A new compound,O-ethyl S-hydrogen N-isoquinolin-1-yl carbonothioimidate(OESIQY) was synthesized,the photophysical behavior in ethanol and water mixed solution at different pH values was studied by fluorescence spectroscopy.It was observed that OESIQY emitted strong fluorescence in its zwitterions.It was also found that by the protonation of nitrogen atoms of OESIQY the intramolecular photoinduced electron transfer(PET) took place in the solution. This PET process depended on the acidity of the solution.
