Versatile optical response of pyridylalkyl naphthalenediimides in the interaction with metal ions

Abstract In this work, the interaction of three different pyridylalkyl mono-core substituted naphthalenedimides (NDIs) with metal ions was studied by UV-Vis and fluorescence spectroscopy. The influence of pyridine substituents position, the spacer length, and solvent over the metal ion recognition was investigated. The most sensible responses observed were with Cu2+ and Fe3+ ions, showing a remarkable change in their colorimetric and fluorescent properties. The prior formation of NDI-Cu2+ (2a and 2b) complexes generates a unique response towards Fe2+ and Mg2+, promoting an OFF/ON response and a colorimetric change Fe2+, acting as a dual probe for Cu2+ and Fe2+ or Cu2+ and Mg2+. Finally, NDIs 2b and 2c show a specific and selective response towards Hg2+ions in water, forming a solid complex removing the Hg2+ from the aqueous media achieving a removal efficiency up to 92%. NDIs 2b and 2c have potential as probes and removal of Hg2+ ions.