Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Several research to explore the possible conversion of CO2 using rhenium(I) tricarbonyl complexes have been reported the last years. In the present work, we investigated a potential use of fac-Re(CO)3(4,4’-di-methyl-2,2’-bipyridyl)L+ complex (C2), where L is an electron-withdrawing ancillary ligands which present an intramolecular hydrogen bond (IHB), in a preliminary electrocatalytic reduction of CO2. The C2 complex was synthesized and characterized according to reported methods earlier. The cyclic voltammogram profile for the C2 complex were studied in dichloromethane under inert atmosphere, and it shows a typical behavior for an electrocatalytic process, the C2 complex illustrate the electrochemical reaction mechanism corresponds to an electrochemical–chemical–electrochemical pathway (ECE). Also, a Vitreous Carbon plate used as working electrode was employed and modified by cycling the anodic region of C2 in CH2Cl2 which involve the oxidative redox response for the -NH2 and -OH groups. The voltammogram profile involve shows a polymeric deposit on the plate surface in a CO2 saturated solution (pH=7.0). A strong electrocatalytic discharge of current is obtained with a wave foot of -1.3 V showing that C2 have the potential to be used in electrocatalyst CO2 reduction.

Single crystals of 1,3-bis(cyanomethoxy)calix[4]arene (1) were grown from Chloroform/Methanol mixture and these were nanodecorated with colloidal gold nanoparticles (AuNps). The single crystals were then characterized by single-crystal X-ray diffraction (XRD) and Scanning Electronic Microscopy (SEM). The nanodecorated crystals were characterized by UV-Visible Absorption Spectroscopy, Transmission Electronic Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). In this work, it is shown that the stabilization of the nanoparticles occurs through of the interactions of these with the nitrile group, maintaining their shape and size.

One of the applications of chitosan is based on its ability to stabilized metallic nanoparticles with minimum chitosan metal molar ratio.This work describes the synthesis and characterization of Ag, Au, Pt, and Cu nanoparticles stabilized by chitosan through chemical reduction of metallic salts by sodium borohydride (NaBH4).The properties of bionanocomposites were studied in terms of their surface plasmon resonance, crystalline structure, average diameter size, particle distributions and functional groups. The samples were characterized by TEM, electron diffraction, UV-Visible and FTIR. The stability of the colloids at room temperature were also measured. A high stability for the colloidal dispersion with chitosan can be observed (> three months). We found that TEM studies show a size distribution between 6 and 10 nm, depending on metals and chitosan metal relation. Electron diffraction analysis for the metallic nanoparticles shows the presence of Ag, Au, Pt and Cu. The FT-IR exhibit the presence of the chitosan in the stabilisation of metallic nanoparticles.

The effect of supports and the addition of CS2 in the feed were studied on hydrodenitrogenation of Quinoline in a continuous flow reactor over ReS2/support catalysts at 300, 325 and 350 °C and 3MPa of H2. The ReS2 supported on TiO2 displayed the highest activity followed by ZrO2, γ-Al2O3 and SiO2 supports. The activity trend was correlated with the Re dispersion on the support. The effect of the addition of CS2 was increased activity until 2.5 v/v % content. At higher CS2 content the activity decreased due to competitive adsorption between CS2 and Quinoline on the active sites. 

Coagulation-flocculation (CF) process studies on aqueous solutions of Acid Black 210 dye (AB-210), were performed to investigate efficiency at different pH, coagulant and polyelectrolyte doses, and sedimentation times. In the adsorption studies of the dye removal, the initial pH and isotherms studies were performed using an activated carbon prepared by microwave-assisted pyrolysis of Tannery sludge. This adsorbent material was characterized by isotherms of N2 adsorption-desorption and density functional theory. Finally, the efficiency of the combined process CF followed by adsorption, was shown using a synthetic effluent identical to that produced in the wet-end process of the leather industry in industrial equipment. Effluent was collected from each treatment bath and analyzed for its physical properties and by ion chromatography. The best conditions found in CF processes were: pH 10.0, sedimentation time of 60 minutes, coagulant dose of 71 mg L-1 (Al2(SO4)3) and dose of flocculant (polyelectrolyte FX AS1) of 0.090 mg L-1. In the adsorption processes, the equilibrium data were best fit to the Liu isotherm model, presenting the maximum sorption capacity (Qmax) for AB-210 of 974.7 mg g-1 at 303.15K at pH 2.0. Using the synthetic effluent, the combined CF followed by adsorption of AB-210 dye demonstrated a removal of 85.2%, indicating that the combined process is efficient for real wastewater treatment.

An efficient and cost effective adsorbent, activated carbon (UTAC) derived from used tea (UT) for the removal of As(III) from aqueous solutions was developed. To increase adsorption, UTAC was then impregnated with (magnetite) iron oxide particles (Fe-UTAC). The prepared adsorbents were characterized by XRD, SEM/EDX, FTIR and surface area analyzer. A comprehensive kinetic study of arsenite adsorption onto Fe-UTAC was conducted at 298-318 K and pH 8. The Richenberg model confirmed film diffusion to be the main rate limiting step. The removal of As(III) from aqueous solution onto Fe-UTAC was carried out as a function of temperature, concentration and pH. The sorption capacity (mol g-1) of Fe-UTAC was observed to increase with increase in arsenite concentration while a decrease in the As(III) uptake was observed by increasing the temperature of the system. The sorption capacity of Fe-UTAC was almost three and six times larger than that of UTAC and UT respectively. The effect of pH on the arsenite adsorption was significant in the pH range 7–8 which may be correlated with the stability of Fe-UTAC as no release of iron from Fe-UTAC was observed. The mean free energy calculated from DR mechanism confirmed adsorption to be chemisorption and followed ligand exchange mechanism. The thermodynamic parameters confirmed adsorption to be exothermic, spontaneous and favorable.

The hexa-coordinated mixed ligand Cu(II), Zn(II), Ni(II) and Co(II) complexes of the type [MLX]Cl2 where X=1,10-phenonthroline and ligand (L) have been synthesised from the condensation of thiophene-2-carboxaldehyde with o-phenylenediamine. They were characterised by elemental analysis, molar conductance, magnetic susceptibility, infrared, electronic absorption, proton magnetic resonance and mass spectral studies. An octahedral geometry has been proposed for all these complexes. The high molar conductance studies of the complexes show their electrolytic nature. The infrared spectra of the complexes show that the imine group of the Schiff base coordinate with the metal ion. The electronic absorption spectra of the complexes show the charge transfer, d-d transitions consistent with their proposed geometry. The proton magnetic resonance spectrum of the ligand shows the presence of CH=N group in the ligand. The mass spectral data also confirms the proposed structure of ligand and its complexes. The mixed ligand complexes possess good catalytic activity in the reaction of oxidation of alcohols using H2O2 as oxidant. The antibacterial activity of the mixed ligand complexes has been carried out by disc diffusion method. Copper (II) complexes exhibit potent antibacterial activity when compared to the standard drug streptomycin. The above complexes also exhibited DPPH radical scavenging activity.

 A sensitive, accurate, precise and reproducible high performance thin layer chromatographic method has been developed for the estimation of clofarabine in their pharmaceutical dosage form. The objective of this validation of an analytical procedure is to demonstrate that the drug Clofarabine is suitable for its intended purpose. The analytical method development recommends the quality, purity and specificity of the drug. Clofarabine injection form during the manufacturing process and hence the standard of drug may not vary, which produce the desirable therapeutic effect.TLC aluminum plates pre-coated with silica gel 60F254used as the stationary phase, while toluene: methanol (8:2, v/v) used as mobile phase. The Rf value was observe 0.34± 0.05 for clofarabine. The densitometric analysis was carried out in absorbance mode at 266 nm. The method was linear in the range of 50 – 1000 ng/spot for clofarabine. The method was validated as per ICH guideline. The limit of detection and limit of quantitation were found to be 17.60ng/spot and 53.35 ng/spot, respectively for clofarabine.The proposed method was successfully applied to the estimation of clofarabinein the pharmaceutical dosage form. Clofarabine was subjected to acid and alkali hydrolysis, chemical oxidation, wet hydrolysis, dry heat degradation and sun light degradation. The degradants peaks were well resolved from the pure drug peak with significant difference in their Rf values. Stressed samples were assayed using proposed TLC method.

In this research article, we have designed triphenylamine (TPA) dyes with D-A-π-A structure and their electro-optical and charge injection properties have been calculated. The computational techniques are used to study the effect of additional acceptor in π-conjugated systems on absorption spectra and electron injection of the dyes. All the dyes have shown absorbance in visible region. The effect of additional acceptor on the performance of sensitizers in dye sensitized solar cells has also been determined. In theoretical examination electron injection efficiency (Фinject.) and light harvesting efficiency (LHE) have been calculated. The results indicate that the combination and selection of appropriate conjugated bridge in dye sensitizer is an important way to design efficient dyes.

The species Croton elegans Kunth, belonging to the family Euphorbiaceae and known with the common name “mosquera”, is a native medicinal plant of Ecuador. Due to its medical applications, we are interested in secondary metabolite composition. After extraction with hexane and preparation of the alkaloid extract, preparative chromatographic fractionation in both normal and direct phase was performed. 1H NMR, 13C NMR, HSQC and HMBC experiments, together with polarimetric measurements, were conducted in order to characterize the purified compunds. Two triterpene metabolites (friedelin and cycloeucalenol) and two morphinan alkaloids ((+)-pallidine and (+)-O-methylpallidine) were obtained in a pure form. This work represents the first report on the phytochemistry of C. elegans and probably the second publication on the natural (+)-pallidine alkaloid.