A new promising fluorescent chemosensor of Al3+ based on a 2-hydroxynaphthaldehyde skeleton was successfully synthesized through double imine formation and demonstrated excellent sensing properties through the ESIPT inhibition mechanism.

A fluorescence compound of benzocoumarin typical skeleton was synthesized and its interaction with various metal ions was evaluated. The synthesis was performed via Knoevenagel condensation whereas identification of the product was accomplished by various spectroscopic techniques. The chemo-sensor test against representative metal ions was monitored by fluorescence spectrophotometry. Density Functional Theory calculation (DFT) (Functional/basis set; M06/6-31G (d, p)) was also carried out to clarify the experimental results and to confirm the mechanism of interaction. The 3-oxo-3H-benzo[f]chromene-2-carboxylic acid 1 was obtained as yellow solid with; 60 % chemical yield, melting point; 235.6 - 236.7?C, ?max UV/Visible, ?em and Stokes shift (MeOH / nm); 374, 445, and 71 nm, respectively. Structure of the compound was identified based on spectroscopic data and literature comparison. The compound 1 exhibited a chelation quenched fluorescence (CHQF) phenomenon toward Na+ ion selectively, with binding stoichiometry (1:2) and LoD and LoQ of 0.14 and 0.48 mg/L, respectively. Based on DFT calculation, compound 1 chelated Na+ ion through mechanism of oxidative (1:1 equivalent) and reductive (2:1 equivalent) Photoinduced Electron Transfer (PET), correspondingly.