Two colorimetric fluorescent turn‐on chemosensors for detection of Al 3+ and N 3 − : Synthesis, photophysical and computational studies

Two new rhodamine derivative L 1 and L 2 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 (Al 3+ ) and azide (N 3 − ) in aqueous acetonitrile solution. Aluminum ion (Al 3+ ) triggers the formation of highly fluorescent ring‐open spirolactam. The fluorescence and colorimetric response of the L 1 ‐Al 3+ and L 2 ‐Al 3+ complexes were quenched by the addition of N 3 − , which extracting the Al 3+ 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.