Hydrocarbon oxidation catalyzed by iron and manganese porphyrins anchored on aminofunctionalized supports

The second-generation metalloporphyrins (MePs) [5,10,15,20-tetrakis(pentafluorophenyl)porphyrin iron(III)] chloride, FeP, and [5,10,15,20-tetrakis(pentafluorophenyl)porphyrin manganese(III)] chloride, MnP, were covalently attached to aminofunctionalized supports, with a view to preparing selective solid catalysts for the oxidation of organic compounds. Montmorillonite K10 functionalized with 3-aminopropyltriethoxysilane (Mont1) or modified with 3-chloropropyltriethoxysilane followed by reaction with 1,6-diaminohexane (Mont2), and silica gel functionalized with 3-aminopropyltriethoxysilane (Sil1) or modified with 3-chloropropyltriethoxysilane followed by reaction with 1,6-diaminohexane (Sil2) were synthesized and characterized by UV-Vis and IR spectroscopies, EPR, TGA, and X-ray diffractometry. The catalytic activities of the MePs immobilized on these supports were investigated for the oxidation of (Z)-cyclooctene, cyclohexane and styrene by PhIO or H2O2. The studied systems were efficient catalysts for the oxidation of all substrates, especially when PhIO was the oxidant. There was no MeP leaching from the supports, indicating that covalent binding is a very efficient method for catalyst immobilization. The immobilized FePs were more efficient catalysts than the corresponding MnPs, even when imidazole was employed as a cocatalyst for the supported MnPs. Although the yields of oxidized products obtained with H2O2 were lower than those achieved with PhIO, some heterogeneous MeP systems were more efficient than the parent MePs in solution, both in terms of product yield and selectivity.As metaloporfirinas de segunda geração (MePs), cloreto de [5,10,15,20-tetraquis(pentafluorofenil)porfirinaferro(III)], FeP, e cloreto de [5,10,15,20-tetraquis(pentafluorofenil)porfirinamanganês(III)], MnP, foram covalentemente ancoradas em suportes aminofuncionalizados, com o objetivo de preparar catalisadores sólidos seletivos para a oxidação de compostos orgânicos. Montmorillonita K10 funcionalizada com 3-aminopropiltrietoxissilano (Mont1) ou com 3-cloropropiltrietoxissilano seguida por reação com 1,6-diaminoexano (Mont2), e sílica gel funcionalizada com 3-aminopropiltrietoxissilano (Sil1) ou modificada com 3-cloropropiltrietoxissilano seguida por reação com 1,6-diaminoexano (Sil2) foram preparadas e caracterizadas por UV-Vis, IR, EPR, TGA e difratometria de raios X. As atividades catalíticas das MePs imobilizadas nestes suportes foram investigadas na oxidação de (Z)-cicloocteno, cicloexano e estireno por iodosilbenzeno (PhIO) ou H2O2. Os sistemas estudados foram catalisadores eficientes da oxidação de todos os substratos, especialmente utilizando PhIO como oxidante. Não se observou lixiviamento das MePs dos suportes, indicando que a ligação covalente é um método muito eficiente para a imobilização de catalisadores. As FePs imobilizadas foram catalisadores mais eficientes que as correspondentes MnPs, mesmo quando imidazol foi empregado como um co-catalisador para as MnPs ancoradas. Embora os rendimentos de produtos oxidados utilizando H2O2 tenham sido mais baixos que aqueles obtidos com PhIO, alguns sistemas heterogêneos envolvendo MePs foram mais eficientes que as correspondentes MePs em solução, tanto em termos de rendimento de produto quanto de seletividade.FAPESPCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)CNP

Iron(III) porphyrin covalently supported onto magnetic amino-functionalized nanospheres as catalyst for hydrocarbon and herbicide oxidations

This work describes the covalent immobilization of an ironporphyrin, 5,10,15,20- tetrakis(pentafluorophenyl)porphyrin iron(III) chloride (FeTFPP), onto maghemite/silica magnetic nanospheres covered with aminofunctionalized silica. The resulting material (γ-Fe2O3/SiO2-NHFeP) was characterized by diffuse reflectance infrared spectroscopy (DRIFTS) and UV-Vis absorption spectroscopy. The catalytic activity of this magnetic ironporphyrin was investigated in the oxidation of hydrocarbons (styrene, (Z)-cyclooctene and R-(+)-limonene) and an herbicide (simazine) by hydrogen peroxide or 3-chloroperoxybenzoic acid. Hydrocarbon and simazine oxidation reaction products were analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively. This catalytic system proved to be efficient and selective for hydrocarbon oxidation, leading to high product yields from styrene (89%), cyclooctene (71%) and R-(+)-limonene (86%). Simazine oxidation was attained with 100% selectivity for a dechlorinated product (OEAT), while several oxidation products were obtained for the same catalyst in homogeneous media. The catalyst can be easily recovered through application of an external magnetic field and washed after reaction. Catalyst reuse experiments for R-(+)-limonene oxidation have shown that the catalytic activity is kept at 90% after 10 consecutive reactions

Characterization of electrodes chemically modified with Mn(III) porphyrin/polypyrrole films as catalytic surfaces for an azo dye

In this study we describe the electrochemical behavior of 5,10,15,20-tetrakis(2'-aminophenylporphyrin)manganese(III) chloride supported on a glassy carbon electrode, as well as the electrochemical preparation and characterization of thin films based on pyrrole-3-carboxylic acid. The electrocatalytic action of the electrode modified with the Mn(III) porphyrin toward an azo dye was tested, and the characteristic strong interaction between the incorporated metalloporphyrin and RR120 dye was verified. Copyright (c) 2006 Society of Porphyrins & Phthalocyanines

Preparation, characterization and catalytic studies of V2O5-SiO2 xerogel composite

In this work, we report the synthesis, characterization and catalytic properties of a vanadium oxide-silicon oxide composite xerogel prepared by a soft chemistry approach. In order to obtain such material, we submitted a vanadium pentoxide gel previously synthesized via protonation of metavanadate species to an ""in situ"" progressive polycondensation into silica gel. The material has been characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Further, the catalytic activity of this material was evaluated for the epoxidation of styrene and cyclooctene using iodosylbenzene, hydrogen peroxide and m-chloroperbenzoic acid as the oxidizing agent

Ironporphyrin immobilized onto montmorillonite as a bimimetical model for azo dye oxidation

In this work, we studied the oxidation of the azo dye Disperse orange 3 (DO3) by hydrogen peroxide, catalyzed by 5,10,15, 20-tetrakis(4-N-methylpyridyl)porphyrin iron(III) chloride immobilized onto montmorillonite K10, FeP-K10. Results showed that the FeP-K10/H2O2 system is efficient for discoloration of the DO3 dye, especially at pH 3.0. The catalyst was shown to be relatively stable and could be recycled many times, leading to good yields. DO3 oxidation products were analyzed by gas chromatography and mass spectrometry, being 4-nitroaniline the main product. Tert-butylhydroperoxide and iodosylbenzene were also used as oxidants, giving rise to 4-nitroaniline as product too. The studied system is a good biomimetic model of oxidative enzymes, being a promising discoloring agent for azo dyes. (C) 2007 Elsevier Ltd. All rights reserved

Synthesis and characterization of a novel series of meso (nitrophenyl) and meso (carboxyphenyl) substituted porphyrins

As porfirinas aniônicas 5,10,15-tris(4-carboxifenil), 20-mono(2-nitrofenil) porfirina (1), 5,10(ou 15)-bis(4-carboxifenil), 15(or 10),20-bis(2-nitrofenil)porfirina (2) and 5-mono(4-carboxifenil), 10,15,20-tris(2-nitrofenil)porfirina (3), foram sintetizadas diretamente através da reação de pirrol com os benzaldeídos substituídos em meio de ácido propiônico/nitrobenzeno. A relação molar dos benzaldeídos foi controlada para otimizar a síntese e purificação das porfirinas desejadas. Esta nova série de porfirinas foi caracterizada por cromatografia em camada delgada, espectrometria de massas (FAB MS), RMN ¹H, UV/Vis, IV e eletroquímica. As porfirinas 5,10,15,20-tetrakis(4-carboxifenil)porfirina (4) e 5,10,15,20-tetrakis(2-nitrofenil)porfirina (5) também foram estudadas para comparação, tornando a série completa. A redução eletroquímica das porfirinas base livre e correspondentes ferro(III) porfirinas foi investigada em eletrodos de carbono e mercúrio. Os potenciais de redução mostraram a dependência esperada do número de grupos nitro, fortemente retirador de elétrons, presentes no anel porfirínico, fornecendo evidências adicionais para a caracterização dos compostos sintetizados.The anionic 5,10,15-tris(4-carboxyphenyl), 20-mono(2-nitrophenyl) porphyrin (1), 5,10(or 15)-bis(4-carboxyphenyl), 15(or 10),20-bis(2-nitrophenyl)porphyrin (2) and 5-mono(4-carboxyphenyl), 10,15,20-tris(2-nitrophenyl)porphyrin (3) were sinthesized directly by reaction of pyrrole with substituted benzaldehydes in nitrobenzene/propionic acid media. The benzaldehydes molar ratio was controlled to optimize the synthesis and purification of the desired porphyrins. This new series of porphyrins was characterised by TLC, mass spectrometry (FAB MS), ¹H NMR, UV/Vis, IR and electrochemistry. 5,10,15,20-Tetrakis(4-carboxyphenyl)porphyrin (4) and 5,10,15,20-Tetrakis(2-nitrophenyl)porphyrin (5) were also characterised for comparative purposes, completing the series The electrochemical reduction was investigated for the free base and corresponding iron(III) porphyrins on glassy carbon and mercury electrodes. The reduction potentials showed the expected dependence on the number of electron-withdrawing nitro groups present on the porphyrin ring providing additional evidences for the characterisation of the synthesised compounds.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Jacobsen catalyst immobilized on chitosan membrane as interface catalyst in organic/aqueous system for alkene oxidation

The Jacobsen catalyst, Mn(salen), was immobilized in chitosan membrane. The obtained Mn(salen)-Chit was characterized by thermogravimetric analysis (TC), differential thermal analysis (DTA), differential scanning calorimetry (DSC), infrared spectroscopy (FT-IR), degree of N-acetylation by (1)H NMR, and UV-vis spectroscopy. The UV-vis absorption spectrum of the encapsulated catalyst displayed the typical bands of the Jacobsen catalyst, and the FT-IR presented an absorption band characteristic of the imines present in the Jacobsen catalyst. The chitosan membranes were available, in a biphasic system, as a catalytic barrier between two different phases: an organic substrate phase (cyclooctene or styrene) and an aqueous solution of either m-CPBA, t-BuOOH or H(2)O(2), and dismissing the need for phase transfer agents and leading to better product yields compared with the catalyst in homogeneous medium. This new catalyst did not leach from the support and was reused many times, leading to high turnover frequencies. (C) 2009 Elsevier B.V. All rights reserved.FAPESPCAPESCNP

Synthesis and Characterization of Semi-Interpenetrating Networks Based on Poly(dimethylsiloxane) and Poly(vinyl alcohol)

Semi-interpenetrating networks (Semi-IPNs) with different compositions were prepared from poly(dimethylsiloxane) (PDMS), tetraethylorthosilicate (TEOS), and poly (vinyl alcohol) (PVA) by the sol-gel process in this study. The characterization of the PDMS/PVA semi-IPN was carried out using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and swelling measurements. The presence of PVA domains dispersed in the PDMS network disrupted the network and allowed PDMS to crystallize, as observed by the crystallization and melting peaks in the DSC analyses. Because of the presence of hydrophilic (-OH) and hydrophobic (Si-(CH(3))(2)) domains, there was an appropriate hydrophylic/hydrophobic balance in the semi-IPNs prepared, which led to a maximum equilibrium water content of similar to 14 wt % without a loss in the ability to swell less polar solvents. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 158-166, 2010FAPEMIGCNPqCAPE