Table 1.
Gibbs free energy obtained with B3LYP/cc-pVDZ (T = 298.15 K) for all the studied species optimised at low, intermediate (for ferrous complexes only) and high spin. The most stable species of each non-protonated compound was used as benchmark. The relative values of protonated and aquo complexes were calculated with respect to the independent corresponding non-protonated species plus H+ or H2O, as applicable.
| Species | Spin | ΔG°/kJ mol−1 |
|---|---|---|
| Fe(III)-PO | 1/2 | 49.73 |
| 5/2 | 0.00 | |
| Fe(III)-PO-H2O | 1/2 | −12.44 |
| 5/2 | 0.86 | |
| Fe(III)-PO-H | 1/2 | 269.21 |
| 5/2 | 307.07 | |
| Fe(II)-PO | 0 | 46.38 |
| 1 | 59.96 | |
| 2 | 0.00 | |
| Fe(II)-PO-H2O | 0 | 25.66 |
| 1 | 63.38 | |
| 2 | 5.13 | |
| Fe(II)-PO-H | 0 | 231.01 |
| 1 | 179.50 | |
| 2 | 221.61 | |
| PO-I | 1/2 | 0.00 |
| 5/2 | 49.61 | |
| PO-I-H2O | 1/2 | 9.95 |
| 5/2 | 59.44 | |
| PO-I-H | 1/2 | 24.06 |
| 5/2 | 86.53 | |
| PO-II | 1 | 0.00 |
| 2 | 56.93 | |
| PO-II-H2O | 1 | 4.53 |
| 2 | 62.60 | |
| PO-II-H | 1 | −48.66 |
| 2 | −9.19 |