A highly selective, colorimetric and ratiometric fluorescent probe for NHNH and its bioimaging.

In this work, we report a novel approach which employed substrate-triggered intramolecular addition-cyclization cascade to develop a highly selective fluorescent probe E)-3-(4-(1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)-1-(2-hydroxylphenyl) prop-2-en-1-one (P-OH) for NHNH. The new sensing mechanism of P-OH for NHNH was investigated in detail by fluorescence spectroscopy, H NMR titration, mass spectrometry and control experiments. The synthesized probe showed ratiometric fluorescent response to NHNH with naked-eye color changes from yellow to colorless. It's noteworthy that this probe displayed high sensitivity and selectivity to NHNH over other species, including primary amines, Cys, Hcy, GSH, HS and HSO. Furthermore, the probe can not only detect NHNH in real water samples but also image NHNH in living cells, indicating its potential utility for NHNH sensing in environmental and biological samples.