Table 1. Binding Energies (kcal/mol) Calculated at the M06/cc-pVTZ and CCSD(T)/cc-pVTZ Levels for σ and π Complexes of the t-Butyl Cation with 3-Ethylindole and for the π3a → π7a Transition State43.
| molecule | M06/cc–pVTZ binding energy (kcal/mol)a | CCSD(T)/cc–pVTZ binding energy (kcal/mol)b |
|---|---|---|
| σ-complex 1 | –36.87 | –48.87 |
| σ-complex 2 | –45.52 | –52.92 |
| σ-complex 3 | –41.50 | –52.58 |
| π-complex 3a | –23.23 | –23.87 |
| σ-complex 3a | –16.79 | –27.03 |
| π-complex 4 | –22.84 | –23.17 |
| σ-complex 4 | –33.03 | –40.43 |
| σ-complex 5 | –35.62 | –43.96 |
| σ-complex 6 | –35.66 | –43.02 |
| π-complex 7 | –21.35 | –22.46 |
| σ-complex 7 | –33.12 | –41.60 |
| π-complex 7a | –22.59 | –23.62 |
| σ-complex 7a | –20.24 | –31.48 |
| π3a → π7a T.S. | –21.32 | –22.20 |
a
M06/cc-pVTZ binding energies are calculated using geometries optimized at the M06/cc-pVTZ level with all stationary points confirmed by harmonic frequency calculations.
b
CCSD(T)/cc-pVTZ energies calculated at the M06/cc-pVTZ-optimized geometries.