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.