Synthesis and anion binding properties of the smallest meso-expanded calix[4]pyrrole

Abstract

Abstract: The smallest core expanded calix[4]pyrrole derivative (5) was synthesized via incorporation of an additional sp3meso-carbon at the periphery of the macrocycle. Anion binding study of the macrocycle reveals clearly the effect of core size on its affinity towards various tested ions (F -, Cl -, Br -, I -, AcO -, H2PO4-, HSO4-, ClO4-, PF6-, NO3-, NO2-, N3- and CN -). The macrocycle displays the highest affinity towards fluoride and acetate ions, albeit with reduced affinities compared to parent octamethylcalix[4]pyrrole. Graphical abstract: SYNOPSIS The first example of the smallest expanded calix[4]pyrrole is reported. Anion binding study of the macrocycle reveals clearly the effect of core size on its affinity towards various tested ions (F -, Cl -, Br -, I -, AcO -, H2PO4-, HSO4-, ClO4-, PF6-, NO3-, NO2-, N3- and CN -).