Design, synthesis and 1H NMR study of C3v-symmetric anion receptors with urethane-NH as recognition group

Abstract C 3v -Symmetric anion receptors 3 and 4 with urethane groups were synthesized by using trindane triol as tripodal molecular framework. In 1 H NMR titration study, the receptors showed noticeable downfield shift/disappearance of the urethane-NH peak in presence of H 2 PO 4 − and F − due to the host–guest complexation occurred through multiple hydrogen bonding and/or the deprotonation of urethane-NH groups. Other tested anions such as Cl − , Br − , HSO 4 − , and NO 3 − showed either no or negligible chemical shift of the urethane groups. The deprotonation event in 4 allowed selective detection of F − by perceptible color change from colorless to yellowish-red with the appearance of a new charge transfer absorption band at 450 nm.