Rationally Designed Fluorescence . OH Probe with High Sensitivity and Selectivity for Monitoring the Generation of . OH in Iron Autoxidation without Addition of H 2 O 2 .

The first sensitive fluorescence . OH probe (1) that is capable of monitoring the generation of trace . OH in iron autoxidation is presented. The probe 1 was designed by utilizing both the unique aromatic hydroxylation and the electrophilicity of . OH, and prepared by incorporating a strong electron-donating methoxy group into a cyanine fluorochrome to enhance the trapping ability for . OH. Reaction of 1 with . OH leads to a larger π-conjugation formation and near-infrared fluorescence off-on response. The capability of probe 1 has been demonstrated by imaging . OH generated in living cells under iron autoxidation as well as various stimuli, which reveals that the basal level of . OH in RAW 264.7 cells is lower than that in HeLa cells. The superior analytical performance of probe 1 makes it useful for detecting trace . OH in some critical physiological and pathological processes associated with iron autoxidation.