A pyridine dicarboxylate based hydrazone Schiff base for reversible colorimetric recognition of Ni 2+ and PPi.

A pyridine dicarboxylate Schiff-base DAS was synthesized for cascade colorimetric recognition of Ni 2+ and PPi. The selectivity and sensitivity of chemosensor DAS was investigated through colorimetric and UV-vis studies in MeOH-PBS (5 : 1, v/v, pH = 7.4). The chemosensor formed a 2 : 1 complex with Ni 2+ metal ions with a binding constant of K a = 3.07 × 10 3 M -2 . Besides, a plausible sensing mechanism is confirmed by single crystal X-ray diffraction (SC-XRD), Job's plot and Benesi-Hildebrand plot (B-H plot) experiments. Furthermore, the DAS-Ni 2+ ensemble formed ' in situ ' was used to selectively recognise PPi. The limit of detection (LOD) of DAS for Ni 2+ was found to be 0.14 μM and that of the DAS-Ni 2+ ensemble for PPi was found to be 0.33 μM. Also, the potential of the chemosensor has been applied for solid state detection of Ni 2+ as well as to mimic the 'INHIBIT' logic gate on the addition of Ni 2+ ions and PPi.