Iron porphyrins bonding

Hemozoin, also known as malaria pigment, is, in teims of its chemical composition, identical to (3-hematin. Hemozoin is formed as a crystallization product of heme under the acidic conditions present in the food vacuole of malarial parasites. In the crystal, the heme molecules are linked into dimers through reciprocal iron-carboxylate bonds to one of the propionate side chains of each porphyrin. The dimers form chains linked by hydrogen bonds. 

Only a handful of rr-bonded iron porphyrin complexes have been structurally characterized, listed in Table HI, and four of these contain porphycene. corrolc. or phthalocyanine ligands rather than porphyrins. " "" Selected data arc given in Table III, and X-ray crystal structures of methyl- and phenyliron porphyrin complexes are shown in Fig. 4. All of the iron(III) porphyrin complexes exhibit... 

Iron porphyrins (containing TPP, picket fence porphyrin, or a basket handle porphyrin) catalyzed the electrochemical reduction of CO2 to CO at the Fe(I)/Fe(0) wave in DMF, although the catalyst was destroyed after a few cycles. Addition of a Lewis acid, for example Mg , dramatically improved the rate, the production of CO, and the stability of the catalyst. The mechanism was proposed to proceed by reaction of the reduced iron porphyrin Fe(Por)] with COi to form a carbene-type intermediate [Fe(Por)=C(0 )2, in which the presence of the Lewis acid facilitates C—O bond breaking. " The addition of a Bronsted acid (CF3CH2OH, n-PrOH or 2-pyrrolidone) also results in improved catalyst efficiency and lifetime, with turnover numbers up to. 750 per hour observed. ... 

Professor Mahy received his Ph.D. in 1990 from the University of Paris 6 on a bioinorganic subject dealing with the importance of the complexes with an Fe—N bond in the chemistry of iron-porphyrin and hemoproteins. 

In the case of heme-containing systems, it is believed that the activation barrier for 0-0 bond cleavage can be lowei by the complexation of the resulting oxygen atom by the iron porphyrin center, i.e. ... 

The triazole group binds perpendicularly to the heme group and gauche to the iron-nitrogen bonds in the porphyrin plane. 

Interactions and reactions of iron porphyrins with dioxygen species,with nitric oxide (see Section 5.4.3.8), with nitrite and with nitrate, and also of complexes containing carbon-bonded ligands, have continued to attract considerable interest and be reviewed. 

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