Abstract
Metalloporphyrins immobilized into NaY zeolite are described as catalysts for hydrocarbon oxyfuntionalization. Manganese(III) and iron(III)tetrakis(4-N-methylpyridyl)-porphyrin (MnP1 and FeP1), and manganese(III) and iron(III) tetrakis(4-N-benzylpiridil)-porphyrin (MnP2 and FeP2) were impregnated (MnP1-NaYimp, FeP1-NaYimp, MnP2-NaYimp, FeP2-NaYimp, respectively) and encapsulated (MnP1-NaY, FeP1-NaY, MnP2-NaY and FeP2-NaY) into the NaY zeolite. These catalysts were used in the oxidation of (Z)-cyclooctene, cyclohexane, and adamantane by iodosylbezene (PhIO). These systems were able to epoxidize (Z)-cyclooctene with cis-epoxycyclooctane yields as high as 100%. By using cyclohexane and adamantane as substrate, the susceptibility of the benzyl groups on the porphyrin ring of the MnP materials, led to a different distribution of the oxidized products. With FePs, this susceptibility was not detected because the species responsible for the oxidations, FeIV(O)P·+, is more active than MnV(O)P. In conclusion, cationic metalloporphyrins immobilized into NaX zeolites, are good cytochrome P-450 models is less polar solvents since the selectivity of the system indicates the “in cage” solvent oxygen rebound oxidative process.
Highlights
The superfamily of cytochrome P-450 enzymes plays an important role in oxidative processes in nature
Cationic metalloporphyrins immobilized into NaX zeolites, are good cytochrome P-450 models is less polar solvents since the selectivity of the system indicates the “in cage” solvent oxygen rebound oxidative process
The MePs were impregnated in the zeolite surface to obtain FeP1-NaYimp, MnP1-NaYimp, FeP2-NaYimp and MnP2-NaYimp, respectively, for comparison purposes. All these materials were characterized by UV-Vis spectroscopy, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTA), scanning electronmicroscopy (SEM), energy dispersive X-ray spectrometry (EDS), and Al27 MAS NMR
Summary
The superfamily of cytochrome P-450 enzymes plays an important role in oxidative processes in nature. One approach to solve this problem is the use of electron withdrawing substituents on the porphyrin periphery, especially halogenated and perhalogenated phenyl porphyrins, producing more robust and resistant catalysts [5,6,9,10,11] Another solution to promoting the stability of MeP catalysts is their immobilization on a solid matrix. The MePs were impregnated in the zeolite surface to obtain FeP1-NaYimp, MnP1-NaYimp, FeP2-NaYimp and MnP2-NaYimp, respectively, for comparison purposes All these materials were characterized by UV-Vis spectroscopy, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTA), scanning electronmicroscopy (SEM), energy dispersive X-ray spectrometry (EDS), and Al27 MAS NMR. The oxidation of (Z)-cyclooctene, cyclohexane, and adamantane catalyzed by these materials were studied using iodosylbenzene (PhIO) as the oxidizing agent in solvent media with different polarities was accomplished in order to evaluate the reaction mechanism in each of the studied systems
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