Novel C3v-symmetric tripodal anion receptors having guanidine recognition motif with 2-aminobenzimidazole (2) and urea recognition motif with coumarin fluorephore (3) were synthesized from cis,cis,cis-2,5,8-tribenzyltrindane-2,5,8-tricarboxylate (1). The C3v-symmetric scaffold 1 has non-polar benzyl moieties on one side and polar ester moieties on the other side. These moieties were selectively functionalized to afford the C3v-symmetric anion molecular sensors to recognize selectively and effectively towards anions with C3v-symmetry guests such as F-, Cl-, Br-, I-, H2PO4-, HSO4-, NO3-, HCO3- ions, expecting shape-selectivity.
Interestingly the tripodal receptor 2 showed a superior recognition towards H2PO4- by NMR titration, but selectively recognized with HSO4- emitting blue fluorescence under UV irradiation, which can be further developed to fluorescent anion sensors. Anion recognition of tripodal urea receptor 3 with coumarin fluorephore also will be presented as potentional fluorescent anion sensor.