Comparison between triplet and singlet molecular oxygen oxidation of fully substituted alkoxyoxazoles

Oxidation by ground-state molecular oxygen of fully substituted alkoxyoxazoles I gave imines IV as major products; diacylcarbamates III were also obtained as minor products. The free radical nature of the autoxidation was established. A mechanistic interpretation of the results is suggested also in the light of the results of the oxidation with singlet oxygen.     

Polyoxometalate monolayers in Langmuir-Blodgett films

Langmuir and Langmuir-Blodgett (LB) films of a variety of polyoxometalates of different shapes, sizes, and charges were prepared by taking advantage of the adsorption properties of these polyanions on a positively charged monolayer of an organic surfactant spread on water. Three different aspects were investigated. 1) The electrochemical and electrochromic properties of LB films containing the easily reducible polyoxoanion [P2Mo18O62]6-. Absorbance changes of these LB films deposited onto an ITO substrate have been induced by repeated switching of the applied potential. These changes are due to the formation of the colored reduced forms of the polyanion. Coloration and bleaching of the LB film occur very quickly and are reversible. 2) The preparation of LB films based on magnetic polyoxometalates, such as the Keggin anions, [CoW12O40]6- and [SiMn(OH2)W11O39]6-, or containing magnetic clusters of increasing nuclearities such as [Co4(H2O)2(PW9O34)2]10- and [Co4(H2O)2(P2W15O62)2]16- based on a Co4O16 ferromagnetic cluster, and the polyoxometalates [Co9(OH)3(H2O)6(HPO4)2(PW9O34)3]16- and [Ni9(OH)3-(H2O)6(HPO4)2(PW9O34)3]16- based on a nonanuclear M9O36 cluster. 3) The preparation of LB films of the giant heteropolyoxomolybdate, [Na3(NH4)12][Mo57Fe6(NO)6O174(OH)3-(H2O)24]76 H2O.     

States of water,surface and rheological characterisation of a new biohydrogel as articular cartilage substitute

PVA based hydrogel was synthesised using, as crosslinking agent, trisodium trimetaphosphate (STMP) and its morphology was modified inducing a microporous structure to obtain potential substitutes for cartilage tissue. The hydrogel was characterised by Infrared Spectroscopy combined with Time of flight mass spectrometry (ToF‐SIMS) that confirmed the successful occurrence of crosslinking reaction, the hyphotised crosslinking arm and its homogeneous distribution. The mechanical spectra of the fully hydrated samples confirmed covalently crosslinked systems with a rheological behaviour similar to that of tibial cartilage. Further analysis in terms of water content measurements, thermal stability and cytotoxicity confirmed the applicability of such a hydrogel as cartilage substitute. Copyright © 2013 John Wiley & Sons, Ltd.     

Colorants and oils in Roman make-ups–an eye witness account

Archaeological cosmetics, as well as revealing ancient knowledge, contain a complex mixture of very different organic and inorganic components with diverse properties. Most information on the preparation of ancient cosmetics comes from classical texts. However, although analysis of products contained in archaeological objects has recently identified some ingredients, there is still little known about how the cosmetics were prepared.Using a multi-analytical approach, we studied the chemical composition of two Roman pink make-ups that were preserved on the surface of a Roman bronze cosmetic tool and in a glass unguentarium. The results revealed that both make-ups were colored by madder lake but prepared in two different ways and with two completely different matrices (i.e. scented oils in the first case and gypsum in the second) highlighting that the make-ups had been prepared thoroughly, the ingredients carefully selected and their properties and possibilities for good cosmetic use had been understood.     

Thermodynamics of Hydrogen Adsorption on Metal‐Organic Frameworks

Interaction between adsorbed hydrogen and the coordinatively unsaturated Mg²⁺ and Co²⁺ cationic centres in Mg‐MOF‐74 and Co‐MOF‐74, respectively, was studied by means of variable‐temperature infrared (VTIR) spectroscopy. Perturbation of the H₂ molecule by the cationic adsorbing centre renders the H? H stretching mode IR‐active at 4088 and 4043 cm^?1 for Mg‐MOF‐74 and Co‐MOF‐74, respectively. Simultaneous measurement of integrated IR absorbance and hydrogen equilibrium pressure for spectra taken over the temperature range of 79–95 K allowed standard adsorption enthalpy and entropy to be determined. Mg‐MOF‐74 showed ΔH⁰=?9.4 kJ mol^?1 and ΔS⁰=?120 J mol^?1 K^?1, whereas for Co‐MOF‐74 the corresponding values of ΔH⁰=?11.2 kJ mol^?1 and ΔS⁰=?130 J mol^?1 K^?1 were obtained. The observed positive correlation between standard adsorption enthalpy and entropy is discussed in the broader context of corresponding data for hydrogen adsorption on cation‐exchanged zeolites, with a focus on the resulting implications for hydrogen storage and delivering.