Ratiometric fluorescence sensing of hypochlorite ion by dansyl hydrazine - Spectroscopic and TD-DFT studies

Abstract

Probe dansyl hydrazine (DH) exhibits highly selective and sensitive fluorescence detection properties towards hypochlorite (OCl−) ions in DMSO and aq. DMSO media. The probe comprises a fluorophore N,N-dimethylnaphthalene unit and an electron-withdrawing –SO2NHNH2 moiety attached to it. Titration of OCl− ions with DH caused C-S bond cleavage reaction that enhanced the fluorescence of DH with a blue shift. 1H NMR and HRMS spectral techniques were used to confirm the OCl−ion-triggered C-S bond cleavage mechanism. Based on DH's significant fluorescence enhancement response to OCl− ions, the detection limit was estimated as low as 18 µM. Moreover, computational density functional theory (DFT) and time-dependant density functional theory (TD-DFT) calculations provided more insight into the probe's absorption and emission spectral properties before and after the addition of OCl− ions. Additionally, the probe DH would be a potential tool for detecting OCl− ion concentration in bleaching powder.