Selective Sensing of Anions with Calix4pyrroles Strapped with Chromogenic Dipyrrolylquinoxalines

摘要

New calix[4]pyrroles bearing dipyrrolylquinoxaline as strapping elements have been synthesized and characterized by spectroscopic means. The binding behavior of these receptors at 25 °C was investigated first by proton NMR spectroscopy in CD3CN/DMSO-d6 (9:1 v./v.), as well as by UV-vis spectroscopy and isothermal titration calorimetry (ITC) in CH3CN/DMSO (97:3 v./v.). The receptors displayed a selective colorimetric response when exposed to the fluoride, dihydrogen phosphate, and acetate anions (studied in the form of the corresponding tetrabutylammonium salts) and an enhanced affinity as compared to a comparable calix[4]pyrrole system lacking the dipyrrolylquinoxaline-containing strap.