Shirley Nakagaki

Synthesis and characterization of zeolite-encapsulated metalloporphyrins

Abstract Metalloporphyrins of FeIII and CuII were prepared inside the large pores of the zeolite NaY by a process of sequential introduction of components followed by assembly inside the void space of the zeolite. The appropriate process chosen for the porphyrin synthesis was using the propionic acid solvent for reaction between pyrrole and benzaldehyde and this solvent was not destructive for zeolite. The powder X-ray diffraction data confirmed that the crystallinity of the zeolite was maintained. The resulting materials were purified by Soxhlet extractor. The zeolite-included metalloporphyrins were identified for studies using UV-Vis, FTIR and EPR Spectroscopy, CA (chemical analysis), AAS (atomic absorption spectroscopy), TG/DSC, XRD, SEM and 13C-NMR techniques. The catalytic activity of these products was examined and the catalyst showed to be a promising catalytic system to aliphatic hydrocarbon oxidation reactions.

Study of metalloporphyrin covalently bound to silica as catalyst in the ortho-dianisidine oxidation

Abstract The model compounds for horseradish peroxidase (HRP) is reported, based on the association of H 2 O 2 with iron and manganese porphyrins immobilized onto a functionalized silica gel. The models were developed in an attempt to find a biomimetical compound for systems containing heme groups. The ortho -dianisidine is a useful substrate model compound for checking the ability of degradation promoted by delignificant natural enzymes. The heterogeneous catalysts were obtained by grafting of three metalloporphyrins: (Fe(TFPP)—iron porphyrin from the 5,10,15,20-tetrakis (pentafluorophenyl) porphyrin—and Mn(TCPP) and Fe(TCPP), iron and manganese porphyrins from the 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin), onto the modified surface of silica gel. The oxidation of ortho -dianisidine was monitored by UV-Vis spectroscopy at room temperature using different ratios of catalyst, oxidant and substrate. At high H 2 O 2 concentration, the perhalogenated iron porphyrin Fe(TFPP) produced best results, showing a turnover number of about 1100. This value was higher than those obtained for Fe(TCPP) and Mn(TCPP) systems.

Cationic iroporphyrins as catalyst in comparative oxidation of hydrocarbons: homogeneous and supported on inorganic matrices systems

Abstract Cationic ironporphyrins in solution and supported on imidazole propyl gel (IPG) and silica gel (SG) as catalyst in cyclohexane hydroxylation using iodosylarene as oxygen donor were studied. FeTM4PyP 5+ , 1 as homogeneous catalyst for cyclohexane hydroxylation, in acetonitrile (CH 3 CN) and ultrasound stirring, gives cyclohexanol (C-ol) yields of 20%. The FeTM2PyP 5+ , 2 as catalyst for cyclohexene oxidation in CH 3 CN and ultrasound stirring is a very efficient system, giving 93% of total yield, with an epoxide:alcohol:ketone selectivity of 77:12:11. The supported systems, 1 -IPG and 1 -SG are particularly efficient in dichloromethane (CH 2 Cl 2 ), giving C-ol yields of 37% and 53%, respectively. These systems consist of polar hemin in isolated sites, which selectively catalyze cyclohexane oxidation in apolar solvent. They represent good cytochrome P-450 model systems. In the same way, the active site of P-450 consists of a polar protohemin in a hydrophobic pocket, promoting selective cyclohexane oxidation. These rigid cationic 1 -IPG, 1 -SG, 2 -IPG, 2 -SG, 3 -IPG and 3 -SG systems can catalyze with very small amounts of ironporphyrins, which correspond to about 30–80 times fewer numbers than the hemin in P-450 catalytic site.

Chemical Reactions Catalyzed by Metalloporphyrin-Based Metal-Organic Frameworks

The synthetic versatility and the potential application of metalloporphyrins (MP) in different fields have aroused researchers’ interest in studying these complexes, in an attempt to mimic biological systems such as cytochrome P-450. Over the last 40 years, synthetic MPs have been mainly used as catalysts for homogeneous or heterogeneous chemical reactions. To employ them in heterogeneous catalysis, chemists have prepared new MP-based solids by immobilizing MP onto rigid inorganic supports, a strategy that affords hybrid inorganic-organic materials. More recently, materials obtained by supramolecular assembly processes and containing MPs as building blocks have been applied in a variety of areas, like gas storage, photonic devices, separation, molecular sensing, magnets, and heterogeneous catalysis, among others. These coordination polymers, known as metal-organic frameworks (MOFs), contain organic ligands or complexes connected by metal ions or clusters, which give rise to a 1-, 2- or 3-D network. These kinds of materials presents large surface areas, Brønsted or redox sites, and high porosity, all of which are desirable features in catalysts with potential use in heterogeneous phases. Building MOFs based on MP is a good way to obtain solid catalysts that offer the advantages of bioinspired systems and zeolitic materials. In this mini review, we will adopt a historical approach to present the most relevant MP-based MOFs applicable to catalytic reactions such as oxidation, reduction, insertion of functional groups, and exchange of organic functions.

Exfoliation and immobilization of anionic iron porphyrin in layered double hydroxides

Mg-Al layered double hydroxide (LDH) intercalated with glycinate anions was synthesized through co-precipitation and exfoliated in formamide and the single-layer suspension was reacted with an aqueous iron porphyrin (FeTDFSPP) solution. The new composite was characterized by powder X-ray diffraction, UV-vis, FTIR, and electron paramagnetic spectroscopies and thermal analyses (simultaneous TG/DSC). The analyses demonstrated that glycinate anions continue to be intercalated and the anionic iron porphyrin is adsorbed at the surface of the layered double hydroxide crystals.

Electrochemical Behavior of Copper Porphyrin Synthesized into Zeolite Cavity: A Sensor for Hydrazine

The copper tetraphenylporphyrin (CuTPP) was prepared within a NaY zeolite cavity to investigate the electrocatalytic behavior of CuTPP upon the oxidation of hydrazine and cysteine. The amount of 0.067 mmol g−1 of CuTPP was obtained in the zeolite cavities. Cyclic voltammetry showed only an anodic peak at 320 mV that was assigned to the oxidation of CuI to CuII. This peak was not affected by the supporting electrolyte nature or by solution pH. The electrode showed electrocatalytic activity to oxidize both cysteine and hydrazine, however for cysteine the activity was weak, possibly as a result of the adsorption of oxidation product (cystine). Although hydrazine oxidation was efficient, neither oxidation was diffusion controlled. A linear correlation between catalytic current and hydrazine concentration allows sensing of hydrazine in the 0.2 × 10−6 to 1.0 × 10−6 mol L−1 concentration range. The detection limit was 1.0 × 10−7 mol L−1, and the response time was 1.1 s. The sensor was stable for at least 6 months under continuous use.

Porphyrin-kaolinite as efficient catalyst for oxidation reactions.

The preparation, characterization, and application in oxidation reactions of new biomimetic catalysts are reported. Brazilian Sao Simao kaolinite clay has been functionalized with [meso-tetrakis(pentafluorophenyl)porphinato]iron(III), Fe(TPFPP). To obtain the functionalized clay, the natural clay was purified by dispersion-sedimentation, expanded by insertion of dimethyl sulfoxide (DMSO), and functionalized with amino groups by substitution of DMSO with ethanolamine. These previous steps allowed clay functionalization with Fe(TPFPP), leading to a layered material with a basal spacing of 10.73 A. Clay functionalization with the porphyrin was confirmed by formation of the secondary amine, as demonstrated by FTIR bands at 3500-3700 cm(-1). UV-vis spectroscopy revealed a red shift in the Soret band of the iron porphyrin in the functionalized material as compared to the parent iron porphyrin catalyst in solution, indicating Fe(III)P --> Fe(II)P reduction. The catalytic performance of the functionalized clay was evaluated in the epoxidation of cyclooctene, with complete selectivity for the epoxide (100% epoxide yield), and ketonization of cyclohexane, cyclohexanone being the major product. The novel catalyst was also evaluated in the Baeyer-Villiger (BV) oxidation of cyclohexanone, with 85% conversion of cyclohexanone in epsilon-caprolactone, with total selectivity to epsilon-caprolactone.

Immobilization of iron porphyrins into porous vycor glass: characterization and study of catalytic activity

Abstract In this paper we report the immobilization and characterization of neutral and pentacationic iron porphyrins into the nanometric pores of an inorganic matrix (porous vycor glass, PVG) and the use of these materials as catalyst in mimetic–enzymatic processes. The concentration of iron porphyrin in the large glass pores depends on the conditions present during the incorporation process. The materials obtained were used as catalyst in the oxidation reaction of cyclohexane and cyclohexene by iodosylbenzene. The catalytic results were promising, evidencing adequate characteristics of PVG for immobilization of iron porphyrin and strong potential of these nanocomposites for heterogeneous catalytic procedures.

Catalytic activity in oxidation reactions of anionic iron(III) porphyrins immobilized on raw and grafted chrysotile

Natural and grafted chrysotile were used as matrices for the immobilization of second generation iron porphyrins. The catalysts obtained were evaluated in the oxidation reaction of cyclohexane, using iodosylbenzene as oxidant agent. The catalyst activity for different conditions was compared with results for the same porphyrins immobilized with 3-APTS grafted disordered silica, obtained from acid-leached chrysotile. Preliminary results have shown that high activity can be obtained with short reaction times, and that the reaction is specific for alcohol.

Synthesis, characterization and catalytic behavior of iron porphyrins immobilized in layered double hydroxides

We report the synthesis, characterization and catalytic behavior of iron(III) porphyrins immobilized in layered double hydroxides (LDH). A combination of EPR, UV-visible spectroscopy and powder X-ray diffraction (PXRD) was used to characterize the products. Three different procedures were used to perform the immobilization of iron porphyrin: a) adsorption into the LDH powder, b) co-precipitation and c) rehydration of calcined LDH. Several different porphyrins (Fe(TSPP), Fe(TCPP), Fe(TPP) and Fe(TDFSPP)) were employed in the study. After characterization, the isolated powders were investigated in the oxidation reaction of cyclohexane by iodosylbenzene and hydrogen peroxide in heterogeneous catalysis in comparison to homogeneous media. Some of these immobilized compounds were very good catalysts for this oxidation reaction, stimulating the future investigation of other substrates.