A mitochondrion-targeted fluorescent probe based on ESIPT phthalimide for the detection of Hg 2+ with large Stokes shift

A novel mitochondrion-targeted Hg 2+ -specific fluorescent probe 1 based on ESIPT phthalimide was designed and synthesized for the first time. Owing to the blockage of the ESIPT process between the hydroxy group and the carbonyl oxygen of the imide by the diphenylphosphinothioate group, 1 was almost nonfluorescent. After reacting with Hg 2+ , 1 exhibited a dramatic fluorescence enhancement due to the recovery of the ESIPT process through Hg 2+ -induced desulfurization-hydrolysis of the diphenylphosphinothioate moiety and the cleavage of the P–O bond. 1 showed a large Stokes shift, rapid response and high sensitivity and selectivity for Hg 2+ over other metal ions. Moreover, 1 was successfully employed to image Hg 2+ in the mitochondria of living cells.