Conducting polymers containing in-chain metal centers: electropolymerization of oligothienyl-substituted {M(tpy)2} complexes and in situ conductivity studies, M = Os(II), Ru(II)

The electropolymerization of a series of Ru and Os bis-terpyridine complexes that form rodlike polymers with bithienyl, quaterthienyl, or hexathienyl bridges has been studied. Absorption spectroscopy, scanning electron microscopy, and cyclic voltammetry have been used to characterize the monomers and resulting polymer films. The absolute dc conductivity of the quaterthienyl-bridged {Ru(tpy)2} and {Os(tpy)2} polymers is unusually large and independent of the identity of the metal center at 1.6 x 10(-3) S cm(-1). The maximum conductivity occurs at the formal potential of each redox process, which typically is observed for systems where redox conduction is the dominant charge transport mechanism. Significantly, the dc conductivity of the metal-based redox couple observed in these polymers is 2 orders of magnitude higher thanthat of a comparable nonconjugated system.     

Chemical synthesis of lymphotactin: a glycosylated chemokine with a C-terminal mucin-like domain

The synthesis of a 93-residue chemokine, lymphotactin, containing eight sites of O-linked glycosylation, was achieved using the technique of native chemical ligation. A single GalNAc residue was incorporated at each glycosylation site using standard Fmoc-chemistry to achieve the first total synthesis of a mucin-type glycoprotein. Using this approach quantities of homogeneous material were obtained for structural and functional analysis.     

Cyclen based bis-macrocyclic ligands as phosphates receptors. A potentiometric and NMR study

The host-guest interaction between orthophosphate, pyrophosphate and triphosphate anions and four cyclen based bis-macrocycles ligands possessing ortho-(BOC), meta-(BMC), para-xylenyl (BPC) or 2,6-pyridinyl (BPyC) linker was investigated by potentiometric measurements and NMR spectroscopy. Each ligand gave protonated species in aqueous solution that further formed ternary complexes after binding with anions; these complexes were analyzed as a result of hydrogen bond formation and Coulombic attraction between the organic host and the inorganic guest. The equilibrium constants for all the detected species are reported and the selectivity, illustrated with species distribution diagrams, is discussed. The results unambiguously showed the importance of the distance between the two cyclen cores and underlined, especially for the triphosphate species, the contribution of the nitrogen atom of the pyridinyl spacer as a supplementary anchoring point in acidic medium.     

Sur le role fondamental du cation alcalin dans les reductions par les hydrures metalliques. Utilisation de coordinats macrocycliques—III : Etude de divers groupements fonctionnels reduits par LiAlH4

The reactions of the following functional groups with LiAlH₄ in Et₂O or DME were studied: ketone, aldehyde, carboxylic acid, amide, ester, nitrile, oxime, tosylate, epoxide, acyl chloride and alkyl bromide. All these reductions are catalysed by Li⁺, as shown by the use of a specific macrocyclic ligand allowing the reaction to be run free of Li⁺. Moreover, in the cases of acyl chloride and alkyl bromide the reaction (free of Li⁺) is catalysed by AlX₃ which is generated in situ. Several new mechanistic features are revealed for reductions by LiAlH₄.     

Host-guest interaction between cyclen based macrotricyclic ligands and phosphate anions. A potentiometric investigation

The host-guest interaction between orthophosphate, pyrophosphate and triphosphate anions and three cyclen based macrotricyclic ligands possessing ortho- (TOC), meta- (TMC) and para-xylenyl (TPC) linkers was investigated by potentiometric measurements. The ternary species present in solution and their stability constants have been determined. The different behaviours are explained in terms of hydrogen bond formation and coulombic attraction between the organic host and the inorganic guest. The selectivity, illustrated with species distribution diagrams, is discussed. The results unambiguously showed the importance of the distance between the two cyclen cores and emphasized the increasing of the triphosphate species selectivity together with the cavity size of the ligand. A comparison of the present results with those obtained with their mono-bridged homologues is also discussed.     

Comparison Theorems for Gibbs Measures

The Dobrushin comparison theorem is a powerful tool to bound the difference between the marginals of high-dimensional probability distributions in terms of their local specifications. Originally introduced to prove uniqueness and decay of correlations of Gibbs measures, it has been widely used in statistical mechanics as well as in the analysis of algorithms on random fields and interacting Markov chains. However, the classical comparison theorem requires validity of the Dobrushin uniqueness criterion, essentially restricting its applicability in most models to a small subset of the natural parameter space. In this paper we develop generalized Dobrushin comparison theorems in terms of influences between blocks of sites, in the spirit of Dobrushin–Shlosman and Weitz, that substantially extend the range of applicability of the classical comparison theorem. Our proofs are based on the analysis of an associated family of Markov chains. We develop in detail an application of our main results to the analysis of sequential Monte Carlo algorithms for filtering in high dimension.     

Tetraazamacrocycles lipophiles : synthese et application a l'extraction de Cu (II), Cd (II) et Pb (II)

The synthesis of three lipophilic n-dodecyl tetraazacycloalkanes is described. Extraction of Cu(II), Cd(II) and Pb(II) is related.     

Bismuth (III) coordination to cyclen and cyclam bearing four appended groups

The synthesis of new cyclam and cyclen derivatives (respectively L₁ and L₂), able to efficiently coordinate to Bi(III) are presented here. The two ligands bearing two different pendant arms (two-pycolyl and two (2-(2-hydroxyethoxy)ethyl)-2-aminoacetamide in trans position) were synthesized in the aim to obtain stable and water soluble complexes. The thermodynamic and kinetic of the formation of the corresponding complexes in aqueous solution were studied by means of NMR and potentiometric investigations. The fast kinetic of complexation and the high stability of the complexes are encouraging for further application with the alpha-emitting ²¹³Bi isotope.