Density functional theory investigations on the binding modes of amidoximes with uranyl ions

Abstract

Density functional theory (DFT) calculations have been carried out to examine the relative facilities of different coordination modes of aromatic amidoximes (AOs) with UO₂(NO₃)₂. Various η¹-, η²- and chelated κ²-coordination modes of the possible neutral AO, tautomerized neutral (TAO, with the hydroxylic hydrogen transferring to the oximic nitrogen atom) and anionic amidoxime (AAO, formed by the deprotonation of AO) were examined. The results indicate that η¹-O of the TAO and η¹-O/η²-NO of AAO are the most plausible coordination modes. Three types of uranyl complexes, i.e. UO₂(NO₃)₂(TAO)(AAO), UO₂(NO₃)₂(AAO)₂ and UO₂(EtOH)₂(AAO)₂ are the predominant binding structures. The good consistency between the calculation results and the experimental observations verifies the proposed conclusions.