Experimental and theoretical insights into the sequential oxidations of 3π-2spiro molecules derived from oligophenylenes: A comparative study of 1,2-b-DiSpiroFluorene-IndenoFluorene versus 1,2-b-DiSpiroFluorene(tert-butyl)4-IndenoFluorene

International audienceCyclic voltammetry and differential pulse voltammetry have shown too distinct behaviours in the sequential oxidation processes of two closely related compounds, namely 1,2-b-DiSpiroFluorene-IndenoFluorene (1,2-b-DSF-IF) and 1,2-b-DiSpiroFluorene(tert-Butyl)4-IndenoFluorene (1,2-b-DSF(tBu)4-IF). 1,2-b-DSF-IF is oxidized after a reversible one-electron transfer and a subsequent irreversible two-electron transfer. In contrast, 1,2-b-DSF(tBu)4-IF undergoes three well separated chemically reversible one-electron processes. Spectroelectrochemical monitoring of the gradual oxidation of the compounds points to a first oxidation centred on the indenofluorenyl core for both molecules. Consistent with the different electrochemical behaviour, the spectroelectrochemical data after the first oxidation is very different for both compounds and points to a specific electronic structure. This is further studied theoretically by DFT calculations of the molecules in their neutral, cationic and dicationic state which suggest an electronic reorganization in the dication 1,2-b-DSF(tBu)4-IF2+

Advanced electrokinetic characterization of composite porous membranes

International audienceThe effect of the streaming current flowing through the porous structure of composite membranes during tangential electrokinetic measurements was investigated. It was shown that neglecting this additional path for streaming current may have dramatic implications in the interpretation of the experimental data and on the determination of the membrane zeta potential. Experimental measurements of both streaming current and electrical conductance were performed with two different composite polymer membranes. By following the procedure proposed by Yaroshchuk and Luxbacher, Langmuir 26 (2010) 10882-10889, in the present work it was possible to determine separately the zeta potential of the membrane surfaces and that of their underlying porous structures. This experimental procedure was shown to provide useful information on the functionalization of an ultrafiltration polyethersulfone membrane by positively charged 4-benzyltriphenylphosphonium groups. Notably we found that the chemical modification leads to a charge reversal (from negative to positive) of the porous substructure of the membrane while the overall charge of the external surface remains negative, although with diminished magnitude

Simplified stress analysis of hybrid (bolted/bonded) joints

The load transfer in hybrid (bolted/bonded) – denoted HBB – single-lap joints is complicated due to the association of two different transfer modes (discrete and continuous) through elements with different stiffnesses. The Finite Element (FE) method can be used to address the stress analysis of those joints. However, analyses based on FE models are computationally expensive and it would be profitable to use simplified approaches enabling extensive parametric studies. Two among the authors of this paper participated in the development of a dedicated 1D-beam approach (Paroissien 2007). This paper presents an extension of this framework enabling (i) the analysis of HBB joints made of dissimilar laminated or monolithic adherends, and (ii) the introduction of non linear material behaviour for both the adhesive layer and the fasteners. The output data are the distributions of displacements and forces in the adherends and fasteners, as well as those of adhesive shear and peeling stresses, allowing for a fast assessment of the material behaviour and strength prediction of HBB joints. The use of this model is illustrated in the identification of the failure mechanisms of HBB joints under quasistatic loadings, based on experimental and numerical tests on single-lap HBB joint. It is worth mentioning that the model can support pure bonded and pure bolted configurations. It can be used during the presizing phase at the design office (possibly independently on commercial software), to obtain quickly mechanical performances and to help in decision making. Moreover, it was shown that the judicious choice of the adhesive material allows for a significant increase of the static and fatigue strength compared to pure bolted or bonded corresponding configurations (Kelly 2006) (Paroissien 2006). The model can then be used to formulate at best adhesive materials to optimize the mechanical performance of HBB joints according to work specifications

A robust pure hydrocarbon derivative based on the (2,1-b)-indenofluorenyl core with high triplet energy level.

International audienceA unique (2,1-b)-indenofluorenyl core flanked with two spirofluorene units, possessing a high triplet energy value and excellent thermal/morphological stability, is reported

Cis and trans-bis(tetrathiafulvalene-acetylide) platinum(II) complexes: syntheses, crystal structures, and influence of the ancillary ligands on their electronic properties.

International audienceA series of four platinum(II) complexes bearing two tetrathiafulvalene acetylide ligands coordinated either cis or trans to the metal center are reported: cis-Pt(bipy)(C≡CMe(3)TTF)(2), cis-Pt(tBu(2)bipy)(C≡CMe(3)TTF)(2), cis-Pt(dppe)(C≡CMe(3)TTF)(2) and trans-Pt(PPh(3))(2)(C≡CMe(3)TTF)(2). The X-ray diffraction studies of the four complexes are reported and discussed. The electrochemical investigations carried out by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) evidenced different redox behavior as a function of the ancillary ligand. Only for the cis-Pt(dppe)(C≡CMe(3)TTF)(2) complex is the first oxidation wave resolved (ΔE = 70 mV) into two one-electron processes. Spectroelectrochemical investigations performed on the four complexes did not evidence any electronic interactions between the two organic electrophores. The splitting of the first oxidation wave observed in cis-Pt(dppe)(C≡CMe(3)TTF)(2) is mainly explained by the non-equivalence of the two TTF moieties induced by the geometrical constraint imposed by the ancillary dppe ligand as found by density functional theory calculations

A versatile route to modify polyethersulfone membranes by chemical reduction of aryldiazonium salts

International audienceUltrafiltration polyethersulfone membranes were modified covalently by chemical reduction of aryl diazonium salts. Functionalizations were performed with four aryl diazonium salts bearing different functional groups (4-benzyltriphenylphosphonium diazonium, 4-nitrophenyl diazonium, 4-benzonitrile diazonium and 4-phenylacetic acid diazonium) so as to demonstrate the versatility of the method. The efficiency of the different functionalizations was checked with various characterization techniques. Attenuated Total Reflectance Fourier Transform Infra Red spectroscopy revealed the presence of 4-nitrophenyl, 4-benzonitrile and 4-phenylacetic acid groups at the surface of the different modified membranes but no characteristic vibration band was detected on the surface of the membrane modified with 4-benzyltriphenylphosphonium diazonium. The presence of 4-benzyltriphenylphosphonium, however, could be demonstrated by both Energy Dispersive X-ray spectroscopy (detection of the Kα ray of phosphorous at 2.015 keV) and streaming current measurements (shift of the membrane isoelectric point). Finally, dead-end filtration of an antibiotic (tylosin) was carried out with the unmodified membrane and the membrane modified by 4-benzyltriphenyl-phosphonium diazonium. Experiments revealed that the transport properties of the grafted membrane were significantly modified, with a significant increase in rejection mainly due to electrostatic repulsions between the surface of the modified membrane and tylosin

Preparation of chiral ruthenium(IV) complexes and applications in regio- and enantioselective allylation of phenols.

International audienceFacile preparations of chiral [Ru(Cp*)]- and [Ru(Cp')]-based allyl complexes featuring N,O chelate derived from (+)-nopinone are described. Single crystal X-ray structural analysis of one complex revealed the preferential configuration of the ruthenium centre and the orientation of the unsymmetrical allylic substituent. Applications of these complexes in catalysis for nucleophilic allylic substitution allowed regio- and enantioselective formation of branched allyl ethers from phenols

Effect of cathode material and its size on the abundance of nitrogen removal functional genes in microcosms of integrated bioelectrochemical-wetland systems

Funding Information: Funding: This study was supported by the Estonian Research Council (PUTJD715, IUT2-16, PRG352 and PRG676); the EU through the European Regional Development Fund (Centre of Excellence EcolChange, Estonia) and by the European Structural and Investment Funds. The financial support from The French National Research Agency (ANR-17-CE04-0004) is gratefully acknowledged. The financial support from the International mobility support for PhD students–DrEAM (University of Lorraine) is gratefully acknowledged.Peer reviewedPublisher PD

Monophyletic group of unclassified γ-Proteobacteria dominates in mixed culture biofilm of high-performing oxygen reducing biocathode

International audienceSeveral mixed microbial communities have been reported to show robust bioelectrocatalysis of oxygen reduction over time at applicable operation conditions. However, clarification of electron transfer mechanism(s) and identification of essential micro-organisms have not been realised. Therefore, the objective of this study was to shape oxygen reducing biocathodes with different microbial communities by means of surface modification using the electrochemical reduction of two different diazonium salts in order to discuss the relation of microbial composition and performance. The resulting oxygen reducing mixed culture biocathodes had complex bacterial biofilms variable in size and shape as observed by confocal and electron microscopy. Sequence analysis of ribosomal 16S rDNA revealed a putative correlation between the abundance of certain microbiota and biocathode performance. The best performing biocathode developed on the unmodified graphite electrode and reached a high current density for oxygen reducing biocathodes at neutral pH (0.9A/m(2)). This correlated with the highest domination (60.7%) of a monophyletic group of unclassified γ-Proteobacteria. These results corroborate earlier reports by other groups, however, higher current densities and higher presence of these unclassified bacteria were observed in this work. Therefore, members of this group are likely key-players for highly performing oxygen reducing biocathodes.[on SciFinder (R)