Synthesis and rapid enantiomeric separation of the chiral mixed ligand [5-(4-hydroxybutyl)-5′-methyl-2,2′-bipyridine]-bis(1,10-phenanthroline)-ruthenium(II) complex by electrokinetic chromatography

The chiral complex [5-(4-hydroxybutyl)-5′-methyl-2,2′-bipyridine]-bis(1,10-phenanthroline)ruthenium(II)-bis(hexafluoroantimonate) was successfully synthesized and fully characterized by two-dimensional ¹H and ¹³C{¹H} NMR techniques (COSY and HMQC) as well as EA- and FAB-MS. A very fast separation of the Δ and Λ enantiomers with excellent efficiency and resolution was achieved by electrokinetic chromatography using anionic carboxymethyl-β-cyclodextrin as a chiral mobile phase additive. The optimum separation conditions were obtained with 50 mM borate buffer at pH 9 and 10 mg/ml of the chiral selector at 20°C. Attempts to separate the well known unmodified tris(2,2′-bipyridine)ruthenium(II) [Ru(bpy)₃] complex into its enantiomers under the same conditions were unsuccessful.     

Einsensteinreihen für einige arithmetisch definierte Untergruppen vonSL 2 (ℍ)

Ohne Zusammenfassung Ich danke dem Max-Planck-Institut für Mathematik für die Unterstützung w?hrend der Niederschrift dieser Arbeit     

Growth and structural characterization of semiconducting Ru2Si3

Recent band structure calculations indicate that ruthenium silicide (Ru₂Si₃) is semiconducting with a direct band gap. Electrical measurements lead to a band gap around 0.8 eV which is technologically important for fiber communications. This makes Ru₂Si₃ a promising candidate for silicon based optical devices, namely LEDs. We present first results on the epitaxial growth of ruthenium silicide films on Si(1 0 0) and Si(1 1 1) fabricated by the template method, a special molecular beam epitaxy technique. Orientational relationships on Si(1 1 1) have been determined. We characterized the films by Rutherford Backscattering and Channeling, X-ray diffraction and transmission electron microscopy.     

Germanium(II)‐, Zinn(II)‐ und Blei(II)‐Derivate des polycyclischen Alumosiloxans [Ph2SiO]8[Al(O)OH]4

Germanium(II)‐, Tin(II)‐ and Lead(II)‐Derivatives of the polycyclic Alumosiloxane [Ph₂SiO]₈[Al(O)OH]₄ Five new derivatives of the polycyclic alumosiloxane [Ph₂SiO]₈[Al(O)OH]₄ have been synthesized by replacement of the protic hydrogen atoms on the hydroxy‐groups attached to the aluminium atoms by the divalent group 14 elements germanium, tin and lead. The compounds can be divided in those with one metal atom per alumosiloxane moiety, [Ph₂SiO]₈[Al(O)OH]₂[AlO₂]M (M=Ge, Sn), and those with complete substitution of the protic hydrogen atoms by metal atoms like [Ph₂SiO]₈[AlO₂]₄M₂ (M= Sn, Pb). Always one element of the series Ge, Sn, Pb is missing in the two types of compounds. Crystal structure analyses of [Ph₂SiO]₈[Al(O)OH]₂[AlO₂]₂M · 2 C₄H₈O₂ (M= Ge ( 1 ), Sn ( 2a )), [Ph₂SiO]₈[Al(O)OH]₂[AlO₂]₂Sn · 2 THF ( 2b ) and [Ph₂SiO]₈[AlO₂]₄M₂ (M= Sn ( 3 ), Pb ( 4 )) have been performed elucidating either polycyclic basket‐type ( 1 , 2a , 2b ) or closed polyhedral structures ( 3 , 4 ).     

Cross section measurements of the Pd(p, γ)Ag, Sn(p, γ)Sb, and Sn(α, γ)Te reactions relevant to the astrophysical rp- and γ-processes

Total cross section measurements for the ¹⁰²Pd(p, γ)¹⁰³Ag and ¹¹⁶Sn(p, γ)¹¹⁷Sb reactions have been performed in the proton energy range 2.6 to 4.25 MeV, and for the ¹¹²Sn(α, γ)¹¹⁶Te reaction over the alpha beam energy range 7.0 to 10.5 MeV. An activation technique was used in which gamma rays from decays of the reaction products were detected off-line by two hyper-pure germanium detectors in a low background environment. Where possible, reaction rates are derived and the results compared to those of calculations generated by the NON-SMOKER and the MOST statistical model codes so as to judge their applicability for describing the cross sections needed for network calculations of nucleosynthesis in explosive astrophysical environments via the γ- and rp-processes.     

Release of selenium and tin from the graphite support in the presence of tungsten and palladium modifiers

Electrothermal atomic absorption spectrometry is applied to investigate the release of the selenium and tin atoms from pyrocoated graphite support. The Coats and Redfern and Sturgeon approaches are used for estimation of the apparent activation energies of atom release. The addition of tungsten and palladium modifiers leads to enhancement of the activation energies and changes the kind of the vaporizing species for analytes.     

Majorations explicites de |L(1,χ)| (quatrième partie)Explicit upper bounds on |L(1,χ)| (part four)

We prove that for any even primitive Dirichlet character χ of odd conductor q_χ>1 we have $\text{|(1?}\text{χ(2)}\text{2}\text{)L(1,χ)|?}\text{1}\text{4}\text{(}\text{log}\text{q}{}_{\mathrm{\chi }}\text{+κ),}$ where κ:=2+γ?log(π/4)=2.81878…. To cite this article: S.R. Louboutin, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 625–628.