Abstract
Synthesis of a simple fluorescent naphthalimide based receptor 4-aminobenzyl-N-methyl-1,8naphthalimide 3 was carried out as a selective fluoride ion sensor. In acetonitrile, interaction of 3 with different anions such as, AcO – , F – , Cl – , Br – , I – , and SCN – revealed significant fluorescence quenching only with the F – anion. In the presence of the fluoride anion, the color of the solution changed from a fluorescent green to violet and this was visible to the naked eye. The probable mode of sensing mechanism by photo-induced electron transfer (PET) reaction is attributed to deprotonation of acidic NH proton in the presence of fluoride which was confirmed by change in optical properties intramolecular charge transfer (ICT) and 1 H NMR spectral data analysis. The Job’s plot analysis displayed a 1:1 stoichiometry for interaction between 3 and F – . The extent of fluorescence quenching was estimated by Stern-Volmer plot.
Highlights
The selective recognition and sensing of anions via a synthetic organic scaffolds as a sensitive fluorescent chemosensor, containing a suitable receptor site and fluorophore have received considerable attention of chemists in past decades.[1]
The ultimate negative charge develop on the receptor would modulate both UV-Vis and fluorescence spectra due to change in intramolecular charge transfer (ICT) and photoinduced electron transfer (PET) reactions (Figure 1)
The variation in charge transfer (CT) reaction upon interaction with F- may be attributed to deprotonation of acidic proton (N–H) present at C-4 position of naphthalimide unit or through hydrogen bonding interaction.[5]
Summary
The selective recognition and sensing of anions via a synthetic organic scaffolds as a sensitive fluorescent chemosensor, containing a suitable receptor site and fluorophore have received considerable attention of chemists in past decades.[1]. Upon addition of different anions (5 equiv) such as, AcO–, F–, I–, Cl–, Br– and SCN– (as their tetrabutylammonium salts) the characteristic absorption spectra modulated significantly only in the presence of F– and two new bands appeared at 530 and 340 nm respectively, attributed to the charge transfer reaction from receptor site to naphthalimide moiety.
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