Association constant Ka valuesa of the XB donor–quinuclidine pairs.
| Entry | XB donor | K a, M−1 |
|---|---|---|
| 1 | 1-OTf | 57 ± 5 |
| 2 | 1-BARF | (1.23 ± 0.01) × 103 |
| 3 | 2-OTf | 257 ± 12 |
| 4 | 2-BF4 | 284 ± 12 |
| 5 | 3-OTf | 703 ± 6 |
| 6 | 3-BARF | (1.1 ± 0.3) × 104 |
| 7 | 4-OTf | <1 |
| 8 | 5-BARF | n.db |
| 9 | 6-OTf | <1 |
| 10 | 7 | 2.0 ± 0.3 |
a
Association constant Ka measured in CDCl3 at 298 K and determined by fitting the 1H NMR titration data to 1 : 1 binding isotherm of BindFit.15 The given Ka and standard error are the calculated mean values of two parallel experiments. Full details given in the ESI.
b
K a could not be determined due to the instability of XB donor during the experiment.