redoxaktiva

Redoxaktiva, or redox-active compounds, are substances that can undergo oxidation-reduction (redox) reactions through reversible transfer of electrons, allowing their oxidation state to change. They function as electron donors or acceptors and are fundamental to many chemical and biological processes.

A defining feature of redox-active materials is their ability to participate in well-defined redox couples with measurable redox potentials. The kinetics of electron transfer, stability of the oxidized and reduced forms, solubility, and the environment (solvent, supporting electrolyte, pH) determine their suitability for a given application. Redox activity can be reversible or, in some cases, irreversible, depending on the stability of the intermediate states.

Redox-active compounds span a broad range of classes. Organic examples include quinones and hydroquinones, viologens, phenazines, and stable nitroxide radicals such as TEMPO. Inorganic and organometallic systems include ferrocene/ferrocenium, ruthenium or manganese bipyridyl complexes, metal oxides, and Prussian blue-type materials. Conductive polymers like polyaniline or polypyrrole also exhibit redox activity, changing color, conductivity, or magnetic properties with oxidation state.

Applications are widespread. In energy storage, redox-active species underpin redox-flow batteries and various battery chemistries. In electrochromic devices, redox transitions drive color change. They serve as mediators and sensors in electrochemistry and biosensing, and as catalysts in redox reactions, including electrocatalysis for oxygen reduction and evolution. In biology, redox-active centers such as iron-sulfur clusters, heme groups, and NAD+/NADH couples mediate electron transfer in metabolism and photosynthesis.

See also: redox potential, electrochemistry, redox couple.