||BODIPY based fluorescence chemosensor BODIPY-NO2 was prepared and characterized by NMR, MALDI-MS, absorption and emission spectrum.|
The absorption, excitation and fluorescence spectra of BODIPY-NO2 exhibit the characteristic properties of the BODIPY fluorophore in CH3CN.In CH3CN, BODIPY-NO2 displays one visible region absorption band at 502 nm (ε: 4.2 × 104 M-1 cm-1) with a shoulder at the shorter wavelength side and an emission maximum (λem) at 543 nm with high quantum yield (Φ: 0.39).The sensing properties of BODIPY-NO2 toward various metal ions are investigated in CH3CN. A highly selective fluorescent turn-off response is observed in the presence of Ni2+ over the other metal ions, as is observed with the addition of 2.0 equiv of Li+, K+, Ca2+, Mg2+, Hg2+ Cu2+, Zn2+, Cd2+ and Mn2+. The fluorescence intensity is almost not influenced by the addition of other metal ions. In this study, the square planar [Ni(BODIPY-NO2)(CH3CN)] metal centre acts as an efficient quencher for the excited-state based on electron-transfer processes. A Job’s plot determining the stoichiometry of BODIPY-NO2 and Ni2+ in CH3CN indicates a simple one-to-one binding process. The binding constant for Ni2+ ion binding to BODIPY-NO2, evaluated from the Benesi-Hildebrand plot is 3.1 × 105 M-1.
By the way the fluorescence quenching will happen in an acid condition, via titration experiment we know that acid condition limit pH 1.5 ~ 4.0.