Heterogenization of manganese porphyrin via hydrogen bond in zeolite imidazolate framework-8 matrix, a host–guest interaction, as catalytic system for olefin epoxidation

A heterogenized meso-tetrakis(2,3-dihydroxyphenyl)porphyrinatomanganese(III) acetate at zeolite imidazolate framework-8 (T(2,3-OHP)PorMn@ZIF-8) is investigated for the catalytic olefin epoxidation reactions at room temperature. Heterogenization is accomplished through a non-classical hydrogen bond proposed between T(2,3-OHP)PorMn bearing O–H groups and C–H of the 2-methylimidazolate linkers in the ZIF-8 structure. The aforementioned compound is characterized by X-ray powder diffraction (XRD), atomic absorption spectroscopy (AAS), nitrogen adsorption−desorption, FT-IR spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The catalytic system with rather high potential of reusability is proposed as a fairly efficient epoxidation catalyst compared to reports in homogeneous media.

Highly selective and efficient oxidation of sulfide to sulfoxide catalyzed by platinum porphyrins

Two platinum porphyrins, meso-tetramesitylporphyrinatoplatinum and meso-tetrakis(pentaflourophenyl) porphyrinatoplatinum, are explored for catalytic application in the selective oxidation of sulfide to sulfoxide by iodosylbenzene. The obtained overall turnover number of 90,000 in the oxidation of thioanisole in the presence of meso-tetrakis(pentaflourophenyl) porphyrinatoplatinum indicates the pronounced catalytic activity of the platinum porphyrins. Perfect selectivity toward sulfoxide or sulfone also was achieved via stoichiometric control of reactants.

Nanoparticle supported, magnetically separable manganese porphyrin as an efficient retrievable nanocatalyst in hydrocarbon oxidation reactions

Magnetically separable manganese porphyrin was prepared by immobilizing on functionalized magnetic nanoparticles via the amino propyl linkage and used as an efficient retrievable nanocatalyst in hydrocarbon oxidation reactions.

New series of monoamidoxime derivatives displaying versatile antiparasitic activity

Following the promising antileishmanial results previously obtained in monoamidoxime series, a new series of derivatives was synthesized using manganese(III) acetate, Wittig reactions and Suzuki-Miyaura cross coupling reactions. Pharmacomodulation in R(1), R(2) or R(3) substituents on the amidoxime structure is shown to influence antiprotozoan activity in vitro: a monosubstituted phenyl group in R1 (32-35) led to an activity against Leishmania donovani promastigotes (32, IC50 = 9.16 μM), whereas a polysubstituted group (36-37) led to an activity against Plasmodium falciparum (36, IC50 = 2.76 μM). Modulating chemical substituents in R(2) and R(3) only influenced the antiplasmodial activity in vitro. This suggests that the amidoxime scaffold has properties that could make it a promising new antiparasitic pharmacophore.

Investigation of axial ligand effects on catalytic activity of manganese porphyrin, evidence for the importance of hydrogen bonding in cytochrome-P450 model reactions

Various nitrogenous bases, such as imidazoles, pyridines and amines were employed as axial ligands in epoxidation reaction of cyclooctene bytetra-n-butylammonium hydrogen monopersulfate (n- Bu 4 NHSO 5), in the presence of Mn ( III )-tetrakis(2,3-dimethoxyphenyl)porphyrin-acetate ( T (2,3- OMeP ) PorMnOAc ). T (2,3- OMeP ) PorMnOAc is a fairly stable catalyst, with the ability of producing hydrogen bonding. High epoxidation yield of 85 ± 6% was obtained in the presence of imidazole axial ligand with 100% selectivity in 30 min. Higher conversion of around 100% was obtained by pyridine axial base, while selectivity was reduced to 69%. Further epoxidation reactions were also performed using Mn ( III )-Tetrakis(2,3-dihydroxyphenyl)porphyrin-acetate ( T (2,3- OHP ) PorMnOAc ) as catalyst. In addition to the usual electronic and steric effects, it is proposed that the catalytic activity depends on the existence and kind of hydrogen bonding between the axial base and the ortho-methoxy or hydroxy groups on the phenyl rings of manganese porphyrin. The cis to trans ratio of cis-stilbene oxide formed by imidazole and pyridine axial bases were obtained as 7.5 and 2.5 respectively. In addition GC-Ms and UV-vis studies were employed to find the nature of active species and product formation. Our DFT calculations disclosed that pyridine hydrogen bonding with moiety of the macrocycle rings strongly affects the relative energies of S/Q spin states in [ T (2,3- OMeP ) PorMn V ( O )( Py )]+, in that it results in the longer Mn – O bond and reactivity toward substrates.

Nanoaggregates of Mn(III)tetraperfluorophenylporphyrin: a greener approach for allylic oxidation of olefins

Organic nanoparticles of metalloporphyrins can be a versatile catalyst for the selective oxidation of alkenes and other hydrocarbons. The catalytic activity of the metalloporphyrin depends on the nature of the central metal atom, peripheral groups, and the architecture of the porphyrin macrocycle. Herein, we report the catalytic activity of organic nanoparticles of 5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphyrinato manganese(III), Mn (III)TPPF20, for the oxidation of cyclohexene using molecular oxygen as an oxidant in aqueous solvent under ambient conditions. While the solvated metalloporphyrins catalytically oxidize alkenes to the corresponding epoxide with a modest turn-over numbers, ca. 30 nm organic nanoparticles of Mn (III)TPPF20 have enhanced catalytic activity with up to a two-fold greater turn-over number and yields only allylic oxidation products. The activity of organic nanoparticles is slow compared to the solvated metalloporphyrins. These organic nanoparticles catalytic systems facilitate a greener reaction since ca. 89% of the reaction medium is water, molecular oxygen is used in place of man-made oxidants, and the ambient reaction conditions require less energy. This organic nanoparticle catalytic system also avoids using halogenated solvents commonly used in solution phase reactions. The enhanced catalytic activity of these organic nanoparticles is unexpected because the metalloporphyrins in the nanoaggregates are in the close proximity and the turn-over number should diminish by self-oxidative degradation.

Effect of hydrogen bonding on catalytic activity of some manganese porphyrins in epoxidation reactions

Mn (III)-tetra phenyl porphyrin-acetate (MnTPPOAc) and some kinds of meso-phenyl substituted porphyrins by hydroxyl groups and their Mn (III) complexes were synthesized. These Mn -porphyrins were used as catalyst in the epoxidation of various alkenes with tetra-n-butylammonium hydrogen monopersulfate (n- Bu4NHSO5 ) as oxidant and tetra-n-butylammonium acetate (n- Bu4NOAc ) as the axial ligand. The following order of catalytic activity was observed for cyclooctene: T(2,3-OHP)PMnOAc ≫ T(2,4,6-OHP)PMnOAc ≥ T(4-OHP)PMnOAc ≥ T(2,6-OHP)PMnOAc ≥ TPPMnOAc and T(2,3-OHP)PMnOAc ≫ TPPMnOAc > T(4-OHP)PMnOAc > T(2,4,6-OHP)PMnOAc > T(2,6-OHP)PMnOAc for other alkenes. Different activity and stability of the catalysts were interpreted based on the hydrogen bonding between hydroxyl groups with appropriate orientation on the meso-position of the phenyl groups and axial bases or oxidant. T(2,3-OHP)PMnOAc catalyst has shown optimal condition for effective hydrogen bonding. In the case of other catalysts, electronic and steric factors overcome the hydrogen bonding effect.