Publications

Abstract The industrial application of ionic liquids (ILs) requires the knowledge of their physical properties and phase behavior. This work addresses the experimental determination of the vapor-liquid equilibria (VLE) of binary systems composed of water + imidazolium-based ILs. The ILs under consideration are 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium thiocyanate, 1-butyl-3-methylimidazolium tosylate, 1-butyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium methanesulfonate, and 1-butyl-3-methylimidazolium acetate, which allows the evaluation of the influence of the IL anion through the phase behavior. Isobaric VLE data were measured at 0.05, 0.07, and 0.1 MPa for IL mole fractions ranging between 0 and 0.7. The observed increase in the boiling temperatures of the mixtures is related with the strength of the interaction between the IL anion and water. The Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was further used to describe the obtained experimental data. The ILs were treated as molecular associating species with two association sites per IL. The model parameters for the pure fluids and the binary interaction parameter k(ij) between water and ILs were determined by a simultaneous fitting to pure-IL densities, water activity coefficients at 298.15 K and VLE data at 0.1 MPa. Pure-IL densities, water activity coefficients, and VLE data were well described by PC-SAFT in broad temperature, pressure, and composition ranges. The PC-SAFT parameters were applied to predict the water activity coefficients at infinite dilution in ILs, and a satisfactory prediction of experimental data was observed.

Abstract So far, no connection between coffee consumption and breast cancer development has been confirmed, although a positive association has been described for specific individuals. The general rule is that coffee consumption has no effect or actually decreases the incidence of breast cancer. Several coffee constituents such as caffeine, lignans, flavonoids, and hydroxycinnamic acids have been investigated in the context of breast cancer. Hydroxycinnamic acids, especially caffeic and ferulic acids, display a potent antioxidant and anti-radical activity in models of breast cancer, acting through different mechanisms. Although caffeic and ferulic acid have well-established properties, some derivatives of both molecules, possessing slight modifications in their structure, have improved chemotherapeutic activity toward breast cancer cells. Therefore, natural phytochemical molecules such as those present in coffee are a promising and pragmatic clinical approach, by presenting low toxicity to normal cells and high activity toward their malignant counterparts.

Abstract Gemini surfactants have been successfully used as components of gene delivery systems. In the present work, a family of gemini surfactants, represented by the general structure [CmH2m+1(CH3)(2)N+(CH2)(s)N (+)(CH3)(2)CmH2m+1]2Br , or simply m-s-m, was used to prepare cationic gene carriers, aiming at their application in transfection studies. An extensive characterization of the gemini surfactant-based complexes, produced with and without the helper lipids cholesterol and DOPE, was carried out in order to correlate their physico-chemical properties with transfection efficiency. The most efficient complexes were those containing helper lipids, which, combining amphiphiles with propensity to form structures with different intrinsic curvatures, displayed a morphologically labile architecture, putatively implicated in the efficient DNA release upon complex interaction with membranes. While complexes lacking helper lipids were translocated directly across the lipid bilayer, complexes containing helper lipids were taken up by cells also by macropinocytosis. This study contributes to shed light on the relationship between important physico-chemical properties of surfactant-based DNA vectors and their efficiency to promote gene transfer, which may represent a step forward to the rational design of gene delivery systems.

Abstract A combined experimental and computational study was developed with the aim of evaluate and understand the structural, energetic and reactivity properties of phenoxazine and phenothiazine. Experimentally, differential scanning calorimetry, static and rotating bomb combustion calorimetries, Knudsen effusion and Calvet microcalorimetry were employed to determine, respectively, the standard (p degrees = 0.1 MPa) molar enthalpies of fusion, Delta H-1(cr)m degrees, at the temperature of fusion, the standard molar enthalpies of formation, in the crystalline phase, Delta H-f(m)degrees(cr), at T = 298.15 K, the temperature-vapor pressures dependences, and the standard molar enthalpies of sublimation, Delta H-g(cr)m degrees, at T = 298.15 K. These data allowed the derivation the experimental standard molar enthalpies of formation, in the gaseous phase, Delta H-f(m)degrees(g), of phenoxazine, (100.8 +/- 4.3) kJ.mol (1), and of phenothiazine, (273.5 +/- 4.7) kJ.mol (1). Computationally, the composite G3(MP2)//B3LYP approach was used to optimize the structures of these two compounds and to estimate their Delta H-f(m)degrees(g) values, which are found to be in very good agreement with the experimental ones. Calculations were also performed for additional analyses of their natural bond orbitals (NBO) and to obtain other gas-phase thermodynamic properties, namely N-H bond dissociation enthalpies, gas-phase acidities and basicities and proton affinities.

Abstract The standard (p(degrees) = 0.1 MPa) molar enthalpy of formation, in the crystalline phase, of N-acetyl-L-cysteine, NAC, at T = 298.15 K, was derived from the standard molar energy of combustion in oxygen, measured by static bomb combustion calorimetry. A value of -(737.8 +/- 1.9) kJ . mol (1) was obtained. For this compound, the standard molar enthalpy of sublimation, at T = 298.15 K, could not be determined due to the decomposition of the compound during the corresponding experiments. A theoretical study at the G3 and G4 levels has been carried out, and a value of -(610.7 +/- 4.0) kJ . mol (1) is recommend for the enthalpy of formation in the gas phase. Using this theoretical value and the experimental enthalpy of formation in the crystalline phase, it is possible to estimate a value of (127.1 +/- 4.4) kJ . mol (1) for the enthalpy of sublimation of this compound.

Abstract A specific methodology based on nitric acid hydrothermal oxidation was used to control the surface chemistry of multi-walled (MWCNTs) and single-walled (SWCNTs) carbon nanotubes (CNTs) with different lengths, and this methodology was adapted to the use of sulphuric acid containing ammonium persulfate as an oxidizing agent. The amount of oxygen-containing surface groups depends on the number and length of the graphene layers of the CNTs, thicker and shorter CNTs having more reactive sites for surface functionalization. In particular, the oxidation of MWCNTs was more pronounced than that of short SWCNTs and less surface groups were introduced into long SWCNTs, regardless of the acid used at any fixed concentration. It was also possible to tailor the surface chemistry of both SWCNTs and MWCNTs by using the adopted methodologies, and the amount of both oxygen-and sulphur-containing functional groups was correlated with the concentration of each oxidizing agent used. Mathematical functions that allow precise control of the amount and type of the surface groups introduced into carbon nanotubes were obtained. Buckypapers were also prepared over a polytetrafluoroethylene commercial membrane. These membranes were tested in direct contact membrane distillation and, under salinity conditions, the membrane prepared using oxidized MWCNTs (instead of SWCNTs) was the most efficient, the permeate flux of the commercial membrane significantly increasing in the presence of these CNTs, while completely rejecting chloride ions. In addition, the permeate flux was precisely correlated with the amount of oxygenated functional surface groups (as well as with the pH of point of zero charge) of the oxidized MWCNTs.

Abstract As demonstrated with the β-(2-furyl)-substituted analogue 1b, β-aryl-α-nitro-α,β-enals(1)behave as heterodienes against enamines and enol ethers using their enal unit (e.g., 1b → 12). α-Nitro-α,β-enals can act as well as highly reactive dienophiles to render adducts endowed with nitrogenated quaternary centers (e.g., 1b → 15a). A hetero-Diels-Alder (HDA)/Diels-Alder (DA) sequence from 1b also proved feasible on serial treatment with ethyl vinyl ether and Danishefsky's diene (1b → 14).

Abstract Thermodynamic properties of ortho, meta and para methoxybenzamides were determined using the Knudsen effusion method and calorimetric experiments as well as computational approaches. The vapour pressure of the crystalline phase of the three isomers was measured and values of the standard (p(o) = 0.1 MPa) molar enthalpy, Gibbs energy and entropy of sublimation, at T = 298.15 K, were derived. Static bomb combustion calorimetry was used to measure the standard molar enthalpies of combustion from which the standard molar enthalpies of formation in the crystalline state, at T = 298.15 K, were derived. Together with the standard molar enthalpies of sublimation, these results yielded the standard molar enthalpies of formation in gaseous phase of the three isomers. The standard Gibbs energies of formation in crystalline and gaseous phases were also derived and used to differentiate the thermodynamic stability of the three isomers. Moreover, differential scanning calorimetry analysis enabled determination of the temperature and molar enthalpies of fusion of the studied compounds. Gas-phase enthalpies of formation of the three compounds were estimated computationally at the G3 and G4 levels of theory and compared with the experimental results.

Abstract This report presents a comprehensive experimental and computational study of the thermodynamic properties of two fluorene derivatives: 2-aminofluorene and 2-nitrofluorene. The standard (p degrees = 0.1 MPa) molar enthalpies of formation in the crystalline phase of these compounds were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. A Knudsen effusion method was used to perform the vapour pressure study of the referred compounds, yielding an accurate determination of the standard molar enthalpies and entropies of sublimation. The enthalpies of sublimation were also determined using Calvet microcalorimetry and the enthalpy and temperature of fusion were derived from DSC experiments. Derived results of standard enthalpy and Gibbs energy of formation in both gaseous and crystalline phases were compared with the ones reported in literature for fluorene. A theoretical study at the G3 and G4 levels has been carried out, and the calculated enthalpies of formation have been compared to the experimental values.