Table 1. Association Constants Ka (M–1) for the Binding of Compounds 1–10 to Various Anions in DMSO-d6 Containing 0.5% Water at 298 K, Following the Most Upfield (Thio)urea NH (errors are within 15%).a.
| Cl– | SO42– | H2PO4– | HCO3– | NO3– | |
|---|---|---|---|---|---|
| Urea-Based Compounds | |||||
| 1 | 882 b | >104 b | 443 c | –b,d | –b,e |
| 2 | 575 | >104 | 452 c | 365 | –e |
| 3 | 166 | >104 f | >104 f | >104 f,g | –e,f |
| 4 | 405 | >104 | 243 c | 156 | –e |
| 5 | 517 | >104 | –h | –i | –e |
| Thiourea-Based Compounds | |||||
| 6 | 191 b | >104 b | 256 c | –b,i | –b,e |
| 7 | 179 | >104 | 227 c | –i | –e |
| 8 | 128 | >104 | 130 | –i | –e |
| 9 | 156 | –d | –h | –i | –e |
| 10 | –d | –d | –h | –i | –e |
a
Anions added as TBA salts, except HCO3– which was added as a TEA salt. Fitted to 1:1 model.
b
Previously published data.17
c
Data for DMSO-d6/10% water, data for DMSO-d6/0.5% water could not be fitted.
d
Data could not be fitted to any model.
e
No significant shift of NH peaks, no binding.
f
Data for neat DMSO-d6 by Ghosh et al.,19 values for DMSO-d6/0.5% water are expected to be lower.
g
2:1 model.
h
New peaks due to deprotonation of bound H2PO4– and subsequent binding of HPO42–.
i
Peak broadening.