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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 [103107] with Gaussian 03 (Frisch et al., 2004).

From: Quantum mechanical calculation of aqueuous uranium complexes: carbonate, phosphate, organic and biomolecular species

Models U Charge UO22+Charge
[UO2(OH2)4]2+-H2Cat (OS)•28(H2O)   
  +2.45 +1.11
[UO2(OH2)4]2+-H2Catechol•28(H2O) +2.46 +1.10
[UO(OH)(OH2)4]2+-HCatechol•28(H2O) +2.47 +0.65
[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
  1. 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.