Octaethylporphyrin
{{Chembox
| ImageFile = H2octaethylporphyrin.png
| ImageSize =
| ImageAlt =
| IUPACName = 2,3,7,8,12,13,17,18-Octaethylporphyrin
| OtherNames = 2,3,7,8,12,13,17,18-Octaethyl-21H,23H-porphine
|Section1={{Chembox Identifiers
| CASNo = 2683-82-1
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = PD85YF7CEP
| EINECS = 220-243-8
| ChemSpiderID = 10445887
| SMILES = CCC1=C(C2=CC3=NC(=CC4=C(C(=C(N4)C=C5C(=C(C(=N5)C=C1N2)CC)CC)CC)CC)C(=C3CC)CC)CC
| StdInChI = 1S/C36H46N4/c1-9-21-22(10-2)30-18-32-25(13-5)26(14-6)34(39-32)20-36-28(16-8)27(15-7)35(40-36)19-33-24(12-4)23(11-3)31(38-33)17-29(21)37-30/h17-20,37,40H,9-16H2,1-8H3/b29-17-,30-18-,31-17-,32-18-,33-19-,34-20-,35-19-,36-20-
| StdInChIKey = HCIIFBHDBOCSAF-MUZKIALCSA-N
| ChEBI = 52183
| PubChem = 102311
| DTXSID = DTXSID2062589
| Beilstein = 379798
}}
|Section2={{Chembox Properties
| C=36|H=46|N=4
| MolarMass =
| Appearance = purple solid
| Density =
| MeltingPt =
| BoilingPt =
| Solubility = }}
|Section3={{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt = }}
}}
Octaethylporphyrin (H2OEP) is an organic compound that is a relative of naturally occurring heme pigments. The compound is used in the preparation of models for the prosthetic group in heme proteins. It is a dark purple solid that is soluble in organic solvents. As its conjugate base OEP2-, it forms a range of transition metal porphyrin complexes. When treated with ferric chloride in hot acetic acid solution, it gives the square pyramidal complex Fe(OEP)Cl.{{cite journal |author1=Chang, C. K. |author2=DiNello, R. K. |author3 =Dolphin, D.| journal = Inorg. Synth. | title = Iron Porphines | year = 1980 | volume = 20 | pages = 147 | doi = 10.1002/9780470132517.ch35}} It also forms the square planar complexes Ni(OEP) and Cu(OEP).
Contrast with other porphyrins
Unlike complexes of the naturally occurring porphyrins, OEP complexes have four-fold symmetry, which simplifies spectroscopic analysis. In contrast to tetraphenylporphyrin and related analogues, H2OEP features unprotected meso positions. In this way, it is a more accurate model for naturally occurring porphyrins.
Synthesis
H2OEP is prepared by condensation of 3,4-diethylpyrrole with formaldehyde. The pyrrole precursor may be synthesised by a Barton-Zard reaction of ethyl isocyanoacetate and 3-nitro-3-hexene; the latter can be generated in situ by elimination of acetic acid from 4-acetoxy-3-nitrohexane. Both the elimination and cyclicization reactions require an equivalent of a non-nucleophilic base such as diazabicycloundecene.{{cite journal|title=3,4-Diethylpyrrole and 2,3,7,8,12,13,17,18-Octaethylporphyrin|first1=Jonathan L.|last1=Sessler|first2=Azadeh|last2=Mozaffari|first3=Martin R.|last3=Johnson|journal=
Org. Synth.|year=1992|volume=70|page=68|doi=10.15227/orgsyn.070.0068}}