Edgar A. Páez-Mozo

Cyclohexene oxidation with an iron cyclam-type complex encapsulated in Y-zeolite

The synthesis and characterization of an iron cyclam-type complex within the cavities of a Y-zeolite is described. By comparing the performance of the heterogeneous system with the free complex in the oxidation of cyclohexene using iodosylbenzene as oxygen donor, a protection effect of the matrix over the active center was evidenced by a higher turnover and yield of products. It was possible to determine, by UV-VIS spectroscopy, that the free complex suffers molecular degradation after two hours of reaction whereas the heterogeneous catalyst remains unaltered and active after 24 hours of reaction. The main products found in the catalyzed reaction were 2-cyclohexen-1-ol, 2-cyclohexen-1-one, epoxycyclohexane and cyclohexanol.

Olefin oxidation with dioxygen catalyzed by porphyrins and phthalocyanines intercalated in α-zirconium phosphate

Abstract Oxidation of cyclohexene and cis -stilbene with dioxygen in presence of metal phthalocyanines or metal tetraphenylporphyrins complexes intercalated in α-zirconium phosphate and isobutyraldehyde were studied. The degradation of free metal complexes in solution in the reaction media was verified. It was observed that the matrix protects the metal complexes from degradation and the activity of the catalytic system is preserved. Oxidation of cyclohexene with intercalated complexes gave epoxide as the predominant product, while allylic oxidation products were obtained in smaller proportion and the product distributions depended on the identity of the individual metal complexes. Since the addition of a free radical inhibitor stops the reaction, a free radical mechanism should be present. Oxidation of cis -stilbene with intercalated metal complexes gives different ratios of cis - to trans -stilbene oxide and of benzaldehyde which depend on the intercalated metal complex, suggesting that in addition to the free radicals there is another active oxidizing agent.

Photochemical Synthesis of the Bioconjugate Folic Acid-Gold Nanoparticles

In this paper we present a rapid and simple one- pot method to obtain gold nanoparticles functionalized with folic acid using a photochemistry method. The bioconjugate folic acid-gold nanoparticle was generated in one step using a photo-reduction method, mixing hydrogen tetrachloroaurate with folic acid in different ratios and varying the illumination time of a mercury lamp (λ= 255 nm). Scanning electron microscopy showed a particle size of around 40-50nm and dynamic light scattering exhibited that the zeta potential varies from -41 to -50mV with different illumination times. Storage in the dark at 4°C prolongs the stability of folic acid-gold nanoparticle suspensions to up to 26 days. Ultraviolet visible and Fourier transform infrared spectroscopy showed a surface plasmon band of around 534nm and fluorescence spectroscopy exhibited a quenching effect on gold nanoparticles in the fluorescence emission of folic acid and thus confirmed the conjugation of folic acid to the surface of gold nanoparticles. In this study we demonstrate the use of a photochemistry method to obtain folic acid-gold nanoparticles in a simple and rapid way without the use of surfactants and long reaction times. The photochemical synthesis of FA-AuNPs opens new perspectives for creating novel functional nanomaterials for biomedical applications.

Bis(3,5-dimethylpyrazol-1-yl)acetate bound to titania and complexed to molybdenum dioxido as a bidentate N,N′-ligand. Direct comparison with a bipyridyl analog in a photocatalytic arylalkane oxidation by O2

Bis(3,5-dimethylpyrazol-1-yl)acetate, well known as a tridentate N,N,O ligand, was bound to MoO2Cl2 in a bidentate N,N manner by anchoring covalently, at first, the ligand onto a titanium oxide surface, followed by its complexation with the molybdenum dioxo entity. It was fully characterized by 13CPMAS NMR and FT-IR spectroscopy. The tethered complex was directly compared with an analogous bipyridyl species in the catalytic ethylbenzene oxidation by O2 at room temperature, atmospheric pressure, and under visible light. The bis(pyrazol-1-yl) catalyst exhibited a significant initial higher oxygen atom transfer (OAT) capability, well in accord with its electron donating property. It was, unfortunately, hampered by a premature leaching phenomenon, totally absent in the comparable bipyridyl system.