An Unexpected Boron Rearrangement Leads to a Fluorogenic and Colorimetric BODIPY Probe

The isolation and characterization of a kinetically stable oxadiazaborinine (ODB) dye are described, which undergoes an unexpected thermal boron rearrangement with a color change and increase in fluorescence. This controllable reaction allows for the use as a practical time‐temperature indicator probe with the advantages of photostability, non‐reversibility, and environmental friendliness. The novel oxadiazaborinin dye described here undergoes a temperature and solvent‐dependent, irreversible O‐ to N‐ rearrangement of the BF2 group or a cleavage of BF2 and acetyl groups, accompanied by a change in color and fluorescence. These changes can be used to quantify the integrated temperature fluctuations of cold‐chain logistics of perishable products.