Table 1.
Association constants (Ka) obtained by UV/Vis or 1H NMR titrations of 1 with various anions added as the tetrabutylammonium salts in 10% DMSO/CHCl3 or the perdeutero-equivalent at 298 K and data fit to an apparent 1:1 binding model using HypNMR 2006 or Hyperquad 2006.[a] Association constants represent an average of at least three titrations.
| Halides (M−1) | Oxoanions (M−1) | ||
|---|---|---|---|
|
| |||
| 1 | 1 | ||
| Cl− | 140±10 | H2PO4− | 78000±2000[b] |
| Br− | 60±5 | HSO4− | 170±20 |
| I− | 40±15 | OAc− | 3200±500 |
| — | — | NO3− | 60±5 |
Data were fit to a 1:1 binding model based on goodness of fit, results of Job plots and extensive non-linear least squares modelling (see ESI). Based on increased goodness of fit it is clear that 1:2 association does occur for HSO4− and the halides, specifically Cl−, at least to some extent during titrations (see Figures S27, S28 for 1:2 fits). We report only 1:1 apparent Ka’s since the 1:2 fits are less reliable due to the need to fit too many unknown variables. Nevertheless, association constant fits (β11, β12) are provided and discussed for 1:2 association in the ESI for the interested reader.
Association constant obtained from UV/Vis titrations.