This study identifies how the amidoximate anion, AO, interacts with the uranyl cation, UO(2)(2+). Density functional theory calculations have been used to evaluate possible binding motifs in a series of [UO(2)(AO)(x)(OH(2))(y)](2-x) (x = 1-3) complexes. These motifs include monodentate binding to either the oxygen or the nitrogen atom of the oxime group, bidentate chelation involving the oxime oxygen atom and the amide nitrogen atom, and η(2) binding with the N-O bond. The theoretical results establish the η(2) motif to be the most stable form. This prediction is confirmed by single-crystal X-ray diffraction of UO(2)(2+) complexes with acetamidoxime and benzamidoxime anions.

A direct estimate of changes in the radiative and nonradiative decay rates of a chromophore near metal nanoparticles is obtained using a quantum mechanical description coupled to the polarizable continuum model. The results account for experimentally observed continuous change from decreased to increased fluorescence. The changes are described as the effects of a dependence on the distance and orientation between the chromophore and the metal nanoparticle, as well as the size, shape, number, and type of the metal particles and the influence of the solvent. The chromophore investigated was N,N′-dimethylperylene-3,4,9,10- dicarboximide in combination with silver and gold particles. The study explains and rationalizes how intrinsic characteristics of the metal predetermine the nanoparticle’s behavior toward chromophore excitation and decay rates. As a result, the optimal setup (shape, position, orientation) that gives the largest enhancement is revealed

The ability to predict the equilibrium constants for the formation of 1:1 uranyl/ligand complexes (log K1 values) provides the essential foundation for the rational design of ligands with enhanced uranyl affinity and selectivity. We use density functional theory (B3LYP) and the integral equation formalism polarizable continuum model (IEF-PCM) to compute aqueous stability constants for UO2(2+) complexes with 18 donor ligands. Theoretical calculations permit reasonably good estimates of relative binding strengths, while the absolute log K1 values are significantly overestimated. Accurate predictions of the absolute log K1 values (root-mean-square deviation from experiment <1.0 for log K1 values ranging from 0 to 16.8) can be obtained by fitting the experimental data for two groups of mono- and divalent negative oxygen donor ligands. The utility of correlations is demonstrated for amidoxime and imide dioxime ligands, providing a useful means of screening for new ligands with strong chelating capability to uranyl.

Poly(acrylamidoximes) play an important role in the uranium extraction from seawater. The present work reports solution studies of simple analogues to address the formation and stability of two binding sites present in these polymers, openchain amidoximes and cyclic imide dioximes, including: (1) conditions that maximize the formation of the cyclic form, (2) the existence of a base-induced conversion from open-chain to cyclic form, and (3) degradation under acid and base conditions.

This paper presents a computational approach to the deliberate design of host architectures that recognize and bind specific guests. De novo molecule building software, HostDesigner, is interfaced with molecular mechanics software, PCModel, providing a tool for generating and screening millions of potential structures. The efficacy of this computer-aided design methodology is illustrated with a search for bis-amidoxime chelates that are structurally organized for complexation with the uranyl cation.