Interionic potentials for some alkali halides from crystal data measured at different temperatures

Values at different temperatures of lattice constants and their derivatives with respect to T. and of elastic constants were used to obtain the derivatives with respect to the minimum interionic distance of the repulsive potentials for the crystals CsCl, CsBr, ClI, NaCl, KCl and KBr. The derivatives thus calculated were then subjected to a computer fitting to yield the aij and b constants of the interionic repulsive pair potential: Rφij = aij exp{ - brij}

Thermodynamics of β-Cyclodextrin/Water Interactions

From a purely enthalpic standpoint, the beta-CD hydration, as studied by semiempirical calculations appears improbable, in contrast to experiment. For the spontaneous hydration process, a compensation mechanism, connected to substrate stabilitazion and/or entropy increase, is suggested, on the basis of simple thermodynamic calculations

Physico-chemical characterization of a novel tricyclic β-lactam antibiotic

GV118819X, a novel tricyclic b-lactam antibiotic of GlaxoWellcome, is a racemic mixture of two diastereoisomers, A and B. Of the two diastereoisomers, only A is available as a pure compound. By analyzing mixtures of GV118819X and A, a partial phase diagram is constructed, which indicates the presence of a eutectic when the A fraction is ~39%. Moreover, the melting enthalpies of the eutectic mixture and of diastereoisomer B can be estimated. With the exception of the pure A form, all mixtures undergo important modifications in morphology and microstructure as a consequence of thermal treatments, which induce melting/amorphization of the eutectic, and crystallization of the A form. Analyses of the sieved fractions of GV118819X demonstrate that it consists of acicular crystals of different composition, with the larger crystals having a larger A fraction than the smaller ones. Grinding causes melting/amorphization of the eutectic and, following hours-long treatments, the formation of a substantial fraction of submicron particles with unusually low melting temperatures

Solid-state characterisation of a novel chemotherapeutic drug.

We present the results of a thermal, spectroscopic, diffractometric, and microscopic study of a novel DNA intercalator synthesized by Novuspharma S.p.A. (code name BRR 2778, purity by high-performance liquid chromatography: 99.4%). We found that the form that is stable at room temperature contains 1.5 water molecules per unit of formula (or about 4.7% in mass): this water is reversibly lost in two stages below 808 and 908°C in dry and wet nitrogen atmosphere, respectively. The hydrated compound is a pseudo-polymorph and dehydration is accompanied by a structural change that modifies the diffraction pattern without changing the shape of the microcrystals. Annealing above 150°C causes decomposition of the anhydrous form and (above 1908C) amorphization of the solid residue occurs