Picket-fence porphyrin structure

Li J, Noll BC, Oliver AG, Schulz CE, Scheldt WR (2013) Correlated ligand dynamics in oxyiron picket fence porphyrins structural and Mossbauer investigations. J Am Chem Soc 135 15627-15641... 

Originally, this temperature variation of AEq was attributed to the dynamic distribution of the terminal oxygen of the Fe02-moiety, as suggested by X-ray structural results for picket-fence porphyrins [26,27]. This view is now supported by NFS studies which provide more information on dynamic processes in iron-containing molecules. 

These strategies have been successful and have led to the X-ray crystallographic structure of the oxygenated picket-fence porphyrin described in Section 4.7. 

From this point of view, some interesting metalloporphyrins have been produced by clever synthetic techniques. Collman etall0l) synthesized the Fe(II) complex of picket-fence porphyrin 42 to favor the five-coordinate structure and inhibit dimerization. Their porphyrin derivative had steric bulkiness on one side of... 

One of the representative models is the picket fence iron porphyrin reported by Coltman and his coworkers (Figure 4). The picket fence porphyrin as a structural model for myoglobin has four bulky pivaloyl groups at the peripheral positions to prevent two of these iron porphyrins from coming together to form a /u.-oxo dimer. The first significant result in their study was to demonstrate the 3D structure of the stable... 

Figure 8 Structure of a lipid bilayer vesicle including a steroid-linked picket-fence porphyrin [202], Reproduced from J. Org. Chem., 53, 3891 (1988) by permission of the American Chemical Society...

Figure 1. Structure of Fe(TpivPP)(L)(02), the oxygen adduct of the picket-fence porphyrin. Double bonds are deleted for clarity.

The mechanism of oxygen activation by P-450 has been extensively studied (7c, 5a, b) however, cmcial intermediates in the catalytic cycle are so unstable that it is not possible to examine their structures and reactivities. Accordingly, model systems for P-450 with synthetic metalloporphyrins have illuminated the enzymic reaction mechanism. For instance, the so-called picket fence porphyrin, /ncjo-tetra(a,a,a,a-pivalamidophenyl)porphyrin (TpivPP) Fe(II), prepared by Collman and co-workers, forms a stable complex with O2 6a, b). An X-ray... 

The structure of the picket-fence porphyrin compound, Fe(PF)(2-MeIm), is shown in Figure 4.28. Minus the pickets, it is essentially a magnified view of the active site of deoxy myoglobin, shown in Figure 4.29. Some metrical details of these structures, of a very similar unsubstituted tetraphenylpor-phyrin,"° and of several other deoxyhemoglobins are listed in Table... 

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