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

Abstract

Abstract 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 (Δλ ∼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.