Publications

Abstract Aiming at evaluating the impact of the cation symmetry on the nanostructuration of ionic liquids (ILs), in this work, densities and viscosities as a function of temperature and small wide angle X-ray scattering (SWAXS) patterns at ambient conditions were determined and analyzed for 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (asymmetric) and 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl) imide (symmetric) series of ionic liquids. The symmetric IL series, [ChinCNnim][NTf2], presents lower viscosities than the asymmetric [C-N/2 C-N/2 im][NTf2] counterparts. For ionic liquids from [C(1)C(1)im][NTf2] to [C(6)C(6)im][NTf2], an odd even effect in the viscosity along the cation alkyl side chain length was observed, in contrast with a linear increase found for the ones ranging between [C(6)C(6)im][NTf2] and [Ci(10)C(10)im][NTf2]. The analysis of the viscosity data along the alkyl side chain length reveals a trend shift that occurs at [C(6)Cim][NTf2] for the asymmetric series and at [C6C6im][NTf2] for the symmetric series. These results are further supported by SWAXS measurements at ambient conditions. The gathered data indicate that both asymmetric and symmetric members are characterized by the occurrence of a distinct degree of mesoscopic structural organization above a given threshold in the side alkyl chain length, regardless the cation symmetry. The data also highlight a difference in the alkyl chain dependence of the mesoscopic cluster sizes for symmetric and asymmetric cations, reflecting a different degree of interdigitation of the aliphatic tails in the two families. The trend shift found in this work is related to the structural segregation in the liquid after a critical alkyl length size (CALS) is attained and has particular relevance in the cation structural isomerism with higher symmetry.

Abstract A computational study has been carried out for xanthene and thioxanthene homologous derivatives with keto, hydroxyl, carboxyl, and carboxamide functional groups on position 9, contributing to the understanding of their energetics and reactivity. For that it is presented and compared with the molecular structures, the electrostatic potential energy maps, and the electronic properties of all these heteropolycyclic compounds. The estimation of the standard molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was made only for the thioxanthydrol, thioxanthene-9-carboxylic acid, and thioxanthene-9-carboxamide using the experimental values available in the literature for the homologous compounds containing oxygen.

Abstract Thermochemical data of dibenzofuran, a compound of considerable industrial and environmental significance, obtained from experimental calorimetric and computational techniques are reported in this work. The enthalpy of fusion, (19.4 +/- 1.0) kJ mol(-1), at the temperature of fusion, (355.52 +/- 0.02) K, was determined by differential scanning calorimetry measurements of dibenzofuran. From the standard (p degrees = 0.1 MPa) molar enthalpies of formation of crystalline dibenzofuran, (-29.2 +/- 3.8) kJ mol(-1), and of sublimation, (84.5 +/- 1.0) kJ mol(-1), determined at T = 298.15 K by static bomb combustion calorimetry and by vacuum drop microcalorimetry, respectively, it was possible to calculate the enthalpy of formation of the gaseous compound, (55.0 +/- 3.9) kJ mol(-1), at the same temperature. The enthalpy of formation in the gaseous phase was also determined from G3(MP2)//B3LYP calculations. The same computational strategy was employed in the calculation of the standard molar enthalpies of formation, at T = 298.15 K, in the gas-phase, of single methylated derivatives of benzofuran and dibenzofuran.

Abstract A new and efficient process for organic synthesis in aqueous media based on a direct ohmic heating reactor is described. Four representative organic transformations, a Diels-Alder cycloaddition, a nucleophilic substitution, an N-alkylation and a Suzuki cross-coupling reaction, were performed using this process. The results, when compared with those obtained under conventional external heating (oil bath) and microwave heating, showed that ohmic reactor allows faster and more uniform heating and an induced increase of dynamics/mobility of charged species leading in several cases to higher reaction yields and shorter reaction times.

Abstract The standard (p degrees = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, of the cyclic anhydrides of glycine and DL-alanine, at T = 298.15 K, were derived from the standard molar energies of combustion in oxygen, measured by static bomb combustion calorimetry. For these compounds, the standard molar enthalpies of sublimation, at T = 298.15 K, were determined from the temperature-vapour pressure dependence, obtained by the Knudsen mass-loss effusion method. Through the values for the heat capacity differences between the gas and the crystalline phases of the studied compounds, the standard (p degrees = 0.1 MPa) molar enthalpies, entropies and Gibbs energies of sublimation, at T = 298.15 K, were derived. From the experimental values, the standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, of glycine anhydride and DL-alanine anhydride were calculated as -(321.0 +/- 1.9) kJ.mol(-1) and -(382.7 +/- 2.0) kJ.mol(-1), respectively. A theoretical study at the G3 and G4 levels has been carried out, and the calculated enthalpies of formation have been compared with the experimental values.

Abstract The structure and membrane interactions of three antimicrobial peptides from the lactoferrin family were investigated through different techniques. Circular dichroism shows that the peptides adopt a secondary structure in the presence of DMPC/DMPG, and DSC reveals that they all interact with these membranes, albeit differently, whereas only LFchimera has an effect in pure zwitterionic membranes of DMPC. DSC further shows that membrane action is weakest for LFcin17-30, increases for LFampin265-284 and is largest for LFchimera. These differences are clearly reflected in a different structure upon interaction, as revealed by SAX. This technique shows that LFcin17-30 only induces membrane segregation (two lamellar phases are apparent upon cooling from fluid phase), whereas LFampin265-284 induces micellization of the membrane with structure compatible to a micellar cubic phase of space group Pm3n, and LFchimera leads to membrane destruction through the formation of two cubic phases, Pn3m and Im3m. These structural results show a remarkable parallel with the ones obtained previously by freeze fracture microscopy of the effect of these peptides against Candida albicans.

Abstract The standard (p degrees = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, of the 2-, 3- and 4-iodobenzonitrile isomers were derived from the combination of the corresponding standard molar enthalpies of formation, in the condensed phase, at T = 298.15 K, and the standard molar enthalpies of sublimation, at the same temperature, calculated respectively from the standard molar energies of combustion in oxygen, measured by rotating-bomb calorimetry, and from the vapour-pressure study of the referred compounds, measured by mass-loss Knudsen effusion technique. The strength of the halogen-halogen and the halogen-cyano intermolecular interactions, in the crystal, are evaluated by the enthalpies and entropies of phase transition of the iodobenzonitrile derived from mass-loss Knudsen technique and differential scanning calorimetry measurements and compared with those reported to fluorobenzonitrile and bromobenzonitrile isomers. The computational calculations complement the experimental work, using different aromaticity criteria (HOMA, NICS, Shannom Aromaticity, PDI and ATI) for the analysis of the electronic behaviour of each iodobenzonitrile isomer.

Abstract Higher Education Institutions (HEI) are increasing the level of cooperation with the society, as well as, private organizations, research institutes and laboratories. This research proposes the discussion of the accounting for sustainability based on the international accreditation standard according to NP EN ISO/IEC 17025 [1] for the Environmental Monitoring and Research Laboratory (with portuguese acronym of LABMIA). The methodology of research is divided in theoretical and empirical analysis. The first is supported on the institutional theory that emphasizes the organizations as more than a mean to produce products and services-they are also social and cultural systems [2]. The second is an empirical analysis that it is entirely supported in archival sources. In the end, following the theoretical framework, we do the economic assessment viability of the LABMIA [3], where it is developed a price market analysis of accredited laboratories, with information published on the website of the government regulator [4], on January 12th of 2012. The discussion of the results shows that consumers of products and services, the government regulators and businesses approves the cooperation between them and the HEI to incorporate value and benefits. Also, the HEI is more sensible to create wealth efficiently and distributed fairly within the national economy through the higher education system. Further analysis could not be developed, because it does not exists public available information. Thus, fewer information sources about quality/cost and the price of individual laboratory analysis are essential to evaluate the legitimacy of HEI and, unfortunately, the institutional context is less studied and less understood.

Abstract Modern societies moved towards academic and professional specialization, and human activity has been rigidly structured and split. The enduring gap between science and art, which academic curricula mirror and sustain, reproduces rather than changes the patterns of social inclusion and exclusion. In this commentary, we review some empirical endeavors to merge poetry with chemistry from an ecological, developmental, and constructivist perspective. It seems Important to involve students in structured activities promoting a socio-historical understanding of the opportunities and constraints acting on chemistry, the significance of chemistry theories and methods, and a holistic approach to chemistry as a field of self-expression and social commitment. By merging poetry with chemistry, we expect not only that students learn chemistry, but also that they develop scientific literacy skills as well as a more critical view on the co-extensiveness of modern challenges.

Abstract The successful high throughput screening of molecule libraries for a specific biological property is one of the main improvements in drug discovery. The virtual molecular filtering and screening relies greatly on quantitative structure-activity relationship (QSAR) analysis, a mathematical model that correlates the activity of a molecule with molecular descriptors. QSAR models have the potential to reduce the costly failure of drug candidates in advanced (clinical) stages by filtering combinatorial libraries, eliminating candidates with a predicted toxic effect and poor pharmacokinetic profiles, and reducing the number of experiments. To obtain a predictive and reliable QSAR model, scientists use methods from various fields such as molecular modeling, pattern recognition, machine learning or artificial intelligence. QSAR modeling relies on three main steps: molecular structure codification into molecular descriptors, selection of relevant variables in the context of the analyzed activity, and search of the optimal mathematical model that correlates the molecular descriptors with a specific activity. Since a variety of techniques from statistics and artificial intelligence can aid variable selection and model building steps, this review focuses on the evolutionary computation methods supporting these tasks. Thus, this review explains the basic of the genetic algorithms and genetic programming as evolutionary computation approaches, the selection methods for high-dimensional data in QSAR, the methods to build QSAR models, the current evolutionary feature selection methods and applications in QSAR and the future trend on the joint or multi-task feature selection methods.