Ferroin

Ferroin
Identifiers
CAS number	14634-91-4
PubChem	84567
ChemSpider	76289 Y
Jmol-3D images	Image 1
SMILES [Fe+2].[O-]S([O-])(=O)=O.n3c2c1ncccc1ccc2ccc3.n3c2c1ncccc1ccc2ccc3.n1c3c(ccc1)ccc2cccnc23
InChI InChI=1S/3C12H8N2.Fe.H2O4S/c3*1-3-9-5-6-10-4-2-8-14-12(10)11(9)13-7-1;;1-5(2,3)4/h3*1-8H;;(H2,1,2,3,4)/q;;;+2;/p-2 Y Key: CIWXFRVOSDNDJZ-UHFFFAOYSA-L Y InChI=1/3C12H8N2.Fe.H2O4S/c3*1-3-9-5-6-10-4-2-8-14-12(10)11(9)13-7-1;;1-5(2,3)4/h3*1-8H;;(H2,1,2,3,4)/q;;;+2;/p-2 Key: CIWXFRVOSDNDJZ-NUQVWONBAU
Properties
Molecular formula	C36H24FeN62+
Molar mass	596.27 g/mol
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Ferroin is the chemical compound with the formula [Fe(o-phen)₃]SO₄, where o-phen is an abbreviation for 1,10-phenanthroline, a bidentate ligand. The term "ferroin" is used loosely and includes salts of other anions such as chloride.

Redox indicator

Phenanthroline Fe(II) (Redox indicator)
E0= 1.06 V
Reduced	↔	Oxidized

This coordination compound is used as an indicator in analytical chemistry. The active ingredient is the [Fe(o-phen)₃]²⁺ ion, which is a chromophore that can be oxidized to the ferric derivative [Fe(o-phen)₃]³⁺. The potential for this redox change is +1.06 volts in 1M H₂SO₄.

Preparation

Ferroin sulfate may be prepared by combining phenanthroline to ferrous sulfate in water.

3 phen + Fe²⁺ → [Fe(phen)₃]²⁺

The iron is low spin and octahedral with D₃ symmetry. The intense color of this ferrous complex arises from a metal-to-ligand charge-transfer transition.