A BODIPY derivative as a highly selective "Off-On" fluorescent chemosensor for hydrogen sulfate anion.

A new fluorescent receptor for 1 anions has been synthesized by the combination of BODIPY dye and indole moiety. The binding and sensing abilities of receptor 1 toward various anions have been studied by absorption, emission and (1)H NMR titrations spectroscopies. Receptor 1 could act as a highly selective "Off-On" fluorescent sensor for hydrogen sulfate anion in CH(3)CN solvent and CH(3)CN-H(2)O medium. The fluorescence response of receptor 1 toward HSO(4)(-) in CH(3)CN solvent could be due to the suppressed PET (photo-induced electron transfer) process induced by the multiple hydrogen bonding interactions between receptor 1 and HSO(4)(-). In CH(3)CN-H(2)O medium, the HSO(4)(-)-induced change is mainly the consequence of a simple protonation of the CH=N- moiety of receptor 1, which inhibited the PET process and "turned on" the fluorescence of 1.