Publications

Abstract Two substituted N-acylthioureas and the respective Ni(II) and Cu(II) complexes were synthesized, namely: N,N-di-n-butyl-N'-thenoylthiourea (Hnbtu); N,N-di-iso-butyl-N'-tlienoylthiourea (Hibtu); bis[N,N-di-n-butyl-N'-thenoylthioureato]nickel(II), [Ni(nbtu)(2)]; bis[N,N-di-n-butyl-N'-thenoylthioureato]copper(II), [Cu(nbtu)(2)]; bis[N,N-di-iso-butyl-N'-thenoylthioureato]nickel(II), [Ni(ibtu)2]; bis[N,N-di-iso-butyl-N'-thenoylthioureato]copper(II), [Cu(ibtu)(2)]. The standard (p degrees = 0.1 MPa) molar enthalpies of formation and sublimation of the two N-acylthioureas were measured, at T = 298.15 K, by rotating-bomb combustion calorimetry and Calvet microcalorimetry, respectively. The standard (p = 0.1 MPa) molar enthalpies of formation of the Ni(H) and Cu(H) complexes were determined, at T= 298.15 K, by high precision solution-reaction calorimetry. From the results obtained, the enthalpies of hypothetical metal-ligand and metal-metal exchange reactions, in the gaseous phase, were derived, thus allowing a discussion of the gaseous phase energetic difference between the complexation of Ni(II) and Cu(II) to 1,3-ligand systems with (S,O) ligator atoms.

Abstract The spontaneous formation of vesicles by the salt-free surfactant hexadecyltrimethylammonium octylsulfonate (TASo) and the features of an unusual vesicle-micelle transition are investigated in this work. In a previous work, we have shown that this highly asymmetric catanionic surfactant displays a rare lamellar miscibility gap in the concentrated regime. Here, we analyze in detail the aggregation behavior in the dilute regime (less than 3 wt % surfactant) as a function of both concentration and temperature. The phase diagram is dominated by a two-phase region consisting of a dispersion of a swollen lamellar phase (L alpha') in the excess solvent phase (L-1). Stable vesicles form in this two-phase region, and upon temperature increase, a transition to a single solution phase containing only elongated micelles occurs. The structural characterization of the aggregates and the investigation of their equilibrium properties have been carried out by light microscopy, cryo-TEM, water self-diffusion NMR, and SANS. Similarly to the lamellar-lamellar coexistence, the changes in microstructure at high dilution and high temperature can be understood from solubility differences, electrostatic interactions, and preferred aggregate curvature. Surface charge in the aggregates stems from the higher solubility of the octylsulfonate (So(-)) ion as compared to that of the hexadecyltrimethylammonium ion (TA(+)). Upon temperature increase, the ratio of free So(-) relative to the neutral TASo increases. Consequently, the surface charge density of the aggregates increases, and this ultimately induces a transition to a higher-curvature morphology (elongated micelles). Vesicles can also be spontaneously formed by cooling solutions from the micellar region, and the mean size obtained is practically independent of cooling rate, suggesting that dissociation/charge effects also control this process.

Abstract The mixed didodecyldimethylammonium bromide (DDAB)-sodium taurodeoxycholate (STDC)-(H2O)-H-2 catanionic system forms a large isotropic (L-1) phase at 25 degrees C. The evolution of microstructure along different dilution lines has been followed by means of rheology and NMR diffusometry. In general, the L, phase is characterised by a weak viscoelasticity and Newtonian response. In the STDC-rich regime (W-s = [DDAB]/[STDC] = 0.2), 5 wt% is an overlapping concentration at which the discrete-to-rodlike micellar transition occurs as indicated from the total surfactant concentration (C-s) dependency of both zero-shear viscosity (eta(0) similar to C-s(3.7)) and surfactant self-diffusion (D-s similar to C-s(-3.0)). As the surfactant molar ratio (W-s >= 1) increases, i.e., DDAB concentration increases, and at constant C-s, eta(0) decreases and D-s increases, indicating the formation of a multiconnected micellar network. (c) 2008 Elsevier Inc. All Fights reserved.

Abstract The first general methodology for the gram-scale preparation of previously overlooked beta-(hetero)aryl-alpha-nitro-alpha,beta-enals (3) is reported. Condensation of (hetero) aromatic aldehydes with 2-nitroethanol gave the E-isomers of uncommon beta-(hetero)aryl-alpha-hydroxymethyl-alpha,beta-unsatured-nitroalkenes (2), as determined by NOE and X-ray studies. alpha-Nitro-alpha,beta-enals 3 were subsequently obtained by hypervalent iodine oxidation of 2 as E-Z-mixtures in solid form. They showed varied stability and solvent-dependent thermal-promoted and photopromoted E-Z interconversion. Starting with furfural, experimental conditions were developed to prepare the corresponding nitroenal 3a enriched in either the E or the Z isomer: E-3a/Z-3a approximate to 90/10 and 20/80, respectively. In contrast with other structurally related compounds, nitroenals 3 have their (hetero)aryl-vinyl unit and their formyl and nitro groups all in a planar arrangement, both in solid form and in solution; accordingly, they are colored compounds with predicted high dipole moments. As deduced from solution-NMR and X-ray data, the C=C and the C=O double bonds in 3 are exclusively s-cis-oriented; this disposition corresponds in fact to the DFT-computed most stable conformer.

Abstract The solubility of water in tetradecyltrihexylphosphonium-based ionic liquids (ILs) with the bromide, bis(trifluoromethylsulfonyl)imide, bis(2,4,4-trimethylpentyl)phosphinate, chloride, decanoate, and dicyanimide anions was measured at temperatures between (288.15 and 318.15) K and atmospheric pressure. The effect of the nature of the IL anion, as well as the influence of temperature, are analyzed and discussed. From the experimental results, it was found that the anion-induced hydrophobicity increases from bis(2,4,4trimethylpentyl)phosphinate < decanoate < chloride < bromide < dicyanimide < bis(trifluoromethylsulfonyl)imide. COSMO-RS, a predictive method based on unimolecular quantum chemistry calculations, was used to predict the solubility of the water-IL binary systems. COSMO-RS was found to provide fine qualitative and quantitative predictions of the experimental data for extremely hydrophobic ILs. Less accurate predictions were observed with the increase of the anion hydrophilic character.

Abstract Vapor pressures of xanthene [CAS Registry No. 92-83-1] and phenoxathiin [CAS Registry No. 262-20-4] were measured in the temperature range from (318 to 382) K [(0.5 to 127) Pa] and from (318 to 373) K [(0.5 to 36) Pa], respectively, using a static method, in both crystalline and liquid phases. The vapor pressures of the crystalline phases of both compounds were also measured in the pressure range (0.1 to 1) Pa using the Knudsen effusion method. From the experimental results, the standard molar Gibbs energies and enthalpies of sublimation/vaporization, at T = 298.15 K, and the triple-point coordinates for these two compounds were derived. The enthalpies and temperatures of fusion were also determined using differential scanning calorimetry. To the best of our knowledge, vapor pressure data reported here are the first for crystalline phenoxathiin and for liquid xanthene.

Abstract Numerical parameters of the molecular networks, also referred as Topological Indices or Connectivity Indices (CIs), have been used in Bioorganic and Medicinal Chemistry to find Quantitative Structure-Activity, Property or Toxicity Relationship (QSAR, QSPR and QSTR) models. QSPR models generally use CIs as inputs to predict the biological activity of compounds. However, the literature does not evidence a great effort to find QSAR-like models for other biologically and chemically relevant systems. For instance, blood proteome constitutes a protein-rich information reservoir, since the serum proteome Mass Spectra (MS) represents a potential information source for the early detection of Biomarkers for diseases and/or drug-induced toxicities. The concept of mass spectrum network (MS network) for a single protein is already well-known. However, there are no reported results on the use of CIs for a MS network of a whole proteome to explore MS patterns. In this work, we introduced for the first time a novel network representation and the CIs for the MS of blood proteome samples. The new network bases on Randic's Spiral network have been previously introduced for protein sequences. The new MS CIs, called here Spiral Markov Connectivity (SMCk) of the MS Spiral graph can be calculated with the software MARCH-INSIDE, combining network and Markov model theory. The SMCk values could be used to seek QSAR-like models, called in this work Quantitative Proteome-Property Relationships (QPPRs). We calculate the SMCk values for 62 blood samples and fit a QPPR model by discriminating proteome MS, typical of individuals susceptible to suffer drug-induced cardiotoxicity from control samples. The accuracy, sensitivity, and specificity values of the QPPR model were between 73.08% and 87.5% in training and validation series. This work points to QPPR models as a powerful tool for MS detection of biomarkers in proteomics.

Abstract The standard (p(o)=0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T=298.15 K, for 2,5-dimethylpyrazine (2,5-DMePz) and for the two dimethylpyrazine-N,N'-dioxide derivatives, 2,3-dimethylpyrazine-1,4-dioxide (2,3-DMePzDO) and 2,5-dimethyl-pyrazine-1,4-dioxide (2,5-DMcPzDO), were derived from the measurements of standard massic energies of combustion, using a static bomb calorimeter, and from the standard molar enthalpies of vaporization or sublimation, measured by Calvet microcalorimetry. The mean values for the molar dissociation enthalpy of the nitrogen-oxygen bonds, < DHmo >(N-O), were derived for both N,N'-dioxide compounds. These values are discussed in terms of the molecular structure of the two N,N'-dioxide derivatives and compared with < DHmo >(N-O) values previously obtained for other N-oxide derivatives.