Octaethylporphyrin (H₂OEP) is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

that is a relative of naturally occurring

heme Heme, or haem (pronounced / hi:m/ ), is a precursor to hemoglobin, which is necessary to bind oxygen in the bloodstream. Heme is biosynthesized in both the bone marrow and the liver. In biochemical terms, heme is a coordination complex "consis ...

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 OEP^2-, it forms a range of

transition metal porphyrin complexes 220px, A picket-fence porphyrin complex of Fe, with axial coordination sites occupied by methylimidazole (green) and dioxygen (R = amide groups). Transition metal porphyrin complexes are a family of coordination complexes of the conjugate base of ...

. When treated with

ferric chloride Iron(III) chloride is the inorganic compound with the formula . Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The col ...

in hot acetic acid solution, it gives the square pyramidal complex Fe(OEP)Cl. It also forms the square planar complexes Ni(OEP) and Cu(OEP). H2OEP in DCM

Contrast with other porphyrins

Unlike complexes of the naturally occurring

porphyrin Porphyrins ( ) are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). The parent of porphyrin is porphine, a rare chemical com ...

s, 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 Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section F ...

.{{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

References

Porphyrins