Editing Ferrocene (section)

=== Redox chemistry ===
[[File:Biferrocene.svg|thumb|left|132px|The one-electron oxidized derivative of [[biferrocene]] has attracted much research attention.]]
Ferrocene undergoes a one-electron oxidation at around 0.4&nbsp;V versus a [[saturated calomel electrode]] (SCE), becoming '''ferrocenium'''.<ref name=federman/> This reversible oxidation has been used as standard in electrochemistry as Fc<sup>+</sup>/Fc&nbsp;= 0.64&nbsp;V versus the [[standard hydrogen electrode]],<ref>{{cite journal | vauthors = Cardona CM, Li W, Kaifer AE, Stockdale D, Bazan GC | title = Electrochemical considerations for determining absolute frontier orbital energy levels of conjugated polymers for solar cell applications | journal = Advanced Materials | volume = 23 | issue = 20 | pages = 2367–2371 | date = May 2011 | pmid = 21462372 | doi = 10.1002/adma.201004554 | bibcode = 2011AdM....23.2367C | s2cid = 40766788 }}</ref> however other values have been reported.<ref>{{citation|surname1=Vitaly V Pavlishchuk, Anthony W Addison|periodical=Inorganica Chimica Acta|title=Conversion constants for redox potentials measured versus different reference electrodes in acetonitrile solutions at 25°C|volume=298|issue=1|at=pp.&nbsp;97–102|date=January 2000 |language=German |doi=10.1016/S0020-1693(99)00407-7|url=https://linkinghub.elsevier.com/retrieve/pii/S0020169399004077|access-date=2022-07-26
}}</ref><ref>{{cite journal | vauthors = Mygind JB, Deissler NH, Li S, Fu X, Kibsgaard J, Chorkendorff I | title = Hydrogen Oxidation Beyond Water: In Search of Proton Mediation Pathways | journal = ACS Electrochemistry | volume = X | issue = X | pages = X-X | date = 1 March 2025 | publisher = American Chemical Society | doi = 10.1021/acselectrochem.5c00009 | url = https://doi.org/10.1021/acselectrochem.5c00009 }}</ref> [[Ferrocenium tetrafluoroborate]] is a common reagent.<ref>{{cite journal | vauthors = Connelly NG, Geiger WE | title = Chemical Redox Agents for Organometallic Chemistry | journal = Chemical Reviews | volume = 96 | issue = 2 | pages = 877–910 | date = March 1996 | pmid = 11848774 | doi = 10.1021/cr940053x }}</ref> The remarkably reversible oxidation-reduction behaviour has been extensively used to control electron-transfer processes in electrochemical<ref>{{cite journal | vauthors = Sirbu D, Turta C, Gibson EA, Benniston AC | title = The ferrocene effect: enhanced electrocatalytic hydrogen production using meso-tetraferrocenyl porphyrin palladium(II) and copper(II) complexes | journal = Dalton Transactions | volume = 44 | issue = 33 | pages = 14646–14655 | date = September 2015 | pmid = 26213204 | doi = 10.1039/C5DT02191J | url = https://eprint.ncl.ac.uk/fulltext.aspx?url=214473/2DD72927-25BC-4809-8636-5FDB014D7CB0.pdf&pub_id=214473 }}</ref><ref>{{cite journal | vauthors = Lennox AJ, Nutting JE, Stahl SS | title = Selective electrochemical generation of benzylic radicals enabled by ferrocene-based electron-transfer mediators | journal = Chemical Science | volume = 9 | issue = 2 | pages = 356–361 | date = January 2018 | pmid = 29732109 | pmc = 5909123 | doi = 10.1039/C7SC04032F | doi-access = free }}</ref> and photochemical<ref>{{Cite journal| vauthors = Dannenberg JJ, Richards JH |date=1965-04-01|title=Photosensitization by Ferrocene. Photochemistry of Higher Electronic Excited States|journal=Journal of the American Chemical Society|volume=87|issue=7|pages=1626–1627|doi=10.1021/ja01085a048|issn=0002-7863}}</ref><ref>{{Cite journal| vauthors = Sirbu D, Turta C, Benniston AC, Abou-Chahine F, Lemmetyinen H, Tkachenko NV, Wood C, Gibson E | display-authors = 6 |date=2014-05-23|title=Synthesis and properties of a meso- tris–ferrocene appended zinc(II) porphyrin and a critical evaluation of its dye sensitised solar cell (DSSC) performance |journal=RSC Advances|language=en|volume=4|issue=43|pages=22733–22742|doi=10.1039/C4RA03105A|bibcode=2014RSCAd...422733S |issn=2046-2069| url = https://eprint.ncl.ac.uk/fulltext.aspx?url=199647/CED25CA5-111E-4500-8188-DCFC5D4D7190.pdf&pub_id=199647}}</ref> systems. 

Substituents on the cyclopentadienyl ligands alters the redox potential in the expected way: electron-withdrawing groups such as a [[carboxylic acid]] shift the potential in the [[anodic]] direction (''i.e.'' made more positive), whereas electron-releasing groups such as [[methyl]] groups shift the potential in the [[Cathode|cathodic]] direction (more negative). Thus, [[decamethylferrocene]] is much more easily oxidised than ferrocene and can even be oxidised to the corresponding dication.<ref>{{cite journal | vauthors = Malischewski M, Adelhardt M, Sutter J, Meyer K, Seppelt K | title = Isolation and structural and electronic characterization of salts of the decamethylferrocene dication | journal = Science | volume = 353 | issue = 6300 | pages = 678–682 | date = August 2016 | pmid = 27516596 | doi = 10.1126/science.aaf6362 | s2cid = 43385610 | bibcode = 2016Sci...353..678M }}</ref> Ferrocene is often used as an [[internal standard]] for calibrating redox potentials in non-aqueous [[electrochemistry]].