J. Połtowicz

Oxidation of cyclohexene over Mn(TMPyP) porphyrin-exchanged Al, Si-mesoporous molecular sieves

The mesoporous silicas of the MMS (HMS)-type, containing different amounts of Al, have been prepared using dodecylamine as a structure directing agent. Encapsulation of the +4 charge cationic chloro[meso-tetra(4-N-methylopyridinio)-porphirynato] manganese(III) tetrachloride (Mn(TMPyP)) metalloporphyrin has been carried out by means of cation exchange. In all Al-substituted materials, the porphyrin species are firmly bound to the solid matrix, in contrast to the purely siliceous support. The preparation procedure provides a simple means of controlling the amount of the supported porphyrin. The solids are active in oxidation of cyclohexene with iodosylbenzene yielding only allylic oxidation products and no epoxide. It is argued that the regioselective effect is due to the narrowness of the structural pores, which prohibits the formation of the transient complex required for the formation of the epoxide. In contrast to previous studies in which increased loading of porphyrin has been found to result in a decrease in activity, in the present case an increase in the catalytic activity with increased porphyrin loading is observed.

The effect of peripheral substituents in metalloporphyrins on their catalytic activity in Lyons system

Manganese porphyrin catalysts with different number of halogens atoms substituted at the phenyl and pyrrole rings were investigated in the Lyons system in oxidation of cyclooctane with molecular oxygen (as air) to cyclooctanone and cyclooctanol without the use of sacrificial co-reductant. The catalytic activity of metalloporphyrins increases with the increase of the redox potential of metalloporphyrins in the investigated system and shows almost linear relationship with the number of the halogens on porphyrin macrocycle. On the basis of obtained results the new reaction mechanism is discussed and proposed.

Metal-dependent reactivity of some metalloporphyrins in oxidation with dioxygen

Abstract p-Tetratolylporphyrins with different metal centres such as Cr3+, Mn3+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+ have been used as catalysts for epoxidation of propylene in the presence of propionaldehyde and dioxygen. It has been found that the induction time as well as the distribution of the main reaction products, i.e. peroxy acid, epoxide and carbon dioxide, vary with the metalloporphyrin applied. These differences in the catalytic behaviour shed light on the character of the active forms of the catalysts and on the mechanism of the investigated reaction.

Manganese porphyrins as catalysts for oxidation of cyclooctane in Lyons system

Abstract Oxidation of cyclooctane with molecular oxygen (as air) in the presence of first generation manganese porphyrins XMn III (TTP), where X=F − , Cl − , Br − , I − , OH − , CH 3 COO − , as catalysts was investigated in the Lyons system. The catalytic activities of the metalloporphyrins in the oxidation of cyclooctane to cyclooctanone and cyclooctanol are covariant with electronegativity of halides as axial ligands and increase with the decrease of the redox potential of metalloporphyrins. It was concluded that axial ligands are involved in the reaction initiating the reaction by generating the radicals with simultaneous reduction of the manganese porphyrin. Relatively high yields of products were obtained without the use of sacrificial co-reductant.

Comparison of photodynamic efficacy of tetraarylporphyrin pegylated or encapsulated in liposomes: In vitro studies

Two photosensitizing systems: (1) tetrakis(4-hydroxyphenyl)porphyrin (p-THPP) encapsulated in sterically stabilized liposomes (SSL) and (2) p-THPP functionalized by covalent attachment of poly(ethylene glycol) (p-THPP-PEG(2000)) were studied in vitro. The dark and photo cytotoxicity of these systems were evaluated on two cell lines: HCT 116, a human colorectal carcinoma cell line, and DU 145, a prostate cancer cell line and compared with these determined for free p-THPP. It was demonstrated that both encapsulation in liposomes as well as attachment of PEG chain result in pronounced reduction of the dark cytotoxicity of the parent porphyrin. The liposomal formulation showed higher than p-THPP-PEG(2000) photocytotoxicity towards both cell lines used in the studies.

Cobalt tetra(p-tolyl)prorphyrin as catalyst in oxidation of propionaldehyde

Abstract The effect of solvent in the homogeneous oxidation of propionaldehyde has been investigated. It was observed that the induction period of the reaction depends on the donor number of the solvent. Changes in the structure of the catalyst during the course of the reaction as revealed spectrophotometrically are discussed, the species which appear are identified and a mechanism for their transformation is proposed.

Liquid phase oxidation of acrolein catalyzed by Co and Mo complexes

Liquid phase catalytic oxidation of acrolein in the presence of Co(III) and Mo(VI) complexes was investigated. The addition of a Mo(VI) complex was found to accelerate the reaction at higher, and retard it at lower, Co(III) concentrations.AbstractБыло исследовано жидкофазное каталитическое окисление акролеина в присутствии комплексов Co(III) и Mo(VI). Добавление комплекса Mo(VI) ускоряет реакцию при высоких концентрациях Co(III) и уменьшает при низких концентрациях Co(III).

Kinetics and mechanism of the co-oxidation of propylene and benzaldehyde in the presence of some cobalt complexes

Abstract Cobalt(II)(p-CH3TPP), Co(NAP)2 and Co(OAc)2·4H2O differ in their catalytic properties and for this reason the acceleration of various steps in the title reaction were studied. It has been found that induction periods as well as variations in the distribution of the principal products, i.e. propylene oxide, CO2 and peracid, depend markedly on the applied catalyst. A reaction scheme is proposed and the active form of the catalyst suggested. The observed dependence of the induction period on the concentration of catalyst and benzaldehyde as well as on the oxygen pressure allows the determination of the exponents in the rate equation for the induction period.

Molybdenum Complexes as Catalysts for the Oxidation of Cycloalkanes with Molecular Oxygen

A group of new polymolybdates was synthesized and tested in the catalytic oxidation of cycloalkanes. Investigated compounds exhibit broad structural diversity including polymolybdates with isolated anionic clusters (0-dim), polymeric anions (1-dim), Mo–O layers (2-dim) as well as hexagonal and orthorhombic molybdenum oxides (3-dim). All studied molybdenum complexes were found to be active in the reaction conditions yielding ketones and alcohols as main products. In the case of layered compounds (2-dim), dicarboxylic acid was detected in the mixture of reaction products. The structure of investigated molybdenum compounds was shown to have influence on yields and selectivities of the investigated reactions. Anionic layers separation (in 2-dim materials) as well as type and charge of organic cations present in the compounds are prime examples of structural factors influencing the oxidation reactions efficiencies. On the basis of obtained results and literature reports a mechanism for the oxidation of cycloalkanes by polymolybdates has been proposed.Graphical Abstract

Polyvanadate-exchanged hydrotalcites as catalysts for selective oxidation of cyclohexene with molecular oxygen

Catalytic activity of polyvanadate-exchanged Mg,Al-, Zn,Al-, and Zn,Cr-hydrotalcites in the selective oxidation of cyclohexene with dioxygen has been investigated and discussed with reference to the composition of the brucite layer, type of the intercalated vanadate anion, vanadium loading and distribution of reaction products.