Twists and turns in the hierarchical self-assembly pathways of a non-amphiphilic chiral supramolecular material

The formation of helical self-assembled fibres by a C-3 symmetric molecule incorporating three tetrathiafulvalene units is shown to be influenced dramatically by the processing conditions, leading to a variety of different chiral forms, including unprecedented croissants

Synthesis, Electronic Properties and WOLED Devices of Planar Phosphorus-Containing Polycyclic Aromatic Hydrocarbons

International audienceWe describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P-containing PAHs exhibit properties expected for an emitter in white organic light-emitting diodes (WOLEDs)

Selective monosulfoxidation of tetrathiafulvalenes into chiral TTF-sulfoxides

Four inner tetrathiafulvalene-sulfoxides have been synthesized upon reaction of tetrathiafulvalene (TTF), tetramethyl-tetrathiafulvalene (TMTTF), tetrakis (thiomethyl)-tetrathiafulvalene (TMT-TTF), and bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) with enantiopure (+) or (−)-(8,8-dichlorocamphorylsulfonyl)-oxaziridine as oxidizing agent. Chiral HPLC studies indicate very weak enantioselectivities for TTF-SO 3 and TMTTF-SO 4, formation of racemic mixture in the case of TMT-TTF-SO 5, and a rather good selectivity, up to 44% ee, in the case of BEDT-TTF-SO 1. The solid state structures of TMTTF-SO 4 and TMT-TTF-SO 5 have been determined by single crystal X-ray diffraction. Both compounds crystallize as racemates in the centrosymmetric triclinic space group P-1. Theoretical calculations at DFT/B3LYP/6-31+G* level afford optimized geometries in good accordance with the experimental structures and emphasize the participation of the chiral sulfoxide group in HOMO and LUMO. Time-dependent DFT calculations corroborated with electronic circular dichroism spectra allow the assignment of the absolute configuration (R) for the major enantiomer of 1 when the (+)-sulfonyl-oxaziridine is used as oxygen transfer reagent. Preliminary semipreparative HPLC separation provided enantioenriched fractions up to 63% ee

Stereoisomeric semiconducting radical cation salts of chiral bis(2-hydroxypropylthio)ethylenedithioTTF with tetrafluoroborate anions

The new chiral TTF-based donor molecule bis(2-hydroxypropylthio)ethylenedithiotetrathiafulvalene has produced enantiopure R,R and S,S radical cation salts with the tetrafluoroborate anion as well as the nearly isostructural meso/racemate mixture. The enantiopure R,R or S,S salts are both 1:1 semiconducting salts with activation energies of 0.19–0.24 eV, both crystallising in the orthorhombic space group C2221. The semiconducting salt containing both meso and racemic donor cations has a very similar crystal structure but crystallising in the monoclinic space group C2/c (β = 91.39°) with similar S⋯S interactions but a smaller activation energy of 0.15–0.17 eV. This is in contrast to previous families of this type where the disordered racemate has a larger activation energy than its enantiopure salts

Distributive Nd-to-Yb Energy Transfer within Pure [YbNdYb] Heterometallic Molecules

Facile access to site-selective hetero-lanthanide molecules will open new avenues in the search of novel photophysical phenomena based on Ln-to-Ln′ energy transfer (ET). This challenge demands strategies to segregate efficiently different Ln metal ions among different positions in a molecule. We report here the one-step synthesis and structure of a pure [YbNdYb] (1) coordination complex featuring short Yb···Nd distances, ideal to investigate a potential distributive (i.e., from one donor to two acceptors) intramolecular ET from one Nd3+ ion to two Yb3+ centers within a well-characterized molecule. The difference in ionic radius is the mechanism allowing to allocate selectively both types of metal ion within the molecular structure, exploited with the simultaneous use of two β-diketone-type ligands. To assist the photophysical investigation of this heterometallic species, the analogues [YbLaYb] (2) and [LuNdLu] (3) have also been prepared. Sensitization of Yb3+ and Nd3+ in the last two complexes, respectively, was observed, with remarkably long decay times, facilitating the determination of the Nd-to-Yb ET within the [YbNdYb] composite. This ET was demonstrated by comparing the emission of iso-absorbant solutions of 1, 2, and 3 and through lifetime determinations in solution and solid state. The comparatively high efficiency of this process corroborates the facilitating effect of having two acceptors for the nonradiative decay of Nd3+ created within the [YbNdYb] molecule

New crystal packing arrangements in radical cation salts of BEDT-TTF with [Cr(NCS)6]3− and [Cr(NCS)5(NH3)]2−

BEDT-TTF forms three packing arrangement styles in its radical cation salts with [Cr(NCS)6]3− in two of which two trans-oriented isothiocyanate ligands penetrate the BEDT-TTF layers either at the point where a solvent (nitrobenzene) is incorporated in a stack of donors or by four donor molecules forming a “tube” motif to accept a ligand at each end along with a small solvent molecule in between (acetonitrile). The [Cr(NCS)5NH3]2− ion forms a related crystal packing arrangement with BEDT-TTF with a reduction in the number of “tube” motifs needed to accept an isothiocyanate ligand

Contrasting crystal packing arrangements in triiodide salts of radical cations of chiral bis(pyrrolo[3,4-d])tetrathiafulvalenes

Crystal structures of six 1 : 1 triiodide salts of a series of enantiopure bis(pyrrolo[3,4-d])TTF derivatives, the first structures of radical cation salts reported for this bis(pyrrolo) donor system, show three different arrangements of triiodide ions, organised either in head-to-tail pairs, in infinite lines, or in a castellated arrangement. The complex crystal structures, obtained by electrocrystallisation, are influenced by the presence of solvent, for example changing an ABCABC packing arrangement to ABAB with inclusion of THF, as well as by the size of the chiral side chain

Supramolecular electroactive organogel and conducting nanofibers with C3-symmetrical architectures

International audienceTwo C3 symmetric tris(TTF) derivatives, based on a central unit containing the rigid core 1,3,5-tricarbonyl-benzene substituted with three 3,3′-diamino-2,2′-bipyridines, have been synthesized by a convergent strategy. Single crystal X-ray analysis of the precursor 3′-[(ethylenedithio-tetrathiafulvalenyl)formylamino]-2,2′-bipyridine-3-amine shows a planar transoid conformation for the bipyridine unit, favored by intramolecular hydrogen bonding. The compound N,N′,N″-tris{3[3′-[bis(ethylthio)-tetrathiafulvalenyl]formylamino]-2,2′-bipyridyl}-benzene-1,3,5-tricarboxamide, having C3 symmetry, presents gelator properties in chlorinated solvents. The gel formed in ortho-dichlorobenzene provided—after evaporation of the solvent—a xerogel constituted by a complex network of thick and thinner fibers as demonstrated by TEM and AFM microscopies. The thick fibers were about 100 nm wide and between 1 and 5 µm long, and the thinner ones between 12 and 18 nm wide and 50 to 500 nm long. Iodine doping of the material induced the formation of a mixed valence system with charge transfer, as indicated by IR-NIR spectroscopic measurements. The doped material has a TTF:I3 ratio of 2.4:1 ten minutes after doping, but slowly loses iodine over days. The morphology of the gel did not change after the doping process, as revealed by SEM and AFM experiments. Current sensing AFM measurements showed that the thicker fibers are more conducting than the thinner ones, a likely consequence of the better ordering and/or more effective interfiber contacts in the former

Pierre Loti au cœur de la révolution maritime et coloniale de la France au xixe siècle

On imagine mal en effet ce que Julien Viaud aurait pu laisser à la postérité si la vocation de Pasteur, entretenue dans l’esprit du jeune enfant au sein de sa famille, avait déterminé son avenir. Le portrait de “Pierre Loti marin” vient d’être présenté par Melle Lacousse : je n’ai rien à y ajouter, sinon tenter de lui donner un relief nouveau en le plaçant dans le cadre de la Révolution Maritime et coloniale de la France au xixe siècle, fille elle-même de la Révolution industrielle et commerc..

TETRATHIAFULVALENES : Ligands Multifonctionnels et Nouveaux Systèmes Donneur-Accepteur

This work exploited the well known electronic properties of tetrathiafulvalene (TTF) in two new systems : TTF-bis-oxazolines and TTF-triazines. By functionalizing TTF with oxazoline groups, we have introduced chirality on the donor. The crystalline structures of synthesized molecules as well as their intermediates are presented. We explored several approaches using these compounds as precursors for multifunctional materials. In another domain, the TTF-bis-oxazolines have been used as chiral ligands for metals. In particular, copper complexes have been tested for homogenous enantioselective catalysis with a look at the influence of the oxidation state of TTF on the catalytic activity and the chiral induction obtained with these complexes. In a second part, we preset the synthesis of new Donor-Acceptor systems involving the TTF (D) bound to a triazine platform (A). Theoretical studies and experiments on a D-A dyad and triad D-A-D have led to the complete characterization of the intramolecular charge transfer which is present in these systems. The 2-TTF-4,6-bis-methoxy-1,3,5-triazine appears as a good candidate for molecular electronics.Ce travail a exploité les remarquables propriétés électroniques du tétrathiafulvalène (TTF) au sein de deux nouveaux systèmes : les TTF-bis-oxazolines et les TTF-triazines. La fonctionnalisation du TTF par des groupements oxazolines a permis l'introduction de la chiralité sur le donneur. Les structures cristallines des molécules synthétisées ainsi que celles de leurs intermédiaires sont reportées. Nous présentons diverses approches employant ces composés comme précurseurs de matériaux mulifonctionnels. Les TTF-bis-oxazolines ont par ailleurs servi comme ligands chiraux pour des matériaux. Des complexes de cuivre ont permis de réaliser différentes réactions de catalyse homogène énantiosélective. Nous nous sommes intéressés, dans ce dernier cas, à l'influence de l'état rédox du TTF sur l'activité catalytique et l'induction chirale de ces complexes. Dans une seconde partie, nous reportons la synthèse de nouveaux systèmes Donneur-Accepteur associant le TTF (D) à une plateforme triazine (A). Les études théoriques et expérimentales réalisées sur une diade D-A et une triade D-A-D ont permis de caractériser parfaitement le transfert de charge intramoléculaire présent dans ces systèmes. La 2-TTF-4,6-bis-méthoxy-1,3,5-triazine apparaît comme un bon candidat pour l'électronique moléculaire