Coumarin-Based Reversible Fluorescent Chemosensors for the Sequential Detection of Copper and Citrate Ions

Two novel coumarin-based Schiff-base chemosensors are presented. Courtesy to an extended conjugation between the coumarin ring and the attached pi-containing groups, both chemosensors display noteworthy photo-physical properties including emission maxima at >550 nm. Both chemosensors function as the selective sensors for the 'turn-off' detection of copper ion with the significant nanomolar detection limits. The sensing event was investigated through proton NMR and mass spectroscopy; pH studies; life-time and quantum yield measurements and DFT studies. The solution-generated [chemosensor-Cu] species illustrated remarkably selective secondary 'turn-on' detection of the citrate ion. The sequential detection of the copper and citrate ions have been utilized for the construction of logic gates as well as several low-cost detection methods.

Automated summary

Two novel coumarin-based Schiff-base chemosensors with extended conjugation exhibit noteworthy photo-physical properties and selective 'turn-off' detection of copper ion with significant nanomolar detection limits. The sensing event and the secondary 'turn-on' detection of the citrate ion by the [chemosensor-Cu] species were investigated through various experiments. The sequential detection of copper and citrate ions has been utilized for the construction of logic gates and low-cost detection methods.