A porphyrin-based microporous network polymer that acts as an efficient catalyst for cyclooctene and cyclohexane oxidation under mild conditions

The highly efficient dibenzodioxin-forming reaction between the (pentafluorophenyl)porphyrin manganese(III) (MnP) and hexahydroxytriptycene (HHT) provide a new microporous network polymer (P1), which demonstrated a large surface area (1080 m2 g− 1) and proved to be an efficient solid for heterogeneous catalysis for cyclooctene and cyclohexane oxidation under mild conditions and with high capacity of recovery and reuse in many catalytic cycles

Nb2O5/SBA-15 catalyzed propanoic acid esterification

A family of niobia (Nb2O5) functionalized SBA-15 solid catalysts have been prepared via wet impregnation with NbCl5 (2–32 wt% Nb) and subsequent thermal processing, for application in the acid catalyzed esterification of propanoic acid with methanol. Bulk and surface physicochemical characterization revealed that highly dispersed niobia species present at low loadings when calcined at 500 °C exhibit strong Brönsted acid character and associated activity for esterification. Increased calcination temperatures are found to result in a decrease in Brönsted:Lewis acid ratio associated with recrystallization of the niobia phase leading to a loss of catalyst activity. Esterification activity is found to be directly proportional to Brönsted:Lewis acid ratio, with the 2 wt% Nb/SBA-15 catalyst pre-calcined at 500 °C found to exhibit highest activity and excellent reusability without deactivation

Preparation of catalysts based on iron(III) porphyrins heterogenized on silica obtained by the Sol-Gel process for hydroxylation and epoxidation reactions

Solid catalysts have been prepared by chemical interaction of iron(III) porphyrins with the surface of the pores of a silica matrix obtained by the sol-gel method. The presence of the complexes in the silica matrix and the morphology of the obtained particles were studied by UV-Vis spectroscopy, powder X-ray diffractometry, infrared spectroscopy, transmission electron microscopy, electron paramagnetic resonance and thermogravimetric analysis. The catalytic activity of the immobilized iron(III) porphyrins in the oxidation of (Z)-cyclooctene, cyclohexene and cyclohexane was evaluated in dichloromethane/acetonitrile 1:1 solvent mixture (v/v) using iodosylbenzene as oxidant. Results were compared with those achieved with the homogeneous counterparts

Avaliação da natureza da atividade catalítica de compostos de bismuto em reações de metanólise do óleo de soja

Sodium bismuthate dihydrate and two species derived from its thermal treatment were investigated as catalysts for soybean oil methanolysis and, regardless of the type of solid used, ester yields always above 76 wt% were obtained. After a single reaction course, both liquid and solid phases were characterized using several analytical methods such as X-ray diffraction and thermogravimetric analysis. As a result, the catalytic phenomenon was shown to be solely due to the leaching of alkalinecatalytic species from the solid materials

Studies of the Catalytic Activity of Iron (III) Porphyrins for the Protection of Carbonyl Groups in Homogeneous Media

The protection of carbonyl groups that produce acetal products is a key reaction in fine chemistry due to the high reactivity of aldehydes and ketones in certain media. This process can be catalyzed by protic or Lewis acids. Since metalloporphyrins often possess free axial positions in the central metal, they can be applied as Lewis acid catalysts, allowing the additional coordination of substrates. Therefore, three ferric complexes were selected to be evaluated as catalysts for the acetalization of benzaldehyde with ethanol and triethyl orthoformate (TEOF) in the homogeneous phase: (i) 5,10,15,20-tetrakis(phenylporphyrin) iron (III) chloride (Fe0F); (ii) 5,10,15,20-tetrakis(2,6-difluorphenylporphyrin) iron (III) chloride (Fe2F); and (iii) 5,10,15,20-tetrakis(pentafluorphenylporphyrin) iron (III) chloride (Fe5F). The complex Fe5F showed the highest catalytic activity, and kinetic parameters were evaluated for this reaction, exhibiting an increasing rate of reaction of about 550-fold in comparison with the non-catalyzed reaction. The reaction scope was also investigated, and Fe5F was found to be active for the acetalization of benzaldehyde and acetophenone, with different protective agents such as alcohols, glycols, glycerol, and epoxide being selective for the formation of cyclic acetals. The protection of benzaldehyde with ethylene glycol and propylene glycol were also studied at different temperatures, and turnover frequency (TOF) values of up to 360 h−1 were determined at 40 °C in homogenous media without the need for solvent or drying agents

Metil coenzima M redutase (MCR) e o fator 430 (F430)

This review presents studies on methyl coenzyme M reductase, the biological system Factor 430 (F430) and the use of nickel(II) complexes as structural and functional models. The ability of F430 and nickel(II) macrocycle complexes to mediate the reductive dehalogenation of cyclohexyl halogens and the CH3-S bond cleavage of methyl CoM (by sodium borohydride and some intermediate species) proposed for the catalytic cycle of the biological system F430 was reviewed. The importance of the structure of the nickel complexes and the condition of the catalytic reduction reaction are also discussed

Metil coenzima M redutase (MCR) e o fator 430 (F430)

This review presents studies on methyl coenzyme M reductase, the biological system Factor 430 (F430) and the use of nickel(II) complexes as structural and functional models. The ability of F430 and nickel(II) macrocycle complexes to mediate the reductive dehalogenation of cyclohexyl halogens and the CH3-S bond cleavage of methyl CoM (by sodium borohydride and some intermediate species) proposed for the catalytic cycle of the biological system F430 was reviewed. The importance of the structure of the nickel complexes and the condition of the catalytic reduction reaction are also discussed

Recent Advances in Catalyzed Sequential Reactions and the Potential Use of Tetrapyrrolic Macrocycles as Catalysts

Complexes of porphyrins and of other similar tetrapyrrolic macrocycles are extensively explored as catalysts for different chemical processes, and the development of solid catalysts for heterogeneous processes using molecules with the ability to act as multifunctional catalysts in one-pot reactions is increasing and can lead to the wider use of this class of molecules as catalysts. This mini review focuses on the application of this class of complexes as catalysts in a variety of sequential one-pot reactions

Highly active manganese porphyrin-based microporous network polymers for selective oxidation reactions

New microporous polymer networks, constructed by a nucleophilic substitution reaction between two different porphyrins and metalloporphyrins are reported. The meso-tetrakis-(pentafluorophenyl)porphyrin HP1 (monomer A1) and/or its manganese complex MP1 (monomer A2) was reacted with the meso-tetrakis-(3,4-dihydroxyphenyl)porphyrin HP2 (monomer B1) and/or its manganese complex MP2 (monomer B2), giving rise to four new porphyrin-based microporous network polymers (P1-P4) with apparent BET surface areas in the range 600–1200 m2 g−1. The catalytic performance of the polymers was evaluated by oxidation reactions using cyclooctene and cyclohexane as substrates and Iodosylbenzene as oxidant in cytochrome P-450 model reactions. The catalytic activity and selectivity of these porous polymer networks are similar or superior to those of the analogous homogeneous manganese porphyrins MP1 and MP2. The robustness of the materials in terms of thermal stability and good recyclability showed that they hold great promise as biomimetic heterogeneous catalysts