BODIPY-based hydroxypyridyl derivative as a highly Ni2+-selective fluorescent chemosensor

Abstract

A novel fluorescent chemosensor based on BODIPY-NO2 was synthesized and characterized by NMR, MALDI-MS, UV-Vis and fluorescence spectrum. Also, the single-crystal structure of BODIPY-NO2 was determined by X-ray crystallography. The chemosensor shows selective “turn-off” fluorescence response to Ni2+ ion over various other competing metal ions such as Li+, K+, Ca2+, Mg2+, Hg2+, Cu2+, Zn2+, Cd2+ and Mn2+ in CH3CN solution. The BODIPY-NO2 showed a visible absorption band at 502 nm with a shoulder at the shorter wavelength side. The fluorescence emission band was observed at 543 nm of the sensor in the presence of Ni2+ ion with high quantum yield (Φ: 0.39). The square planar [Ni(BODIPY-NO2)(CH3CN)] metal center acts as an efficient quencher for the excited-state based on electron-transfer processes. The BODIPY-NO2 to Ni2+ sensitive nature was determined from the limit of detection 1.7 × 10−7 M in fluorescence emission. The chemosensor BODIPY-NO2 binds to Ni2+ in a 1:1 molar ratio calculated by the job's plot and the binding constant is determined to be 3.1 × 105 M−1. The fluorescence quenching occurred in an acid condition, using the titration experiment with pH 1.0–4.0.