Deuterium exchange of pyrrolic NH protons accelerated by fluoride and bicarbonate in CDCl<sub>3</sub>, CD<sub>3</sub>CN, and DMSO-<i>d</i><sub>6</sub>

Abstract

The anion binding features of pyrrole- and benzene-strapped calix[4]pyrroles 1 and 2, in particular, for F- and HCO3- have been examined by means of NMR spectroscopy in DMSO-d6, CDCl3, and CD3CN, respectively. Receptors 1 and 2 were found to bind F- and HCO3- tightly via slow binding/release equilibria in these solvents. A combination of 1H and 19F NMR spectroscopic analyses with mass spectrometry revealed that contacting calix[4]pyrroles 1 and 2 with F- and HCO3- salts prompts deuterium exchange of the NH protons in the three nominally aprotic deuterated solvents considered in this study.