Metalloporphyrins functions

Rollman (4 3) synthesized a series of polymer-bonded metalloporphyrins. Functionalized tetraphenyIporphyrines were attached to porous polystyrene resins via amine, carbonyl and ester linkages and metal ions (Co,Ni,Cu,Zn) were then incorporated into the structures. The porphyrin polymers that contained both oxidation (Co) and proton-acceptor sites (amine and carboxylate groups) were effective catalysts for the oxidation of thiols to disulfides. When the catalyst was exposed to a refinery stream containing only 180 ppm mercaptan sulfur, deactivation occurred. Deactivation was thought to occur via oxidation of the porphyrins by free radicals known to be present in such catalytic systems. 

Beer, P. D., Gormode, D. P. and Davis, J. J., Zinc metalloporphyrin-functionalized nanoparticle anion sensors, Chem. Commun., 2004, 414-415. 

A behavior envisaging possible application in electroanalysis is found in Ref. [88] the shift of the potential exhibited by the redox system due to the Fe-porphyrin complex in a metalloporphyrin functionalized PTh is shown to depend on the concentration of 2,4,5-trichlorophenol in solution. Interactirai of the chlorinated phenol with the Fe centre is hypothesized to cause the modification of the electron... 

Functionalization can be used to alter the redox properties of the zinc metalloporphyrin the zinc heptanitroporphyrin shows facile reduction to the air-stable 7r-anion radical.768 Modification of the zinc porphyrin at the, 8 position with chlorine or bromine to induce saddling of the... 

Dendritic derivatives of these macrocycles can be placed in the wider context of studies on metalloporphyrins with sterically hindered faces which have been designed in attempts to mimic the properties of heme proteins and chlorophylls, and there are suggestions that steric isolation of the metalloporphyrin nucleus is important in certain biological functions, The redox properties of metalloporphyrins are well-documented they are dominated by two, reversible one-electron transfers involving both the metal and the ligand. The first dendritic porphyrins of general structure 47 and their Zn complexes were reported by Inoue et al. who... 

Various theoretical methods and approaches have been used to model properties and reactivities of metalloporphyrins. They range from the early use of qualitative molecular orbital diagrams (24,25), linear combination of atomic orbitals to yield molecular orbitals (LCAO-MO) calculations (26-30), molecular mechanics (31,32) and semi-empirical methods (33-35), and self-consistent field method (SCF) calculations (36-43) to the methods commonly used nowadays (molecular dynamic simulations (31,44,45), density functional theory (DFT) (35,46-49), Moller-Plesset perturbation theory ( ) (50-53), configuration interaction (Cl) (35,42,54-56), coupled cluster (CC) (57,58), and CASSCF/CASPT2 (59-63)). 

A large number of different types of DFT calculation have appeared over the years. Probably nearly all available DFT functionals have now been used to describe the properties and reactivity of metalloporphyrins, with the B3LYP (64,65) functional being the most popular choice. 

This chapter has reviewed certain experimental results and computational studies involving some of the metalloporphyrins (Fe(II)P, Co(II), and others). The present investigation also explored the accuracy of several DFT methods. The geometries of MP-XO complexes and XO binding energy were found to depend very strongly on the functional and basis set used. In many cases, model systems should be described at least with a triple- quality basis set. 

Oxidation Catalyzed by Metalloporphyrins. Much attention has been devoted to the metal-catalyzed oxidation of unactivated C—H bonds in the homogeneous phase. The aim of these studies is to elucidate the molecular mechanism of enzyme-catalyzed oxygen atom transfer reactions. Additionally, such studies may eventually allow the development of simple catalytic systems useful in functionalization of organic compounds, especially in the oxidation of hydrocarbons. These methods should display high efficiency and specificity under mild conditions characteristic of enzymatic oxidations. 

Other metalloporphyrins can also be found in Nature, though they do not seem to perform any vital physiological function. For example, the copper(II) complex of uroporphyrin-III (Table 1) occurs in high concentrations in the wing feathers of Turacus indicus, and is the source of most commercial samples of uroporphyrin-III. Chlorophyll degradation products, as the nickel and vanadium complexes, are found in oil shales and as a troublesome contaminant in crude petroleum oils. 

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