Table 2.
Cation-π Binding Energies (kcal/mol)a
| Benzene | F-Benzene | F2-Benzene | F3-Benzene | |||
|---|---|---|---|---|---|---|
| 1,3 | 1,4 | 1,2,3 | 1,3,5 | |||
| Sodium | 26.8 | 22.7 | 19.2 | 18.9 | 16.1 | 15.6 |
| Potassium | 20.3 | 17.7 | 14.6 | 14.4 | 12.0 | 11.7 |
| Ammonium | 19.5 | 16.2 | 12.8 | 12.9 | 10.1 | 10.1 |
| Tetramethylammonium (1) | 6.5 | 5.3b | 4.3b | - | 2.9b | 3.0 |
| Tetramethylammonium (2) | 8.7 | 7.2b | 5.5b | 5.7 | 4.0b | - |
| Tetramethylammonium (3) | 10.8 | 9.0b | 7.1b | 7.0 | 5.3b | 5.4 |
| Guanidinium (T-Shaped) | 14.9 | 12.3 | 10.4 | 9.8 | 7.0b | 7.9 |
| Guanidinium (Stacked) | 8.6 | 7.2b | 5.8b | - | 4.6b | 5.1 |
a
M06/6-31G(d,p) calculations; full geometry optimization unless otherwise noted.
b
Binding energy obtained via single point method