Table 4. Barrier Heights ΔTSGenz° for the Methyl Transfer from bSAM+ to X– and the Number of H2O Molecules nH2O Solvating X– in AtHTMT1 Obtained from a Single QM/MM MD Simulation with Four Different Semi-empirical Methods and the AMBER 14SB Force Fielda.
| PM7 |
PM6-D3 |
AM1 |
PM6-D3H4 |
|||||
|---|---|---|---|---|---|---|---|---|
| X– | ΔTSGenz° | nH2O | ΔTSGenz° | nH2O | ΔTSGenz° | nH2O | ΔTSGenz° | nH2O |
| Cl– | 75.7 | 7 | 89.5 | 7 | 19.0 | 7 | 71.1c | 7 |
| Br– | 70.4 | 7 | 83.0 | 8 | 5.9 | 6 | 60.9 | 7 |
| I– | 87.2 | 5 | 54.3 | 5 | —b | 5 | 42.4 | 5 |
| NCO– | 119.1 | 7 | 87.8 | 7 | 45.1 | 7 | 76.8 | 7 |
| OCN– | 86.1 | 5 | 69.6 | 5 | 72.4 | 5 | 69.5 | 5 |
| NCS– | 60.6 | 3 | 59.8 | 5 | —b | 3 | 51.7 | 5 |
| SCN– | 100.6 | 3 | 93.1 | 3 | 69.4 | 3 | 87.6 | 3 |
a
All energies are in kJ mol–1.
b
No apparent maximum in the free energy curve.
c
Average of six simulations, std. dev. 1.2 kJ mol–1.