The structural influence of Ca²⁺ counter-ions on uranyl(vi) tricarbonate in aqueous solution

Abstract

The presented study elucidates the influence of calcium(II) counter-ions on the structure of the environmentally relevant uranyl tricarbonates using hybrid quantum mechanical/molecular mechanical (QM/MM) MD simulations. Since experimental investigations may be subject to limitations in detecting the presence of counter-ions in solution, the present study is of importance to obtain a profound understanding of the effects counter-ions may have on coordination complexes. It can be concluded from the obtained simulation data that two calcium(II) ions are essential for stabilizing the experimentally observed uranyl tricarbonate complex in aqueous solution. Including only one calcium(II) ion in the coordination sphere was found to be insufficient to form a six-fold equatorial coordination of carbonates, but a five-fold coordination is adopted similar to the counter-ion free case in aqueous solution reported in a previous study.

A combined DFT and molecular dynamics study of U(VI)/calcite interaction in aqueous solution

“…S2 online). This finding was also supported by another simulation study [35]. The UO 2 (CO 3 ) 3 Ca 2 species prefers to locate at pair site A with two of its CO 3 2À ligands bound to surface Ca atoms, respectively, forming complex SUO 2 (CO 3 ) 3 Ca 2 as shown in Fig.…”

Determination of formation constants and specific ion interaction coefficients for CanUO2(CO3)3(4−2n)−complexes in NaCl solution by time-resolved laser-induced luminescence spectroscopy

“…The counter-ion effects of Ca 2+ were proven to help stabilizing the fourfold negatively charged complex UO2(CO3)3 4-in aqueous environment with hybrid quantum mechanical/molecular mechanical molecular dynamics simulations. 76,77 Furthermore, classical molecular dynamics simulations have successfully described the impact of Na + on the binding between UO2(CO3)3 4-and Ca 2+ ions by simulating the effect of 0.1 mol L -1 NaCl as background electrolyte. 71 The presence of sodium provoked a distortion of carbonate denticity and thus yielded space for entering one water molecule in the primary coordination sphere in CaUO2(CO3)3 2-.…”

Multilinear analysis of Time-Resolved Laser-Induced Fluorescence Spectra of U(VI) containing natural water samples

“…Quantum chemical modelling led to realistic values of vibrational frequencies of each species individually (few percent errors) and geometry of Ca2UO2(CO3)3 0 well comparable with literature [96,97]. And because the differences between gs of different species are, in some cases, rather parts in percent (i.e.…”