Iron(III) citrate

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Iron(III) citrate
Fe2CITdianion.svg
One of several ferric citrate complexes [1]
Names
IUPAC name
iron(3+) 2-hydroxypropane-1,2,3-tricarboxylate
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.020.488 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/C6H8O7.Fe/c7-3(8)1-6(13,5(11)12)2-4(9)10;/h13H,1-2H2,(H,7,8)(H,9,10)(H,11,12);/q;+3/p-3
    Key: NPFOYSMITVOQOS-UHFFFAOYSA-K
  • C(C(=O)[O-])C(CC(=O)[O-])(C(=O)[O-])O.[Fe+3]
Properties
C6H5FeO7
Molar mass 244.944 g·mol−1
Appearancedark orange-red brown solid [2]
~5 g/L in water
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Ferric citrate or iron(III) citrate describes any of several complexes formed upon binding any of the several conjugate bases derived from citric acid with ferric ions. Most of these complexes are orange or red-brown. They contain two or more Fe(III) centers. [3]

Contents

Ferric citrates contribute to the metabolism of iron by some organisms. Citrates, which are released by plant roots and by some microorganisms, can solubilize iron compounds in the soil. For example ferric hydroxide reacts with citrates to give form soluble complexes. This solubilization provides a pathway for the absorption of the ferric ions by various organisms. [4]

Ferric citrate is used in medicine to regulate the blood levels of iron in patients with chronic kidney disease on dialysis. It acts by forming an insoluble compound with phosphate present in the diet and thus minimizing its uptake by the digestive system. [5]

Structure

Citrate forms a variety of coordination complexes with ferric ions. [6] [1] Some might be oligomers, and polymers. Thus, ferric citrate is not a single well-defined compound, but a family of compounds, many with similar formulas. These various forms can coexist in equilibrium. [7] At physiological pH, ferric citrate forms an insoluble red polymer. In other conditions, it forms anionic complexes like [FeC
6
H
4
O
7
]2(H
2
O
)2]2−. In the present of excess citrate anions, the iron forms negatively charged complexes like [Fe(C
6
H
4
O
7
)2]5− and [Fe
9
O
(C
6
H
4
O
7
)8(H
2
O
)3]7−. [3] [4]

Photoreduction

The Fe3+
ion in ferric citrate (as in many iron(III) carboxylates) is reduced by exposure to light, [8] especially blue and ultraviolet, to Fe2+
(ferrous) ion with concomitant oxidation of the carboxyl group adjacent to the hydroxyl, yielding carbon dioxide and acetonedicarboxylate:

2Fe3+
+ R2-C(OH)-CO
2
→ 2Fe2+
+ R2-C=O + H+
+ CO
2

where -R represents the group -CH
2
CO
2
. This reaction plays an important role in plant metabolism: iron is carried up from the roots as ferric citrate dissolved in the sap, [9] and photoreduced in the leaves to iron(II) that can be transported into the cells.

Additional reading

Abrahamson, Harmon B.; Rezvani, Ahmad B.; Brushmiller, J.George (1994). "Photochemical and Spectroscopic Studies of Complexes, of Iron(III) with Citric Acid and Other Carboxylic Acids". Inorganica Chimica Acta. 226 (1–2): 117–127. doi:10.1016/0020-1693(94)04077-X.

See also

Related Research Articles

<span class="mw-page-title-main">Citric acid</span> Weak organic acid

Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms.

<span class="mw-page-title-main">Ferric</span> The element iron in its +3 oxidation state

In chemistry, Ferric refers to the element iron in its +3 oxidation state. Ferric chloride is an alternative name for iron(III) chloride (FeCl3). The adjective ferrous is used instead for iron(II) salts, containing the cation Fe2+. The word ferric is derived from the Latin word ferrum, meaning "iron".

<span class="mw-page-title-main">Ferrous</span> The element iron in its +2 oxidation state

In chemistry, iron(II) refers to the element iron in its +2 oxidation state. The adjective ferrous or the prefix ferro- is often used to specify such compounds, as in ferrous chloride for iron(II) chloride (FeCl2). The adjective ferric is used instead for iron(III) salts, containing the cation Fe3+. The word ferrous is derived from the Latin word ferrum, meaning "iron".

In chemistry, a reducing agent is a chemical species that "donates" an electron to an electron recipient.

Iron(III) chloride describes the inorganic compounds with the formula FeCl3(H2O)x. Also called ferric chloride, these compounds are some of the most important and commonplace compounds of iron. They are available both in anhydrous and in hydrated forms which are both hygroscopic. They feature iron in its +3 oxidation state. The anhydrous derivative is a Lewis acid, while all forms are mild oxidizing agents. It is used as a water cleaner and as an etchant for metals.

<span class="mw-page-title-main">Cobalt(II) chloride</span> Chemical compound

Cobalt(II) chloride is an inorganic compound, a salt of cobalt and chlorine, with the formula CoCl
2
. The compound forms several hydrates CoCl
2
·nH
2
O
, for n = 1, 2, 6, and 9. Claims of the formation of tri- and tetrahydrates have not been confirmed. The anhydrous form is a blue crystalline solid; the dihydrate is purple and the hexahydrate is pink. Commercial samples are usually the hexahydrate, which is one of the most commonly used cobalt salts in the lab.

<span class="mw-page-title-main">Iron(III) oxide-hydroxide</span> Hydrous ferric oxide (HFO)

Iron(III) oxide-hydroxide or ferric oxyhydroxide is the chemical compound of iron, oxygen, and hydrogen with formula FeO(OH).

<span class="mw-page-title-main">Ammonium ferric citrate</span> Chemical compound

Ammonium ferric citrate has the formula [NH+4]5[Fe(C6H4O7)2]5−. The iron in this compound is trivalent. All three carboxyl groups and the central hydroxyl group of citric acid are deprotonated. A distinguishing feature of this compound is that it is very soluble in water, in contrast to ferric citrate which is not very soluble.

<span class="mw-page-title-main">Iron(III) nitrate</span> Chemical compound

Iron(III) nitrate, or ferric nitrate, is the name used for a series of inorganic compounds with the formula Fe(NO3)3.(H2O)n. Most common is the nonahydrate Fe(NO3)3.(H2O)9. The hydrates are all pale colored, water-soluble paramagnetic salts.

Iron shows the characteristic chemical properties of the transition metals, namely the ability to form variable oxidation states differing by steps of one and a very large coordination and organometallic chemistry: indeed, it was the discovery of an iron compound, ferrocene, that revolutionalized the latter field in the 1950s. Iron is sometimes considered as a prototype for the entire block of transition metals, due to its abundance and the immense role it has played in the technological progress of humanity. Its 26 electrons are arranged in the configuration [Ar]3d64s2, of which the 3d and 4s electrons are relatively close in energy, and thus it can lose a variable number of electrons and there is no clear point where further ionization becomes unprofitable.

<span class="mw-page-title-main">Oxygen compounds</span> Different oxidation states of Oxygen

The oxidation state of oxygen is −2 in almost all known compounds of oxygen. The oxidation state −1 is found in a few compounds such as peroxides. Compounds containing oxygen in other oxidation states are very uncommon: −12 (superoxides), −13 (ozonides), 0, +12 (dioxygenyl), +1, and +2.

<span class="mw-page-title-main">Iron(II) citrate</span> Chemical compound

Ferrous citrate, also known as iron(II) citrate or iron(2+) citrate, describes coordination complexes containing citrate anions with Fe2+ formed in aqueous solution. Although a number of complexes are possible (or even likely), only one complex has been crystallized. That complex is the coordination polymer with the formula [Fe(H2O)6]2+{[Fe(C6H5O7)(H2O)]}2.2H2O, where C6H5O73- is HOC(CH2CO2)2(CO2, i.e., the triple conjugate base of citric acid wherein the three carboxylic acid groups are ionized. Ferrous citrates are all paramagnetic, reflecting the weak crystal field of the carboxylate ligands.

<span class="mw-page-title-main">Stephen J. Lippard</span> American chemist

Stephen James Lippard is the Arthur Amos Noyes Emeritus Professor of Chemistry at the Massachusetts Institute of Technology. He is considered one of the founders of bioinorganic chemistry, studying the interactions of nonliving substances such as metals with biological systems. He is also considered a founder of metalloneurochemistry, the study of metal ions and their effects in the brain and nervous system. He has done pioneering work in understanding protein structure and synthesis, the enzymatic functions of methane monooxygenase (MMO), and the mechanisms of cisplatin anticancer drugs. His work has applications for the treatment of cancer, for bioremediation of the environment, and for the development of synthetic methanol-based fuels.

<span class="mw-page-title-main">Ferric EDTA</span> Chemical compound

Ferric EDTA is the coordination complex formed from ferric ions and EDTA. EDTA has a high affinity for ferric ions. It gives yellowish aqueous solutions.

Cobalt(III) chloride or cobaltic chloride is an unstable and elusive compound of cobalt and chlorine with formula CoCl
3
. In this compound, the cobalt atoms have a formal charge of +3.

<span class="mw-page-title-main">Hydromelonic acid</span> Chemical compound

Hydromelonic acid, is an elusive chemical compound with formula C
9
H
3
N
13
or (HNCN)
3
(C
6
N
7
)
, whose molecule would consist of a heptazine H3(C
6
N
7
)
molecule, with three cyanamido groups H–N=C=N– or N≡C–NH– substituted for the hydrogen atoms.

<span class="mw-page-title-main">Iron(II) nitrate</span> Chemical compound

Iron(II) nitrate is the nitrate salt of iron(II). It is commonly encountered as the green hexahydrate, Fe(NO3)2·6H2O, which is a metal aquo complex, however it is not commercially available unlike iron(III) nitrate due to its instability to air. The salt is soluble in water serves as a ready source of ferrous ions.

<span class="mw-page-title-main">Transition metal oxalate complex</span>

Transition metal oxalate complexes are coordination complexes with oxalate (C2O42−) ligands. Some are useful commercially, but the topic has attracted regular scholarly scrutiny. Oxalate (C2O42-) is a kind of dicarboxylate ligand. As a small, symmetrical dinegative ion, oxalate commonly forms five-membered MO2C2 chelate rings. Mixed ligand complexes are known, e.g., [Co(C2O4)(NH3)4]κ+.

<span class="mw-page-title-main">Aluminium citrate</span> Chemical compound

Aluminium citrate is a chemical compound with the chemical formula AlC
6
H
5
O
7
. This white, crystalline salt is produced by mixing aluminium chloride hexahydrate and citric acid.

Cobalt compounds are chemical compounds formed by cobalt with other elements.

References

  1. 1 2 Shweky, Itzhak; Bino, Avi; Goldberg, David P.; Lippard, Stephen J. (1994). "Syntheses, Structures, and Magnetic Properties of Two Dinuclear Iron(III) Citrate Complexes". Inorganic Chemistry. 33 (23): 5161–5162. doi:10.1021/ic00101a001.
  2. Sigma-Aldrich: Product Specification - Iron(III) citrate, technical grade. Accessed on 2017-03-09.
  3. 1 2 Bino, Avi; Shweky, Itzhak; Cohen, Shmuel; Bauminger, Erika R.; Lippard, Stephen J. (1998). "A Novel Nonairon(III) Citrate Complex: A "Ferric Triple-Decker"". Inorganic Chemistry. 37 (20): 5168–5172. doi:10.1021/ic9715658.
  4. 1 2 Pierre, J. L.; Gautier-Luneau, I. (2000). "Iron and Citric Acid: A Fuzzy Chemistry of Ubiquitous Biological Relevance". Biometals. 13 (1): 91–96. doi:10.1023/A:1009225701332. PMID   10831230. S2CID   2301450.
  5. Lewis, Julia B.; Sika, Mohammed; Koury, Mark J.; Chuang, Peale; Schulman, Gerald; Smith, Mark T.; Whittier, Frederick C.; Linfert, Douglas R.; Galphin, Claude M.; Athreya, Balaji P.; Nossuli, A. Kaldun Kaldun; Chang, Ingrid J.; Blumenthal, Samuel S.; Manley, John; Zeig, Steven; Kant, Kotagal S.; Olivero, Juan Jose; Greene, Tom; Dwyer, Jamie P.; Collaborative Study Group (2015). "Ferric Citrate Controls Phosphorus and Delivers Iron in Patients on Dialysis". Journal of the American Society of Nephrology. 26 (2): 493–503. doi:10.1681/ASN.2014020212. PMC   4310662 . PMID   25060056.
  6. Xiang Hao, Yongge Wei, Shiwei Zhang (2001): "Synthesis, crystal structure and magnetic property of a binuclear iron(III) citrate complex". Transition Metal Chemistry, volume 26, issue 4, pages 384–387. doi : 10.1023/A:1011055306645
  7. Silva, Andre M. N.; Kong, Xiaole; Parkin, Mark C.; Cammack, Richard; Hider, Robert C. (2009). "Iron(III) citrate speciation in aqueous solution". Dalton Transactions (40): 8616–25. doi:10.1039/B910970F. PMID   19809738.
  8. Wu Feng and Deng Nansheng (2000): "Photochemistry of hydrolytic iron (III) species and photoinduced degradation of organic compounds: A minireview". Chemosphere, volume 41, issue 8, pages 1137–1147. doi : 10.1016/S0045-6535(00)00024-2
  9. Rellán-Álvarez, Rubén; Giner-Martínez-Sierra, Justo; Orduna, Jesús; Orera, Irene; Rodríguez-Castrillón, José Ángel; García-Alonso, José Ignacio; Abadía, Javier; Álvarez-Fernández, Ana (2010). "Identification of a Tri-Iron(III), Tri-Citrate Complex in the Xylem Sap of Iron-Deficient Tomato Resupplied with Iron: New Insights into Plant Iron Long-Distance Transport". Plant and Cell Physiology. 51 (1): 91–102. doi: 10.1093/pcp/pcp170 . PMID   19942594.