Squaramide-substituted calix[4]pyrrole: Synthesis and ion binding studies

Squaramide-substituted calix[4]pyrrole 2 was synthesized and its anion-binding properties were investigated. On the basis of UV spectroscopy, H-1 NMR spectroscopic and computational DFT model analyses, compared with the parent calix[4]pyrrole 1, compound 2 shows significantly enhanced binding affinities for anions in CH2Cl2, and it was concluded that this increase in affinity is ascribed to participation of the squaramide unit in anion binding. (C) 2019 Elsevier Ltd. All rights reserved.