A fluoran-based fluorescent probe via a strategy of blocking the intramolecular photoinduced electron transfer (PET) process

A novel fluoran-based fluorescent probe 2 has been designed and synthesized by using a strategy of blocking the intramolecular photoinduced electron transfer (PET) process. The probe keeps a ring-closed spirolactone structure in aqueous buffer solution. However, the oxidation of the probe by ClO^? perturbs a new equilibrium of the structural interconversion between the nonfluorescent spirolactone and the fluorescent ring-opened zwitterion, which generates a highly selective fluorescent probe for ClO^?. Meanwhile, the probe is cell membrane permeable and can be utilized as fluorescent probe for imaging ClO^? in living cells.