Two colorimetric fluorescent turn-on chemosensors for detection of Al3+ and N3 - : Synthesis, photophysical and computational studies

Abstract

Two new rhodamine derivative L₁ and L₂ bearing 2-methoxy-1-naphthaldehyde and 5-bromo-3-methoxy salicylaldehyde units were designed and synthesized using microwave-assisted organic synthesis and utilized towards sequential fluorescence detection of aluminum ion (Al³⁺ ) and azide (N₃ ^- ) in aqueous acetonitrile solution. Aluminum ion (Al³⁺ ) triggers the formation of highly fluorescent ring-open spirolactam. The fluorescence and colorimetric response of the L₁ -Al³⁺ and L₂ -Al³⁺ complexes were quenched by the addition of N₃ ^- , which extracting the Al³⁺ from the complexes and turn-off the sensors, confirming that the recognition process is reversible. The recognition ability of the sensors was investigated by fluorescence titration, Job's plot, ¹ H-NMR spectroscopy and density functional theory (DFT) calculations.

Keywords: Al3+ and N3−; colorimetric; fluorescence; rhodamine.