Fig. 6. The 1H NMR titrations of CHIR-98014 4 and tetrabutylammonium fluoride in DMSO-d6.Figure optionsDownload full-size imageDownload as PowerPoint slide
In addition, the interactions of receptors 1–3 with fluoride ions have also been evaluated by the 1H NMR titration. The results indicated that the N–H protons of receptor 1 bind with fluoride ions by double hydrogen bonding interactions (see Fig. S6). The signals of N–H protons of receptor 1 almost vanished upon addition of 1 equiv. of F− or even excessive F−, whereas the similar proton peak of [HF2]− was not observed at 16.1 ppm. Similarly, the variations of the signals for receptor 2 and 3 with fluoride ions can also be observed in the same conditions. The results suggested that receptors 1–3 bound with anions by double hydrogen bonding interactions instead of deprotonation.
AcknowledgmentsWe gratefully acknowledge the supporting from the National Natural Science Foundation of China (No. 20672121) and the Talent Introduction Project of Sichuan University of Science and Engineering (No. 2011RC14).