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Pyrene-based materials have gained considerable attention as stimuli-responsive chemical sensors. We designed a polysulfurated arene system based on a tetra(phenylthio)pyrene core decorated with four carboxylic acid units. Three different regioisomers, ortho, meta and para were studied in organic and aqueous solution. These systems are soluble in water at pH≥8 due to the deprotonation of carboxylic acids. The addition of metal ions cannot only quench the fluorescence of the central pyrene core, but also control the formation of three-dimensional nanoscopic objects in a dual mode function. Several divalent metal ions were tested and compared. Addition of ethylenediaminetetraacetic acid (EDTA) disassembles the non-emissive supramolecular system and restores the initial fluorescence of the pyrene core.

The synthesis of regioisomeric asterisks (5) and (6) incorporating a benzene core with six 1-naphthylthio or six 2-naphthylthio arms are reported in search for new materials with optoelectronic properties. The consequences on the extension of a pi system surrounding a persulfurated benzene core provide a new avenue to study the structural, photophysical, and chemical properties of such family of all-organic phosphors. It also diverts the persulfuration mechanism after two radical cyclizations for making a [5]dithiohelicene by-product (7) and favors dynamic sulfur component exchange reactions surrounding the core. These exchanges convert asterisks (5) and (6), non-phosphorescent at 20 degrees C to the highly phosphorescent (4) (phi similar to 100 %, solid state at 20 degrees C). For asterisks (5) and (6), the absence of the typical phosphorescence of the per(phenylthio)benzene core in the solid state at 20 degrees C and the presence of a weak naphthalene-based phosphorescence at 77 K is attributed to an energy transfer from the triplet state of the persulfurated benzene core to the outer naphthalene moieties, resulting in an antenna system.

The chiral self‐assembly of trispentahelicene propellers on a gold surface has been investigated in ultrahigh vacuum by means of scanning tunneling microscopy and time‐of‐flight secondary ion mass spectrometry. The trispentahelicene propellers aggregate into mirror domains with an enantiomeric ratio of 2 : 1. Thermally induced cyclodehydrogenation leads to planarization into nanographenes, which self‐assemble into closed‐packed layers with two different azimuths. Further treatment induces in part dimerization and trimerization by intermolecular cyclodehydrogenation., From helical to planar: Molecular propellers built up by three pentahelicene subunits self‐assemble on a gold surface into enantiomerically unbalanced two‐dimensional crystal domains. Upon thermal treatment of the close‐packed monolayer, intramolecular cyclodehydrogenation into planar nanographenes occurs. Further thermal treatment leads in part to fusion into larger graphene flakes of up to four nanographene units by intermolecular cyclodehydrogenation.

International audience; We report a molecular design and concept using p-system elongation and steric effects from helicenes surrounding a triphenylene core toward stable chiral polycyclic aromatic hydrocarbons (PAHs) with a maximal p-distortion to tackle their aromaticity, supramolecular and molecular properties. The selective syntheses, and the structural, conformational and chiroptical properties of two diastereomeric large multi-helicenes of formula C90H48 having a triphenylene core and embedding three [5]helicene units on their inner edges and three [7]helicene units at their periphery are reported based on diastereoselective and, when applicable, enantiospecific (!) Yamamoto-type cyclotrimerizations of racemic or enantiopure 9,10-dibromo[7]helicene. Both molecules have an extremely distorted triphenylene core, and one of them exhibits the largest torsion angle recorded so far for a benzene ring (twist = 36.9º). The analysis of aromaticity distribution in these model molecules using magnetic criteria revealed a non-aromatic character of their triphenylene cores and provides a new look at aromaticity in threedimensional PAHs. One diastereomer can complex up to three silver(I) ions in the bay region (cavities) of its peripheral [7]helicene units, opening the door to chiral cationic metal-nanographene hybrids.

Room temperature phosphorescence by metal-free chromophores is quite a rare phenomenon. Hexasulfurated benzene-cored molecules with phenyl substituents, hereafter named asterisks, display bright green phosphorescence in the solid state at room temperature, while they are not luminescent in solution, because of fast non-radiative decay of the lowest excited state. Some of these asterisks are also among the most phosphorescent compounds. Following a search for structure-property relationships, we report here the synthesis, characterization, crystal structure and optical properties of three pentasulfurated benzene-cored asterisks, carrying at the sixth position of the benzene core a cyano (A5CN), a carboxaldehyde (A5CHO), or a vinyl group (A5CC). The most luminescent compound is A5CN displaying an intense orange phosphorescence in the solid state: our actual aim is to try and correlate the optical properties together with the crystal structure in this series of compounds.

International audience

Hexakis(phenylthio)benzene compounds carrying six carboxylic acid groups at their periphery combine aggregation-induced phosphorescence, water-solubility and metal-binding properties: the para-isomer is a selective and sensitive turn-on phosphorescent sensor of Pb2+ ions in water.

Room temperature phosphorescence is usually a prerogative of metal complexes. Molecules with a hexakis(phenylthio)benzene core constitute a rare example of all-organic chromophores with phosphorescence induced by environmental rigidification. Here we report covalent encapsulation of functionalized persulfurated benzene chromophores into silica nanoparticles as a method of rigidification for induction of phosphorescence. The developed nanoparticles display bright phosphorescence at ambient temperatures and possess high colloidal stability in water. The method permits incorporation of a large number of chromophores (ca. 40) per nanoparticle while preserving their emissivity. The luminescence of the nanoparticles is sensitive to quenching by molecular oxygen in the physiological oxygen range, potentially making them suitable as probes for phosphorescence lifetime imaging of oxygen in biological systems.

Persulfurated asterisks functionalized with six carboxylic groups form a strongly green phosphorescent coordination polymer upon addition of Pb2+ ions in aqueous solution. The self-assembly process is selective and reversible, enabling Pb2+ sensing with a detection limit of 6.0 × 10−7 M.

Self-assembly of a covalently-bound lipophilic drug to a dendronic scaffold for making organic nanoparticles is reported as a proof of concept in nanovectorization. A minimalist structural approach with a small PEG-dendron conjugated to paclitaxel (PTX), incorporating safe succinic and gallic acids, is efficient to provide the expected anticancer bioactivity, but also significantly retards and targets intracellular delivery of PTX in 2D and 3D lung cancer cell cultures. A branching effect of dendrons is crucial, when compared to linear PTX conjugates. Transmission electron microscopy (TEM) and dynamic light-scattering (DLS) studies indicate the formation of stable, low-disperse nanoparticles at 10-5 m in H2 0, which could also be responsible for the biological effects. An ultrasensitive LC-MS/MS method was used for the determination of intracellular PTX concentration over time, along with the survival rates of cancer cells. Similarly, cell survival assays were successfully correlated to a 3D cell culture with spheroids for mimicking tumors, when treated with PTX conjugates. Our work opens the way to a full evaluation program required for new chemical entities.

We report here the study of the stability under subcritical water conditions of one of the most popular polysaccharide chiral stationary phase (CSP): Chiralcel OD. This CSP was used under high temperature and reversed phase conditions with acetonitrile and 2-propanol as modifier, respectively. The evolution of selectivity and resolution was investigated both in normal and reversed mode conditions with five racemates after packing, heating at 150 °C and separations of some racemic compounds under different high temperatures and mobile phase conditions. The results show that after using at high temperature and subcritical water conditions the selectivity was only moderately affected while the resolution fell dramatically especially in reversed mode due to the creation of a void at the head of the columns which reflects the dissolution of the silica matrix.

La cyberintimidation est une forme de violence de plus en plus préoccupante pour la société et pour le milieu scolaire. Souvent commises dans Internet ou sur le téléphone cellulaire, les agressions ont des conséquences psychologiques, sociales et scolaires très graves chez les victimes, les agresseurs et les témoins, et il est important d’intervenir adéquatement. Cette étude vise à mieux connaître les types d’intervention utilisés par les enseignants auprès des élèves qui ont des comportements de cyberintimidation et à mieux comprendre les bases qui expliquent ces choix d’intervention. Des entrevues menées auprès de 10 enseignants des 7e, 8e et 9e années ont permis de relever leurs interventions les plus courantes pour gérer et traiter les comportements de cyberintimidation de leurs élèves, connaître leur perception de l’efficacité de ces pratiques et explorer les fondements théoriques sur lesquels ils s’appuient dans leurs choix d’intervention. L’analyse de leurs témoignages, mise en perspective avec la littérature scientifique sur le sujet, permet de proposer un nouveau modèle d’intervention auprès des auteurs de cyberintimidation. Après avoir confronté les résultats au modèle d’intervention d’Hinduja et Patchin (2009), les auteures suggèrent de nouvelles pistes d’intervention pour améliorer la formation des enseignants dans ce domaine., Cyberbullying is a form of online violence that is of growing concern in our society and in the school environment. In light of the fact that the aggressions, made on the Internet and on cellular phones, can have serious psychological, social and academic consequences for the victims, the bystanders and the cyberbullies, it is important to intervene appropriately. This study aims to understand teachers’ perception of their interventions with students who cyberbully and the theoretical basis or concepts guiding these interventions. Semi-structured interviews, conducted with ten teachers of grades 7, 8 and 9, revealed the most popular reactions of teachers to their students’ cyberbullying behaviours. This study also explores the basis influencing the teachers’ choices of interventions and their perception of the effectiveness of these practices. The analysis of the teachers’ accounts, put in perspective with a literature review, suggests ways to improve their training to address cyberbullying. A new intervention model is suggested.

International audience; A one-step synthesis of a nanographene propeller with a D 3-symmetry was obtained starting from 7,8-dibromo[5]helicene by Yamamoto nickel(0) couplings. It afforded a chiral polyaromatic hydrocarbon (PAH) embedding six enantiomerically stable [5]helicene units. This dense accumulation of helical strain resulted in a distorted geometry, but stable stereochemistry. The conformational, structural, chiroptical, and photophysical properties of the molecule are reported.

Myriaporone 3/4, a cytotoxic polyketide, has been reported as an inhibitor of eukaryotic protein synthesis. However, the mechanism by which it inhibits translation was unknown. Here we show that myriaporone 3/4 stalls protein synthesis in the elongation phase by inducing phosphorylation of eukaryotic elongation factor 2. The phosphorylation results from direct binding of myriaporone 3/4 to eukaryotic elongation factor 2 kinase. Our study also shows that myriaporone 3/4 in the nanomolar range inhibits in vitro tube formation by endothelial cells without being cytotoxic. In general, myriaporone 3/4 was at least 300 times less toxic to primary cells than to tumor cells.

A hexathiobenzene molecule carrying six terpyridine (tpy) units at the periphery has been designed to couple the aggregation induced phosphorescence, displayed by the core in the solid state, to the metal binding properties of the tpy units. Upon Mg(2+) complexation in THF solution, phosphorescence of the hexathiobenzene core is turned on. Metal ion coordination yields the formation of a supramolecular polymer which hinders intramolecular rotations and motions of the core chromophore, thus favoring radiative deactivation of the luminescent excited state. Upon excitation of the [Mg(tpy)2](2+) units of the polymeric structure, sensitization of the core phosphorescence takes place with90% efficiency. The light-harvesting polymeric antenna can be disassembled upon fluoride ion addition, thereby switching off luminescence and offering a new tool for fluoride ion sensing. This unique system can, thus, serve as cation or anion sensor.

This review covers the synthetic contributions leading to the syntheses of the polyketides tedanolide, 13-deoxytedanolide and the structurally related myriaporones. Fragment syntheses that lead to valuable insight into the subtle synthetic problems of the tedanolides are also presented.

We have designed a new multichromophoric system based on a tetra(phenylthio)pyrene core appended with four terpyridine units. The system behaves as a molecular antenna that collects light with the peripheral units and funnels the energy to the very highly luminescent core. The addition of metals ions to the investigated system can not only switch the direction of the intramolecular energy transfer, but also control the formation of three-dimensional nanoscopic objects in a dual function.

A series of functionalized persulfurated benzene molecules were synthesized. Their photophysical properties and crystal structures were analyzed. All compounds are non-emitting in solution at room temperature, but in a sharp contrast, quantum yields can be very high (up to 100%) in the solid state at 298 K or in a rigid matrix at low temperatures. This is a consequence of a decrease of intramolecular rotations and motions, but conformational and rotamer issues along with substituent effects might also play a role. These compounds are among the rare examples of highly phosphorescent organic materials, due to a Crystallization Induced Phosphorescence or to an Aggregation Induced Phosphorescence. Compound 1 is among the most phosphorescent solid known to date. They thus represent an alternative to heavy metal ion-based triplet emitters in solid state.

Benzylic-type couplings are key reactions to make non-racemic helicenes. Their simplicity contributes to a short, efficient, and scalable asymmetric route to functionalized [7]helicenes. It widens the scope and uses of enantiopure helicenes, which are unequivocally needed for new chiroptical-electronic materials. A mechanistic proposal featuring an electrocyclization is based on experiments, X-ray crystallography and calculations.

Sulfur-containing glycodendrimers have steadily emerged over a few decades and this review describes the first survey of this field. Although the contribution of sulfur chemistry to glycodendrimers could be seen at the moment as a development of various linking strategies, there is more than synthesis because the presence of sulfur itself modulates unique photophysical and electrochemical properties. This fact has long been recognized in materials science, for instance. Emphasis on the numerous advantages of sulfur in glycosylated dendrimers is thus put forward in this review. The synergy between sulfur, dendrimers, and carbohydrate chemistry conveys novel synthetic avenues, properties, and applications toward innovative perspectives in chemistry, glycobiology, materials science and nanoscience, with a particular significance for biosensors.

Sulfur-containing glycodendrimers have steadily emerged over a few decades and this review describes the first survey of this field. Although the contribution of sulfur chemistry to glycodendrimers could be seen at the moment as a development of various linking strategies, there is more than synthesis because the presence of sulfur itself modulates unique photophysical and electrochemical properties. This fact has long been recognized in materials science, for instance. Emphasis on the numerous advantages of sulfur in glycosylated dendrimers is thus put forward in this review. The synergy between sulfur, dendrimers, and carbohydrate chemistry conveys novel synthetic avenues, properties, and applications toward innovative perspectives in chemistry, glycobiology, materials science and nanoscience, with a particular significance for biosensors.

For the structural determination of a ligand bound to an amorphous macromolecular system, solid-state NMR can be used to provide interatomic distances. It is shown here that selective labeling in discrete locations with tritium enables accurate measurement of long-range distances owing to the high gyromagnetic ratio of this nucleus, without structural modification of the molecule. This approach gives access to the largest NMR distance ever measured between two nuclei (14.4 A). (3)H MAS NMR appears to be a promising tool for structural applications in the biological and material sciences.

Covering: up to the end of 2007 This Highlight covers the synthetic contributions leading to the syntheses of tedanolide and 13-deoxytedanolide or the corresponding macrolactones, respectively. Additionally, the first SAR data for 13-deoxytedanolide (published by Fusetani) are presented.

(R = Me) [59218-87-0] C9H27F2N3SSi (MW 275.55) InChI = 1S/C6H18N3S.C3H9F2Si/c1-7(2)10(8(3)4)9(5)6;1-6(2,3,4)5/h1-6H3;1-3H3/q+1;-1 InChIKey = JMGVTLYEFSBAGJ-UHFFFAOYSA-N (R = Et) [59201-86-4] C15H39F2N3SSi (MW 359.73) InChI = 1S/C12H30N3S.C3H9F2Si/c1-7-13(8-2)16(14(9-3)10-4)15(11-5)12-6;1-6(2,3,4)5/h7-12H2,1-6H3;1-3H3/q+1;-1 InChIKey = WRVWLZUYPSYYEW-UHFFFAOYSA-N (anhydrous fluoride ion source; synthesis of CF compounds by nucleophilic displacement of sulfonates;3 promoter for electrophilic reactions of silyl enolates of ketones and esters;4-6 source of sulfonium cation capable of stabilizing or imparting high nucleophilic reactivity to other anions;4, 6, 8a,10a activator of vinylsilanes in Pd-catalyzed cross-coupling reactions;7 also used for generation8 and reactions10 of α- and β-halo carbanions; hydrosilylation11 and cyanomethylation14 of ketones) Alternate Name: TASF. Physical Data: R = Me, mp 98–101 °C; R = Et, mp 90–95 °C. Solubility: R = Me, sol MeCN, pyridine, benzonitrile; partially sol THF. R = Et, sol THF, MeCN. Both react slowly with MeCN. Form Supplied in: R = Me, white crystalline solid, ∼90% pure; major impurity is tris(dimethylamino)sulfonium bifluoride [(Me2N)3S+ HF2−]. Analysis of Reagent Purity: mp; 19F NMR δ (at 200 MHz, CFCl3 standard) TASMe3SiF2 (CD3CN) δ −60.3; TASHF2 −145.8 (d, JHF = 120 Hz). Preparative Methods: the methyl derivative is prepared by the reaction of dimethylaminotrimethylsilane and Sulfur Tetrafluoride at −70 °C to rt in ether; the precipitated solid is filtered off.1a The ethyl derivative is best prepared by the reaction of N,N-Diethylaminosulfur Trifluoride (DAST) and diethylaminotrimethylsilane.1b,11b Handling, Storage, and Precautions: because of the extreme hygroscopic nature of this compound, it is best handled in a dry box or a polyethylene glove bag filled with high purity nitrogen. Use in a fume hood.

Myriaporones are naturally occurring compounds which structurally resemble the southern hemisphere of the tedanolide family of macrolide antitumor agents. Despite the fact that myriaporone 3/4 represents only a portion of tedanolide, it nonetheless retains much of its biological activity. We show here that like tedanolide, myriaporone 3/4 inhibits protein synthesis and proliferation of mammalian cells with low nanomolar potencies but displays no prokaryotic growth inhibitory effect. Moreover, myriaporone 3/4 displays a very rapid, reversible and p21-independent activity to block S phase progression in mammalian cells. Structure-activity relationship studies revealed that the C18-C19 epoxide and the C14 hydroxymethyl group (tedanolide numbering) of myriaporone 3/4 are required for cell cycle inhibition. These constitute previously unidentified and/or novel pharmacophores for myriaporone 3/4. Our results show that the important biological activities associated with the structurally complex tedanolides are present and can be harnessed in the chemically much simpler myriaporones. This greatly increases the value of the latter as investigative tools for biochemical research as well as for development of potential therapeutics.

Most dialysis patients receiving erythropoesis-stimulating agents (ESA) also receive parenteral iron supplementation. There are few data on the risk of hemosiderosis in this setting.We prospectively measured liver iron concentration by means of T1 and T2* contrast magnetic resonance imaging (MRI) without gadolinium, in a cohort of 119 fit hemodialysis patients receiving both parenteral iron and ESA, in keeping with current guidelines.Mild to severe hepatic iron overload was observed in 100 patients (84%; confidence interval, [CI] 76%-90%), of whom 36% (CI, 27%-46%) had severe hepatic iron overload (liver iron concentration201 μmol/g of dry weight). In the cross-sectional study, infused iron, hepcidin, and C-reactive protein values correlated with hepatic iron stores in both univariate analysis (P.05, Spearman test) and binary logistic regression (P.05). In 11 patients who were monitored closely during parenteral iron therapy, the iron dose infused per month correlated strongly with both the overall increase and the monthly increase in liver iron concentration (respectively, rho=0.66, P=.0306 and rho=0.85, P=0.0015, Spearman test). In the 33 patients with iron overload, iron stores fell significantly after iron withdrawal or after a major reduction in the iron dose (first MRI: 220 μmol/g (range: 60-340); last MRI: 50 μmol/g (range: 5-210); P.0001, Wilcoxon's paired test).Most hemodialysis patients receiving ESA and intravenous iron supplementation have hepatic iron overload on MRI. These findings call for a revision of guidelines on iron therapy in this setting, especially regarding the amount of iron infused and noninvasive methods for monitoring iron stores.

Covering: up to the end of 2007 This Highlight covers the synthetic contributions leading to the syntheses of tedanolide and 13-deoxytedanolide or the corresponding macrolactones, respectively. Additionally, the first SAR data for 13-deoxytedanolide (published by Fusetani) are presented.