The structures and phase transitions of AgNbO 3 were investigated using neutron powder diffraction and restricted single-crystal x-ray diffraction. Both methods have revealed the high temperature M 3 -O 1 , O 2 -T and T-C phase transitions but have not given any significant evidence of low temperature M 1 -M 2 and M 2 -M 3 ones. The refinements of neutron diffraction patterns allowed us to determine the symmetry, space group and crystal structure for all phases except the O 1 one. The existence of structural disorder in the T and probably O 2 phases was found. The high temperature paraelectric phase transitions can be interpreted on the basis of consecutive condensation of oxygen octahedron tilts around the main axis. The ferroelectric and antiferroelectric behaviour has been associated with Ag and Nb cations. The reason why phase transitions between low temperature ferroelectric and antiferroelectric phases are not detectable by diffraction methods is discussed. The sequence of phase transitions in AgNbO 3 can then be understood in the framework of a long range and/or local orderdisorder type arrangement.

In order to accommodate an increasing demand for glassy carbon products with tailored characteristics, one has to understand the origin of their structure-related properties. In this work, through the use of high-resolution transmission electron microscopy, Raman spectroscopy, and electron energy loss spectroscopy it has been demonstrated that the structure of glassy carbon at different stages of the carbonization process resembles the curvature observed in fragments of nanotubes, fullerenes, or nanoonions. The measured nanoindentation hardness and reduced Young's modulus change as a function of the pyrolysis temperature from the range of 600-2500°C and reach maximum values for carbon pyrolyzed at around 1000°C. Essentially, the highest values of the mechanical parameters for glassy carbon manufactured at that temperature can be related to the greatest amount of non-planar sp 2 -hybridized carbon atoms involved in the formation of curved graphene-like layers. Such complex labyrinth-like structure with sp 2 -type bonding would be rigid and hard to break that explains the glassy carbon high strength and hardness.

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The aim of this article is to examine the crystallization tendencies of three chemically related amorphous anti-inflammatory agents, etoricoxib, celecoxib, and rofecoxib. Since the molecular mobility is considered as one of the factors affecting the crystallization behavior of a given material, broadband dielectric spectroscopy was used to gain insight into the molecular dynamics of the selected active pharmaceutical ingredients. Interestingly, our experiments did not reveal any significant differences in their relaxation behavior either in the supercooled liquid or in the glassy state. Hence, as a possible explanation for the enhanced physical stability of etoricoxib, its ability to undergo a tautomerization reaction was recognized. The occurrence of intramolecular proton transfer in the disordered etoricoxib was proven experimentally by time-dependent dielectric and infrared (IR) measurements. Additionally, IR spectroscopy combined with density functional theory calculations pointed out that in the etoricoxib drug, being in fact a binary mixture of tautomers, the individual isomers may interact with each other through a hydrogen bonding network. A possible explanation of this issue was achieved by performing dielectric experiments at elevated pressure. Since compression results in etoricoxib recrystallization, the possible influence of pressure on the observed stabilization effect is also carefully discussed.

We have studied the structural and magnetic properties of two compounds from the Me32+(Fe3+(CN)6-)23-.H2O family, where Me=Ni and Co. From x-ray analysis we find that the compounds crystallize in the face-centred cubic structure with the space group of F43m. Both the Fe and Me ions are coordinated octahedrally by six carbon atoms and six nitrogen atoms, respectively. The Fe ions are in a strong crystalline field, while the Me ions are in an intermediate field with cubic symmetry. From the magnetic studies a quantitative bulk ferromagnetic behaviour (a spontaneous magnetization and a hysteresis loop) has been established for both complex compounds. In addition, from the magnetization against temperature curves we obtained, for both compounds, the Curie as well as Curie-Weiss temperatures, the Curie constants and the effective moments in the paramagnetic state. From the assumed value of the spin for every cation we fitted the chi T=F(T) curves and from the field dependence of the magnetization we determined the high-field susceptibility. The magnetic properties of the compounds were analysed in the framework of the mean-field theory.

Thiosemicarbazones (TSCs) are an interesting class of ligands that show a diverse range of biological activity, including anti-fungal, anti-viral and anti-cancer effects. Our previous studies have demonstrated the potent in vivo anti-tumor activity of novel TSCs and their ability to overcome resistance to clinically used chemotherapeutics. In the current study, 35 novel TSCs of 6 different classes were designed using a combination of retro-fragments that appear in other TSCs. Additionally, di-substitution at the terminal N4 atom, which was previously identified to be critical for potent anti-cancer activity, was preserved through the incorporation of an N4-based piperazine or morpholine ring. The anti-proliferative activity of the novel TSCs were examined in a variety of cancer and normal cell-types. In particular, compounds 1d and 3c demonstrated the greatest promise as anti-cancer agents with potent and selective anti-proliferative activity. Structure-activity relationship studies revealed that the chelators that utilized “soft” donor atoms, such as nitrogen and sulfur, resulted in potent anti-cancer activity. Indeed, the N,N,S donor atom set was crucial for the formation of redox active iron complexes that were able to mediate the oxidation of ascorbate. This further highlights the important role of reactive oxygen species generation in mediating potent anti-cancer activity. Significantly, this study identified the potent and selective anti-cancer activity of 1d and 3c that warrants further examination.

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