Iron complexes with porphyrin

Porphyrins 21 are the backbone of major players in life cycles—cytochromes (Scheme 8). There are three types of cytochromes, classified by their color, or more precisely by their long-wavelength absorption band, as a (600 mn), b (563 nm), and c (550 nm). They are protein conjugates of a porphyrin complex with iron(II), which is a coenzyme called heme (22). In plants, porphyrins form a complex with magnesium-(II) chlorophylls a and b (23), vital in photosynthesis. Porphyrin derivatives are used in photodynamic therapy for dermatological diseases such as psoriasis, and for skin or subcutaneous cancer.5c-e... 

Aryl platinum(II) dendrimers, characteristics, 12, 491-492 Aryl porphyrin complexes, with iron, 6, 107 Arylpyridines, arylations, 10, 229 2-Arylpyridines, intramolecular C-H functionalizations,... 

Another iron porphyrin complex with 5,10,15,20-tetrakis(2, 6 -dichloro-3 -sulfonatophenyl)porphyrin was applied in ionic liquids and oxidized veratryl alcohol (3,4-dimethoxybenzyl alcohol) with hydrogen peroxide in yields up to 83% to the aldehyde as the major product [145]. In addition, TEMPO was incorporated via... 

High-valent iron also occurs in -nitrido bridged dimers with linear [Fe °-N=Fe" ]" and [Fe =N=Fe ] " cores [209, 210] (and references therein). Such compounds have been prepared first by thermolysis [247] or photolysis [248] of iron(III)-porphyrin complexes with an azide ligand, (N3). Mixed-valent iron-nitrido porphyrin dimers exhibit valence delocalization as can be inferred from the... 

The bis-hydroxylamine adduct [Fe (tpp)(NH20H)2] is stable at low temperatures, but decomposes to [Fe(tpp)(NO)] at room temperature. [Fe(porphyrin)(NO)] complexes can undergo one-and two-electron reduction the nature of the one-electron reduction product has been established by visible and resonance Raman spectroscopy. Reduction of [Fe(porphyrin)(NO)] complexes in the presence of phenols provides model systems for nitrite reductase conversion of coordinated nitrosyl to ammonia (assimilatory nitrite reduction), while further relevant information is available from the chemistry of [Fe (porphyrin)(N03)]. Iron porphyrin complexes with up to eight nitro substituents have been prepared and shown to catalyze oxidation of hydrocarbons by hydrogen peroxide and the hydroxylation of alkoxybenzenes. ... 

This review is intended to give an overview of the recent progress in the area of the formation of metalloporphyrins (the mechanism of the direct metalation reaction) and their reactions with small molecules (CO, NO, H20, 02). Although the emphasis is on less studied examples, a selection of recent results on iron (II) porphyrin complexes with CO and NO is also included. 

A close-up view of the iron-porphyrin complex with the F helix in deoxyhemoglobin. Note that the iron atom is displaced slightly above the plane of the porphyrin. (Illustration copyright by Irving Geis. Reprinted by permission.)... 

Reaction of free-base porphyrin compounds with iron(II) salts in an appropriate solvent results in loss of the two N—H protons and insertion of iron into the tetradentate porphyrin dianion ligand. Five-coordinate iron(III) porphyrin complexes (hemins), which usually have the anion of the iron(II) salt for the fifth or axial ligand, are isolated if the reaction is carried out in the presence of air. Iron(II) porphyrin complexes (hemes) can be isolated if the reaction and workup is conducted under rigorously anaerobic conditions. Typically, however, iron(II) complexes are obtained from iron(III) porphyrin complexes by reduction with dithionite, thiolate, borohydride, chromous ion, or other reducing agents. 

Nam, W., Goh, Y. M., Lee, Yoon J., Lim, M. H., and Kim,. (1999) Biomimetic alkane hydroxylations by an iron(III) porphyrin complex with H2O2 and by a high-valent iron(IV) oxo porphyrin cation radical complex, Inorg. Chem. 38, 3238-3240. 

D. Mansuy, New Iron-Porphyrin Complexes with Metal-Carbon Bond - Biological Implications, Pure Appl. Chem. 52, 681-690 (1980). 

Gunter and coworkers have synthesized a lateral macrobicyclic molecule 197 where a phorphyrin ring is capped by a bridging unit which contains a pyridino subunit. This model system for cytochrome c oxidase is in fact a heterodinuclear complex with iron(III) complexed to the porphyrin unit and copper(II) complexed to the lateral pyridino bridge. A series of these complexes have been made with... 

Iron porphyrin complexes with axial (7-alkyl and (7-aryl groups have been prepared and fully characterized by several groups (17,18). Addition of a chemical oxidant to (19, 20), or electrochemical oxidation of (21), the low-spin iron(III)-alkyl (-aryl) porphyrins results in transient formation of an iron(IV) (7-alkyl (a-aryl) complex that undergoes reductive elimination to give the iron(II) N-substituted product as shown in Scheme 2. The iron(IV) intermediate has been directly observed by low temperature lH NMR spectroscopy (22) and spectroelectrochemistry (21). 

The IV, V and VI oxidation states of iron are all known in oxyanions. However, relatively few well-characterized complexes with iron in an oxidation state higher than three are known. A review59 concerned with these oxidation states was published in 1974. Complexes containing iron(IV) are not large in number. This appears to be the highest oxidation state of iron in the catalases,60 and a considerable body of information has been collected on the strongly oxidizing iron(IV) porphyrins.61,62... 

Chevrier, B., R. Weiss, M.C. Lange, J.C. Chottard, and D. Mansuy (1981). An iron(lll)-porphyrin complex with a vinylidene group inserted into an iron-nitrogen bond Relevance of the structure of the active oxygen complex of catalase. J. Am. Chem. Soc. 103, 2899-2901. 

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