A bis-terpyridine-based trimetallic Co/Fe/Ni metallo-supramolecular polymer for electrochemical detection of 4-nitrophenol: kinetic and mechanistic insights.

A bis-terpyridine-based trimetallic Co/Fe/Ni metallo-supramolecular polymer (polyCoFeNi) was synthesized by one-pot coordination of Co, Fe, and Ni precursors with 4',4‴-(1,4-phenylene)bis(2,2':6',2″-terpyridine) and investigated as an electrode modifier for electrochemical determination of 4-nitrophenol (4-NP). UV-vis spectroscopy, FTIR, FESEM, EDS, XPS, and viscosity measurements supported formation of a Co/Fe/Ni-containing coordination material with a rough, sponge-like morphology and metal-nitrogen coordination environments. Because the one-pot synthesis and available spectroscopic data do not establish an ordered Co-Fe-Ni sequence or unique mixed-valence states, the structural interpretation is kept conservative. The polyCoFeNi-modified glassy carbon electrode showed higher O1/R 2 responses than the bare electrode and the investigated monometallic analogues. Cyclic voltammetry revealed an initial irreversible reduction followed by a reversible oxidation/reduction couple, while scan-rate analysis indicated mixed diffusion-adsorption control. Under optimized conditions, a linear response was obtained over 2-2000 µM with limits of detection of 0.28 and 0.65 µM for the anodic and cathodic processes, respectively. The modified electrode also showed good reproducibility, operational stability, selectivity, and satisfactory performance in spiked water samples. These results demonstrate the potential of Co/Fe/Ni-containing bis-terpyridine metallo-supramolecular materials as electrochemical interfaces for 4-NP sensing.