Metalloporphyrins tetraphenylporphyrin

The metalloporphyrin-catalyzed decomposition of ethyl azidoformate in the presence of an arene has been investigated but with little success in improving the yields of the 1 //-azepines.151 The nickel and copper complexes had no effect, whereas the cobalt-tetraphenylporphyrin complex accelerated the decomposition rate of the azido ester but produced more A-arylurethane rather than 1//-azepine. 

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. 

Metallooctaethylporphyrins Zinc tetra(benzo-15-crown-5)porphyrin See also Metallotetraphenylporphrins dimerization effects, 141,147 Zinc tetrabenzoporphyrin—See Metalloporphyrins Zinc tetraphenylporphyrin See also Metalloporphyrins See also... 

Complexes of rhenium(bipyridine)(tricarbonyl)(picoline) units linked covalently to magnesium tetraphenylporphyrins via an amide bond between the bipyridine and one phenyl substituent of the porphyrin 19 exhibited no signs of electronic interaction between the Re(CO)3(bpy) nnits and the metalloporphyrin units in their gronnd states. However, emission spectroscopy revealed a solvent-dependent quenching of porphyrin emission upon irradiation into the long-wavelength absorption bands localized on the porphyrin. 

Zinc-5,10,15,20-tetraphenylporphyrin (ZnTPP) has been used as a coating material in ammonia sensors by immobilizing it on the surface of silicone rubber. Absorbance and fluorescence emission were the modes of detection. A spectral change is caused by the coordination of NH3 molecules to the Zn11 ion in the immobilized metalloporphyrins. Sensing films made from the ZnTPP immobilized in silicone rubber were found to be the most sensitive for NH3 sensing (20). 

Figure 11. 15N NMR MAS NMR spectra and tensor results for [15N4]-ring labeled metalloporphyrins. A, 8.45 Tesla 15N MAS NMR spectrum of Fe(tetraphenylporphyrinate)(PhNO)( 1 -methylimidazole), vr = 2.6 kHz. B, graph showing correlation between experimental and DFT computed I5N tensor elements for Fe(TPP)(PhNO)( 1 -Melm) ( ) and Fe(TPP)(CO)(l-MeIm) (O). The mean experimental and theoretical shieldings over the four non-equivalent sites in each molecule are shown since the solid state shifts are not specifically assigned. Slope = 0.847, R2 = 0.995.

Such metal-complexed nitrenes were also generated by the reaction of (tosyliminoio-do)benzene (106) with Mn(m)- or Fe(n)-tetraphenylporphyrin, 107, in a mimic of cytochrome P-450 but with a tosylimino group instead of an oxygen atom on the metals (108) [179]. It was able to functionalize cyclohexane solvent, by nitrogen insertion into a C-H bond to form 109. Furthermore, the metalloporphyrins also catalyzed an intramolecular nitrogen insertion converting 110 into 111 [180]. 

The use of a synthetic model system has provided valuable mechanistic insights into the molecular catalytic mechanism of P-450. Groves et al. [34]. were the first to report cytochrome P-450-type activity in a model system comprising iron meso-tetraphenylporphyrin chloride [(TPP)FeCl] and iodosylbenzene (PhIO) as an oxidant which can oxidize the Fe porphyrin directly to [(TPP)Fe =0] + in a shunt pathway. Thus, (TPP)FeCl and other metalloporphyrins can catalyze the monooxygenation of a variety of substrates by PhIO [35-40], hypochlorite salts [41, 42], p-cyano-A, A -dimethylanihne A -oxide [43-46], percarboxylic acids [47-50] and hydroperoxides [51, 52]. Catalytic activity was, however, rapidly reduced because of the destruction of the metalloporphyrin during the catalytic cycle [34-52]. When (TPP)FeCl was immobilized on the surface of silica or silica-alumina, catalytic reactivity and catalytic lifetime both increased significantly [53]. There have been several reports of supported catalysts based on such metalloporphyrins adsorbed or covalently bound to polymers [54-56]. Catalyst lifetime was also significantly improved by use of iron porphyrins such as mew-tetramesitylporphyrin chloride [(TMP)FeCl] and iron mcA o-tetrakis(2,3,4,5,6-pentafluorophenyl)por-phyrin chloride [(TPFPP)FeCl], which resist oxidative destruction, because of steric and electronic effects and thereby act as efficient catalysts of P-450 type reactions [57-65]. 

The Metallophlorin Spectrum. This is the spectrum of a metalloporphyrin in any oxidation state, which has added an extra substituent at one methine bridge. It is also found very often in various oxidation or protonation products of tetraphenylporphyrins. It is very similar to the spectrum of metallo-bilatrienes with an opened macro-cyclic ring [Wasser (195) e.g. Peychal-Heyling (147)]. 

In 10-2 M HC1, [In(tmpyp)]5+ has bands at 424 nm (e = 390,000), 518 nm (e = 3690), 558 nm (c = 23,200), and 597 nm (e = 4660). The spectrum is similar to that of indium(III)-tetraphenylporphyrin.16 The [In(tmpyp)]5+ is fully water soluble, and rapid acid solvolysis occurs only above 3 M HC1 levels. Refluxing a divalent metal chloride with H2tmpyp in water, and keeping the pH between 3 and 5, is the general method used to prepare the Cu2+, Zn2+, Ni2+, Mn3+, Fe3+, and Co3+ compounds.6 The 642-nm free-base porphyrin band disappears when the incorporation reaction is complete. The high-pH conditions (a) reduce the concentration of unreactive centrally protonated15 porphyrins, (b) minimize the extent of acid catalyzed metalloporphyrin solvolysis reactions,17 and (c) increase the concentration of the often more reactive hydrolyzed metal ion forms.18... 

In such porphine compounds, the Mg atom. is CormaIIy-4-coorinteraction with either water or other solvent molecules is a common, if not universal, occurrence further, in chlorophyll, interaction with the keto group at position 9 in another molecule is also established. It also appears that 5-coordination is preferred over 6-coordination as in the structure of magnesium tetraphenylporphyrin hydrate,30 where the Mg atom is out of the plane of the N atoms and is approximately square pyramidal. Although Mg and other metalloporphyrins can undergo oxidation31 by one-electron changes, for Mg it is the macrocycle and not the metal that is involved. 

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