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Porphyrin tetraphenylporphyrin

Tetracation of tetrakis(N-methyl-4-pyridinio)porphyrin T ris(octyloxyphenyI)porphyrin Tetrakis(octylsulphonamido)phthalocyanine Tetrapyrrole (unspecified) Tetrakis(a,a,a,a-o-pivalamidophenyl)porphyrin Tetraphenylporphyrin... [Pg.137]

LB Films of Porphyrins and Phthalocyanines. The porphyrin is one of the most important among biomolecules. The most stable synthetic porphyrin is 5,10,15,20-tetraphenylporphyrin (TPP). Many porphyrin and phthalocyanine (PC) derivatives form good LB films. Both these molecules are important for appHcations such as hole-burning that may allow information storage using multiple frequency devices. In 1937 multilayers were built from chlorophyll (35). [Pg.533]

Similar results are observed in the conjugative addition of CH-acidic methylene compounds with the metal derivatives of 2-nitro-5,10,15.20-tetraphenylporphyrin (6). The nickel porphyrin 6 (M = Ni) yields with an excess of dimethyl malonate the cyclopropane derivative 7 whereas the copper porphyrin 6 (M — Cu) forms with two equivalents of malononitrile the bisadduct 8.111... [Pg.608]

The observation that addition of imidazoles and carboxylic acids significantly improved the epoxidation reaction resulted in the development of Mn-porphyrin complexes containing these groups covalently linked to the porphyrin platform as attached pendant arms (11) [63]. When these catalysts were employed in the epoxidation of simple olefins with hydrogen peroxide, enhanced oxidation rates were obtained in combination with perfect product selectivity (Table 6.6, Entry 3). In contrast with epoxidations catalyzed by other metals, the Mn-porphyrin system yields products with scrambled stereochemistry the epoxidation of cis-stilbene with Mn(TPP)Cl (TPP = tetraphenylporphyrin) and iodosylbenzene, for example, generated cis- and trans-stilbene oxide in a ratio of 35 65. The low stereospecificity was improved by use of heterocyclic additives such as pyridines or imidazoles. The epoxidation system, with hydrogen peroxide as terminal oxidant, was reported to be stereospecific for ris-olefins, whereas trans-olefins are poor substrates with these catalysts. [Pg.202]

A comparison between two families of dendrimers containing polyfaryl ether) dendrons and either a Zn porphyrin (GnPZn) or a tetraphenylporphyrin (G/JTPPH2) core up to the fourth generation (30 and 31) shows that the core... [Pg.177]

In the second oxidation method, a metalloporphyrin was used to catalyze the carotenoid oxidation by molecular oxygen. Our focus was on the experimental modeling of the eccentric cleavage of carotenoids. We used ruthenium porphyrins as models of cytochrome P450 enzymes for the oxidation studies on lycopene and P-carotene. Ruthenium tetraphenylporphyrin catalyzed lycopene oxidation by molecular oxygen, producing (Z)-isomers, epoxides, apo-lycopenals, and apo-lycopenones. [Pg.185]

A similar system, but with a more hindered porphyrin (tetramesitylporphyrin = tetraphenylporphyrin bearing three methyl substituents in ortho and para positions on each phenyl group), was tested for P-carotene oxidation by molecular oxygen. This system was chosen to slow the oxidation process and thus make it possible to identify possible intermediates by HPLC-DAD-MS analysis. The system yielded the same product families as with lycopene, i.e., (Z)-isomers, epoxides, and P-apo-carotenals, together with new products tentatively attributed to diapocarotene-dials and 5,6- and/or 5,8-epoxides of P-apo-carotenals. The oxidation mechanism appeared more complex in this set-up. [Pg.187]

For electrocatalysis, compounds of the porphyrin series are of major interest monomeric and polymeric phthalocyanines, tetraphenylporphyrins, tetraazaporphy-rins, tetraazaannulenes, and other complexes. The structures of some of these complexes are shown in Fig. 28.5. [Pg.547]

Shi C, Anson EC. 1990. Catalytic pathways for the electroreduction of oxygen by iron tetra-kis(4-iV-methylpyridyl)porphyrin or iron tetraphenylporphyrin adsorbed on edge plane pyrol3dic graphite electrodes. Inorg Chem 29 4298. [Pg.692]

Fig. 1. Structures of oxidatively electropolymerizable tetraphenylporphyrins. The porphyrins can be polymerized as metallated forms, or the metal can be inserted into the polymer in some cases. Fig. 1. Structures of oxidatively electropolymerizable tetraphenylporphyrins. The porphyrins can be polymerized as metallated forms, or the metal can be inserted into the polymer in some cases.
Dloxygen reduction electrocatalysis by metal macrocycles adsorbed on or bound to electrodes has been an Important area of Investigation (23 ) and has achieved a substantial molecular sophistication in terms of structured design of the macrocyclic catalysts (2A). Since there have been few other electrochemical studies of polymeric porphyrin films, we elected to inspect the dloxygen electrocatalytic efficacy of films of electropolymerized cobalt tetraphenylporphyrins. All the films exhibited some activity, to differing extents, with films of the cobalt tetra(o-aminophenylporphyrin) being the most active (2-4). Curiously, this compound, both as a monomer In solution and as an electropolymerized film, also exhibited two electrochemical waves... [Pg.417]

The consequences of polychlorination of porphyrins on redox properties of complexes has been investigated.1404 The highly chlorinated porphyrin 3-octachloro-/ /c.vo-tetrakis(3,5-dichloro-2,6-dimethoxyphenyl)porphyrin exhibits a substantial anodic shift for reduction of over 0.5 V and a smaller shift for oxidation versus the unchlorinated precursor. Contrastingly, small potential shifts for the octabromo-substituted 5,10,15,20-tetraphenylporphyrinate arise from the dominance of macrocycle ruffling over electronic effects. In the polychloro complex, distortion does not compensate fully for electron-withdrawing effects of the Cl substituents. [Pg.119]

When multiple peripheral substituents, as in [Ni(2,3,5,7,8,10,12,13,15,17,18,20-dodecaphenyl-porphyrin)], [Ni(5,10,15,20-tetra(/-butyl)porphyrin)], [Ni(2,3,7,812,13,17,18-tetracyclohexenyl-5,10,15,20-tetraphenylporphyrin)], and [Ni(OETPP)], cause the macrocycles to become nonplanar,283,284 the HOMOs of the porphyrins are destabilized and the molecules become easier to oxidize.283,285 In accord with the general discussion above, these compounds are oxidized to tt cation radicals and remain so even at low temperatures in CH2C12. However, upon addition of... [Pg.269]

The functionalization of zinc porphyrin complexes has been studied with respect to the variation in properties. The structure and photophysics of octafluorotetraphenylporphyrin zinc complexes were studied.762 Octabromoporphyrin zinc complexes have been synthesized and the effects on the 11 NMR and redox potential of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraarylporphyrin were observed.763 The chiral nonplanar porphyrin zinc 3,7,8,12,13,17,18-heptabromo-2-(2-methoxyphenyl)-5,10,15,20-tetraphenylporphyrin was synthesized and characterized.764 X-ray structures for cation radical zinc 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrin and the iodinated product that results from reaction with iodine and silver(I) have been reported.765 Molecular mechanics calculations, X-ray structures, and resonance Raman spectroscopy compared the distortion due to zinc and other metal incorporation into meso dialkyl-substituted porphyrins. Zinc disfavors ruffling over doming with the total amount of nonplanar distortion reduced relative to smaller metals.766 Resonance Raman spectroscopy has also been used to study the lowest-energy triplet state of zinc tetraphenylporphyrin.767... [Pg.1216]

A heta-substituted porphyrin, such as hefa-nitro-meso-tetraphenylporphyrin le, also reacts with o-benzoquinodimethane to give the corresponding nitrochlorin 2e, together with the naphthoporphyrin 4a and the bis-naphthoporphyrin (bisadduct) 7 the formation of these 4a and 7 derivatives imply HNO2 elimination and dehydrogenation reactions <06TL8437>. [Pg.46]

In 1995, Boyd and co-workers <95TL7971 > covalently linked a porphyrin to fullerene Cgo through a 1,3-dipolar cycloaddition reaction involving the porphyrinic azomethine ylide 28 (Scheme 8). The ylide was generated in situ from befa-formyl-meso-tetraphenylporphyrin 27 and A -methylglycine, and provided the porphyrin-C6o diad 29 in good yield. [Pg.49]

Extension of the 1,3-DC approach to the synthesis of novel pyrazoline-fused chlorin 78 by the reaction of P-nitro-meso-tetraphenylporphyrin le with diazomethane has also been explored by Cavaleiro and co-workers (Scheme 27) <02S 1155>. The resulting chlorin 78 could be further converted into the pyrazole-fused porphyrin 79 by treatment with DBU or into the methanochlorin 80 by refluxing in toluene. [Pg.64]


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