Publications

Abstract A computational study of the structural and thermochemical properties of N-phenyl (open) and N-alkyl (cyclic) ureas, through the use of M05-2X and B3LYP density functional theory calculations has been carried out. The consistency of the literature experimental results has been confirmed, and using mainly isodesmic reactions, the unknown Delta fH(0)(g) of the other urea derivatives were estimated. The experimental results together with the theoretical information have permitted the study of the effect of phenyl, p- and m-chlorophenyl, alkyl, and carbonyl substitutions on the thermodynamical stability of urea and its cyclic derivatives. The peculiar behavior of the N-tert-butyl substituent in cyclic ureas has been related to geometric deformations.

Abstract The Knudsen mass-loss effusion technique was used to measure the vapor pressures at different temperatures of the following dihydroxybenzoic acids: 2,3-dihydroxybenzoic acid, between (345.22 and 363.18) K; 2,4-dihydroxybenzoic acid, between (376.22 and 392.11) K; 2,5-dihydroxybenzoic acid, between (372.14 and 388.92) K; 2,6-dihydroxybenzoic acid, between (347.14 and 365.17) K; 3,4-dihydroxybenzoic acid, between (387.12 and 403.26) K; and 3,5-dihydroxybenzoic acid, between (345.22 and 363.18) K. From the temperature dependences of the vapor pressure of the crystalline compounds, the standard (p(0) = 10(5) Pa) molar enthalpies and Gibbs energies of sublimation, at T = 298.15 K, were derived. For each of the six isomers the standard (p(0) = 0.1 MPa) molar enthalpy of formation in the crystalline phase was derived from the experimental standard molar energy of combustion, in oxygen, measured by static-bomb combustion calorimetry at T = 298.15 K. The combination of the standard molar enthalpy of formation in the crystalline phase with the standard enthalpy of sublimation yields the standard molar enthalpy of formation in the gaseous phase of the studied compounds.

Abstract The present work reports the thermodynamic study performed on three monofluorinated nitrobenzene derivatives by a combination of experimental techniques and computational approaches. The standard (p degrees = 0.1 MPa) molar enthalpies of formation in the liquid phase of the three isomers of fluoronitrobenzene were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by rotating bomb combustion calorimetry. The vapor pressure study of the referred compounds was done by a static method and, from the obtained results, the phase diagrams were elaborated, and the respective triple point coordinates, as well as the standard molar enthalpies of vaporization, sublimation and fusion, at T = 298.15 K, were determined. The combination of some of the referred thermodynamic parameters yielded the standard (p degrees = 0.1 MPa) molar enthalpies of formation in the gaseous phase, at T = 298.15 K, of the studied compounds: Delta(f)H(m)degrees(2-fluoronitrobenzene, g) = -(102.4 +/- 1.5) kJ.mol(-1), Delta(f)H(m)degrees(3-fluoronitrobenzene, g) = -(128.0 +/- 1.7) kJ.mol(-1), and Delta(f)H(m)degrees(4-fluoronitrobenzene, g) = -(133.9 +/- 1.4) kJ.mol(-1). Using the empirical scheme developed by Cox, values of standard molar enthalpies of formation in the gaseous phase were estimated and afterwards compared with the ones obtained experimentally, and both were interpreted in terms of the molecular structure of the compounds. The theoretically estimated gas-phase enthalpies of formation were calculated from high-level ab initio molecular orbital calculations at the G3(MP2)//B3LYP level of theory. The computed values compare very well with the experimental results obtained in this work and show that 4-fluoronitrobenzene is the most stable isomer from the thermodynamic point of view. Furthermore, this composite approach was also used to obtain information about the gas-phase basicities, proton and electron affinities and, finally, adiabatic ionization enthalpies.

Abstract Methamphetamine (METH) causes irreversible damage to brain cells leading to neurological and psychiatric abnormalities. However, the mechanisms underlying life-threatening effects of acute METH intoxication remain unclear. Indeed, most of the hypotheses focused on intra-neuronal events, such as dopamine oxidation, oxidative stress and excitotoxicity. Yet, recent reports suggested that glia may contribute to METH-induced neuropathology. In the present study, we investigated the hippocampal dysfunction induced by an acute high dose of METH (30 mg/kg; intraperitoneal injection), focusing on the inflammatory process and changes in several neuronal structural proteins. For that, 3-month-old male wild-type C57BL/6J mice were killed at different time-points post-METH. We observed that METH caused an inflammatory response characterized by astrocytic and microglia reactivity, and tumor necrosis factor (TNF) system alterations. Indeed, glial fibrillary acidic protein (GFAP) and CD11b immunoreactivity were upregulated, likewise TNF-alpha and TNF receptor 1 protein levels. Furthermore, the effect of METH on hippocampal neurons was also investigated, and we observed a downregulation in beta III tubulin expression. To clarify the possible neuronal dysfunction induced by METH, several neuronal proteins were analysed. Syntaxin-1, calbindin D28k and tau protein levels were downregulated, whereas synaptophysin was upregulated. We also evaluated whether an anti-inflammatory drug could prevent or diminish METH-induced neuroinflammation, and we concluded that indomethacin (10 mg/kg; i.p.) prevented METH-induced glia activation and both TNF system and beta III tubulin alterations. In conclusion, we demonstrated that METH triggers an inflammatory process and leads to neuronal dysfunction in the hippocampus, which can be prevented by an anti-inflammatory treatment.

Abstract This work reports the experiunental and computational thermochemical study performed on time dilluorinated nitrobenzene isomers: 2,4-dilluoronitrobenzene (2,4-DFNB), 2,5-di fluoronitrobenzene (2.5-DFN13), and 3,4difluoronitrobenzene (3.4-DFNI3). The standard (p(o) = 0.1 WIN) molar enthalpies of formation in the liquid phase of these compounds were derived from the standard molar energies of combustion, in oxygen, at 7' = 298.15 K, measured by rotating bomb combustion ealorimetry. A static method was used to perform the vapor pressure study of the referred compounds allowing the construction of the phase diagrams and determination of the respective triple point coordinates, as well as the standard molar enthalpies of vaporization, sublimation, and fusion for two of the isomers (2,4-DFN13 and 3,4-DFN113). For 2,5-dilluoronitrobenzene, only liquid vapor pressures were measured enabling the determination of the standard molar enthalpies of vaporization. Combining the thermodynamic parameters of the compounds studied, the following standard (p(o) = 0.1 MN) molar enthalpies of formation in the gaseous phase, at T = 298.15 K, were derived: Delta(f)H(m)(o)(2,4-DFNB, g) = (296.3 +/- 1.8) kJ.mol(-1), Delta(f)H(m)(o)(2,5-DFNB, g) = (288.2 +/- 2.1) kJ.mol(-1), and Delta(f)H(m)(o)(3,4-DFNB, g) = -(302.4 +/- 2.1) kJ.mol(-1). Using the empirical scheme developed by Cox, several approaches were evaluated in order to identify the best method for estimating the standard molar gas phase enthalpies of.formation of these compounds. The estimated values were compared to the ones obtained experirrientally, and the approach providing the best comparison with experiment was used to estimate the thermodynamic behavior of the other difluorinated nitrobenzene isomers not included in this study. Additionally, the enthalpies of formation of these compounds along with the enthalpies of formation of the other isomers not studied experimentally, i.e., 2,3-DFNB, 2,6-DFNB, and 3,5-DFNB, were estimated using the composite G3MP2B3 approach together with adequate gas-phase working reactions. Furthermore, we also used this computational approach to calculate the gas-phase hasicities, proton and electron affinities, and, finally, adiabatic ionization enthalpies.

Abstract The energetic study of 1,2,3-triphenylbenzene (1.2,3-TPhB) and 1,3,5 -triphenylbenzene (1,3,5-TPhB) isomers was carried out by making use of the mini-bomb combustion calorimetry and Knudsen mass-loss effusion techniques. The mini-bomb combustion calorimetry technique was used to derive the standard (p degrees = 0.1 MPa) molar enthalpies of formation in the crystalline state from the measured standard molar energies of combustion for both isomers. The Knudsen mass-loss effusion technique was used to measure the dependence with the temperature of the vapour pressure of crystalline 1.2.3-TPhB, which allowed the derivation of the standard molar enthalpy of sublimation, by application of the Clausius-Clapeyron equation. The sublimation study of 1,3,5-TPhB had been performed previously. From the combination of data obtained by both techniques, the standard molar enthalpies of formation in the gaseous state, for both isomers. at T = 298.15 K, were calculated. The results indicate a higher stability of the 1,3,5-TPhB isomer relative to 1,2,3-TPhB, similarly to the terphenyls. Nevertheless, the 1,2,3-TPhB isomer is not as energetically destabilized as one might expect, supporting the existence of a pi-pi displacive stacking interaction between both pairs of outer phenyl rings. The volatility difference between the two isomers is ruled by the enthalpy of sublimation. The volatility of the 1,2,3-TPhB is two orders of magnitude higher than the 1,3,5-TPhB isomer, at T = 298.15 K. [GRAPHICS]

Abstract This work aims at providing experimental and theoretical information about the water-perfluorocarbon molecular interactions. For that purpose. experimental solubility results for water in cyclic and aromatic perfluorocarbons (PFCs), over the temperature range between (288.15 and 318.15) K, and at atmospheric pressure. were obtained and are presented. From the experimental solubility dependence on temperature, the partial molar solution and solvation thermodynamic functions such as Gibbs free energy, enthalpy and entropy were determined and are discussed. The process of dissolution of water in PFCs is shown to be spontaneous for cyclic and aromatic compounds. It is demonstrated that the interactions between the non-aromatic PFCs and water are negligible while those between aromatic PFCs and water are favourable. The COSMO-RS predictive capability was explored for the description of the water solubility in PFCs and others substituted fluorocompounds. The COSMO-RS is shown to be a useful model to provide reasonable predictions of the solubility values, as well as to describe their temperature and structural modifications dependence. Moreover, the molar Gibbs free energy and molar enthalpy of solution of water are predicted remarkably well by COSMO-RS while the main deviations appear for the prediction of the molar entropy of solution.

Abstract The present work studied and compared the capacity of four important olive oil polyphenolic compounds, oleuropein, hydroxytyrosol, and the oleuropein aglycones 3,4-dihydroxyphenylethanol-elenolic acid (3,4-DHPEA-EA) and 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde (3,4-DHPEA-EDA), to protect red blood cells (RBCs) from oxidative hemolysis induced by the physiological initiator H(2)O(2). The amount of hemolysis was evaluated spectrophotometrically. The compounds were also tested in the presence and absence of the naturally occurring antioxidant ascorbic acid. All compounds were revealed to significantly protect RBCs from oxidative hemolysis induced by H(2)O(2) at 40 and 80 mu M, with the order of activity being 3,4-DHPEA-EDA > 3,4-DHPEA-EA > hydroxytyrosol = oleuropein. At 20, 10, and 5 mu M, only 3,4-DHPEA-EDA showed a significant protection against the oxidative injury. In the presence of ascorbic acid at physiological concentration, the addition of individual compounds at 40 mu M increased the stability of erythrocytes. The addition of phenolic compounds at 20 and 10 mu M did not produce further protection when compared with the protection given by ascorbic acid alone, except for 3,4-DHPEA-EDA. This compound was shown to produce further protection even at 5 mu M. In summary, 3,4-DHPEA-EDA plays an important protective role against reactive oxygen species-induced oxidative injury in RBCs, and this effect is more potent than the one evidenced by hydroxytyrosol or oleuropein.

Abstract An optical fiber sensor for Hg(II) in aqueous solution based on sol-gel immobilized carbon dots nanoparticles functionalized with PEG(200) and N-acetyl-t-cysteine is described. This sol-gel method generated a thin (about 750 nm), homogenous and smooth (roughness of 2.7 +/- 0.7 a) film that immobilizes the carbon dots and allows reversible sensing of Hg(II) in aqueous solution. A fast (less than 10 s), reversible and stable (the fluorescence intensity measurements oscillate less than 1% after several calibration cycles) sensor system was obtained. The sensor allow the detection of submicron molar concentrations of Hg(II) in aqueous solution. The fluorescence intensity of the immobilized carbon dots is quenched by the presence of Hg(II) with a Stern-Volmer constant (pH = 6.8) of 5.3 x 10(5) M(-1).

Abstract While cationic/anionic surfactant mixtures have been reported to form strongly non-ideal mixed aggregates in aqueous solution the micellization of true catanionic surfactants i e the salt free ion paired compounds obtained from the mixtures has been much less investigated However if there is a significant solubility mismatch between the paired chains these surfactants may show less conventional aggregation features in water such as a temperature driven vesicle-micelle transition and the coexistence of two lamellar phases in equilibrium In this work we carry out micellization studies for a catanionic surfactant of the type C(16)(+)C(8)(-) cetyltrimethylammonium octylsulfonate (TASo) by surface tension and conductivity measurements For comparison purposes the catanionic mixture cetyltrimethylammonium bromide (CTAB)/sodium octylsulfonate (SOSo) at different mixing ratios and the neat SOSo have also been studied For the non ideal CTAB/SOSo mixture Rubingh s model has been applied to determine the beta interaction parameter and the mixed micelle composition The cmc of TASo has been investigated as a function of temperature salt and excess ionic surfactant displaying some differences with respect to conventional ionic and nonionic surfactants The trends in the thermodynamic parameters of micellization of the three types of systems are comparatively rationalized