An ICT-based fluorescent probe with a large Stokes shift for measuring hydrazine in biological and water samples.

As a strong reductant and highly active alkali, hydrazine (NH) has been widely used in chemical industry, pharmaceutical manufacturing and agricultural production. However, its high acute toxicity poses a threat to ecosystem and human health. In the present study, a ratiometric fluorescent probe for the detection of NH was designed, utilizing dicyanoisophorone as the fluorescent group and 4-bromobutyryl moiety as the recognition site. 4-(2-(3-(dicyanomethylene)-5,5-dimethylcyclohex-1-enyl) phenyl 4-brobutanoate (DDPB) was readily synthesized and could specially sense NH via an intramolecular charge transfer (ICT) pathway. The cyclization cleavage reaction of NH with a 4-bromobutyryl group released phenolic hydroxyl group and reversed the ICT process between hydroxy group and fluorophore, turning on the fluorescence in the DDPB-NH complexes. DDPB exhibits a low cytotoxicity, reasonable cell permeability, a large Stokes shift (186 nm) and a low detection limit (86.3 nM). The quantitative determination of environmental water systems and the visualization fluorescence of DDPB test strips provides a strong evidence for the applications of DDPB. In addition, DDPB is suitable for the fluorescence imaging of exogenous NH in HeLa cells and zebrafish.