2-(2′-Hydroxyphenyl)-benzothiazole (HBT)-terpyridine conjugate: A highly specific ICT based fluorescent probe for Zn2+ ions and its application in confocal cell imaging

A new fluorescent sensor based on benzothiazole-terpyridine conjugate is reported. It functions as a fluorescent sensor that is highly selective for the Zn2+ ions via internal charge transfer (ICT) mechanism in DMSO: H2O medium. The 42 nm blue-shifted emission upon addition of Zn2+ to the sensor is attributed to the capture of Zn2+ by the terpyridine moiety that inhibits ICT from the terpyridine to the benzthiazole moiety. The sensing is supported by the Job's plot, ESI-MS, H-1 NMR titration experiments. Importantly, this probe shows high selectivity over other biologically relevant metal ions. Also, anions do not show any effect. In addition, the detection limit is found to be up to 35 nM which is acceptable within the EPA (US) limit. The probe is also able to function within a broad biological pH range of 6-8. (C) 2017 Published by Elsevier B.V.