Merocyanine-Benzothiazole Chromophore-based sensor for selective picric acid detection

Abstract

We report synthesis of (2E,4E)-2-(benzo[d]thiazol-2-yl)-4-(1,3,3-trim ethylindolin-2-ylidene) but-2-enenitrile (MC-BTH-1) chromophore and employed for picric acid sensing. MC-BTH-1 was prepared by Knoevenagel condensation of 2-(benzo[d]thiazol-2-yl) acetonitrile and (Z)-2-(1,3,3-trimethylindolin-2-ylidene)acetaldehyde in the presence of catalytic amount of piperidine in dry ethanol. The MC-BTH-1 conjugate displayed a remarkable sensing property towards picric acid in presence of interfering nitroaromatic compounds. The sensing of nitroaromatic compounds was investigated by means of UV-vis absorption, fluorescence and Sup(1) H NMR spectroscopic. Furthermore, colorimetric visualization of receptor MC-BTH-1 with the addition of various analytes under 365-nm UV light shows only color change from green to dark green for 2,4,6-trinitrophenol (TNP) and no significant color change was observed for other analytes. Under optimized condition the detection limit towards TNP and 2,4-dinitrophenol (DNP) are 1.58x10 sup(-9) M and 1.48x10 sup(-9) M, respectively. These results clearly show high sensitivity of system at low concentration with fluorescence quenching quantum efficiency approx. 88 percent.