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Saponins are secondary metabolites that are abundant and diversified in echinoderms. Mass spectrometry is increasingly used not only to identify saponin congeners within animal extracts but also to decipher the structure/biological activity relationships of these molecules by determining their inter-organ and inter-individual variability. The usual method requires extensive purification procedures to prepare saponin extracts compatible with mass spectrometry analysis. Here, we selected the sea star Asterias rubens as a model animal to prove that direct analysis of saponins can be performed on tissue sections. We also demonstrated that carboxymethyl cellulose can be used as an embedding medium to facilitate the cryosectioning procedure. Matrix-assisted laser desorption/ionization (MALDI) imaging was also revealed to afford interesting data on the distribution of saponin molecules within the tissues. We indeed highlight that saponins are located not only inside the body wall of the animals but also within the mucus layer that probably protects the animal against external aggressions. Graphical Abstract Saponins are the most abundant secondary metabolites in sea stars. They should therefore participate in important biological activities. Here, MALDI imaging is presented as a powerful method to determine the spatial distribution of saponins within the animal tissues. The inhomogeneity of the intra-organ saponin distribution is highlighted, paving the way for future elegant structure/activity relationship investigations.

Tandem mass spectrometry is increasingly applied to polymer ions in the context of in-depth structural characterization. In particular, the well-known collision-induced dissociation (CID) methodology is nowadays advantageously used to characterize end-groups and to distinguish isomeric polymer ions. When applied to sodium-cationized polyesters, CID was demonstrated to mainly involve charge remote fragmentation processes and consecutive as well as competitive dissociation pathways. In the present report, an experimental and theoretical study of collision induced dissociation of isomeric sodium cationized polylactide was investigated. The investigated polymers were designed to obtain oligomers only differentiated on the basis of regioisomeric end-groups, using ortho-, meta-, and para-methylbenzyl alcohols as initiators. The CID spectra revealed the presence of competitive charge driven and charge remote fragmentations. In particular, the charge induced fragmentations allowed the minute distinction between the three isomeric end-groups. The intermediacy of an ion/neutral complex was proposed to account for the observed decomposition and some theoretical calculations were performed to support the proposal.

We just clicked: A convergent approach consisting of two successive copper(I)-catalyzed azide-alkyne cycloaddition "click" reactions leads to a diblock copolymer in which the two blocks are linked by a rotaxane-type mechanical bond (see scheme). Rotaxane formation is templated by a square-planar PdII complex. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The use ofdifferent phosphazene bases has been investigated as catalysts in polymerization of [R,S]-4-benzyloxycarbonyl-3,3-dimethyl-2-oxetanone (dMMLABz) in presence of carboxylic acids used as initiators. Whatever the catalyst considered (P 1 -t-Bu, P 2 -t-Bu, or P 4 -t-Bu) a very good control over the polymerization has been obtained in terms of polyester molecular weights and end-groups fidelity as attested by spectroscopic techniques such as 1 H NMR, gel permeation chromatography (GPC) and matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) experiments. Characterized by a complete absence of transfer reactions, the system allows for the generation of very high molecular weight PdMMLABz trough a mechanism selectively involving the "O-alkyl" scission of the β-lactone monomer. A clear dependence of the basicity of the phosphazene catalyst on the overall polymerization kinetics has been observed where the most basic catalytic species, i.e., 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranyl-idenamino]-2Λ 5 ,4Λ 5 -catenadi-(phosphazene) (P 4 -t-Bu), shows the highest active ion-pair. Accordingly, P 4 -t-Bu allowed for the synthesis of PdMMLABz chains characterized by a number-average molecular weight higher than 1.5 x 10 6 g mol -1 .

International audience; Aromatic substitution reactions of selected ionized benzenes derivatives (chlorobenzene, nitrobenzene, dimethylphtalates) and phenoxy cation using neutral methyl isocyanide as a nucleophile are shown to efficiently occur in the gas phase. Nitrilium ions are produced in high abundance during these processes. These reactions have been performed in the hexapole collision cell of a large-scale hybrid tandem mass spectrometer. Computed 298 K enthalpy diagrams at the B3LYP/6-31+G(d,p) level of theory confirm the exothermic formation of the N-methylbenzonitrilium ions starting with ionized chloro- and nitrobenzene molecular ions. In this last case, two other exothermic processes are also detected: (i) an oxygen atom transfer yielding ionized nitrosobenzene and neutral methyl isocyanate and (ii) a loss of carbon monoxide from the ion/molecule reaction product generated when metastably generated phenoxy cations (produced in the hexapole collision cell) react with methyl isocyanide. Using extended theoretical calculations, several reaction pathways have been derived. The behavior of the three isomeric dimethyl phthalates has been investigated in the same way.

In this paper, we describe the design and characterization of regioregular poly(3-hexylthiophene)-poly(e-caprolactone) di- and tri-block copolymers (RRP3HT- b -PCL and PCL- b -RRP3HT- b -PCL). The well-controlled synthesis of (di)hydroxyl-terminated RRP3HT makes possible to design block copolymer structures with a narrow molecular weight distribution. The microscopic morphology is investigated by atomic force microscopy, which reveals self-assembled fibrillar structures with the RRP3HT nanoribbons separated by narrow domains of insulating PCL. The charge transport properties are characterized in thin films field-effect transistors, and comparison between the devices performances is carried out in view of the nanoscale morphology within the transistor channel.

Regioregular poly(3-hexylthiophene) has been successfully incorporated into various poly(N,N-dimethylamino-2-ethyl methacrylate)-based block copolymers, i.e., P3HT-b-PDMAEMA, via Grignard metathesis (GRIM) method and atom transfer radical polymerization (ATRP) reactions. The structure of the diblock copolymers was fully confirmed by FT-IR, H-1 NMR spectroscopy, gel permeation chromatography (GPC), and ultraviolet-visible spectroscopy (UV-vis). The recovered copolymers could be treated by protonation of the pending tertiary amine functions and depending on the relative content in PDMAEMA, the copolymers could be solubilized in more polar solvents where P3HT alone proved to be totally insoluble.

Using MS/MS/MS experiments and quantum chemical calculations, it is demonstrated that oxygen (carbonyl) methylated phthalic anhydride cations are produced when metastable dimethyl phthalate molecular ions expel a methoxyl radical. At higher internal energies, isomeric acyl ions are competitively generated.

International audience; The chemistry leading to the competitive eliminations of H, CH(3), and OCOCH(3) from adducts of ionized methyl benzoate and neutral methyl isocyanide has been explored using density functional theory molecular orbital calculations. The energies of the various reactants and transition structures were estimated at the B3LYP/6-31+G(d,p) level of theory. Nucleophilic aromatic substitution is proposed to account for the H and OCOCH(3) eliminations. The corresponding sigma-complex intermediates, B(1ipso) and B(1ortho), are stable species lying in deep energy wells situated 70 and 120 kJ/mol, respectively, below the reactants, ionized methyl benzoate and methyl isocyanide. The latter complex, B(1ortho), may be also at the origin of a multistep rearrangement involving hydrogen migrations and methyl elimination from the original methoxy group of the benzoate moiety.

In a previous study on the pyridine ion (1) and the pyridine-2-ylid isomer (2), we reported that ions 2 readily react with H2O to produce 2-pyridone ions at m/z 95, by O-atom abstraction. The mechanism for this intriguing reaction, however, was not established. This prompted us to use model chemistry calculations (CBS-QB3) to probe various mechanistic scenarios and to perform complementary experiments with the new, more versatile, ion–molecule reaction chamber of the Mons Autospec 6F mass spectrometer. It appears that H2O is not reacting neutral that produces the 2-pyridone ion of the above reaction, but rather O2 from air co-introduced with the water vapour. Theory and experiment agree that the exothermic reaction of O2 with the pyridine-2-ylid ion leads to loss of 3O from a stable peroxide-type adduct ion at m/z 111. Similarly, pyridine-3-ylid ions (3) generate 3-pyridone ions, but the reaction in this case is thermoneutral. The m/z 111:95 peak intensity ratios in the spectra of the ion–molecule products from ions 2 and 3 may serve to differentiate the isomers.

In this letter, the authors would like to present a rapid method for mass-scale calibration of metastable dissociation in an orthogonal-axis time-of-flight instrument. The calibrating ion is a protonated polyhedral oligomeric silsesquioxane (POSS) generated in electrospray ionization. In addition, dissociation mechanisms for protonated POSS are proposed. Finally, the interest of the method is illustrated in the context of a collision-induced dissociation investigation of a sodium-cationized polylactide.

Chiral recognition of enantiomers by host compounds is one of the most challenging topics in modern host-guest chemistry. Amongst the well-established methods, mass spectrometry (MS) is increasingly used nowadays, due to its low detection limit, short analysis time, and suitability for analyzing mixtures and for studying chiral effects in the gas phase. The development of electrospray-ionization (ESI) techniques provides an invaluable tool to study, in the gas phase, diastereoisomeric complex ions prepared from enantiomer ions and a chiral selector. This paper reports on an ESIMS and ESIMSMS study of the molecular mechanisms that intervene in the chiral-recognition phenomena observed between amino acids and a chiral crown ether. The modified crown ether, namely (+)-([18]crown-6)-2,3,11,12-tetracarboxylic acid, is used as the chiral selector when covalently bound on a stationary phase in liquid chromatography. This study was stimulated by the fact that, except with threonine and proline, consistent elution orders were observed, which indicates that the D enantiomers interact more strongly with the chiral selector than the L enantiomers. For proline, the lack of a primary amino group is likely to be responsible for the nonresolution of the two forms, whereas the second stereogenic center on threonine could explain the reversed elution order. In light of those observations, we performed mass spectrometry experiments to understand more deeply the enantiomeric recognition phenomena, both in solution by the enantiomer-labeled guest method and in the gas phase by gas-phase ligand-exchange ion/molecule reactions. The results have been further supported by quantum chemical calculations. One of the most interesting features of this work is the identification of a nonspecific interaction between proline and the crown ether upon ESIMS analysis.

Ruthenium(ii) polyazaaromatic complexes have gained interest in recent decades as biomolecular tools, especially in the development of new phototherapeutic agents. These light emissive Ru complexes based on π-deficient ligands were first designed to allow a photo-induced electron transfer (PET) with the guanine base in DNA since their 3MLCT state is highly photo-oxidizing. Later the field of research was extended to proteins with the highlighting of a PET process with the tryptophan residue. This paper reports the kinetics of the luminescence quenching of [Ru(TAP)2phen]2+ by several selected peptide sequences containing at least one tryptophan residue. By using a peptide library we highlight the important parameters influencing the kinetics of the photo-electron transfer process, such as the net electrostatic charge and the number of tryptophan residues. The best peptide candidates were selected to study the formation of photo-products by MALDI-ToF mass spectrometry. A high photoreactivity of the [Ru(TAP)2phen]2+ complex was observed and multiple photoadducts were characterized, among them inter-peptidic adducts as well as intra-peptidic adducts.

Novel organocobalt complexes featuring weak C-CoL2 bonds (L = acetylacetonate) are prepared and used as sources of halomethyl radicals. They permit the precision synthesis of α-halide functionalized and telechelic polymers in organic media or in water. Substitution of halide by azide allows derivatization of polymers using the CuAAC click reaction.

The covalent photoadduct (PA) between [Ru(TAP)3](2+) (TAP = 1,4,5,8-tetraazaphenanthrene) and guanosine monophosphate (GMP) opened the way to interesting photobiological applications. In this context, the PA's capability upon illumination to give rise to the addition of a second guanine base is especially interesting. The origins of these intriguing properties are for the first time thoroughly investigated by an experimental and theoretical approach. The PA's spectroscopic and redox data combined with TDDFT results corroborated with resonance Raman data show that the properties of this PA (pKa around 7) depend on the solution pH. Theoretical results indicate that the acid form PA.H(+) when excited should relax to MLCT (metal-to-ligand charge transfer) excited states, in contrast to the basic form PA whose excited state should have LLCT/ILCT (ligand-to-ligand charge transfer/intra ligand charge transfer) characteristics. Ultrafast excitation of PA.H(+) at pH 5.9 produces continuous dynamic processes in a few hundred picoseconds involving coupled proton-electron transfers responsible for luminescence quenching. Long-lived species of a few microseconds capable of reacting with GMP are produced at that pH, in agreement with the formation of covalent addition of a second GMP to PA, as shown by mass spectrometry results. In contrast, at pH 8 (mainly nonprotonated PA), other ultrafast transient species are detected and no GMP biadduct is formed in the presence of GMP. This pH dependence of photoreaction can be rationalized with the different nature of the excited states, thus at pH 8, unreactive LLCT/ILCT states and at pH 5.9 reactive MLCT states. ispartof: Journal of Physical Chemistry B vol:119 issue:12 pages:4488-500 ispartof: location:United States status: published

© 2014 American Chemical Society. The synthesis of a block copoly(3-alkylthiophene) consisting of two different P3AT blocks equipped with an H-donor and -acceptor functionality is presented. The P3ATs were synthesized using a functionalized Ni-initiator. By a series of postpolymerization reactions, including click chemistry, an H-donor and -acceptor entity was attached to the end of the polymer chains. Evidence for a quantitative functionalization of the polymers was provided by 1H NMR and MALDI-ToF analyses. Chiral side chains were implemented on one of both blocks, allowing the study of the influence of the H-bond formation on the chiral self-assembly using UV-vis and circular dichroism spectroscopy. ispartof: Macromolecules vol:48 issue:1 pages:90-98 status: published

© 2015 American Chemical Society. Different protected thiol-functionalized initiators were prepared and used to polymerize end-functionalized poly(3-hexylthiophene)s in which the spacer between the thiol and the P3HT chain is varied. The protected thiol P3HTs were in situ deprotected and anchored onto Au nanoparticles (NPs) to form P3HT/Au hybrids. The influence of the length of the linker between the P3HT and the Au NP surface on the fluorescence quenching was investigated. The strongest quenching was observed for the shortest linkers. Also, a protected thiol poly(3-octylselenophene) (P3OS) was polymerized and anchored together and separately with P3HT to a Au NP. The effect of the presence of P3OS on the quenching was investigated, and an additional quenching was observed when P3OS is anchored on the same NP as P3HT. For all polymers, 1H NMR and MALDI-ToF analysis confirmed the successful functionalization and strong control over the polymerization. ispartof: Macromolecules vol:48 issue:24 pages:8752-8759 status: published

An efficient oxidation reaction of various electron-poor quinoxaline-core-containing compounds, such as quinoxalines, 1,4,5,8-tetraazaphenanthrenes, and 1,4,5,8,9,12-hexaazatriphenylene, using [bis(trifluoroacetoxy)iodo]benzene is reported. These compounds are converted into the corresponding quinoxalinediones in good to high yields at room temperature using an acetonitrile/water solvent mixture. This unprecedented reaction should enable the synthesis of a wide variety of compounds useful in several fields of chemistry.

International audience; Amphiphilic diblock copolythiophenes were synthesised by an efficient two-step synthetic strategy. The diblock copolyelectrolytes were obtained via the quasi-living Kumada catalyst-transfer polycondensation followed by quaternisation of the bromohexyl side chains of one of the monomer constituents into N-methylimidazolium, pyridinium, trimethylammonium or trimethylphosphonium units. The effects of the nature of the charged group on the thermal properties were investigated by Rapid Heat-Cool (RHC) calorimetry measurements. The solvent-driven assembly of these block copolyelectrolytes in chloroform (CHCl3), water, methanol (MeOH), water:MeOH mixtures and in subsequently prepared thin films was investigated using a combination of photoluminescence, scattering and microscopic techniques. The rigid rod-structure of the block copolyelectrolytes lead to the formation of core-shell cylindrical aggregates in solution, with features determined by the nature of the solvent. AFM studies revealed that the aggregates formed in solution can be transferred into thin films allowing for the reliable control of the self-organisation process and the resulting nanoscale architecture.

International audience; In this communication we report the first homopolymerization of a variety of methacrylates by an NMP process at moderate temperature (40-50 degrees C), using an easily accessible and inexpensive nitroxide precursor. The combination of a low temperature azo-initiator with a hindered nitroso-compound produces a mixture of hindered nitroxides in the polymerization medium that act as efficient polymerization control agents. Results of Electron Spin Resonance (ESR) spectroscopy experiments combined with mass spectrometric studies support the proposed in situ NMP mechanism. The hindered structure of the nitroxides formed in situ is believed to be responsible for the efficiency of the process by allowing it to proceed at low temperature, therefore limiting the side reactions generally observed in NMP of methacrylates.

We report the first structure determination of a covalent photoadduct between a Ru(II)-tap complex and a tryptophan-containing peptide (AlaTrpAla) by mass spectrometry and NMR spectroscopy. Ru(II)-tap complexes could thus be exploited as photodamaging agents of Trp-containing polypeptides or proteins.

An efficient oxidation reaction of various electron-poor quinoxaline-core-containing compounds, such as quinoxalines, 1,4,5,8-tetraazaphenanthrenes, and 1,4,5,8,9,12-hexaazatriphenylene, using [bis(trifluoroacetoxy)iodo]benzene is reported. These compounds are converted into the corresponding quinoxalinediones in good to high yields at room temperature using an acetonitrile/water solvent mixture. This unprecedented reaction should enable the synthesis of a wide variety of compounds useful in several fields of chemistry.

International audience; Noncovalent interactions between several protonated amines and an original ditopic receptor, nor-seco-cucurbit[10]uril, are investigated by combining mass spectrometry-based methods and computational chemistry. Electrospray ionization is used to transfer the intact supramolecular assemblies from their acidic solution to the gas phase, provided fine-tuning of the source parameters is achieved. Ternary complexes, associating two guest molecules and one host cavity, are observed systematically in the mass spectrometry analyses and the quasi-exclusive occurrence of these 2:1associations reveals the allosteric nature of the complexation reaction. It is demonstrated that the binary 1:1complex ions that are detected arise from collision-induced dissociation processes undergone by the ternary complex ions inside the ion source. Based on ion mobility experiments supported by theoretical calculations, the inclusion nature of the gas-phase ternary complexes is clearly evidenced independent of the size of the probed guest molecule and the charge state of the complex ions. The allosteric nature of the complexation reactions is dictated by size criteria. This is demonstrated on the basis of mass spectrometry experiments by analyzing solutions containing ligands of different sizes in competition for inclusion within the guest cavity. Computational chemistry is also used to characterize the three-dimensional structures of the complexes.

Saponins are natural molecules that the common sea star Asterias rubens produces in the form of steroid glycosides bearing a sulfate group attached on the aglycone part. In order to highlight the inter-organ and inter-individual variability, the saponin contents of five distinct body components, namely the aboral body wall, the oral body wall, the stomach, the pyloric caeca and the gonads, from different individuals were separately analyzed by mass spectrometry. MALDI–ToF experiments were selected as the primary tool for a rapid screening of the saponin mixtures, whereas LC–MS and LC–MS/MS techniques were used to achieve chromatographic separation of isomers. First of all, our analyses demonstrated that the diversity of saponins is higher than previously reported. Indeed, nine new congeners were observed in addition to the 17 saponins already described in this species. On the basis of all the collected MS/MS data, we also identified collision-induced key-fragmentations that could be used to reconstruct the molecular structure of both known and unknown saponin ions. Secondly, the comparison of the saponin contents from the five different body components revealed that each organ is characterized by a specific mixture of saponins and that between animals there are also qualitative and quantitative variability of the saponin contents which could be linked to the sex or to the collecting season. Therefore, the observed high variability unambiguously confirms that saponins probably fulfill several biological functions in A. rubens. The current results will pave the way for our future studies that will be devoted to the clarification of the biological roles of saponins in A. rubens at a molecular level.

International audience; Regioregular head-to-tail -bromo--carboxystyryl poly(3-hexylthiophene) (P3HT-COOH) has been prepared by a Wittig reaction of -bromo--formyl poly(3-hexylthiophene) (P3HT-CHO) with [(4-carboxyphenyl)methyl]triphenylphosphonium bromide. This carboxylic end-group functionalized polymer was used to functionalize TiO2 nanoparticles in view of improving the miscibility between poly(3-hexylthiophene) and the nanoparticles, for future photovoltaic applications. The anchoring of the polymer on the surface of the TiO2 nanoparticles was demonstrated by sedimentation tests in THF, and by thermogravimetric analysis (TGA), Transmission Electron Microscopy (TEM), 1H MAS solid-state NMR, UV-Vis and X-ray photoelectron spectroscopies. Films were produced by solvent casting and the dispersion of the TiO2 nanoparticles was evaluated by Atomic Force Microscopy (AFM). Fluorescence quenching studies in CHCl3 were performed on these hybrids materials.

RuII-TAP complexes have been shown to be very attractive compounds in the frame of developments of new anticancer drugs targeting the genetic material. This increasing interest originates from observations of covalent bond formations, triggered by photo-induced electron transfer (PET) between RuII-TAP complexes and guanine bases of DNA. This photoreaction has recently been extended to the tryptophan (Trp) amino acid for future applications involving peptides. Thus, a double photo-addition of Trp residues of peptides on RuII complexes is demonstrated by mass spectrometry with some structural issues. Such bi-adduct formations offer the possibility of photocrosslinking two Trp-containing biomolecules, which is investigated in this study. Thus, photocrosslinking between two complementary oligonucleotides (ODNs) derivatized by Trp-containing tripeptides is demonstrated by polyacrylamide gel electrophoresis (PAGE) in the presence of RuII-TAP complexes. Both PAGE and MS indicate that such photocrosslinkings arise from two reaction pathways: either via the double addition of Trp residues on the Ru complex or from dimerization of Trp radicals. The competition between these two pathways depends on the experimental conditions. Heterobridgings between guanine bases and tryptophan residues mediated by RuII-TAP complexes is also examined, opening the way to ODN-peptide photocrosslinkings. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

Polythiophenes with alcohol, tosylate, azide, ethynylene, carboxylic acid, and amine end groups were prepared by a combination of functionalized nickel initiators and postpolymerization reactions. The azide and ethynylene polymers were subsequently used in a click reaction to produce a conjugated block copolymer. Finally, a conjugated triblock-copolymer was synthesized by means of a chain growth polymerization initiated by a binuclear nickel initiator. ispartof: Macromolecules vol:44 issue:15 pages:6017-6025 status: published

Nowadays, numerous experimental and theoretical studies are devoted to the research field of polythiophenes and other electroconjugated polymers due to the huge potentialities of those conducting polymers. Synthetic procedures are now developed to reach the highest control over both polymerization and analytical methodologies allowing an in-depth and straightforward characterization of the polymer samples without any required doubt. Mass spectrometry methodologies and in particular MALDI-ToF measurements are definitively suitable to meet the characterization requirements. In the present study, trans-2-[3-(4-t-butyl-phenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) was shown to afford better results than the reported terthiophene and dithranol matrices as far as sensitivity and signal-to-noise ratio are concerned. We tentatively proposed that the ionization of the P3HT molecules is performed by charge exchange in the condensed phase (clusters) with matrix molecule radical cations and subsequent neutral matrix molecule evaporation from the clusters. The putative key parameters to account for the really high efficiency of DCTB for the MALDI analysis of P3HT are (1) the highest ionization energy of DCTB amongst the three matrices, (2) the really high absorptivity of the matrix molecule at the laser wavelength and (3) the presence of the tertiobutyl group on the matrix molecule. The presence of this substituent is likely to decrease the intermolecular interactions in the condensed phase rendering the evaporation of the neutral matrix molecules less energy demanding. We also demonstrated for polymer samples presenting an average number molecular weight (Mn) below 10 000 g mol−1 that the systematic overestimation of the low mass oligomers upon MALDI measurements ends up with wrong Mn and polydispersity index (PDI) values. A systematic Soxhlet extraction against heptane was shown to allow the recording of absolute Mn and PDI. Copyright © 2011 John Wiley & Sons, Ltd.

International audience; Cobalt‐mediated radical coupling (CMRC) is a straightforward approach to the synthesis of symmetrical macromolecules that relies on the addition of 1,3‐diene compounds onto polymer precursors preformed by cobalt‐mediated radical polymerization (CMRP). Mechanistic features that make this process so efficient for radical polymer coupling are reported here. The mechanism was established on the basis of NMR spectroscopy and MALDI‐MS analyses of the coupling product and corroborated by DFT calculations. A key feature of CMRC is the preferential insertion of two diene units in the middle of the chain of the coupling product mainly according to a trans‐1,4‐addition pathway. The large tolerance of CMRC towards the diene structure is demonstrated and the impact of this new coupling method on macromolecular engineering is discussed, especially for midchain functionalization of polymers. It is worth noting that the interest in CMRC goes beyond the field of polymer chemistry, since it constitutes a novel carbon–carbon bond formation method that could be applied to small organic molecules.

The low-kinetic energy collision-induced dissociation (CID) behavior of different sodium-cationized polylactide (PLA) oligomers was thoroughly investigated to shed some light on the analytical potentialities of CID experiments in the context of polymer characterization. Indeed, investigation of several end-groups modified PLA reveals that, in addition to the expected end-group specific dissociations, collisionally-excited PLA.Na(+) suffer from a backbone cleavage. The so-obtained sodium-bound dimer cations consecutively undergo the loss of a monomeric residue that corresponds to neutral acrylic acid. The experimental observations, performed on a hybrid Q-ToF instrument, were totally corroborated by a theoretical study involving DFT calculations, molecular mechanics, and molecular dynamics calculations.

International audience; The self-assembly of functional polythiophenes was studied by a bottom-up approach “from molecule to polymer”. The synthesis and the X-ray structure of 2,5-dibromo-3-styryl and 3-2',3',4',5',6'-pentafluorostyryl-thiophenes revealed a supramolecular arrangement controlled by π-π interactions between the aromatic rings. A [2+2] photocyclization reaction in the solid state of (E)-1-2',5'-dibromo-3'-thienyl-2-pentafluorophenylethene triggers the formation of a rare cycloadduct composed by thiophene rings. The X-ray analysis confirmed its rctt stereochemistry. The synthesis of P3HT-b-P3ST and P3HT-b-P3STF block oligomers was achieved by a GRIM method in good yields. An indirect proof of well-defined nanostructured organization was provided by the partial photocyclization of pendant styryl moieties under UV-irradiation.

International audience; Cobalt-mediated radical coupling (CMRC) is successfully applied to poly(vinyl acetate) (PVAc) and poly(N-vinylpyrrolidone) (PNVP) precursors for the first time. The coupling process is based on addition of isoprene onto polymer chains preformed by controlled radical polymerization with cobalt complexes (CMRP). The extents of coupling were high (>90%) to moderate (75−80%) for PVAc and PNVP precursors, respectively. Effects of the length of the polymer precursors and conditions used in the polymerization step on the coupling efficiency are discussed. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) analyses conducted on the coupling products demonstrate the preferential insertion of two isoprene units in the final polymers. The CMRC mechanistic proposal, supported by DFT calculations, is based on this microstructure feature. Finally, illustration of the macromolecular engineering potential of this technique is given by the preparation of symmetrical PVAc-b-PNVP-b-PVAc triblock copolymers starting from the corresponding PVAc-b-PNVP-[Co] diblock copolymer.

This manuscript investigates the use of arylnickel complexes for the synthesis of functionalized conjugated polymers is. The scope of the catalyst-transfer polycondensation of poly(3-alkylthiophene) using nickel was expanded by functionalizing and isolating the nickel initiator. o-Methyl substituted arylnickel complexes were isolated and used to initiate the polymerization of various substituted poly(thiophene)s and poly(p-phenylene). Finally, the living nature of the polymerization of poly(3-alkylthiophene) was exploited to prepare a polymer with two different end-groups – one arising from the Ni-initiator and one from the end-capper. ispartof: Macromolecules vol:42 issue:20 pages:7638-7641 status: published

Electron ionization of methyl isocyanide in various chemical ionization conditions is reported and, depending on the energy conditions used, different ion/molecule reactions are observed. It is proposed, on the basis of combined quantum chemical (DFT) calculations and tandem mass spectrometric experiments, that a common intermediate could be a cumulenic ionized dimer dissociating in the ion source following two energy depending competitive channels, a loss of a hydrogen atom and a loss of a methyl group. Proposed structures for new cumulenic ions are supported by collision experiments in the high (collisional activation) or/and low (collision-induced dissociations) translational energy regime.

The ring-opening polymerization (ROP) of L-lactide in dichloromethane with (+)-sparteine is described. Under aprotic conditions, (+)-sparteine leads to controlled cyclic polyesters mainly obtained by a backbiting process from the in situ generated tertiary amine-containing symmetrical binary zwitterion.

In view of preparing Cu polynuclear complexes with dipyrromethene ligands, the mononuclear complexes [Cu(II)(dipy)2] (dipyH = 5-phenyldipyrromethene) and [Cu(II)(dpdipy)2] (dpdipyH = 1,5,9-triphenyldipyrromethene) have been prepared and characterized by X-ray crystallography, mass spectrometry and EPR spectroscopy. Their peculiar redox and spectroscopic (absorption/emission) behaviours are discussed. In contrast to Cu(II) complexes of 1,1'-bidypyrrin, the reduction electrolysis of [Cu(II)(dpdipy)2] leads to decomposition products on a time scale of a few hours. Moreover in relation to this observation, [Cu(I)(dpdipy)2](-) could not be synthesized in spite of the Cu(I) core protection by the phenyl substituents in ortho position of the nitrogen atoms. Theoretical calculations provide some explanations for this instability. Interestingly [Cu(II)(dipy)2] and [Cu(II)(dpdipy)2] display weak luminescence at room temperature, attributed to a ligand centered emission.

The synthesis of poly[(4,4′-(dihexyl)dithieno(3,2-b;2′,3′-d)silole)] has been carried out through Kumada catalyst transfer polycondensation and its copolymerization with 3-hexylthiophene (3HT) leads to well-defined diblock copolymers in terms of molecular characteristics. These copolymers show a wider absorption window than P3HT, which is of potential interest for photovoltaic applications.

Highly dispersible graphene nanosheets were straightforwardly synthesized by in situ reduction in the presence of hydroxyl-functionalized imidazolium ionic liquids as a supramolecular template. Therefrom, a biodegradable poly(e-caprolactone) (PCL)/graphene nanocomposite was prepared via a “grafting-from” approach based on the hydroxyl functionalities available from as-modified graphene nanosheets. The work opens up a path for a wide range of strategies in the fabrication of graphene/polymer nanocomposites.

International audience; High-regioregular poly{3-[n-(1-methylimidazolium-3-yl)alkyl]thiophene-2,5-diyl bromide} (n = 4, 6, 8) (10-12) have been prepared by reaction of poly[3-(n-bromoalkyl)thiophene-2,5-diyl] (n = 4, 6, 8) (7-9) with 1-methylimidazole. Acid-catalyzed hydrolysis and polycondensation of tetraethoxysilane (TEOS) were carried out in the presence of these polymers. The strong ionic interactions between the imidazolium moieties of the polythiophene and the charged silanol groups enabled the homogeneous dispersion of the polythiophene within silica. The resulting composite materials were characterised by SEM, TEM and tapping mode atomic force microscopy (TM-AFM). The optical and thermal properties were investigated by UV and TGA measurements

Poly(l-lactide) end-functionalized by an imidazolium ring was synthesized by ring-opening polymerization of l-lactide from a hydroxylated ionic liquid. When challenged with CNTs in solution, this polyester exhibited significant binding ability towards the nanotube surface with respect to omega-pyrene poly(l-lactide).

Recent advances in catalysis enriched the toolbox to prepare well-defined polyester materials such as polylactide (PLA). Herein, we report the use of crown ethers to speed up the polymerization of L-lactide (L-LA) initiated by an exogenous alcohol and catalyzed by potassium acetate (KOAc). With KOAc, the crown ethers played a crucial role as a complexing agent, with 18-crown-6 enabling the fastest polymerization kinetics outpacing the one obtained with the pristine catalyst by not less than 73. Experimental results suggested that the 18-c-6 crown ether complexed the KOAc ion pair to in situ produce free ions, which was much more appropriate to activate the propagating alcohol for the ring-opening reaction of L-LA.