Bonding mode of a bifunctional P approximately Si-H ligand in the ruthenium complex "Ru(PPh2CH2OSiMe2H)3"

The phosphinosilane compound PPh 2CH 2OSiMe 2H is potentially a bifunctional P approximately Si-H ligand. By treatment with the Ru (II) precursor RuH 2(H 2) 2(PCy 3) 2, the complex Ru(PPh 2CH 2OSiMe 2H) 3 ( 2), resulting from the coordination of three ligands and the displacement of two PCy 3 and two dihydrogen ligands, was formed. The different bonding modes for each of the three bifunctional P approximately Si-H ligands are discussed on the basis of multinuclear NMR, X-ray diffraction, and density functional theory studies. One ligand acts as a monodentate phosphine ligand with a pendant Si-H group, whereas the two others act as bidentate ligands with different Si-H bond activations. Indeed, an intermediate structure between two arrested forms 2a and 2b can be proposed: a dihydrido(disilyl)ruthenium(IV) species (form 2a) resulting from two Si-H oxidative additions or a hydrido(silyl)ruthenium(II) species (form 2b) presenting an agostic Si-H bond and only one oxidative addition.     

Cationic carbon nanotubes bind to CpG oligodeoxynucleotides and enhance their immunostimulatory properties

Functionalized cationic carbon nanotubes are able to form a stable complex with CpG ODN based on charge interaction and to increase the immunostimulatory activity of CpG motifs.     

The influence of structure and composition of a reverse SDS microemulsion on enzymatic activities and electrical conductivities

The activity of the enzyme horse radish peroxidase (HRP) is studied in a series of reverse microemulsions composed of dodecane, aqueous buffer, sodium dodecylsufate (SDS) and alcohols of the homologous series 1-butanol to 1-octanol. The HRP catalyzed reaction is the oxidation of a classical water soluble substrate, the 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) by hydrogen peroxide. In parallel electrical conductivity measurements are performed on the same solutions. The structural changes in the microemulsions, as inferred by the conductivity measurements, correlate remarkably well with the changes in the enzymatic activities. In particular it is found that (a) the maximum activity of the enzyme is always related to its optimum hydration and that this hydration can be related to the microemulsion structures, (b) the enzyme inhibition caused by the alcohols in microemulsions is a consequence of both the solubility of the alcohols in the buffer and the rigidity of the interfacial film. Consequently, it can be concluded that enzymatic activity measurements are a valuable tool to study confined systems such as microemulsions and, in particular, the amount of available hydration water. Enzymatic activities can be finely tuned by small changes in microemulsion structures, probably in a predictive way.     

Synthesis, structure and coordination of the ambiphilic ligand (2-picolyl)BCy2

The new pyridine-borane compound (2-picolyl)BCy2, readily prepared from 2-picolyllithium and ClBCy2, adopts a head-to-tail dimeric structure in the solid state as indicated by X-ray diffraction analysis and according to NMR and DFT studies, the dimeric form equilibrates in solution with a strained monomeric structure; the ambiphilic behavior of the new compound is illustrated by its bridging coordination to the (p-cymene)RuCl2 unit.     

Two‐Coordinate Iron(I) Complex [Fe{N(SiMe3)2}2]−: Synthesis,Properties, and Redox Activity

First‐row two‐coordinate complexes are attracting much interest. Herein, we report the high‐yield isolation of the linear two‐coordinate iron(I) complex salt [K(L)][Fe{N(SiMe₃)₂}₂] (L=18‐crown‐6 or crypt‐222) through the reduction of either [Fe{N(SiMe₃)₂}₂] or its three‐coordinate phosphine adduct [Fe{N(SiMe₃)₂}₂(PCy₃)]. Detailed characterization is gained through X‐ray diffraction, variable‐temperature NMR spectroscopy, and magnetic susceptibility studies. One‐ and two‐electron oxidation through reaction with I₂ is further found to afford the corresponding iodo iron(II) and diiodo iron(III) complexes.     

Design and effective synthesis of the first 4-aza-2,3-didehydropodophyllotoxin rigid aminologue: a N-methyl-4-[(3,4,5-trimethoxyphenyl)amino)]-1,2-dihydroquinoline-lactone

The first N1-alkyl-4-amino-1,2-dihydroquinoline-lactone has been prepared by a five-step sequence in a 51% overall yield via the corresponding furo[3,4-b]quinolin-1(3H)-one. A new practical synthesis of this intermediate was carried out using versatile, commercially available starting materials and constitutes the shortest and highest yielding route. These synthetic pathways could be widened with a view toward the preparation of different substituted derivatives, which could be considered as rigid aminologues of 4-aza-2,3-didehydropodophyllotoxins.     

Inclusion complex of n-octyl beta-D-glucopyranoside and alpha-cyclodextrin in aqueous solutions: thermodynamic and structural characterization

Complex formation between octyl beta-D-glucopyranoside (OG) and alpha-cyclodextrin (alphaCD) was investigated on the basis of three highly accurate and appropriate experimental techniques. First, surface tension measurements showed that alphaCD directly acts on the surfactant monomers in the aqueous phase, leading to progressive depletion of the air-water interface with increasing cyclodextrin contents. Significant shift of OG critical micelle concentration (cmc) was consequently observed: the higher alphaCD concentration, the higher the cmc value. Experiments performed at surfactant and cyclodextrin concentrations in the Gibbs regime of surface tension versus OG content were performed on one hand to establish Job's plot that showed 1:1 stoichiometry of the OG-alphaCD complex and on the other hand to calculate the association constant found equal to (1.85 +/- 0.35) x 10(3) L mol(-1). An inclusion process of the surfactant alkyl residue within the cyclodextrin cavity was confirmed by one-dimensional (1)H NMR, and the structure of the mixed assembly was extensively characterized by two-dimensional NOESY (1)H NMR. OG penetrates alphaCD so that its hydrocarbon chain is embedded inside the cyclodextrin cavity, and its polar head as well as the alpha-methylene group emerges outside the alphaCD secondary face. Solubility behavior of the OG-alphaCD complex in a wide range of host-guest ratios and concentrations was finally examined by turbidity recording and optical microscopy. At very low free cyclodextrin levels in the solution, the complex presented high solubility behavior up to more than 70 mM. By increasing nonassociated alphaCD in the mixture, propensity of the cyclodextrin molecules to crystallize was observed at concentrations far below the 100 mM aqueous solubility of the pure cyclodextrin. The hexagonal shape of the crystals seen in the optical microscopy images suggested they were, partially at least, composed of the solid complex.     

Dehydrogenation processes via C-H activation within alkylphosphines

Phosphines are commonly used in organometallic chemistry and are present in a wide variety of catalytic systems. This feature article highlights the advances made in dehydrogenation processes occurring within alkylphosphines, with the aim of further developing catalytic processes involving C-H activation together with potential applications in the field of hydrogen storage.     

Detailed structure of diamond-type lipid cubic nanoparticles

Supramolecular three-dimensional self-assembly of nonlamellar lipids with fragments of the protein immunoglobulin results in a bicontinuous cubic phase fragmented into nanoparticles with open water channels (cubosomes). The structure of the diamond-type cubic nanoparticles is characterized experimentally by freeze-fracture electron microscopy, and it is mathematically modeled with nodal surfaces emphasizing the fluid-like undulations of the cubosomic interfaces. Based on scaling-up and scaling-down approaches, we present stable and intermediate-kind nanoparticles resulting from the cubosomic growth. Our results reveal the smallest stable diamond-type cubosomic entity that can serve as a building block of more complex nanostructured fluid drug delivery vehicles of therapeutic proteins. The evidence presented for lipid-bilayer undulations in the surface region of the protein/lipid cubosomes could have important consequences for possible applications of these hierarchically organized porous nanoparticles.