Exploiting the INHIBIT-ESIPT mechanism for the design of fluorescent chemosensor with a large blue-shift in emission

A set of two novel fluoroscent receptors 2a and 2b with sulfonamide binding site and 2-(2'-aminophenyl)benzothiazole scaffolding as a signaling unit have been synthesized by condensation approach, which can undergo excited-state intramolecular proton transfer (ESIPT) upon excitation. In CH3CN solution of 2a, this ESIPT phenomenon was perturbed and showed a remarkable hypsochromic shift (Delta lambda similar to 83 nm), by capturing of Zn2+ metal ion selectively out of other interfering metal ions including Na+, K+, Mg2+, Al3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Cd2+ and Hg2+. Similarly, the deprotonation of the sulfonamide proton of this acidic receptor 2a by basic anions such as F-, AcO-, and H2PO4- also resulted in a substantial blue shift due to disruption of ESIPT. This blue shift was accompanied by enhancement of emission intensity and fluorescent color change from dark blue to light blue. (C) 2016 Elsevier B.V. All rights reserved.