Hydroxo-iron porphyrin

DIOXYGEN REACTIVITY MODELS FOR CYTOCHROME C OXIDASE SYNTHESIS AND CHARACTERIZATION OF 0X0 AND HYDROXO-BRIDGED PORPHYRIN-IRON/COPPER DINUCLEAR COMPLEXES... 

Synthesis from Hydroxo-Iron(III) Porphyrin, [Cu(II)(TMPA)] +, and Base... 

The HNMR spectra of the diaqua and aqua (hydroxo) hemin complexes encapsulated in micelles have been reported [20] (Fig. 5). The heme methyl resonances in the diaqua species lie in the same region as those of the high-spin bis(dimethyl sulphoxide) iron (III) porphyrin complex [37-39], while those of the aqua (hydroxo) complex appear in a more upheld region. The positions and linewidths of the heme methyl resonances in these complexes are similar to those observed in the aqua and hydroxo hemoproteins [19,40]. The broadness of the ring methyl resonances of both the diaqua and aqua (hydroxo) species in micelles has been ascribed to arise from the hindered rotational tumbling motion of the heme inside the micelles. The spread and linewidth of these resonances are much larger than those of similar high-spin model heme complexes in simple solution [3]. 

The dithionite reduction of the micelle encapsulated aqua (hydroxo) ferric hemes at pH 10 (in inert atmosphere) gives an iron (II) porphyrin complex whose optical spectrum [21] shows two well-defined visible bands at 524 and 567 nm and a Soret band split into four bands (Fig. 10). Such spectral features are typical of four-coordinate iron (II) porphyrins. The magnetic moment (p = 3.8 + 0.2 Pb) of this sample in the micellar solution is also typical of intermediate spin iron(II) system and is similar to that reported for four-coordinate S = 1 iron(II) porphyrins and phthalocyanine [54-56]. The large orbital-contribution (ps.o. = 2.83 p for S = 1) observed in this iron(II) porphyrin... 

A characteristic feature is the formation of oxo and/or hydroxo bridges.42 Binu-clear systems may be (a) doubly bridged and (b) singly bridged with a linear or bent FeOFe. The bent ones are known with 4-, 5-, and 6-coordinate iron(III) an example is [(salen)Fe]2(/x-0). Porphyrin and phthalocyanine complexes are linear bridged species of the type (porph Fe)2/x-X where X = O, N, and C. 

Meunier, B. and J. Bernadou (2000). Active iron-0X0, and iron-peroxo species in cytochrome P450 and peroxidases oxo-hydroxo tautomerism with water-soluble porphyrins. In B. Meunier and Waldemar Adam (ed.). Metal-Oxo and Metal-Peroxo Species in Catalytic Oxidations, Vol. 97. Springer-Verlag, Berlin, pp. 1-35. 

---