Novel Benzothiazole-Based Highly Selective Ratiometric Fluorescent Turn-On Sensors for Zn and Colorimetric Chemosensors for Zn, Cu, and Ni Ions.

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 Zn, Cu, and Ni. The sensing studies of showed a ratiometric as well as colorimetric response toward Zn, Cu, and Ni ions and color changes from colorless to yellow and is found to be insensitive toward various metal ions (Cd, Cr, Mn, Pb, Ba, Al, Ca, Fe, Fe, Mg, K, and Na). Further, exhibited ratiometric as well as -enhanced fluorescence response toward Zn ions and response for Cu and Ni ions. The Job plots revealed that the binding stoichiometry of and metal ions is 2:1. The detection limits were found to be 0.25 ppm for Zn, while it was 0.30 ppm and 0.34 ppm for Ni and Cu, respectively. In addition, density functional theory results strongly support the colorimetric response of metals, and the reversibility studies suggested that can be used as a powerful chemosensor for the detection of Zn, Cu, and Ni ions. The bioimaging data illustrated that is a very effective ratiometric sensor for Zn ions in live cells.