Porphyrins models

Holmstead RL (1976) Studies of the degradation of mirex with an iron (II) porphyrin model system. J Agric Food Chem 24 620-624. 

We shall return to the discussion of the orientation and electronic structure of the dioxygen ligand during the next section which is primarily concerned with recent advances in the synthesis and physical characterization (particularly X-ray analysis) of oxygencarrying metal porphyrin model compounds. 

Two strategies for preparation of neutral and monocationic porphyrin models were used. The presence of a spacer arm directly attached to the meso phenyl position of the porphyrins gave access to a series of dimers with different substituents on the meso position and with different geometries. 

Table 3.4 lists values for A Eq and for some important oxidation and spin states found in bioinorganic molecules. Data are taken from reference 24 and from Table 1 of reference 25 for hemoglobin, myoglobin, and the picket-fence porphyrin model compound, FeTpivPP(l-Melm).25 The myoglobin and hemoglobin model compounds are discussed in Section 4.8.2. Reference 26 provides the Table 3.4 data on iron sulfur clusters found in many bioinorganic species.26 The unusual iron-sulfur and iron-molybdenum-sulfur clusters found in the enzyme nitrogenase are discussed more fully below and in Chapter 6. 

Figure 4.18 Picket-fence porphyrin models. (A) Model for T-state. (B) Model for R-state. (Adapted with permission from Figure 5 of Collman, J. P. Inorg. Chem., 1997, 36, 5145-5154. Copyright 1997, American Chemical Society.)...

Simonneaux G, Le Maux P (2006) Carbene Complexes of Heme Proteins and Iron Porphyrin Models. 17 83-122... 

These minimalistic peptide scaffolds potentially provide a biologically relevant laboratory in which to explore the details of heme-peptide interactions and, with development, perhaps approach the observed range of natural heme protein fimction. These heme-peptide systems are more complex than typical small molecule bioinorganic porphyrin model compoimds, and yet are seemingly not as enigmatic as even the smallest natural heme proteins. Thus, in the continuum of heme protein model complexes these heme-peptide systems lie closer to, but certainly not at, the small molecule limit which allows for the effects of single amino acid changes to be directly elucidated. 

Unraveling the individual molecular interactions in these very complex photosystems is a challenging focus of current research, particularly since the demand for alternative energy sources has become critical in the past few years. Progress in this area is hampered, however, due to the extreme complexity of the natural systems coupled with the fact that the synthesis of biomimetic porphyrin models is quite challenging. Experimental... 

III. Iron-Porphyrin Model Compounds A. Fe(III) Hemin Compounds... 

Collman, J. P., Gagne, R. R., Halbert, T. R., Marchon, J. C., Reed, C. A., Reversible oxygen adduct formation in ferrous complexes derived from a picket fence porphyrin - model for oxymyoglobin. J. Am. Chem. Soc. 1973, 95, 7868-7870. 

Collman JP et al (1973) Reversible oxygen adduct formation in ferrous complexes derived from a picket fence porphyrin - model for oxymyoglobin. J Am Chem Soc 95 7868-7870... 

Reoxidation of Fe(II) Porphyrins. Model systems for the activation of molecular oxygen via coordination to an Fe(II) porphyrin have not been reported because of the rapid irreversible autooxidation of the Fe(II) to the Fe(III) oxo-bridged dimer (C) (Reaction 16). Since the... 

Porphyrins, model systems for studying structural relations ... 

---