New fluorescent chemosensor for wide-range pH detection

ORGN 592

Go Nishimura, Yasuhiro Shiraishi, shiraish@cheng.es.osaka-u.ac.jp, and Takayuki Hirai. Research Center for Solar Energy Chemistry, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, 560-8531, Japan
Design of fluorescent molecules behaving as pH sensor is an intense research activity. A large number of pH sensors have been proposed; however, most of them are applicable to detection in limited pH range. Here we report that a family of polyamines bearing anthracene (AN) and benzophenone (BP) moieties at the respective ends behaves as a fluorescent pH sensor applicable to wide-range pH detection. The pH–fluorescence intensity profile of these molecules demonstrates a “gentle slope” over pH 2–10 range. This function involves two consecutive intramolecular processes: i) an electron transfer from photoexcited AN to BP promoted via a pH-induced bending of polyamine and ii) an electron transfer from nitrogen atom to photoexcited AN promoted via a pH-induced deprotonation of polyamine.