New non-covalent charge–transfer complex of calix[4]pyrrole–chloranil: as a potential colorimetric anion sensor

Non-covalent calix[4]pyrrole–chloranil complex, a new class of supramolecular assembly, is reported. The formation of the complex is mainly attributed to the charge–transfer interactions between calix[4]pyrrole with electron-rich pyrrole rings and the electron-deficient chloranil subunit. As potential colorimetric anion sensors, the charge–transfer aggregation may be used for effective and selective detection of F− and H2PO4− by means of dramatic visual color changes.