A Novel Rhodamine Functionalized Schiff Base Type Ratiometric Fluorescent Chemosensor for the Sensing of Hg 2+ Ions; Experimental and Theoretical Approach.

A new Rhodamine functionalised Schiff Base sensor 3',6'-bis(diethylamino)-2-((4-hydroxybenzylidene)amino)spiro[isoindoline-1,9'-xanthen]-3-one (SBRB1) was designed and synthesized. The recognition ability of sensor SBRB1 towards Hg ²⁺ was studied by using UV-Vis and fluorescence spectroscopy. The fluorescence results showed that the sensor SBRB1 has specific selectivity as well as sensitivity towards Hg ²⁺ among other competitive metal ions as the fluorescence intensity at 479 nm quenched only in the presence of Hg ²⁺ . This sensitivity towards Hg ²⁺ was due to the chelation between ligand and Hg ²⁺ . From the fluorescence titration the binding constant and detection limit of SBRB1:Hg ²⁺ complex were calculated and found to be 5.114 × 10 ⁶ M ^-1 and 2.91 × 10 ^-5 M respectively. It showed The 1:1 complexation between SBRB1 and Hg ²⁺ which was conformed from the DFT and TD-DFT study of SBRB1 in both solvent and gas phase.
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