A selective “off–on” rhodamine-based chemosensor for the detection of Cu2+ ions: colorimetric, theoretical and biological study

Abstract

Herein, an “off–on” chemosensor (RH) based on a rhodamine moiety was synthesized, which exhibited selective detection towards Cu²⁺ ions based on the spirocyclic ring-opening mechanism of the rhodamine unit. The chemosensor (RH) was colourless owing to intramolecular spirocyclization. In the presence of Cu²⁺ ions, the ring opening of RH occurred via complex formation, as observed in UV-Vis spectra. The absorption maxima shifted to 556 nm accompanied by an intense visible pink colour of the RH solution. RH showed high selectivity towards Cu²⁺ ions over other metal ions, and the limit of detection (LOD) was calculated to be 2.75 μM. Quantum chemical calculations validated the formation of RH@Cu²⁺. The chemosensor also showed good cell viability and low cell cytotoxicity toward ACHN and HEK-293 cell lines.