Iron deuteroporphyrin

Mansuy and coworkers [32] reported the first isolated metalloporphyrin-carbene complex in 1977 and it was an iron porphyrin carbene complex. It was suggested by the authors that iron carbene complexes could be involved in the metabohsm of xenobiotics. Thus, the five-coordinated (TPP)Fe(CCl2) was prepared as a purple red solid by treatment of (TPP)FeCl with CCI4 in the presence of an excess of iron powder (90% yield) [32]. It must be emphasized that the possible formation of carbene complexes after the reduction of iron deuteroporphyrin in CCI4 was initially proposed by Brault and coworkers [79]. An original method of reduction by aqueous sodium dithionite solution was described but, under these conditions, it was not possible to isolate any complex although the reaction leads to a compound of unusually good stability towards air. 

Experiments on the addition of hemin to the culture medium of chick embyro liver cells [25] showed that relatively low concentrations of hemin (2 x 10 M) decreased porphyrin synthesis by half. Iron deuteroporphyrin and manganese protoporphyrin were less inhibitory. 

The starting material for the synthesis was the iron compound of deuteroporphyrin in which c and d = H. By means of the Friedel-Crafts reaction (SnCl4 in place of A1C13), acetyl groups were introduced at c and d, the diketone formed was reduced to the glycol (haemato-porphyrin, c and d = CHOH.CHs), and the latter converted into protoporphyrin with elimination of water. 

Early workers appeared to show that electrophilic substitution reactions could not be carried out on porphyrins, and began to question the aromaticity of porphyrins since this classical pre-requisite of aromatic character could not be accomplished. However, they had concentrated on reactions of metal-free systems, and since many electrophilic substitution reactions utilize acidic conditions (nitration, sulfonation), they were actually dealing with the non-nucleophilic porphyrin dication. But, as early as 1929, H. Fischer had realised that diacetylation of deuteroporphyrin-IX (Table 1) had to be carried out on a metal complex, such as the iron (III) derivative chelation with a metal ion which cannot be removed under the acid conditions of the subsequent reaction, effectively eliminates dication formation. A judicious choice of metal complex therefore needs to be made for any particular reaction. For example, though magnesium(II) produces an extremely reactive substrate for electrophilic substitution reactions, it is removed by contact with the mildest of acids and is, consequently, of little use for this purpose. 

A more quantitative estimate of the pseudocontact shifts in DeutCN was obtained from comparison of the methylester resonances in DeutCN and deuteroporphyrin IX zinc(II) (114). Under identical conditions these resonances were both at —3.72 ppm from DSS in the diamagnetic complex, and at —3.78 and —3.82 ppm in DeutCN. The observed shift of ca. —0.08 ppm has to come almost entirely from pseudocontact coupling, since delocalization of unpaired spin density to these positions must be negligibly small, and a small change of the porphyrin ring current field, which might result from the zinc(II) vs. iron(III) substitution, would hardly be noticeable at the methylester positions either. With the assumption of an axially symmetrical g-tensor, and rj -values for the different protons of 10.0, 6.4, 5.7, and 4.5 A (Hoard (41)), one then estimates from the fj 3-dependence (Eq. 10) that the corresponding... 

Kurland et al. (64) observed hyperfine-shifted resonances of ferrimyoglobin between —20 and —90 ppm. Comparison with the spectra of the iron(III)-complexes with protoporphyrin IX, deuteroporphyrin IX, and mesoporphyrin IX seems to indicate that four of the low field resonances correspond to the four ring methyl groups. Additional lines at high fields from DSS were observed in ferrimyoglobin (116), and in high spin porphyrin-iron(III) complexes (Caughey et al. (19)). The observation... 

Table I. Spectroscopic Properties of Deuteroporphyrin IX Dimethyl Ester Iron (III) Compounds...

Figure 2. Absorption spectra for deuteroporphyrin IX dimethyl ester iron-fill) derivatives in chloroform ligands correspond to X of Figure I...

Figure 4. Proton magnetic resonance spectra at 100 MHz of azido (upper) and phenoxo (lower) derivatives of deuteroporphyrin IX dU methyl ester iron(III) in CDCI3 at 35°C...

Early studies of the catalytic decomposition of hydrogen peroxide have been performed with various iron(III) proto- and deuteroporphyrins, and also with metalloporphyrins soluble in organic solvents. The formation of the analogue of Cat-Cpd I has been well studied with nonaggregating iron(III) or manganese(III) sulfonated porphyrins. 

Several other research groups are actively contributing in this field of CcO model chemistry. Naruta et al. have reported tris(2-pyridylmethyl)amine Cu complex-linked iron meso-tetra-phenylporphyrin derivatives and well-characterized Fe—(O2)—Cu species that are similar to [( L)Fe -(0 )-Cu ]+ (Structure (7)). A CcO model developed by Casella and co-workers is a natural porphyrin derivative, in which a polybenziimidazole residue for the Cu coordination site is attached to the propionic acid side chain of the deuteroporphyrin. A new class of picket porphyrin, bearing covalently linked, axially placed tris(heterocycle) chelates for a copper ion, has been synthesized and characterized by Wilson and co-workers. ... 

Steady-state pulse radiolysis of methylene chloride solutions containing ferric deute-roporphyrin or the chemical reduction of ferric deuteroporphyrin solutions containing methyl iodide led to iron methyl o-bonded species which were spectrophotometrically characterized ... 

Iron(II) and iron(III) deuteroporphyrins react with methyl radicals with rate constants of 3.9 x 10 and 2.9 x s respectively, giving... 

Fe(III)-CH3- and Fe(IV)-CH3-containing species. The latter undergoes a methyl transfer reaction with iron(II) deuteroporphyrin to give the Fe(III)-CH3 compound with a second-order rate constant of 4 x s. An... 

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