Ferrocyanide is the name of the
anionFe(CN)64−. In aqueous solutions, this coordination complexis relatively unreactive. It is usually available as the potassium salt potassium ferrocyanide, which has the formula K4Fe(CN)6.
[Fe(CN)6] 4− is a diamagnetic species, featuring low-spin iron(II) center in an octahedral ligand environment. Although many salts of cyanide are highly toxic, ferro- and ferricyanides are less toxic because they tend not to release free cyanide.Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.] Its most important reaction is its oxidation to
ferricyanide:: [Fe(CN)6] 4− [Fe(CN)6] 3− + e−This conversion can be followed spectroscopically at 535 nm with an absorption coefficientof 21600 M−1 cm−1.
Treatment of ferrocyanide with ferric-containing compounds affords
Prussian Blue, an intensely blue compound that is widely used as a pigment.
Use in biochemistry
Ferrocyanide and its oxidized product ferricyanide, [Fe(CN)6] 3−, are impermeable to the
plasma membrane. For this reason ferrocyanide has been used as a probe of extracellular electron receptor in the study of redox reactions in cells. Ferricyanide is used thus any increase in ferrocyanide can be attributed to secretions of reductants or "Trans Plasma Membrane Electron Transport" (TPMET) activity. Potassium ferricyanideis often used as a mediator in the test strips used with blood glucose meters by people suffering from diabetes. It is used in this application because it is easily reduced to potassium ferrocyanide.
According to the recommendations of IUPAC, ferrocyanide should be called "hexacyanoferrate(II)."
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