Publications

Abstract The present work reports the first experimental thermochemical study of mono-N-oxides derived from quinoxaline, namely, 3-methoxycarbonyl-2-methyl-quinoxaline N-oxide and 3-ethoxycarbonyl-2-methyl-quinoxaline N-oxide. The values of the enthalpies of formation, in the condensed state, and of the enthalpies of sublimation, derived from static bomb calorimetry and Calvet microcalorimetry measurements, respectively, are combined to derive the standard molar enthalpies of formation in the gaseous phase for these two compounds. From the latter values, the first and second N-O bond dissociation enthalpies for the corresponding di-N-oxides have been obtained. The gas-phase experimental results are also compared with calculated data obtained with a density functional theory approach. Copyright (c) 2008 John Wiley & Sons, Ltd.

Abstract This paper focuses on the removal of nitro substituted polycyclic aromatic hydrocarbon compounds (NPAHs) from water using low cost synthesized zirconium phosphate mesoporous materials. These materials are lamellar type incorporating n-alkyl-(n = 12 and n = 16) trimethylamonium bromide molecules with different concentrations. For comparison of their performance as adsorbents and in the recovery of NPAH, their results were compared with commercial ENVI-18 extraction tubes and three dimensional type material incorporating hexadecyl-trimethyl ammonium bromide. The adsorption yield for the new materials were almost 100% and the recovery factors with dichloromethane as eluent was nearly 100%. Best results were obtained by preparing lamellar zirconium and titanium phosphates in the presence of n-dodecyl-trimethylammonium. This material has several environmental advantages because zirconium salts are non-toxic and their synthesis costs is relatively small.

Abstract New classes of acidic or basic ionic liquids (ILs) are gaining special attention, since the efficiency of many processes can be enhanced by the judicious manipulation of these properties. The absorption of sour gases can be enhanced by the basic character of the IL. The fluorination of the cation or the anion can also contribute to enhance the gas solubility. In this work these two characteristics are evaluated through the study of the gas-liquid equilibrium of two ionic liquids based on similar anions, 1-butyl-3-methylimidazolium acetate ([C(4)mim] [Ac]) and 1-butyl-3-methylimidazolium trifluoroacetate ([C(4)mim] [TFA]), with carbon dioxide (CO2) at temperatures up to 363 K and pressures up to 76 MPa. The data reported are shown to be thermodynamically consistent. Henry's constants estimated from the experimental data show the solubility of CO2 on the [C(4)mim][Ac] to be spontaneous unlike in [C(4)mim][TFA] due to the differences in solvation enthalpies in these systems. Ab initio calculations were performed on simple intermolecular complexes of CO2 with acetate and trifluoroacetate using MP2/6-31G(d) and the G3 and G3MP2 theoretical procedures to understand the interactions between CO2 and the anions. The theoretical study indicates that although both anions exhibit a simultaneous interaction of the two oxygen of the carboxylate group with the CO2, the acetate acts as a stronger Lewis base than the trifluoroacetate. C-13 high-resolution and magic angle spinning (HRMAS) NMR spectra provide further evidence for the acid/base solvation mechanism and the stability of the acetate ion on these systems. Further similarities and differences observed between the two anions in what concerns the solvation of CO2 are discussed.

Abstract The energetic and structural Study of three diphenylpyridine isomers is presented in detail. The three isomers, 2,6-, 2,5-, and 3,5-diphenylpyridines, were synthesized via Suzuki-Miyaura methodology based on palladium catalysis, and the crystal structures of the isomers were obtained by X-ray diffraction. The relative energetic stabilities in the condensed and gaseous phases as well as volatilities and structures of the three studied isomers were evaluated, regarding the position of the phenyl groups relative to the nitrogen atom of the pyridine ring. The temperature, standard molar enthalpies, and entropies of fusion were measured and derived by differential scanning calorimetry. The vapor pressures of the considered isomers were determined by a static apparatus based on a MKS capacitance diaphragm manometer. The standard molar enthalpies, entropies, and Gibbs energies of sublimation, at T = 298.15 K, were derived, and the phase diagram near the triple point coordinates were determined for all isomers. The standard (p degrees = 0.1 MPa) molar enthalpies of combustion of all crystalline isomers were determined, at T = 298.15 K, by static bomb combustion calorimetry. The standard molar enthalpies of fori-nation, in the crystalline and gaseous phases, at T = 298.15 K, were derived. The experimental results for the energetics in the gaseous phase of the three compounds were compared and assessed with the values obtained by ab initio calculations at different levels of theory (DFT and MP2) showing that, at this level of theory, the computational methods underestimate the energetic stability, in the gaseous phase, for these molecules. In order to understand the aromaticity in the central ring of each isomer, calculations of NICS (B3LYP/6-311G++(d,p) level of theory) values on the pyridine ring were also performed.

Abstract Thermochemical data of dibenzothiophene were studied in the present work by experimental techniques and computational calculations. The standard (p degrees = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, in the gaseous phase, was determined from the enthalpy of combustion and sublimation, obtained by rotating bomb calorimetry in oxygen, and by Calvet microcalorimetry, respectively. This value was compared with estimated data from G3(MP2)//B3LYP computations and also with the other results available in the literature.

Abstract Twenty-two aromatic derivatives bearing a chlorine atom and a different chain in the para or meta position were prepared and evaluated for their in vitro antifungal activity against the phytopathogenic fungi Botrytis cinerea and Colletotrichum gloeosporioides. The results showed that maximum inhibition of the growth of these fungi was exhibited for enantiomers S and R of 1-(4'-chlorophenyl)-2-phenylethanol (3 and 4). Furthermore, their antifungal activity showed a clear structure-activity relationship (SAR) trend confirming the importance of the benzyl hydroxyl group in the inhibitory mechanism of the compounds studied. Additionally, a multiobjective optimization study of the global antifungal profile of chlorophenyl derivatives was conducted in order to establish a rational strategy for the filtering of new fungicide candidates from combinatorial libraries. The MOOP-DESIRE methodology was used for this purpose providing reliable ranking models that can be used later.

Abstract The multiobjective optimization technique based on the desirability estimation of several interrelated responses (MOOP-DESIRE) has been recently applied to quantitative structure-activity relationship (QSAR) studies. However, the advantage of applying this new methodology to the study of selectivity and affinity to competitive targets has been little explored. We used the MOOP-DESIRE methodology and a variation of this, to study the arylpiperazine derivates that could interact with 5-HT1A and 5-HT2A. serotonin receptor subtypes with the objective of designing more selective molecules for the 5-HT1A receptor. We did show that the model results are in agreement with the available pharmacophore descriptions, guaranteeing an appropriate structural correlation and proving the methodology, as a useful tool for the important problem of selective drug design.

Abstract Isothermal titration calorimetry (ITC) measurements were performed using solutions of whey protein isolate (WPI) and chitosan with different deacetylation degrees (DD), in acetate buffer solutions, pH 3-6. Turbidity measurements were performed in parallel in order to follow the changes in aggregation. so as to get deeper insight on the interaction mechanism. The viscosity-average molar mass of chitosan was obtained from intrinsic viscosity measurements, and the interaction enthalpies were derived at the studied pH values. Further, the denaturation process of alpha-lactalbumin and beta-lactoglobulin within WPI was characterized by differential scanning calorimetry (DSC). At pH 3, where both chitosan and the proteins are positively charged, a weak carbohydrate-protein interaction is observed. When the pH is raised to 6, where the protein charge is expected to be negative, a much stronger interaction takes place. The results are discussed with special emphasis on the effect of pH on the interactions observed in this complex system.

Abstract More than 100 transthyretin (TTR) variants are associated with hereditary amyloidosis. Approaches for TTR amyloidosis that interfere with any step of the cascade of events leading to fibril formation have therapeutic potential. In this study we tested (-)-epigallocatechin-3-gallate (EGCG), the most abundant catechin of green tea, as an inhibitor of TTR amyloid formation. We demonstrate that EGCG binds to TTR "in vitro" and "ex vivo" and that EGCG inhibits TTR aggregation "in vitro" and in a cell culture system. These findings together with the low toxicity of the compound raise the possibility of using EGCG in a therapeutic approach for familial amyloidotic polyneuropathy, the most frequent form of hereditary TTR amyloidosis. Structured summary: MINT-7294529: TTR (uniprotkb:P02766) and TTR (uniprotkb:P02766) bind (MI:0407) by comigration in non-denaturing gel electrophoresis (MI:0404)

Abstract The crystal structure of 2-thoiphenecarboxamide is described. The compound crystallizes in the orthorhombic Pna2(1) space group with unit cell parameters a = 10.044 (3) angstrom, b = 14.203 (4) angstrom and c = 15.941 (3) angstrom; V = 2,274.1 (10) angstrom(3). The asymmetric unit contains four independent molecules which are linked by N-H center dot center dot center dot O hydrogen bonds. The asymmetric unit at (x, y, z) is connected with another one, produced by the a-glide plane at 0.75 along the b-axis, that lies at (x + 0.5, -y + 1.5, z) by two N-H center dot center dot center dot O hydrogen bonds and by a C-H center dot center dot center dot O weak hydrogen bond to form a one-dimensional tube. Adjacent tubes are linked by C-H center dot center dot center dot pi interactions to form a three-dimensional framework.