A novel AIEE active anti-B₁₈H₂₂derivative-based Cu²⁺and Fe³⁺fluorescence off-on-off sensor

A novel fluorescence sensor for successive detection of Cu²⁺and Fe³⁺based on anti-B₁₈H₂₂derivative which possesses 5-hydroxyisoquinoline as an ionophore was synthesized via a one-pot and its structure and photophysical properties were characterized by NMR, HRMS, FTIR, UV-vis, PL and theoretical calculation. The fluorophore displays two emission peaks at 460 nm and 670 nm in THF solution coming from the emission of the locally excited state and intramolecular charge transfer fluorescence, respectively. The complex exhibited obvious aggregation-induced emission enhancement (AIEE) characteristics in THF/H₂O solution by increasing the aqueous concentration from 70% to 95%. The AIEE molecules showed a high selectivity towards Cu²⁺over other metal ions by forming a 2:1 metal-to-ligand complex in THF/H₂O (fw = 20%) solution, the fluorescence intensity increased as a linear function of the Cu²⁺concentration at 460 nm due to the inhibition of PET effect. The fluorescent emission was quenched linearly by the addition of Fe³⁺, which provides a method for successive determination of Cu²⁺and Fe³⁺based on 'off-on-off' fluorescence of the fluorescent. The detection limit of Cu²⁺and Fe³⁺was 5.7 × 10^-6M and 7.2 × 10^-5M respectively. Morever, a rapid identification of Cu²⁺in the aqueous solution by naked eyes can be realized. In addition, the molecules were pH-sensitive, the fluorescence quenching can be observed in strongly alkaline environment. The method has been applied to the determination of copper ions in water samples with satisfactory results.