A photolabile H+-donor used in fluorescence imaging; releases acid when excited at 405 nm; has been used for fluorescence imaging, in conjunction with pH sensitive fluorescent probe cSNARF1, to study nuclear proton dynamics, acid venting from cancer cells, and hemoglobin-restricted diffusion in the cytoplasm of red blood cells; has been used as a precursor for [18F]fluoride displacement reactions in the synthesis of NCA 6-[18F]fluoro-L-dopa