Internal and External Induced Circular Dichroism in Cyclodextrin Complexes: A Study of the Complexes of α-Cyclodextrin with (R)-3-Methylcyclopentanone and Cyclopentanone

The circular dichroism (CD) of (R)-3-methylcyclopentanone 1 in the presence of a-cyclodextrin (aCx) in -water has been measured. The formation constant (K\u27 = 24 mol-1 litre) of al-l complex, specific CD (do = +1.74) of 1 in water solution, and specific CD of this complex in water (t1c\u27 = +1.4,5)have been calculated. Similarly, the induced CD (ICD) of cyclopentanone 2 in the presence of aCx in water has been measured. The formation constant (K = 25 mol-1 litre) of a 1-1 complex and the specific CD (t1c\u27 = -0.034)of this complex have been calculated. A model is presented for the interpretation of the lCD data. Various theoretical possibi1ities are discussed. A comparison with X-Ray and low-temperature neutron-diffraction data for the (2-aCx) complex is attempted. It seems reasonable to conclude that there is only a weak chiral discrimination in this complex in water solution at room temperature

Internal and External Induced Circular Dichroism in Cyclodextrin Complexes: A Study of the Complexes of α-Cyclodextrin with (R)-3-Methylcyclopentanone and Cyclopentanone

The circular dichroism (CD) of (R)-3-methylcyclopentanone 1 in the presence of a-cyclodextrin (aCx) in -water has been measured. The formation constant (K\u27 = 24 mol-1 litre) of al-l complex, specific CD (do = +1.74) of 1 in water solution, and specific CD of this complex in water (t1c\u27 = +1.4,5)have been calculated. Similarly, the induced CD (ICD) of cyclopentanone 2 in the presence of aCx in water has been measured. The formation constant (K = 25 mol-1 litre) of a 1-1 complex and the specific CD (t1c\u27 = -0.034)of this complex have been calculated. A model is presented for the interpretation of the lCD data. Various theoretical possibi1ities are discussed. A comparison with X-Ray and low-temperature neutron-diffraction data for the (2-aCx) complex is attempted. It seems reasonable to conclude that there is only a weak chiral discrimination in this complex in water solution at room temperature

Dipole-moments and Polarizabilities of Some Substituted Pyridine-1-oxides For Optoelectronics

The electronic properties of pyridine-oxide and some of its substituted derivatives have been studied at the ab initio LCGO-SCF level. The results for pyridine-1-oxide and nitro-pyridine-oxide are in good agreement with experiment. As regards 3-methyl-4-nitro-pyridine-1-oxide (POM), the dipole moment of 0.22 or 0.48 D obtained for the two C(s) conformations considered in this work do not confirm the value suggested by the analysis of the electronic density maps obtained from cristallographic data (3.5 D). The polarizabilities ( = 81 a.u.) and the hyperpolarizabilities (beta(z) = 1050 a.u.) are the first ones obtained theoretically. Although they cannot be compared with experimental results because of the difficulty of measuring them, they allow to understand why POM is an organic material interesting for optoelectronics

Les formulations cosmétiques de l'Egypte ancienne retrouvées grâce à la diffraction des rayons X

Les très nombreux objets découverts dans les tombes égyptiennes sont une extraordinaire source d'étude des coutumes de la vie quotidienne durant l'Egypte ancienne. Les fouilles archéologiques de certaines tombes ont ainsi livré de véritables coffrets de maquillage qui contenaient des miroirs, des épingles à cheveux, des stylets et des récipients encore parfois remplis de produits cosmétiques. Des échantillons de fard ont été prélevés dans des récipients en pierre, céramique, bois ou roseau, conservés au Département des Antiquités égyptiennes du Musée du Louvre et provenant de plusieurs sites datés entre 2100 et 1100 avant J.-C. Les phases minérales des poudres ont été identifiées par diffraction des rayons X, après avoir été analysées en microscopie électronique à balayage. Des diagrammes de diffraction ont été enregistrés en haute résolution à l'ESRF et au LURE et l'utilisation d'un programme d'affinement de profil de type Rietveld a permis la quantification des phases minérales. Nous discuterons des limites de la méthode, non-destructive, appliquée à des échantillons archéologiques prélevés en très petite quantité (environ 1mm3) et composés parfois de plus de 10 phases minérales. L'analyse quantitative de vingt-huit poudres cosmétiques nous permettra de réfléchir sur les différentes formulations cosmétiques élaborées il y a 4000 ans.Funerary furniture found in Egyptian tombs is an extraordinary source for studying the customs in the everyday life during the Ancient Egypt. Some excavations of tombs have provided some genuine toilet bags, with mirrors, hairpins, eyeliner applicators and makeup receptacles, sometimes still filled with cosmetic compounds. Make-up samples have been taken from pots made of stone, ceramic, wood or reed, conserved in the Department of the Egyptian Antiquities of the Louvre Museum and coming from several sites dated between 2100 and 1100 BC. The mineral phases present in the powders have been identified by X-ray diffraction, after SEM observations. Diffraction patterns have been collected in high-resolution mode at the ESRF and at the LURE and the use of a Rietveld profile refinement method has allowed the quantification of mineral phases. We will discuss the limits of this non-destructive method, applied to extremely small archaeological samples (about 1mm3) and to mixtures of up to ten phases. The quantitative analysis of twenty-eight cosmetic powders will allow us to think about the different eye make-up formulations elaborated 4000 years ago

EVIDENCE OF THE URANIUM III AND URANYL COMPLEXATION BY MACROCYCLES FROM EXAFS

L'analyse EXAFS d'un échantillon en poudre de UIII3(BH4)9 (18-crown-6)2 a montré la présence d'atomes de carbone au voisinage de l'atome d'uraniurn, et par la suite prouvé que tous les atomes d'oxygène du macrocycle sont directement liés au métal. L'étude EXAFS du complexe d'uranyle U VIO2(18-crown-6)(C104)2 a permis de vérifier l'insertion de l'ion uranyle à l'état solide et montré sa désinsertion partielle dans une solution d'acétonitrile.EXAFS analysis er formed on powdered sample U3 (BH4)9 (18-crown-6)2 has shown the presence of carbon atoms in the vicinity of the uranium atom and hence has proved that all the oxygen atoms of the crown-ether are directly coordinated to the metal. EXAFS study on the uranyl complex UO2(18-crown-6)(C104)2 has verified the insertion of the uranyl ion in solid state and given evidence for its partial desinsertion in an acetonitrile solution

Apport du rayonnement synchrotron à l'étude de cheveux archéologiques

La préservation dans certains contextes archéologiques des cheveux humains et des fibres animales est favorisée par leur transformation chimique au contact d'objets métalliques. Afin de mieux comprendre les phénomènes complexes mis en jeu, nous avons étudié expérimentalement la fixation de cations métalliques (Cu et Pb) dans des cheveux modèles à partir de différentes méthodes de caractérisation utilisant le rayonnement X synchrotron. Nous avons ainsi pu mettre en évidence la fixation spécifique d'une partie de ces cations au sein des lipides structurés du cheveu. La comparaison entre échantillons modèles et archéologiques apporte de nouvelles données concernant les premières étapes d'altération des cheveux archéologiques