The relative permittivity of 1,2-ethanediol+2-methoxyethanol+water ternary mixtures

The relative permittivities for the ternary 1,2-ethanediol (component 1) + 2-methoxyethanol (2) + water (3) solvent system have been measured for 66 mixtures covering the whole mole fraction composition 0X₁/X₂/X₃ 1 range at –10, –5 and 0 °C. The experimental data were used to test some empirical relations stating the dependence of = (X₁, X₂, X₃). A comparison between the calculated and experimental data show that these equations can be usefully employed to predict values in correspondence of the experimental data gaps.     

Thermogravimetric and kinetic methods to date wood finds. First results

Fresh (larch and fir, in its white and red varieties) and ancient wood samples (dating respectively to the 13th, 15th and 17th centuries) were subjected to thermogravimetric analysis (TG and DTG). The resulting thermogravimetric data were then used to construct archeometric curves for the wood varieties tested. In a preliminary approach, it was attempted to correlate the onset temperature of the thermogravimetric step corresponding to cellulose decomposition with the age (expressed in centuries) of the samples, although the results obtained were anything but brilliant. More encouraging results were obtained by examining the relationship between wood sample age and the value of the (percent cellulose/percent lignin) ratio computed from the thermogravimetric data. Lastly, a procedure for processing data obtained from the TG curves was applied to a kinetic analysis of the processes that take place when wood samples are subjected to a temperature regime with a constant heating rate, obtaining values for the activation energy of the TG step corresponding to the decomposition of cellulose. Also using these data it was attempted to construct archeometric curves, obtaining results that varied quite significantly according to the wood species tested.     

Heptagon-Containing Nanographene Embedded into [10]Cycloparaphenylene

We report the synthesis and characterization of a novel type of nanohoop, consisting of a cycloparaphenylene derivative incorporating a curved heptagon-containing π-extended polycyclic aromatic hydrocarbon (PAH) unit. We demonstrate that this new macrocycle behaves as a supramolecular receptor of curved π-systems such as fullerenes C₆₀ and C₇₀, with remarkably large binding constants (ca. 10⁷ M⁻¹), as estimated by fluorescence measurements. Nanosecond and femtosecond spectroscopic analysis show that these host-guest complexes are capable of quasi-instantaneous charge separation upon photoexcitation, due to the ultrafast charge transfer from the macrocycle to the complexed fullerene. These results demonstrate saddle-shaped PAHs with dibenzocycloheptatrienone motifs as structural components for new macrocycles displaying molecular receptor abilities and versatile photochemical responses with promising electron-donor properties in host-guest complexes.     

Catalytic Alkyne Semihydrogenation with Polyhydride Ni/Ga Clusters

The bimetallic, decanuclear Ni₃Ga₇-cluster of the formula [Ni₃(GaTMP)₃(μ²-GaTMP)₃(μ³-GaTMP)] ( 1 , TMP=2,2,6,6-tetramethylpiperidinyl) reacts reversibly with dihydrogen under the formation of a series of (poly-)hydride clusters 2 . Low-temperature 2D NMR experiments at −80 °C show that 2 consist of a mixture of a di- ( 2_Di ), tetra- ( 2_Tetra ) and hexahydride species ( 2_Hexa ). The structures of 2_Di and 2_Tetra are assessed by a combination of 2D NMR spectroscopy and DFT calculations. The cooperation of both metals is essential for the high hydrogen uptake of the cluster. Polyhydrides 2 are catalytically active in the semihydrogenation of 4-octyne to 4-octene with good selectivity. The example is the first of its kind and conceptually relates properties of molecular, atom-precise transition metal/main group metal clusters to the respective solid-state phase in catalysis.     

Experimental Design in Ion Chromatography: Effect of the Organic Modifier and Complexing Agent on the Retention of Alkaline and Alkaline Earth Ions

A Box–Behnken experimental design combined with response surface methodology was applied to investigate the effect of the eluent composition on the retention of common cations in ion chromatography. In particular, we modelled the retention factors of Na⁺, K⁺, NH₄ ⁺, Ca⁺⁺ and Mg⁺⁺ and the chromatogram resolution. Response surfaces were evaluated to assess interactive effects of nitric acid, pyridine-2,6-dicarboxylic acid and percentage of acetonitrile in the eluent on the above parameters. Nitric acid concentration and acetonitrile content appeared as the most and the least influential components of the eluent in determining the retention factors of individual ions or the global resolution of the chromatogram, while the concentration of the complexing agent exhibits an intermediate role. As expected, acidification of the mobile phase produces a decrease in the retention factors and a progressive worsening of resolution, and this effect can be modulated by the concentration of the complexing agent. The proposed approach seems suitable to investigate the retention phenomena in ion chromatography under application of complex eluent phases.     

Spectrophotometric determination of advanced products of non-enzymatic glycosylation of lysine by means of their reaction with diazonium salts

A typical product (glycosyl lysine) formed by reaction of lysine with glyceraldehyde is measured at 490 nm after coupling with diazotized sulfanilic acid. Reaction with 4-dimethylaminobenzaldehyde was less satisfactory.     

Synthesis of pyrazolo[4,5-d]- and pyrazolo[4,5-c][1]benzazepine derivatives. IV

Following our reports on synthetic tricyclic analogues of antitumor anthramycin the synthesis of some isomers pyrazolo[4,5-d]- and pyrazolo[4,5-c][1]benzazepine derivatives is reported.     

Atomistic Simulations of Integranular Fracture in Symmetric-Tilt Grain Boundaries

Fracture experiments on symmetric-tilt grain boundaries in Cu are interpreted using the Peierls-Nabarro continuum model of dislocation nucleation as a starting point. Good agreement is found only when the continuum model is modified according to the results of atomistic simulations. The same experiments are also reproduced by direct Molecular Dynamics simulations of fracture propagation and dislocation emission from a microcrack placed in the interface plane of the symmetric-tilt (221)(221) grain boundary in fcc Cu. Direction-dependent fracture response is observed, namely the microcrack advancing by brittle fracture along the [11 ] direction and being blunted by dislocation emission along the opposite [ 4] direction. Moreover, the simulations allow us to establish important differences with respect to the continuum-model predictions due to the shielding of the stress field at the crack-tip and to the presence of the residual stress at the interface.