Parrinello molecular dynamics simulations are reported for aqueous UO(2)(H(2)O)(n)(C(2)O(4)) (n = 3, 4), calling special attention to the binding modes of oxalate and the thermodynamics of the so-called chelate effect. Based on free energies from thermodynamic integration (BLYP functional), the kappa(1),kappa(1')-binding mode of the oxalate (with one O atom from each carboxylate coordinating) is more stable than kappa(2) (2 O atoms from the same carboxylate) and kappa(1) forms by 23 and 39 kJ mol(-1), respectively. The free energy of binding a fourth water ligand to UO(2)(H(2)O)(3)(kappa(1)-C(2)O(4)) is computed to be low, 12 kJ mol(-1). Changes of the hydration shell about oxalate during chelate opening are discussed. Composite enthalpies and free energies, obtained from both experiment and quantum-chemical modeling, are proposed for the formation of monodentate UO(2)(H(2)O)(4)(kappa(1)-C(2)O(4)). These data suggest that the largest entropy change in the overall complex formation occurs at this stage, and that the subsequent chelate closure under water release is essentially enthalpy-driven.
Place, publisher, year, edition, pages
2011. Vol. 40, no 42, 11192-11199 p.
IdentifiersURN: urn:nbn:se:kth:diva-50330DOI: 10.1039/c1dt10796hISI: 000296024000017ScopusID: 2-s2.0-80054983535OAI: oai:DiVA.org:kth-50330DiVA: diva2:480333
QC 201201192012-01-192011-12-052012-01-19Bibliographically approved