A novel electrochemical and chromogenic guest-responsive anisidine-based chemosensor for transition metallic cations

• New anisidine-based chemosensors for the chelation of metallic cations.
• Important anodic shifts of the oxidation potentials induced by chelation.
• High selectivity to zinc(II) although high sensitivity to nickel(II).
• Chromogenic guest-responsive probes confirming the electrochemical studies.

A new family of N,N-disubstituted p-anisidine-based electroactive ligands bearing dipyridinylamino- (1), difuranylamino- (2) and dithiophenylamino- (3) binding sites has been prepared by reductive alkylation of anisidine. The electrochemical investigations, in 0.1 mol/dm−3 LiClO4 acetonitrile solution, showed that upon the addition of metallic cations, the redox features of 1 underwent drastic changes due to the cation chelation. The chemosensor complexation with Ni(II), Zn(II), Cd(II) and Pb(II) led to large anodic shifts of the oxidation potential peaks up to 700 mV depending on the metal cation. A particularly high sensitivity toward nickel(II) with a higher selectivity to zinc(II) were observed. However, in the same conditions, thiophenyl- and furfuranyl- derivatives showed no sensitivity for any of the investigated cations. Moreover, UV–visible spectroscopy studies of 1 showed that the compound can act as a chromogenic guest-responsive and in presence of metallic cations, the absorption bands of compound 1 shifted due to a participation of the nitrogen lone pairs in the cation complexation. UV–visible spectroscopy did also allow to distinguish between the Ni(II) and Zn(II) complexes. Electrochemical and UV–visible spectroscopic investigations showed that the complexes have 1:2 stoichiometry [M(1)2]2+ (M: Zn, Ni, Cd and Pb).

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