Ninhydrin and isatin appended 2-Hydrazinobenzothiazole based simple Schiff bases for colorimetric selective detection of Cr3+and Pb2+ions

A simple and easily synthesizable chromogenic small molecules probe L4(2-(2-(benzo[d]thiazol-2-yl)hydra-zono)-1H-indene-1,3(2H)-dione) and L5 (2-(2-(benzo[d]thiazol-2-yl)hydrazono)indolin-3-one) have been syn-thesized and characterized by various spectroscopy techniques such as FT-IR, NMR, and HRMS. The colorimetric naked eye detection of probe L4 showed a color change towards Cr3+ from orange color to pale yellow, whereas in case of L5 Pb2+ yellow to orange color was witnessed. The jobs plot analyses indicate the 1:1 binding stoi-chiometric for Cr3 thorn and 1:2 binding stoichiometric for Pb2+ ions with probes L4 and L5 respectively. The binding association constant (ka) values for L4 and L5 were found to be 6.651 x 10-5 M for Cr3+ and 6.493 x 10-5 M for Pb2 thorn ions. The limit of detection was found to be for Cr3+ (1.69 x 10-7 M) and Pb2+ (1.208 x 10- 7 M) are far below than the limit set by the World Health Organization (WHO) for drinking water. Finally, the designed probes were applied for visible colorimetric test kits and real samples for rapid detection of Cr3+ and Pb2+ for all practical purposes, indicating their potential use in environmental samples.

Automated summary

A simple and easily synthesizable chromogenic small molecules probe L4 and L5 were successfully synthesized and characterized. L4 and L5 showed colorimetric naked eye detection of Cr3+ and Pb2+ ions, with good binding properties and low detection limits. The designed probes were applied for rapid detection of Cr3+ and Pb2+ in environmental samples, indicating their potential use.