Novel 2‐Arylbenzothiazoles: Selective Chromogenic and Fluorescent Probes for the Detection of Picric Acid

Abstract

AbstractA series of 2‐arylbenzothiazoles has been designed and synthesized as chromogenic and fluorescent probes for the detection of picric acid (PA) over other nitro analytes. A straightforward condensation of a variety of aryl nitriles with 2‐aminobenzenethiol under metal‐ and base‐free conditions afforded the corresponding products in 26–98% yields. All 2‐arylbenzothiazoles could efficiently sense PA at micromolar levels. The highly sensitive compound 2‐(4‐((2‐methyl‐1H‐imidazol‐1‐yl)methyl)phenyl)benzo[d]thiazole (3c) showed 95% fluorescence quenching on addition of 1.0 eq of PA which can be attributed to hydrogen bonding and ground state charge transfer complex formation with a detection limit of 19.0 μM. The high sensitivity of 3 c for PA detection was also established by test strips experiment. The sensing mechanism was explored by 1H NMR titrations and Job's plot.