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International audience; Pure nanocrystalline chromium disilicide (CrSi2) were synthesized for the first time by a fast Chlorine-Transfer-Reaction between chromium chloride and silicon with the support of thermodynamics calculation. The use of sodium and lithium chloride diluent enables to decrease the aggregates size from ∼2000 nm to ∼500 nm and to reach a nanocrystallite size ranging from 50 to 200 nm suitable for new applications

In order to understand the electronic contribution of the thienopyrazine building block on the electronic properties of π-conjugated systems, small molecules containing thiophene and thienopyrazine moieties are synthesized and jointly studied by theoretical (DFT) and experimental methods (UV-Vis, UPS). Taking advantages of these preliminar attractive results, four low band gap extended structures have been elaborated on the base of Donor-Acceptor-Donor sequences (DAD); these elongated π-conjugated molecules exhibit noticeable electronic and absorption properties spreading from the near UV to NIR regions.

International audience; Chromium disilicide (CrSi2) particles were synthesized by arc melting furnace followed by mechanical milling. XRD and DLS analyses show that aggregates of around 3 µm containing about 10 nm sized crystallites were obtained. These aggregates were functionalized in solution by coupling agents with different anchoring groups (silane, phosphonic acid, alkene and thiol) in order to disperse them into an organic polymer. Dodecene was used to modify CrSi2 surface during mecano-synthesis in a grinding bowl with quite little solvent quantity and the optimization step allowed to reduce the aggregates size to 500 nm. A thermoelectric composite was then made between alkene CrSi2 grafted samples and poly(p-phénylène-2,6-benzobisoxazole). This study opens the route of new surface grafting of intermetallic silicides for applications linked to electronic and/or energy.

International audience; We describe the synthesis of two new polymerizable monomers, and the subsequent polymers functionalized by tetrazine pendant groups, along with their electrochemical behaviour and fluorescence properties. In all cases a very stable conducting polymer is obtained, featuring both the redox activity of the main chain in oxidation and of the tetrazine functional group upon reduction. One of the polymers in addition exhibits an electrofluorochromic behaviour.

International audience; Anew type of DNA ligand that contains a phosphate-binding group and a photoresponsive azobenzene moiety is reported. When the azobenzene is in trans configuration, the ligand binds to the minor groove of a double-stranded DNA, whereas it partially desorbs upon trans –cis isomerisation with light.The ability to photoswitch the ligand upon interaction with DNA is evidenced by (chir)optical signatures, and deciphered by the differences of binding geometry, stability, and dynamics of the DNA/ligand complexes for the two isomers. We exploit these properties to photomodulate DNA-templated self-assembly, through the incorporation of another pi-stacking DNA ligand, which together with the photoresponsive ligand form mixed supramolecular complexes along DNA. Our study demonstrates that well-designed photoresponsive DNA binders can be used to modulate multicomponent supramolecular DNA assemblies.

The electronic and optical properties of a large series of symmetrical D–π–A–π–D chromophores are investigated. Vertical transition energies and related wavelengths, as well as absorption strengths, are computed by means of density functional theory and analyzed in the light of structural and electronic parameters such as torsional angles, bond length alternation, ground-state charge transfer and photo-induced charge displacement. This computational design allows establishing structure-property relationships linking the chemical structure of the chromophores to their absorption capability in the near-infrared (NIR) region, providing comparative guidelines for eventual syntheses.

A series of bulky end-capped [1]benzothieno[3,2-b]benzothiophenes (BTBTs) are developed in order to tune the packing structure via terminal substitution. A coupled theoretical and experimental study allows us to identify 2,7-di-tert-butylBTBT as a new high-performance organic semiconductor with large and well-balanced transfer integrals, as evidenced by quantum-chemical calculations. Single-crystal field-effect transistors show a remarkable average saturation mobility of 7.1 cm(2) V(-1) s(-1) .

International audience; Self-assembled monolayers (SAMs) on gold were obtained by the direct absorption of a fully conjugated phenylenethienylene derivative (4) presenting robust silylethane-thiol protecting groups as anchoring agents. The thiol deprotection and SAM formation have been evidenced by quartz crystal microbalance (QCM) measurements and X-ray photoelectron spectroscopy (XPS), and have been compared to the SAM obtained from its thioacetate analog (5). The chemically robust silylethane-thiol protecting group appeared as a surprisingly effective anchoring agent for the preparation of aromatic SAMs on Au(111), suitable for subsequent post-functionalization.

Polymorphism of α,ω-dioctylterthiophene (DOTT) thin films (less than 100 nm-thick) deposited onto standard silicon substrates is investigated by combining specular and in-plane grazing incidence X-ray diffraction measurements. Two crystal phases are revealed: the bulk phase (b) and the surface-induced phase (s). Previous results showed that s-phase was the most favored close to the substrate surface while b-phase is predominant at the DOTT-air interface. We show here that the relative proportion of these polymorphs is related to sample preparation. Indeed, the preferential crystallization of one phase or the other can be tuned as a function of substrate temperature during film deposition, s-phase being mainly present at high substrate temperature while b-phase is most observed at low substrate temperature. Particularly noteworthy is that thin films exhibiting only b-phase or only s-phase can be obtained according to sample preparation. Furthermore, when samples are annealed above the melting temperature (smectic G phase), the polymorph observed after cooling back to room temperature depends upon the cooling rate, s-phase being predominant at high cooling rate while it is rather b-phase for slow cooling. This behavior is independent of the crystalline phase that was present at room temperature before annealing.

The molecular arrangements of two different alkylsubstituted oligothiophenes, α,α′-dihexylquaterthiophene (DH4T) and α,α′-dioctylterthiophene (DOTT), in monolayers on molybdenum disulfide (MoS2) were studied with a joint theoretical/experimental approach. Scanning tunneling microscopy was used both at the liquid/solid interface and in dry conditions to investigate the ordering of the conjugated oligomers in two-dimensional layers. DH4T and DOTT form well-ordered monolayers at large scales with interdigitated packing on MoS2. In addition, DOTT exhibits an arrangement in which a dimer-type stacking of the conjugated backbone with an interlocking of the alkyl side chains is formed. Molecular modeling simulations have been used to provide insights into the microscopic morphology and to assess the stability of the different assemblies of DOTT and DH4T on MoS2.

Two quaterthiophene-based dimers including an ethylene bridge have been designed and efficiently prepared; experimental and computational studies show a promising potential as semiconducting material with a charge transport of higher dimensionality compared to quaterthiophene.

The synthesis and characterization of two new anthradithiophene (ADT) derivatives substituted by thiophenyl or 2-octylthiophenyl units at the 5,11-positions and donor (triphenylamine) or acceptor (aldehyde functions) moieties at the 2,8-positions of their backbone are described. Optical measurements were performed to evaluate the effect of electron-rich/-poor substituents on their stability towards photo-oxidation and were supported by quantum chemical calculations and cyclic voltammetry experiments. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

Derivatives 2–6 were prepared as models for studying intra- and intermolecular C(sp2)–H···O hydrogen bonding. Their X-ray structures confirm the presence of intramolecular hydrogen bonds in derivatives of the “a” series: the corresponding C···O distances vary between 2.91 and 2.97 A. The corresponding 13C–1H coupling constants are increased by about 7.5 Hz, and the 1H chemical shifts in CDCl3 are 9.1–10.7 ppm. No intramolecular hydrogen bonds can form in derivatives of the isomeric “b” series. In this series, the chemical shifts of the corresponding aromatic protons exhibit strong solvent dependency; in particular, they are as sensitive as the proton in chloroform to the presence of DMSO. The vinylic protons activated by the electron-accepting COOR groups behave similarly. Quantum mechanical calculations in the gas phase and in DMSO reproduce the experimental observations. Energies of the intramolecular hydrogen bonds evaluated by two independent approaches vary between 3.7 and 4.4 kcal mol–1 in the gas phase and still amount to at least 2.5 kcal mol–1 in 2a in DMSO. These estimates are practically independent of the computational method (HF, MP2, and DFT B3LYP were employed for derivatives 2). We conclude that the behavior of both activated aromatic and vinylic C(sp2)–H atoms in the studied derivatives is qualitatively and quantitatively similar to the behavior of the C(sp3)–H atom in chloroform. The existence of hydrogen bonds involving these atoms can easily be detected by NMR spectroscopy.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Two thienoacene dimers based on the thieno[3,2-b]thiophene moiety were efficiently synthesized, characterized and evaluated as active hole-transporting layers in organic thin-film field-effect transistors. Both compounds behaved as active p-channel organic semi-conductors showing averaged hole mobility of up to 1.33 cm2 V−1 s−1.

The morphology, the viscoelastic, the dielectric properties and the dynamics of phase transformation are studied in symmetrically and asymmetrically substituted alkyl[1]benzothieno[3,2-b][1]benzothiophenes (C8-BTBT) by X-ray scattering, rheology, and dielectric spectroscopy. The interlayer spacing reflects the molecular and supramolecular ordering, respectively, in the symmetrically and asymmetrically substituted BTBTs. In the asymmetric BTBT, the core layer is double in size with a broader network of intermolecular interactions though the increased S-S contacts that is prerequisite for the development of high performance OFET devices. Two crystal states with elastic and viscoelastic responses were identified in the symmetric compound. In contrast, the SmA phase in the asymmetric compound is a viscoelastic solid. A path-dependent dielectric environment with a switchable dielectric permittivity was found in both compounds by cooling below 0 °C with possible implications to charge transport. The kinetics of phase transformation to the crystalline and SmA phases revealed a nucleation and growth mechanism with rates dominated by the low activation barriers.

International audience; A detailed structural study of the bulk and thin film phases observed for two potential high-performance organic semiconductors has been carried out. The molecules are based on [1]benzothieno[3,2-b]benzothiophene (BTBT) as conjugated core and octyl side groups, which are anchored either symmetrically at both sides of the BTBT core (C8-BTBT-C8) or nonsymmetrically at one side only (C8-BTBT). Thin films of different thickness (8-85 nm) have been prepared by spin-coating for both systems and analyzed by combining specular and grazing incidence X-ray diffraction. In the case of C8-BTBT-C8, the known crystal structure obtained from single-crystal investigations is observed within all thin films, down to a film thickness of 9 nm. In the case of C8-BTBT, the crystal structure of the bulk phase has been determined from X-ray powder diffraction data with a consistent matching of experimental and calculated X-ray diffraction patterns (Rwp = 5.8%). The packing arrangement of C8-BTBT is similar to that of C8-BTBT-C8, that is, consisting of a lamellar structure with molecules arranged in a "herringbone" fashion, yet with lamellae composed of two head-to-head (or tail-to-tail as the structure is periodic) superimposed molecules instead of only one molecule for C8-BTBT-C8. As for C8-BTBT-C8, we demonstrate that the same phase is observed in bulk and thin films for C8-BTBT whatever the film thickness investigated.

International audience; Five functionalized quaterthiophene dimers including a non-conjugated bridge have been designed and efficiently synthesized. The synthetic pathways explored toward these dimers revealed unexpected features, such as the direct formation of secondary and tertiary quaterthiophene amines through a procedure initially developed for the preparation of primary amine exclusively. All these dimers possess a promising potential for the elaboration of semiconducting materials with a charge transport of higher dimensionality compared to quaterthiophene. (c) 2012 Elsevier Ltd. All rights reserved.

International audience; This work reports the first example of electrochemical cation binding transductionvianitroxyl groups. It shows the possibility to transduce a complexation without a π-conjugated bridge between the redox and the host moieties. As expected, we confirm that the host/redox probe distance is a key point for transduction.

The synthesis and characterization of two new anthradithiophene (ADT) derivatives bearing electron donating (triphenylamine) or accepting (5-formylthiophen-2-yl unit) moieties have been performed to assess their potential as materials for organic photovoltaics. Optical spectroscopy was used to evaluate the effect of electron rich/poor substituents on the visible absorption spectrum and on the stability towards photo-oxidation. The results are interpreted with the assistance of quantum-chemical calculations and cyclic voltammetry experiments.

Herein, we evaluated the influence of hydrogen interactions in bithiophene self-assembled monolayers on gold. We have elaborated SAMs from different thiol derivatives in which the number and position of amide functionality is varied to compare their electrochemical behavior. Preliminary, optimal conditions of the monolayer formation from our synthesized compounds were determined (thiol concentrations and incubation times). Electrochemical studies of the SAMs highlight a pronounced influence of the hydrogen bond when located in the outer extremity (electrochemical stability, interactions). The behavior observed with SAMs containing two amide moieties emphasizes the important impact of the number of hydrogen bonds inside the organic layer.

The dianion of 2,2′,2′′,2′′′-dicyclopenta[b,g]naphthalene-1,3,6,8-tetraylidenetetramalononitrile 4 exhibits relatively strong electron-accepting properties and undergoes reversible electrochemical reductions to the tetra- and hexaanionic species.

International audience

A general approach toward Janus diones involving the reaction of pyromellitic or naphthalenetetracarboxylic dianhydrides with ethyl(triphenylphosphoranylidene)acetate and subsequent rearrangement of the products is described. This approach allows avoiding the formation of poorly soluble intermediates, in which purity cannot be effectively controlled. Dicyclopenta[b,g]naphthalene-1,3,6,8(2H,7H)-tetraone 3, a promising precursor of molecular and polymeric advanced materials is described.

2,3,6,7-Naphthalenetetracarboxylic dianhydride was prepared and characterized by UV, IR, and NMR spectra. Its structure was confirmed by single crystal X-ray determination. It is a moderate strength electron acceptor, stronger than p-benzoquinone and weaker than pyromellitic anhydride according to quantum mechanical calculations and electrochemical measurements.

The new heterocyclic system, dibenzo[2,3:5,6]pyrrolizino[1,7-bc]indolo[1,2,3-lm]carbazole 3, which can be considered as a planar hybrid of carbazole and p-phenylenediamine, can readily be prepared from commercial precursors and possesses high thermal stability and strong electron donor properties comparable to tetra- and pentacene.