Porphyrin complexes applications

Although photochemically induced cleavage of Al—C bonds in the aluminum porphyrin complexes has been exploited in several applications, relatively little is known about the intimate mechanism of this process. Similar reactivity is observed for the organo-gallium and indium porphyrins, and for these elements... 

Porphyrin complexes, however, are prone to oxidative decomposition and therefore synthetic applications are hampered by rapid catalyst deactivation. This problem can be overcome by attaching electron-withdrawing groups to the periphery of the porphyrin system. Another problem is the poor chemoselectivity. In many cases, addition to the C=C double bond and formation of the epoxide are much faster than the corresponding hydrogen abstraction, which leads to the allylic alcohols. This is... 

A decade ago, almost every metal had been inserted into a porphyrin, i.e., the periodic table of metalloporphyrins was nearly completed [8, 29], A review article devoted to the porphyrin complexes of individual metals gave examples for metal insertions according to following reactions (1) to (8) [8] for abbreviations see Table 1. Recent applications and improvements are noted below the respective equations. 

Other SOD mimics that show promise for medical applications include porphyrin complexes such as Mn 5,10,15,20-te/rafe(Ar-methylpyridinium-4-yl) porphyrin (MnniTMPyP5+) 19 [48] and its octabromo derivative 20 (Figure 7) [49],... 

It has been suggested [95] that the synthesis of structured porphyrins with controllable steric ambience is a strategic direction in the reproduction of enzyme protein cavities, which control the selectivity and stability of biochemical reactions such as cytochrome P-450. Such an approach to the synthesis of biomimics has considerable potential, especially in their application on mineral matrices silicon dioxide, alumina and zeolites. Data exist on the synthesis of a biomimic [96] with a complex porphyrin complex (5-pentafluorophenyl-10,15,20-tri(2,6-dichlorophenyl)porphyrin (FeMPFDCPP)) covalently linked to aminopropyl silicon dioxide, which is applied in oxidation of ds-cyclooctene, cyclohexene, cyclohexane and adamantane with participation of iodosylbenzene dissolved in dichloromethane. 

Apart from potential industrial applications, homogeneous catalytic systems with metal-oxo intermediates have direct relevance to certain biological oxidation reactions. The biological reactions involve metalloenzymes such as Cyt P450, which has an iron-porphyrin complex in its active site. The enzyme catalyzes hydroxylation of a hydrocarbon by oxygen. This hydroxylation does not proceed through a radical-chain mechanism. There is sufficient evidence to indicate that a catalytic intermediate with an Fe=0 group is responsible for the hydroxylation reaction. 

Porphyrin derivatives, synthesis and application of 88YGK681. Porphyrin complexes, oxygenation of hydrocarbons with 89ZC88. Porphyrin molecular complexes, photonics of triplet states of 88-UK1087. 

A significant step to the combination of our knowledge about the static structure in liquids and their kinetic behavior has recently been made by application of an in-laboratory stopped flow EXAFS experiment [32]. This is an EXAFS spectrometer operated in the dispersive mode and a stopped-flow unit positioned along the x-ray path. Since results of very short time measurements can be accumulated in this way, with the appropriate selection of the system structural studies of reaction intermediates can be determined, which has not been possible before. Results are reported [33] on a partial structural change around the Cu(II) ion of a reaction intermediate at the formation of a Cu(II) porphyrin complex in the metal substitution reaction of the Hg(II) porhyrin complex with the Cu( o ion in an aqueous acetate buffer solution. The measurements showed that the Cu-N distance in the reaction intermediate are elongated by about 0.04A in comparison with the final product. 

When Nd or Yb complexes of a similar macrocycle are covalently linked to a palladium porphyrin complex, this sensitizes near-IR emission from the lanthanide, enhanced in the absence of oxygen and in the presence of a nucleic acid7 Another application of luminescence accompanies the terbium complex shown in (39) whose luminescence is enhanced by binding to zinc, and can therefore signal for that metal. " ... 

C. P. Wong, Syntheses, Characterization and Applications of Some Lanthanide and Actinide Porphyrin Complexes, Ph.D. thesis, The Pennsylvania State University, University Park, PA 16802, Part I, 1975. 

Five types of Fe porphyrin complexes have been reported, all of which have spin state 5=1 (1) the deep red, five-coordinate ferryl, (Fe =0) +, complexes and the six-coordinate adducts of these ferryl complexes, the (B) (Fe = 0) + complexes (2) the Fe -phenyl complex (3) iron(IV) carbene complexes " " " (4) iron(IV) hydrazine complexes and (5) the six-coordinate d complex [TPPFe(OMe)2] "" mentioned briefly in Section 7 above. The ferryl and Fe - phenyl cases have direct application to active states of heme proteins, particularly the cytochromes P450, peroxidases, catalases, and related enzymes. 

The oxidation of OH by [Fe(CN)6] in solution has been examined. Application of an electrical potential drives the reaction electrochemically, rather than merely generating a local concentration of OH at the anode, as has been suggested previously, to produce both O and [Fe(CN)6] in the vicinity of the same electrode. With high [OH ] or [Fe(CN)6] /[Fe(CN)6] ratio, the reaction proceeds spontaneously with a second-order rate constant of 2.2 x 10 M s at 25 °C. Under anaerobic conditions, iron(III) porphyrin complexes in dimethyl sulfoxide solution are reduced to the iron(II) state by addition of hydroxide ion or alkoxide ions. Excess hydroxide ion serves to generate the hydroxoiron(II) complex. The oxidation of hydroxide and phenoxide ions in acetonitrile has been characterized electrochemically " in the presence of transition metal complexes [Mn(II)L] [M = Fe,Mn,Co,Ni L = (OPPh2)4,(bipy)3] and metalloporphyrins, M(por) [M = Mn(III), Fe(III), Co(II) por = 5,10,15,20-tetraphenylpor-phinato(2-), 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphinato(2-)]. Shifts to less positive potentials for OH and PhO are suggested to be due to the stabilization of the oxy radical products (OH and PhO ) via a covalent bond. Oxidation is facilitated by an ECE mechanism when OH is in excess. 

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