N-ferrocenylpyridazinones and new organic analogues: synthesis, cyclic voltammetry, DFT analysis and in vitro antiproliferative activity associated with ROS-generation

Employing an optimized Pd-catalyzed cross-coupling reaction promoted by CuI, novel N-ferrocenylpyridazinones along with N-phenyl- and N-(2-pyridyl) analogues were synthesized from readily available heterocyclic precursors, iodoferrocene, iodobenzene and 2-bromopyridine. With exception of the ferrocenylation of 6-ferrocenylpyridazin-3(2H)-one yielding both N- and O-substituted products, the studied reactions exclusively afforded N-aryl lactams. The novel compounds exhibited cytotoxicity towards HEPG2 and HT-29 human malignant cells under in vitro conditions. The measured IC50 values supplemented with the results of cyclic voltammetry and DFT calculations suggest that the cytotoxic activity of the N- and O-ferrocenyl-substituted derivatives and the decreased effect of the N-phenyl analogues seem to be at least partly associated with the potential to generate reactive oxygen species (ROS). This interpretation, allowing the prediction of characteristic substituent-dependent SAR, was supported by the results of related studies on the practically inactive N-(2-pyridyl)pyridazinones assumed to be present in protonated chelate forms with highly a decreased propensity to undergo\ud ionization

Study of PtOx/TiO2 Photocatalysts in the Photocatalytic Reforming of Glycerol: The Role of Co-Catalyst Formation

In this study, relationships between preparation conditions, structure, and activity of Pt-containing TiO2 photocatalysts in photoinduced reforming of glycerol for H2 production were explored. Commercial Aerolyst® TiO2 (P25) and homemade TiO2 prepared by precipitation-aging method were used as semiconductors. Pt co-catalysts were prepared by incipient wetness impregnation from aqueous solution of Pt(NH3)4(NO3)2 and activated by calcination, high temperature hydrogen, or nitrogen treatments. The chemico-physical and structural properties were evaluated by XRD, 1H MAS NMR, ESR, XPS, TG-MS and TEM. The highest H2 evolution rate was observed over P25 based samples and the H2 treatment resulted in more active samples than the other co-catalyst formation methods. In all calcined samples, reduction of Pt occurred during the photocatalytic reaction. Platinum was more easily reducible in all of the P25 supported samples compared to those obtained from the more water-retentive homemade TiO2. This result was related to the negative effect of the adsorbed water content of the homemade TiO2 on Pt reduction and on particle growth during co-catalyst formation

Enhanced activity of sol-gel prepared SnOx-TiO2 in photocatalytic methanol reforming

Objective: In this contribution a simple method is elaborated for the preparation of Pt/SnOx-TiO2 catalysts which are active in the photocatalytic reforming of methanol. The region of low tin content (Sn/Ti atomic ratio: 0-0.015) is explored. Tin content related activity changes of the catalysts are discussed in terms of the results of structural characterization. Methods: Tin-modified anatase TiO2 samples were obtained from sol-gel method by use of Ti-isopropoxide, SnCl4 or Sn(OBu)4 and citric acid in absolute ethanol solution followed by calcinations at 400°C in air. After loading Pt by impregnation the catalytic activity has been tested irradiating the slurry of the catalysts suspended in mixture of water and methanol by means of two different light sources, one working exclusively in the visible region and one in a broader spectral range including a UV-component, respectively. Hydrogen production activity has been correlated with structural data obtained from different characterization techniques such as ESR spectroscopy, XRD, XPS, SEM and Raman spectroscopy as well as diffuse reflectance UV-Vis spectrophotometry. Results: According to ESR spectroscopic measurements the presence of oxygen vacancies was responsible for the slight visible light absorption. XRD, XPS, SEM and Raman spectroscopic results indicated that highly dispersed SnOx accumulated in the surface region of TiO2, no tin incorporation into the lattice was observed. The fundamental band gap was not influenced by the presence of tin. Loading of the tin-modified samples by 0.5 wt% Pt increased the hydrogen production in comparison to 0.5 wt% Pt/TiO2 samples. Conclusions: The improvement in the catalytic activity was explained by formation of new tin related charge carrier traps leading to (i) prevention of electron-hole recombination and (ii) additional modification of the adsorption of reactants. Details of the two different working mechanisms are described. Practice implication The increased hydrogen production over the tin modified samples provides a promising step toward practical usage of light for hydrogen production. © 2013 Elsevier B.V. All rights reserved

Study of PtOx/TiO2 Photocatalysts in the Photocatalytic Reforming of Glycerol: The Role of Co-Catalyst Formation

In this study, relationships between preparation conditions, structure, and activity of Pt-containing TiO2 photocatalysts in photoinduced reforming of glycerol for H2 production were explored. Commercial Aerolyst® TiO2 (P25) and homemade TiO2 prepared by precipitation-aging method were used as semiconductors. Pt co-catalysts were prepared by incipient wetness impregnation from aqueous solution of Pt(NH3)4(NO3)2 and activated by calcination, high temperature hydrogen, or nitrogen treatments. The chemico-physical and structural properties were evaluated by XRD, 1H MAS NMR, ESR, XPS, TG-MS and TEM. The highest H2 evolution rate was observed over P25 based samples and the H2 treatment resulted in more active samples than the other co-catalyst formation methods. In all calcined samples, reduction of Pt occurred during the photocatalytic reaction. Platinum was more easily reducible in all of the P25 supported samples compared to those obtained from the more water-retentive homemade TiO2. This result was related to the negative effect of the adsorbed water content of the homemade TiO2 on Pt reduction and on particle growth during co-catalyst formation

Effect of the Microstructure of the Semiconductor Support on the Photocatalytic Performance of the Pt-PtOx/TiO2 Catalyst System

The influence of the semiconductor microstructure on the photocatalytic behavior of Pt-PtOx/TiO2 catalysts was studied by comparing the methanol-reforming performance of systems based on commercial P25 or TiO2 from sol–gel synthesis calcined at different temperatures. The Pt co-catalyst was deposited by incipient wetness and formed either by calcination or high-temperature H2 treatment. Structural features of the photocatalysts were established by X-ray powder diffraction (XRD), electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS), optical absorption, Raman spectroscopy and TEM measurements. In situ reduction of Pt during the photocatalytic reaction was generally observed. The P25-based samples showed the best H2 production, while the activity of all sol–gel-based samples was similar in spite of the varying microstructures resulting from the different preparation conditions. Accordingly, the sol–gel-based TiO2 has a fundamental structural feature interfering with its photocatalytic performance, which could not be improved by annealing in the 400–500 °C range even by scarifying specific surface area at higher temperatures