Publications

Abstract Partial molar heat capacities at infinite dilution, C(p,2)infinity, have been determined calorimetrically for D-mannitol and D-sorbitol in water, dimethyl sulfoxide and formamide, at 298.15 K. The C(p,2)infinity values obtained, which are similar for the three solvents, are much higher than the heat capacities for the pure compounds. The large DELTAC(p)infinity values for the dissolution process are believed to be partly due to the existence of several rotamers in solution. Sorbitol seems to be more sensitive than mannitol to specific solvent effects.

Abstract 1,3-Dihydroxy-2-methylxanthone (X1), its 4-chloro and 4-bromo derivatives (X1-Cl and X1-Br), and 1,3-dihydroxy-4-methylxanthone were investigated for their inhibition activities toward MAO. A hyperbolic function was derived to fit the data and to calculate IC50 values. The compounds proved to be reversible and selective inhibitors of MAO-A, with X1 displaying the highest activity (IC50 = 3.7 muM).

Abstract A general procedure for the simultaneous analysis of phenolic compounds by a reversed-phase high performance liquid chromatography (RP-HPLC) is described. The series of compounds embraces the cis/trans isomers of caffeic, ferulic and isoferulic acids and the coumarins - esculetin, scopoletin and isoscopoletin. In order to establish the experimental conditions, leading to an optimal resolution, several test mixtures were analysed. HPLC separation was carried out on a reversed-phase column ( Lichrosorb RP-8, 5 mum), using aqueous tetrahydrofuran as a mobile phase.

Abstract Potentials of zero charge, E(sigma=0), and the temperature coefficients of E(sigma=0) for stepped surfaces of sold single crystals (511), (533), (331) and (311) were obtained from the minimum of the differential capacity curve in dilute HClO4 solutions. The results are compared with those obtained for the low index faces and dilute in terms of the effect of the surface density of steps and the step orientation. The possible relevance of the effect of steps on the interaction of water with gold surfaces is discussed.

Abstract The Knudsen mass-loss effusion technique was used to measure the vapour pressure as a function of temperature for six halogen-substituted 8-hydroxyquinolines. From the temperature dependence of the vapour pressure, the standard molar enthalpies of sublimation Δg crHo m(Tm), at the mean temperature Tm of the experimental temperature range were derived, and the standard molar enthalpies of sublimation at T = 298.15 K were calculated. {A figure is presented}. The results obtained in this work together with the previously reported ones for other hydroxyquinolines, allowed us to find the correlation: Δcr g Hm o (T0.5 Pa) / (kJ {dot operator} mol- 1) = 0.313 (T0.5 Pa / K) - 3.68,. where T0.5 Pa is the temperature at which the equilibrium vapour pressure of each substance is 0.5 Pa.

Abstract The standard (po = 0.1 MPa) molar enthalpy of combustion in oxygen at 298.15 K of liquid 3-methylpentane-2,4-dione (HMeacac) was measured by static bomb calorimetry as -(3353.2±1.7) kJ · mol-1. The standard molar enthalpy of formation of the crystalline copper(II) complex with 3-methylpentane-2,4-dione was determined, at the temperature 298.15 K, by solution-reaction calorimetry. The vapour pressures of the complex were measured as function of temperature by the Knudsen-effusion technique, and the standard molar enthalpy of sublimation Δg crHo m(396.70 K)/(kJ · mol-1) = 130.7 ± 1.0, was derived by the Clausius-Clapeyron equation. From this value, the standard molar enthalpy of sublimation was calculated as Δg crHo m(298.15 K)/(kJ · mol-1) = 135.6 ± 1.0. Measurement of the standard molar enthalpy of sublimation using a direct microcalorimetric method, confirmed the value from the Knudsen technique.

Abstract Using a static-bomb combustion calorimeter, the standard (p° = 0.1 MPa) molar enthalpy of combustion at the temperature 298.15 K of 3-nitrophenol was determined: - ΔcH°m(cr)/(kJ·mol-1) = 2870.0±1.5. The vapour pressure of the crystals was measured, as a function of the temperature T, by the Knudsen-effusion technique and the standard molar enthalpy of sublimation at T = 323.13 K was derived by the Clausius-Clapeyron equation: Δg crH°m(323.13 K)/(kJ·mol-1) = 98.92±0.58. From this value the standard molar enthalpy of sublimation at T = 298.15 K was calculated as Δg crH°m(298.15 K)/(kJ·mol-1) = 100.2±0.6.

Abstract The standard (p(empty set) = 0.1 MPa) molar enthalpies of formation of the following crystalline copper(II) amino acid complexes were determined at 298.15 K by solution-reaction calorimetry: DELTA(f)H(m)empty set[Cu(gly)2, cr] = - 943.7 +/- 1.3 kJ mol-1; DELTA(f)H(m)empty set[Cu(ala)2, cr]= - 1003.7 +/- 1.5 kJ mol-1; DELTA(f)H(m)empty set[Cu(val)2, cr] = - 1124.1 +/- 2.2 kJ mol-1; DELTA(f)H(m)empty set[Cu(leu)2, cr] = - 1177.8 +/- 2.1 kJ mol-1; DELTA(f)H(m)empty set[Cu(isol)2, cr] = - 1156.3 +/- 1.8 kJ mol-1; DELTA(f)H(m)empty set[Cu(Phgly)2, cr] = - 772.3 +/- 1.9 kJ mol-1; DELTA(f)H(m)empty set[Cu(Phala)2, cr] = - 831.8 +/- 2.6 kJ mol-1. The results suggest a linear correlation between the standard molar enthalpies of formation of the crystalline copper(II) amino acid complexes and those of the corresponding crystalline amino acids. Estimations of the standard molar enthalpies of sublimation of the copper(II) amino acid complexes are presented. The total binding energy between the copper(II) and the amino acid ligand is derived and compared with the corresponding parameter for copper(II) acetylacetonate.

Abstract The standard (p(empty set) = 0.1 MPa) molar enthalpies of formation of the following crystalline nickel(IU) amino acid complexes were determined, at 298.15 K, by solution-reaction calorimetry: DELTA(f)Hm(empty set([Ni(gly)2, cr] = - 994.2 +/- 1.8 kJ mol-1; DELTA(f)H(m)empty set[Ni(ala)2, cr] = - 1072.4 +/- 2.3 kJ mol-1; DELTA(f)H(m)empty set[Ni(val)2, cr] = - 1173.7 +/- 2.5 kJ mol-1; DELTA(f)H(m)empty set[Ni(leu)2, cr] = - 1243.4 +/- 2.7 kJ mol-1; DELTA(f)H(m)empty set[Ni(isol)2, cr] = - 1224.1 +/- 2.1 kJ mol-1; DELTA(f)H(m)empty set[Ni(Phgly)2, cr] = - 857.0 +/- 2.8 kJ mol-1; DELTA(f)H(m)empty set[Ni(Phala)2, cr] = - 898.6 +/- 3.0 kJ mol-1. A linear correlation between the standard molar enthalpies of formation of the crystalline nickel(II) amino acid complexes and the crystalline amino acids is established. Estimations of the standard molar enthalpies of sublimation of the nickel(II) amino acid complexes are presented. The total binding energies in nickel(II) complexes of amino acids and of beta-diketonate ligands are compared.