Highly sensitive naphthalimide based Schiff base for the fluorimetric detection of Fe.

A simple 1,8-naphthalimide based Schiff base probe ()-6-((4-(diethylamino)-2-hydroxybenzylidene)amino)-2-(2-morpholinoethyl)-1-benzo[de]isoquinoline-1,3(2)-dione (NDSM) has been designed and synthesized for the specific detection of Fe based on a fluorimetric mode. The absorbance of NDSM at 360 nm increased significantly in acetonitrile : water (7 : 3, v/v) medium only in the presence of Fe ions with a visible colour change from yellow to golden yellow. Likewise, fluorescence emission intensity at 531 nm was almost wholly quenched in the presence of Fe. However, other competitive ions influenced insignificantly or did not affect the optical properties of NDSM. Lysosome targetability was expected from NDSM due to the installation of a basic morpholine unit. The LOD was found to be 0.8 μM with a response time of seconds. The fluorescence reversibility of NDSM + Fe was established with complexing agent EDTA. Fe influences the optical properties of NDSM by complexing with it, which blocks C[double bond, length as m-dash]N isomerization in addition to the ICT mechanism. The real-time application of Fe was demonstrated in test paper-based detection, by the construction of a molecular logic gate, quantification of Fe in water samples and fluorescence imaging of Fe.