Table 3.
Uranium-catechol aqueous Gibbs free energies (Hartrees/molecule) and charges as calculated with the B3LYP/6-31G(d,p) basis set on H, C and O and the Stuttgart ECP60MWB on U using the natural bond orbital analysis program [103-107] with Gaussian 03 (Frisch et al., 2004).
| Models | U Charge | UO22+Charge |
| [UO2(OH2)4]2+-H2Cat (OS)•28(H2O) | ||
| +2.45 | +1.11 | |
| Singlet | ||
| [UO2(OH2)4]2+-H2Catechol•28(H2O) | +2.46 | +1.10 |
| Triplet | ||
| [UO(OH)(OH2)4]2+-HCatechol•28(H2O) | +2.47 | +0.65 |
| Quintet | ||
| [U(OH)2(OH2)4]2+-Catechol•28(H2O) | +2.28 | +0.13 |
| [U(OH)2(OH2)4]2+-Quinone•28(H2O) (OS) | +2.52 | +0.32 |
A modified l607 routine was used for the explicitly solvated models to include the U 6d electrons in the valence space for the natural population analysis [40]. The multiplicities (singlet, triplet and quintet) correspond to U formal oxidation states of +6, +5 and +4. The "U Charge" and "UO22+Charge" headings indicate the actual charge calculated using NBO. Note that the protonation state of the catechol (H2Catechol, HCatechol and Catechol) indicates a H+transfer to the uranyl group simultaneous with the electron transfer.