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

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.