Ferrocene as an iconic redox marker: From solution chemistry to molecular electronic devices

Ferrocene since its inception in the year 1951, has been extensively exploited as a crucial redox probe to unravel electrochemical charge-transfer dynamics in a variety of platforms ranging from solution-based systems and molecular thin-films to solid-state molecular electronics and spintronic devices. Having completed almost 71 years of its existence, ferrocene has now become one of the most widely studied organometallic compounds. Several experimental and theoretical frameworks are made to understand ferrocene's electronic and electrochemical properties. Ferrocene is an 18-electron metallocene that shows interesting metal-ligand coordination and has led to the preparation of a great number of impor-tant molecules. Ferrocene and its numerous derivatives have brought a breakthrough in metallocene chemistry. Ferrocene represents a chemically and thermally stable system that undergoes reversible elec-trochemical oxidation and reduction processes. Ferrocene-based self-assembled monolayers (SAMs) are considered as model system for performing on-surface redox reactions and have been applied to create nanoelectronic devices for molecular switching, rectification, and low-voltage operational memory devices. The present review discusses the recent progress made toward a ferrocene-containing molecular system that have been utilized in redox reactions, surface attachment, spin-dependent electrochemical processes to understand spin polarization, photo-electrochemistry, and molecular electronic devices. This review provides an excellent platform for understanding the electrochemical properties and the rational design of ferrocene-based molecular systems for optoelectronic applications.(c) 2022 Elsevier B.V. All rights reserved.