An NIR Emissive Donor-?-Acceptor Dicyanomethylene-4H-Pyran Derivative as a Fluorescent Chemosensor System towards Copper (II) Detection

A novel donor-?-acceptor fluorescent dye as a chemosensor for Cu2+ ions is herein presented. The fluorophoric core consists of 3,5-diphenyl-dicyanomethylene-4H-pyran (DCM), with extended styryl chains on positions 2 and 6, bearing terminal di-(2-picolyl)amine (DPA) groups metal coordination. Optical characterization the reveals an absorption maximum at ca. 500 nm strong bathochromic shift in emission, reaching 750 polar solvents. This solvatochromic behavior, which yields very large Stokes shifts (up to ~6700 cm?1), characteristic intramolecular Charge Transfer (CT) nature this chromophoric system. While has demonstrated no changes its optical properties over wide pH range (2–12), quenching effect was observed upon coordination, 1:1 binding stoichiometry, indicating that only one DPA unit capable effectively chelating Cu2+, rendering second motif inactive. constant determined be 7.5 × 107 M?1, high sensitivity, LOD 90.1 nM. Competition assays have highly selective towards even presence excesses other mono- di-valent cations. Co2+ Ni2+ proved strongest interferents, particularly luminescent response. Paper test-strips prepared embedded sensor showed fluorometric response different copper (II) concentrations, attested potential used determination content aqueous media, in-field applications.