Selective recognition of Zn(II) by a novel Schiff base chemosensor with the formation of an AIE active Zn(II) complex having picric acid detection ability: Application in live cell imaging study

The present work highlights the development and spectroscopic identification of a Schiff base chemosensor, (Z)-4-bromo-2-(((1-methoxybutan-2-yl)imino)methyl)phenol, (HL), for selective detection Zn(II) via turn-on fluorescence among a number of competing cations in a 9:1 DMSO-water media. The high binding constant value, measured during titration of HL and Zn(II), boosts to conduct a straightforward condensation reaction between HL and Zn(II) which results in solid crystals of Zn(II) complex (complex 1). In 7:3 DMSO-water media, complex 1 display Aggregation Induced Emission (AIE) behavior, as a result of which, with increasing the water percentage, under UV light optically the cyan color complex 1 solution converts to green color with the enhancement of fluorescence intensity. The UV, fluorescence, DLS, and SEM studies, fully approve the probe's AIE active behavior. The AIE active property of complex 1 is implemented to detect picric via turn-off fluorescence. The chelation-induced enhanced fluorescence (CHEF) on and Excited state internal proton transfer (ESIPT) off are the key factors in showing the luminescence property of complex 1 and the distortion of aggregation behavior of complex 1 in the presence of picric acid leads to the turn-off fluorescence of the complex 1 solution. The mass spectral and IR spectral analysis supports the 1:1 stoichiometric addition of the probe and analyte and the structure of the probe-analyte complexes is optimized using density Functional Theory (DFT) study. Finally, the live cell imaging study enables us to independently verify the biosensing behavior of complex 1 and HL towards Zn(II) and picric acid respectively.