Publications

Abstract In the title compound, [Ni(C9H10NO2S2)2], the NiII ion adopts a distorted cis-NiS2O2 square-planar geometry arising from the two S,O-bidentate ligands. The thio-phene rings in each ligand are disordered, with site occupancy ratios of 0.874 (3):0.126 (3) and 0.741 (2):0.259 (2). © International Union of Crystallography 2007.

Abstract In the title compound, C17H13N, the dihedral angles between the pyridine ring and the phenyl rings are 29.68 ( 18) and 26.58 (17)degrees. In the crystal structure, the molecules are linked by a weak C-H center dot center dot center dot pi interaction, leading to [0(1) over bar 1] chains. There are no further significant intermolecular interactions.

Abstract The standard (p(0)=0.1 MPa) molar enthalpies of formation, at T=298.15 K, in the gaseous phase, for three tetradentate Schiff bases involving a N2O2 set, N,N'-bis(salicylaldehydo)cyclohexanediimine (H(2)salch), N,N'-bis(acetylacetone)cyclohexanediimine (H(2)acacch) and N,N'-bis(benzoylacetone)cyclohexanediimine (H(2)bzacch), were determined from their enthalpies of combustion and sublimation, obtained by static bomb calorimetry in oxygen and by the Knudsen effusion technique, respectively. The results are compared with identical parameters for related compounds previously studied, resulting from the condensation of salicylaldehyde or beta-diketone with aliphatic diamines.

Abstract In the title complex, [Ni(C14H21N2OS2)(2)], the Ni-II ion is in a square-planar coordination enviroment. The ligands assume a cis arrangement with respect to each other around the Ni-II ion, which lies on a crystallographic twofold rotation axis running parallel to the c axis. The title complex is isostructural with the copper(II) analogue.

Abstract The standard (p degrees = 0.1 MPa) molar enthalpies of formation of the crystalline diaquobis(dibenzoylmethanate)nickel(II), Ni(DBM)(2)(H2O)(2), diaquobis(thenoyltrifluoroacetonate)nickel(II), Ni(TTFA)(2)(H2O)(2) bis(monothiodibenzoylmethanate)nickel(II), Ni(DBMS)(2) and bis(monothiothenoyltrifluoroacetonate)nickel(II), Ni(HTTFAS)(2) were determined, at T = 298.15 K, by high precision solution-reaction calorimetry. The standard molar enthalpy of sublimation of the monothiothenoyltrifluoroacetone (HTTFAS) complex was measured by high-temperature Calvet microcalorimetry. From the standard molar enthalpies of formation of the complexes in the gaseous state, the mean nickel(II)-ligand molar dissociation enthalpies, < D-m >(Ni-L), were derived. Delta H-f(m)degrees(cr)/(kJ . mol(-1)) Diaquobis(dibenzoylmethanate)nickel(II), Ni(DBM)(2)(H2O)(2) -993.3 +/- 3.8 Diaquobis(thenoyttrifluoroacetonate)nickel(II), Ni(TTFA)(2)(H2O)(2) -2452.0 +/- 8.3 Bis(monothiodibenzoylmethanate)nickel(II), Ni(DBMS)(2) -42.1 +/- 5.9 Bis(monothiothenoyltrifluoroacetonate)nickel(II), Ni(TTFAS)(2) -1473.5 +/- 8.1

Abstract We synthesized and characterized a series of new polymers-hydrophobically modified cationic polysaccharides-based on dextran having pendant N-(2-hydroxypropyl)-N,N-dimethyl-N-alkylammonium chloride groups randomly distributed along the polymer backbone. These polymers are good candidates for studying the hydrophobic effect on polymer/surfactant association. In previous papers we reported their interactions with oppositely charged surfactants. For further insight into the relative importance of the hydrophobic interaction in the association process now we studied the thermodynamics of the interaction of these hydrophobically modified polymers with surfactants of the same charge (DMRX/C(n)TAC) by isothermal titration calorimetry (ITC). In order to try to discriminate the solution behavior of these polymer/surfactant systems, we analyzed separately the interaction of unmodified dextran with ionic surfactants and the interactions between the corresponding cationic surfactants. The interaction enthalpies for DMRX/C(n)TAC systems were derived from a proposed thermodynamic model with equations that describe the polymer-surfactant interactions. The thermodynamic parameters for the DMRX/C(n)TAC aggregation process as well as surfactant micellization in the presence of the polymer were also calculated. From all the results we were able to ascertain the effect on the interactions of changing the alkyl chain length of the polyelectrolyte pendant groups or the surfactant. The importance of the polymer aggregation state on the mechanism of interaction was also addressed.

Abstract The title complex, [Cu(C14H21N2OS2)(2)], is isostructural with the nickel analogue, forming a square-planar coordination enviroment. The Cu atom lies on a crystallographic twofold rotation axis.

Abstract Methamphetamine (METH) is a powerful psychostimulant that increases glutamate (Glu) levels in the mammalian brain and it is currently known that hippocampi are particularly susceptible to METH. Moreover, it is well established that the overactivation of N-methyl-D-aspartate (NMDA) and AMPA ionotropic Glu receptors causes excitotoxicity. In the present study, we investigated the effect of acute (30 mg/kg) versus escalating dose (ED) administration of METH on NMDA receptor 1, NMDA receptor 2 and glutamate receptor 2 (GluR2) subunit expression in the hippocampus and on memory. Adult Sprague-Dawley rats were injected s.c. during six consecutive days with saline (control and acute groups) or with a growing dose of METH (10, 15, 15, 20, 20, 25 mg/kg/day; ED group). On the 7th day, both METH groups were injected with a 'bolus' of 30 mg/kg METH whereas controls received saline. Western blot analysis showed an increase of GIuR2 and NR2A expression levels and no alterations on NR1 subunit in the acute group. On the other hand, in the ED group, GluR2 and NR2A expression levels were unaltered and there was a decrease on NR1 levels. Moreover, we did not observe neurodegeneration with both administration paradigms, as assessed by Fluoro-Jade C staining, but we did observe a strong astrogliosis in the acute administration group by using both immunohistochernistry and Western blot analysis. The impact of METH on working memory was evaluated using the Y maze test and revealed significant mnemonic deficit in the rats acutely treated with the drug. Overall, our results suggest a protection mechanism under conditions of METH administration by decreasing permeability and/or functionality of NMDA and AMPA receptors, which has implications on memory. So, the participation of the glutarnatergic system should be considered as an important pharmacological target to design new strategies to prevent or diminish the harmful effect of drug consumption.

Abstract The standard (p(0) = 0.1 MPa) molar enthalpies of combustion of six aminomethylbenzoic acids were measured at T = 298.15 K by static bomb calorimetry. With these values, the standard molar enthalpies of formation in the crystalline state were obtained. Combining these results with the standard molar enthalpies of sublimation, the standard molar enthalpies of formation in the gaseous phase were derived. For the 10 possible isomers, the obtained experimental results were compared to and correlated with the relative stability obtained by ab initio calculations at the B3LYP/6-311++G(d,p) level of theory. Seeking a better understanding of the aromatic behavior and energetics of aminomethylbenzoic acids in the gas phase, calculations of NICS values, HOMA indices, and dihedral angles between the aromatic carbon and the amino group, Phi(Ar-NHH), were also performed computationally. The significant differences observed in the energetics, as well as in the NICS values, HOMA indices, and (D(Ar-NHH) dihedral angles for these 10 isomers suggest a strong dependency on the identity and relative position of the three substituents on the benzene ring. This study points out a marked tendency for a decrease of the ring aromaticity, accompanied by an increase in the respective system stability, as the conjugation between the substituents becomes more extensive.

Abstract Molar enthalpies of vaporization, delta H-g(1)m(0)(T), of a homologous series of 1-alkyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imides, [C(n)mim][NTf2], (with 2 <= n <= 8) were directly determined for the first time. The results obtained in this study emphasize and constitute clear experimental support for the novel concept that these liquid salts are composed of polar and nonpolar domains; that is, they exhibit microphase segregation.