Metallo-porphyrin

Work related to heme proteins is described under Biological NMR. Most of the studies reported in this section relate to Fe(III) porphyrins and are organized according to spin state. 

---

It is not surprising then that the first reported surface mediated reaction made use of vicinal dihalides. In addition to poly-p-nitrostyrene immobilized metallo-porphyrins and viologens were found to be catalytically active. Recently,... 

Much effort has also been directed toward mimicking electron transfer on natural photosynthetic systems. Recently, the group of Harada has been able to prepare monoclonal antibodies against metallo porphyrins and show that the biological edifice can control photoinduced electron transfer from the porphyrin to organic acceptor molecules in solution. As it was important to design a biomolecule able to accommodate not only the metalloporphyrin unit but also organic substrates, Harada recently used a hexacoordinated phosphorus... 

N. Diab, J. Oni, A. Schulte, I. Radtke, A. Blochl, and W. Schuhmann, Pyrrole functionalised metallo-porphyrins as electrocatalysts for the oxidation of nitric oxide. Talanta 61, 43-51 (2003). 

Another study by Neta and coworkers169, on the redox chemistry of several metallo-porphyrins in aqueous solution where metals were Zn, Pd, Ag, Cd, Cu, Sn and Pb, shows them to have well defined oxidation and reduction steps, yet the metals seem to exert merely an inductive effect on the porphyrin tt level. 

Among the main goals of electrochemical research are the design, characterization and understanding of electrocatalytic systems, (1-2) both in solution and on electrode surfaces. (3.) Of particular importance are the nature and structure of reactive intermediates involved in the electrocatalytic reactions.(A) The nature of an electrocatalytic system can be quite varied and can include activation of the electrode surface by specific pretreatments (5-9) to generate active sites, deposition or adsorption of metallic adlayers (10-111 or transition metal complexes. (12-161 In addition the electrode can act as a simple electron shuttle to an active species in solution such as a metallo-porphyrin or phthalocyanine. 

Dozens of electrochemical and spectroelectrochemical papers on transition metal and main group metal-carbon a-bonded metallo-porphyrins were published between 1984 and 1987 and a summary of these results are well covered in three recent reviews(1-3). Therefore, a characterization of chemically synthesized metal-carbon porphyrins will not be discussed in this paper. 

Coordination of small organic molecules by porphyrin complexes gives rise to either five- or six-coordinate ligand—metallo-porphyrin complexes (Eqs. (1) and (2)) ... 

Chelation with metal ions dramatically affects the reactivity of the porphyrin macrocycle, and this can be used to advantage in many cases. For example, for efficient electrophilic substitution of the ring, metals can be chosen (vide infra) which effectively release electron density to the organic porphyrin ligand, while reductions are best carried out on metallo-porphyrins in which the metal tends to deplete the porphyrin ligand of its electron density by way of back-bonding. 

Figure 6B.7. Basic structures of metallo-porphyrin and -salen complexes,...

Fig. 6. 38 Metallo-porphyrin dendrimers (according to Moore, Suslick et al.)...

Metals (particularly vanadium and nickel) are found in most crude oils. Heavy oils and residua contain relatively high proportions of metals either in the form of salts or as organometallic constituents (such as the metallo-porphyrins), which are extremely difficult to remove from the feedstock. Indeed, the nature of the process by which residua are produced virtually dictates that all the metals in the original crude oil are concentrated in the residuum (Speight, 1999). Those... 

Charvatova, J., Kasicka, V., Barth, T., Deyl, Z., Mikski, I., and Krai V. (2003) Separation of Structurally Related Peptides by Open-tubular Capillary Electrochromatography Using (Metallo) Porphyrins as the Adsorbed Stationary Phase, J. Chromatogr. A 1009, 73-80. 

Metal-catalyzed silylene extrusion from hexamethylsilirane 20 was also used to generate transition metal silylenoids [equation (7.2)] 47 In the presence of a metallo-porphyrin, [Os(TTP)]2 (where TTP = the dianion of meso-tetra-p-tolylporphyrin), hexamethylsilirane 20 extruded dimethylsilylene to produce the THF-stabilized osmium silylenoid complex 21. Despite the coordinated THF molecule, crystallographic analysis of the silylosmium complex 21 revealed the sp2 nature of the silicon atom (Os-C-Si bond angles 121° and 117°). Osmium silylenoid 21 was also synthesized from the reaction of [Os(TPP)]2- and dimethyldichlorosilane.47... 

Oxygenation potential of zeolite encapsulated metallo-porphyrins. 216... 

The flexible ligand method, consisting of the tetramerization of pyrrole and an aldehyde, can be used for the entrapment of metallo-porphyrins (MePOR) in situ in the supercages of faujasite-type zeolites (Scheme 10.7).[74]... 

---