Spirolactam ring locking and unlocking tuned solvent regulated unique Hg(II) sensing by a novel AIE active Rhodamine −1, 2 diamino propane-based Schiff chemosensor and its pH sensor performance

Abstract

The present study highlights the development, identification, and solvent-regulated chemosensing property of a Schiff base chemosensor (E)-2-(2-((5-chloro-2-hydroxybenzylidene)amino)propyl)-3′,6′-bis(diethylamino)spiro[isoindoline-1,9′-xanthen]-3-one (RBAS). The Schiff base RBAS is developed by the simple condensation of 5-chloro salicylaldehyde and rhodamine-1,2 diamino propane derivative (RBAP). Interestingly this probe can optically as well as fluorometrically exhibit pH sensor activity and the spirolactam ring opening and the conversion from enol to keto form in lower and higher pH regions respectively are the main key factors to show pH sensor activity. Several spectroscopic, Dynamic Light Scattering (DLS), and scanning electron microscopy (SEM) studies confirm the AIE active property of the probe in 2:8 DMSO-water and ethanol-water mediums where the probe exhibits strong luminescence properties. Interestingly in ethanol-water and DMSO-water medium, it can detect Hg(II) via turn-on and off fluorescence respectively. Actually, in different solvent mediums, the presence of Hg(II) plays a crucial role in the spirolactam ring opening and closing of the developed probe. Simultaneously in an ethanol-water medium, it can detect picric acid by turning off fluorescence. By using mass and NMR spectrum analysis, the 1:1 stoichiometric addition of the probe and target analytes has been verified and the density functional theory (DFT) study is implemented in optimizing the probe-analyte structure. The live cell imaging study gives the approval of the biosensing ability of the probe. Impressively the probe can be successfully used to detect Hg(II) in real soil samples.