A DFT study of uranyl hydroxyl complexes: structure and stability of trimers and tetramers

A DFT study of U(VI) hydroxy complexes was performed with special attention paid to the [(UO(2))(3)(OH)(5)(H(2)O)(4–7)](+) and [(UO(2))(4)(OH)(7)(H(2)O)(5–8)](+) species. It was established that the ionicity of the U=O bond increased when moving from [(UO(2))(H(2)O)(5)](2+), [(UO(2))(2)(OH)(H(2)O)(8)](3+), [(UO(2))(2)(OH)(2)(H(2)O)(6)](2+), [(UO(2))(3)(OH)(5)(H(2)O)(4–6)](+) to [(UO(2))(4)(OH)(7)(H(2)O)(5–8)](+) species. In both [(UO(2))(3)(OH)(5)(H(2)O)(4–6)](+) and [(UO(2))(4)(OH)(7)(H(2)O)(5–8)](+) complexes, the U=O bond was observed to have a range of different lengths which depended on the composition of the first coordination sphere of UO(2) (2+). The cyclic structures of trimeric complexes were somewhat more stable than their linear structures, which was probably due to the steric effect. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10967-017-5305-z) contains supplementary material, which is available to authorized users.