Département de chimie moléculaire

Static ab initio and d.-functional computations, as well as Car-Parrinello mol. dynamics simulations in aq. soln. are reported for [UO2(OH)($ąppa$2-O2)(H2O)2]- and [UO2(OH)2($ąppa$1-O2H)(H2O)]-. Whereas the $ąppa$1-hydroperoxo isomer is found to be more stable than the $ąppa$2-peroxo form in the gas phase, the order of stability is reversed in explicit bulk soln. Based on free energies from thermodn. integration (BLYP functional), the peroxo form is favored by ca. 32 kJ mol-1 in water. This stabilization is discussed in terms of the hydration shells about the individual ligands and dipole moments of the complexes in water, and highlights the importance of explicit solute-solvent interactions and bulk solvation for the speciation of uranyl(VI) compds. [on SciFinder(R)]