Novel Benzothiazole-Based Highly Selective Ratiometric Fluorescent Turn-On Sensors for Zn2+and Colorimetric Chemosensors for Zn2+, Cu2+, and Ni2+Ions

Abstract

Metal ions play a very important role in environmental as well as biological fields. The detection of specific metal ions at a minute level caught much attention, and hence, several probes are available in the literature. Even though benzothiazole-based molecules have a special place in the medicinal field, only very few chemosensors are reported based on this moiety. The current work describes the design and synthesis of the benzothiazole-based chemosensor for a highly selective and sensitive detection of biologically important metal ions such as Zn2+, Cu2+, and Ni2+. The sensing studies ofcompound-1showed a ratiometric as well as colorimetric response toward Zn2+, Cu2+, and Ni2+ions and color changes from colorless to yellow and is found to be insensitive toward various metal ions (Cd2+, Cr3+, Mn2+, Pb2+, Ba2+, Al3+, Ca2+, Fe2+, Fe3+, Mg2+, K+, and Na+). Further,compound-1exhibited ratiometric as well asturn-on-enhanced fluorescence response toward Zn2+ions andturn offresponse for Cu2+and Ni2+ions. The Job plots revealed that the binding stoichiometry ofcompound-1and metal ions is 2:1. The detection limits were found to be 0.25 ppm for Zn2+, while it was 0.30 ppm and 0.34 ppm for Ni2+and Cu2+, respectively. In addition, density functional theory results strongly support the colorimetric response of metals, and the reversibility studies suggested thatcompound-1can be used as a powerful chemosensor for the detection of Zn2+, Cu2+, and Ni2+ions. The bioimaging data illustrated thatcompound-1is a very effective ratiometric sensor for Zn2+ions in live cells.