A Comprehensive Review on the Electrochemical and Computational Insights into Substituent Effects of Ferrocene Derivatives on Fe(III)/Fe(II) Redox Behavior for Energy Storage Applications

The Fe(III)/Fe(II) redox pair in ferrocene derivatives has long been recognized as a model system for understanding redox processes and as a promising platform for electrochemical energy storage applications. This review critically synthesizes experimental and computational studies that investigate substituent effects on the redox behavior of ferrocene derivatives, with particular emphasis on redox potential modulation, cyclic voltammetry (CV) characteristics, and structure–property relationships. The reviewed literature demonstrates that electron-donating and electron-withdrawing substituents induce systematic shifts in Fe(III)/Fe(II) redox potentials by altering the electronic structure of the ferrocene core. Strong linear correlations between redox potentials (E₁/₂) and Hammett substituent constants are consistently reported, highlighting the predictive value of substituent-based electronic descriptors. These experimental trends are further supported by Density Functional Theory (DFT) calculations, which reveal how substituent-induced changes in frontier molecular orbital energies govern redox thermodynamics and electron-transfer behavior. To extend the relevance of substituent-controlled redox tuning beyond ferrocene systems, related redox-active organic frameworks such as substituted s-tetrazines are also discussed. Literature reports show that substituent effects enable controlled adjustment of discharge voltages, heterogeneous electron-transfer rates (k₀), and Li-ion diffusivity (Dₗᵢ) in Li-ion cell electrodes. By linking molecular-level electronic modulation with electrochemical performance, this review provides a coherent framework for the rational design of efficient and tunable redox-active molecular materials, contributing to the advancement of next-generation energy storage technologies, with improved performance, resource efficiency, and long-term sustainability.

کلیدواژه ها:

Ferrocene derivatives ، Redox potential tuning ، Cyclic Voltammetry ، Substituent effects ، Li-ion cell electrode materials ، Sustainable energy storage materials