Electrochemical and computational analysis of Fe(III)–adenine metallo-drug complex formation

Abstract

The electrochemical behavior of the Fe(III)–adenine system was systematically investigated using cyclic voltammetry (CV) to elucidate metal–ligand coordination, stoichiometry, and stability. Job’s continuous variation method revealed a maximum peak current at a normalized mole fraction of 2.5:7.5, confirming the formation of a stable 1:3 Fe(III)-adenine complex. This stoichiometry was independently validated by spectrophotometric analysis using Ardon’s method. Electrochemical measurements demonstrated that increasing Fe 3 ⁺ (1–6 mM) and adenine (1–6 mM) concentrations led to pronounced increases in anodic and cathodic peak currents, accompanied by positive shifts in peak potentials, indicating enhanced electron transfer and stronger complex formation. A lower peak current at 4 mM adenine further supports maximum stability at the 1:3 metal–ligand ratio. Scan-rate studies showed a linear relationship between peak current and the square root of scan rate, confirming a diffusion-controlled process with a calculated diffusion coefficient of 2.29 cm 2 s⁻ 1 . Step height, pH, and electrolyte studies revealed decreased current with increasing step height, preferential complex formation under acidic conditions (pH 1.5–5.5), and superior electrochemical performance in KCl electrolyte. The novelty of this work lies in the integrated, multi-parameter electrochemical profiling of Fe(III)–adenine complexation, providing comprehensive mechanistic insight relevant to biosensing and metal-based therapeutic research.