Table 3. Thermodynamics of Ligand Loss from FeII/IIIa.
| B(20HF)P86b | FeII-S(Met) | FeIII-S(Met) | ΔΔcS(Met) | FeII-N(His) | FeIII-N(His) | ΔΔN(His) | FeII-H2O | FeIII-H2O | ΔΔH2O |
|---|---|---|---|---|---|---|---|---|---|
| ΔE | 5.0 | 7.1 | 2.1 | 9.9 | 16.9 | 7.0 | –0.5 | 6.7 | 7.2 |
| ΔH | 2.6 | 5.5 | 5.5 | 7.2 | 14.7 | 7.5 | –2.0 | 5.3 | 7.3 |
| ΔG | –13.9 | –8.8 | 5.1 | –9.1 | –0.4 | 8.8 | –12.3 | –4.2 | 8.1 |
| expd | 3.6 | 0.6 | –3.0 | 4.7 | 4.9 | 0.2 | |||
| exp corr.e | 3.6 | 8.7 | 5.1 | 4.7 | 13.0 | 8.3 |
a
All energies are in kcal/mol.
b
6-311+G(d,p) basis set for all atoms and PCM corrections (ε = 4.0).
c
ΔΔ is the difference in FeIII and FeII axial ligand bond strengths.
d
ΔG0 values obtained from dissociation constants for AcMet and imidazole.10
e
Experimental values corrected for the calculated ΔΔG of H2O dissociation from Fe(III) (i.e., 8.1 kcal/mol)