A terpyridine-appended hexaarylbenzene fluorophore: synthesis, photophysical properties and application for the colorimetric detection of Fe2+ in aqueous solution

Abstract

The hexaarylbenzene (HAB)-based push–pull fluorophore HAB-MeO-TPy with the 2,2′:6′,2″-terpyridine (TPy) unit as an acceptor and the methoxy (MeO) group as a donor was developed. It was observed that HAB-MeO-TPy exhibited an unusual uphill-type emission with increasing solvent polarity from cyclohexane to DMSO. By comparison with a previously reported fluorophore HPB-MeO-DCV, a structure–property relationship regarding this uncommon fluorescence behavior was disclosed. Furthermore, the sensing properties of HAB-MeO-TPy for metal ions were also investigated. In the presence of Fe²⁺, HAB-MeO-TPy displayed a visual color change from colorless to magenta, indicating that HAB-MeO-TPy can act as a “naked eye” sensor for Fe²⁺ detection. From absorption titration experiments, the detection limit was determined to be 1.50 × 10⁻⁷ M. In addition, HAB-MeO-TPy was successfully applied to detect Fe²⁺ in real water samples.