Synthesis and evaluation of an imidazo-benzocrown ether functionalised amino acid as a new fluorimetric chemosensor for metal ion detection

The field of fluorescent chemosensors has grown in recent years due to their importance in applications such as in material sciences, biomedical, analytical chemistry and environmental sciences. Following our research interests that include the synthesis and application of fluorimetric chemosensors for anions and cations based on heterocycles and amino acids, a new imidazo-benzocrown ether functionalised amino acid 3 was synthesized in 70% yield by condensation of functionalised phenylalanine 1 with 4-amino-5-nitrobenzo-15-crown-5-ether 2 in the presence of Na₂S₂O₄ in DMSO. Compound 3 was studied by fluorescence spectroscopy in the presence of increasing amount of metal ions such as Ca²⁺, Cd²⁺, Co²⁺, Cr³⁺, Cu²⁺, Fe²⁺, Fe³⁺, Hg²⁺, Na⁺, Ni²⁺, Pd²⁺ and Zn²⁺. The metal cation sensing properties displayed by 3 showed that it is a promising candidate for sensory applications.