Inverse Redox Induction of Cobalt(II) Iron(II) Redox Couple: An Evaluation of N,N‐ Bidentate Ligand‐Modulated Redox Potentials for Redoximetric Expansion

Differential stabilization of metal ion oxidation states in a redox couple by coordinated ligands provides a rational strategy for tuning redox potentials. N,N ‐bidentate set of chelating ligands was selected to evaluate sigma donation, pi back‐acceptance and preorganizational factor on redox modulation of iron(II), cobalt(II) redox couples. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) investigations provided complementary mechanistic insight into ligand‐dependent effects. CV experiments revealed a shift in the Fe ³⁺ /Fe ²⁺ reduction potential toward more positive values and that of Co ³⁺ /Co ²⁺ potential toward more negative values. This opposing trend corroborates stabilization of the t _2g ⁶ configuration of octahedral d ⁶ iron(II) and cobalt(III). EIS demonstrated that ligand character influences interfacial electron transfer, with stronger π‐acceptor complexes exhibiting higher heterogeneous electron‐transfer rate constants k ⁰ , and lower charge‐transfer resistance ( R _ct ). The observed inverse redox induction of N,N ‐bidentate ligand field has been developed as an analytical method for simultaneous estimation of iron and cobalt binary mixture. CV and differential pulse voltammetry provided distinct and well‐resolved responses enabling reliable simultaneous binary metal ion quantification with selectivity, sensitivity and limits of detection. The findings demonstrated ligand‐modulated redox behavior can enhance electrochemical resolution and broaden the scope of redoximetric analysis for the simultaneous determination of closely related metal ions.