Synthesis and metal ion-sensing properties of fluorescent PET chemosensorsbased on the 2-phenylimidazo[5,4-a]anthraquinone chromophore

Novel fluorescent chemosensors in which an aza-crown is linked to a 2-pheny limidazoanthraquinone fluorophore by a methylene spacer have been synthesiz ed for the sensing of metal cations. A dramatic fluorescence enhancement at 515 nm was observed upon binding of the metal ions, which was interpreted in terms of the control of a photoinduced electron transfer (PET) process. This system can recognize the charge and the size of alkali and alkaline-ea rth metal cations and can transform its information sensitively and precise ly into the magnitude of the enhanced fluorescence.