A Novel Rhodamine Functionalized Schiff Base Type Ratiometric Fluorescent Chemosensor for the Sensing of Hg²⁺ Ions;...

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 Hg²⁺ 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 Hg²⁺ among other competitive metal ions as the fluorescence intensity at 479 nm quenched only in the presence of Hg²⁺. This sensitivity towards Hg²⁺ was due to the chelation between ligand and Hg²⁺. From the fluorescence titration the binding constant and detection limit of SBRB1:Hg²⁺ complex were calculated and found to be 5.114 $\times$ 10⁶ M^-1 and 2.91 $\times$ 10^-5 M respectively. It showed The 1:1 complexation between SBRB1 and Hg²⁺ which was conformed from the DFT and TD-DFT study of SBRB1 in both solvent and gas phase.