Selective interaction of N,N-bis(aminobenzyl)naphthalenediimides with fluoride anion

In this work, the optical properties of N,N-bis(aminobenzyl)naphthalenediimides 2a–2d (BzNDIs) and their interaction with fluoride were studied. The results demonstrated that the amino group position in the benzyl substituent exerts an effect in the absorption and emission properties. Particularly, the N,N-bis(2-aminobenzyl)NDI 2b presented non-typical absorption and emission bands which indicate an intramolecular charge transfer from the amino phenyl group to the NDI core. As the concentration of 2b increases, the solution turns from colourless to a pale orange colour. The interaction of BzNDIs 2a–2d with anions was selective towards fluoride and the affinity was in the order para > ortho > meta with respect to the position of the amino group in the aminophenyl ring. Interestingly, the colour change in the solution of 2b upon addition of fluoride makes it a good candidate for a fluoride colorimetric detection. The voltammetry analysis indicates the ability of these molecules to accept two electrons, in consequence the interaction of two fluoride anions with the BzNDIs was observed.