Publications

Abstract We report a study on the energetics and structural properties of naphthalene-based proton sponges and their corresponding protonated cations. In particular, we have determined the experimental standard enthalpies of formation in the gas phase at T = 298.15 K, Delta fH(m)(o) m (g), for the neutral and protonated DMAN [1,8-bis (dimethylamino)-naphthalene], (221.0 +/- 7.3) and (729.0 +/- 11.1) kJ.mol(-1), respectively. A reliable experimental estimation of enthalpy associated with "strain'' effect and hydrogen bond intramolecular (included within "enhanced basicity'', EB) contributions to the basicity of DMAN, were deduced from isodesmic reactions, -(29.1 +/- 4.6) and (87.1 +/- 11.9) kJ.mol(-1), respectively. The gas-phase basicities (GB) of naphthalene-based proton sponges are compared with the corresponding aqueous basicities (pKa), covering a range of 149 kJ.mol(-1) in GB and 11.5 in pKa. Density functional calculations at the M05-2X/6-311++G(d,p) level of theory were used to check the consistency of the experimental results and also to estimate the unavailable GB values of the considered species.

Abstract In this work, the interplay between structure and energetics in some representative phenylnaphthalenes is discussed from an experimental and theoretical perspective. For the compounds studied, the standard molar enthalpies, entropies and Gibbs energies of sublimation, at T = 298.15 K, were determined by the measurement of the vapor pressures as a function of T, using a Knudsen/quartz crystal effusion apparatus. The standard molar enthalpies of formation in the crystalline state were determined by static bomb combustion calorimetry. From these results, the standard molar enthalpies of formation in the gaseous phase were derived and, altogether with computational chemistry at the B3LYP/6-311++G(d,p) and MP2/cc-pVDZ levels of theory, used to deduce the relative molecular stabilities in various phenylnaphthalenes. X-ray crystallographic structures were obtained for some selected compounds in order to provide structural insights, and relate them to energetics. The thermodynamic quantities for sublimation suggest that molecular symmetry and torsional freedom are major factors affecting entropic differentiation in these molecules, and that cohesive forces are significantly influenced by molecular surface area. The global results obtained support the lack of significant conjugation between aromatic moieties in the alpha position of naphthalene but indicate the existence of significant electron delocalization when the aromatic groups are in the beta position. Evidence for the existence of a quasi T-shaped intramolecular aromatic interaction between the two outer phenyl rings in 1,8-di([1,1-biphenyl]4-yl)naphthalene was found, and the enthalpy of this interaction quantified on pure experimental grounds as -(11.9 +/- 4.8) kJ.mol(-1), in excellent agreement with the literature CCSD(T) theoretical results for the benzene dimer.

Abstract In the recent decades, numerous drug delivery systems based on nanoparticles have been developed. To deliver drugs to a specific site, many vehicles have been designed, including liposomes, lipid and polymeric nanoparticles. However these systems can suffer some limitations such as thermal and physical instability as well as opsonization by reticuloendothelial system. This chapter addresses the development and application of silica gel nanoparticles (nanogels) for drug delivery. The synthesis of nanoparticles by sol-gel technology offers new possibilities and many advantages for embedding organic compounds within silica, controlling their release from the host matrix into a surrounding medium, being a great potential for a variety of drug delivery applications, such as the site-specific delivery and intracellular controlled release of drugs, genes, and other therapeutic agents. © 2012 Springer-Verlag Berlin Heidelberg. All rights are reserved.

Abstract The energetic study of 4-nitro-2,1,3-benzothiadiazole has been developed using experimental techniques together with computational approaches. The standard (p degrees = 0.1 MPa) molar enthalpy of formation of crystalline 4-nitro-2,1,3-benzothiadiazole (181.9 +/- 2.3 kJ . mol(-1)) was determined from the experimental standard molar energy of combustion -(3574.3 +/- 1.3) kJ . mol(-1), in oxygen, measured by rotating-bomb combustion calorimetry at T = 298.15 K. The standard (p degrees = 0.1 MPa) molar enthalpy of sublimation, at T = 298.15 K, (101.8 +/- 4.3) kJ . mol(-1), was determined by a direct method, using the vacuum drop micro-calorimetric technique. From the latter value and from the enthalpy of formation of the solid, it was calculated the standard (p degrees = 0.1 MPa) enthalpy of formation of gaseous 4-nitro-2,1,3-benzothiadiazole as (283.7 +/- 4.9) kJ . mol(-1). Standard ab initio molecular orbital calculations were performed using the G3(MP2)//B3LYP composite procedure and several working reactions in order to derive the standard molar enthalpy of formation 4-nitro-2,1,3-benzothiadiazole. The ab initio results are in good agreement with the experimental data.

Abstract The use of a good chemical calibration or test reaction in Isothermal Titration Calorimetry is crucial for getting reliable enthalpy values that can be compared across different laboratories. Indeed most titration calorimeters are used to measure both equilibrium constants and molar enthalpies of reaction. But a necessary prerequisite for such measurements is to first perform the enthalpy measurement accurately and precisely. The values of the equilibrium constant(s) are then calculated by regression from an appropriate model. As such, we found it timely to extensively test a previously proposed test reaction, the dilution of propan-1-ol into water, using two calorimeters of different design (heat conduction and power compensation calorimeters) and sensitivity. Experiments were performed at 298.15 K for the previously suggested 10% mass fraction propan-1-ol solution, as well as for the lower concentrations of 5% and 2% mass fractions. Due to our capacity to use insertion heaters with one of the used calorimeters, which allows for very accurate calibration constants to be obtained, we also determined a value for the enthalpy of dilution of 10% mass fraction solution at 308.15 K, previously not available, and closer to the temperatures commonly used in titration experiments involving biological samples. The observed change in the enthalpy of dilution was found to decrease in absolute value, but to an extent that did not justify the determination of new values for the less concentrated solutions. The values obtained with the two calorimeters are in excellent agreement, as well as with the values from the literature for the 10% mass fraction solution at 298.15 K. This reaction is thus again proposed as an excellent test reaction and the detailed conditions of their use depending on instrument sensitivity are suggested. In summary, the values for the enthalpies of dilution to infinite dilution Delta H-dil(m)infinity at 298.15 K are -(1.540 +/- 0.021) kJ . mol (1), -(0.604 +/- 0.020) kJ . mol (1), and -(0.186 +/- 0.011) kJ . mol (1) for the 10%, 5%, and 2% mass fraction solutions, respectively, and at 308.15 K -(1.486 +/- 0.017) kJ . mol (1) for the 10% mass fraction solution.

Abstract Liposome dispersions obtained from the mixture of gemini surfactants of the type alkane-alpha,omega-diyl-bis(alkyl-dimethylammonium bromide) and helper lipid DOPC create complexes with DNA showing a regular inner microstructure, identified by small angle X-ray diffraction as condensed lamellar phase (L-alpha(c)). In addition to the L-alpha(c) phase, a coexisting lamellar phase L-B was also identified in the complexes formed, with periodicities in the range similar to 8.8-5.7 nm, at ionic strengths corresponding to 50-200 mM NaCl. The periodicities of L-B phase did not correspond to those identified in liposome dispersion without DNA using small angle neutron scattering. The observed phase separation is shown to depend on the interplay between the surface charge density of cationic liposomes, ionic strength and method of complex preparation. The effect of ionic strength on complex formation was studied by isothermal titration calorimetry and zeta potential measurements. High ionic strength reduces the fraction of bound DNA in the complexes, and the isoelectric point is attained at a ratio of DNA/gemini surfactant which is lower than the one that can be estimated by calculation based on nominal charges of CLs and DNA.

Abstract The use of deep eutectic solvents for metal electrodeposition has become an area of interest in the recent years. In this study, ethaline, propeline, and reline were used as solvents for the electrodeposition of Sn-Zn alloys. Ethaline, propeline, and reline displayed identical voltammetric profiles for the reduction of Zn(II) and Sn(II). Further studies were carried out in ethaline which is the liquid with lowest viscosity. To improve physical and morphological properties of the Sn-Zn deposits, additives were added to the ionic liquid solution. In this study, the addition of three chelators (EDTA, HEDTA, and Idranal VII) and their effects on the voltammetric behavior of zinc and tin and the resultant morphology was described. The structure and composition of the Zn-Sn deposit was largely affected by the additives with the largest effect being obtained in the presence of Idranal VII.