Table 14.
Association constants (Ka/M−1) between ion pair receptor 95 and halides recorded in the presence and absence of alkali metal salts (1.0 equiv.) in 10% (v/v) DMSO-d6/CD3CN at 297 ± 1 K
| Halidea | Cation additive | Association constant/M−1 |
|---|---|---|
| Cl− | None | 7 |
| LiClO4 | 120 | |
| NaClO4 | 14 000 | |
| KPF6 | 6200 | |
| Br− | None | —b |
| LiClO4 | 24 | |
| NaClO4 | 600 | |
| KPF6 | 200 | |
| I− | None | —b |
| LiClO4 | 9 | |
| NaClO4 | 61 | |
| KPF6 | 45 |
a
Halide anions were studied as the corresponding tetrabutylammonium salts.
b
The chemical shift changes during the titration were too small to determine accurately an association constant.