Sodium ion chemosensor of 3-oxo-3H-benzo[f]chromene-2-carboxylic acid: An experimental and computational study Scientific paper

Abstract

A fluorescence compound with the typical skeleton of benzocoum­arin 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 chemosensor test against representative metal ions was monitored by fluore­cence spectrophotometry. A density functional theory calculation (DFT, functional/basis set; M06/6-31G (d, p)) was also performed to clarify the expe­rimental results and to confirm the mechanism of interaction. 3-Oxo-3H-benzo­[f]chromene-2-carboxylic acid 1 was obtained as a yellow solid in 60 % chem­ical yield. Melting point; 235.6–236.7 °C and λ_max UV/Vis, λem and Stokes shift (MeOH, nm) of 374, 445 and 71 nm, respectively. The structure of the compound was identified based on spectroscopic data and literature com­par­ison. Compound 1 exhibited a chelation quenched fluorescence (CHQF) phen­menon selectively toward the Na⁺, with a binding stoichiometry (1:2) and LoD and LoQ of 0.14 and 0.48 mg/L, respectively. Based on DFT calcul­ations, compound 1 chelated Na+ through mechanism of oxidative (1:1 equivalent) and reductive (2:1 equivalent) photoinduced electron transfer (PET), corres­pond­ingly.