Stable, triplet ground state BODIPY-TEMPO diradical as a selective turn on fluorescence sensor for intracellular labile iron pool

Intracellular labile iron pool (LIP) has been associated with cellular toxicity, and regarded as one of the factors affecting many diseases. However, fluorescence probes for detection of LIP are limited. Herein, we present a novel, BODIPY based, triplet ground state pro-fluorescent dinitroxide, as a turn on sensor for similar purpose. The biradical probe has been synthesized, and was seen to be highly effective in detecting LIP, more importantly in a concentration-dependent manner, in a variety of cell lines. The probe showed high sensitivity with Fe(II)-selective turn-on response via reduction of the biradical. This is a first example of a BODIPY based fluorescence turn-on sensor selective towards Fe(II).