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PE and EVOH compatibilization is investigated upon functionalization of PE with ODIN, a fluorescent molecule forming multiple H-bonds with EVOH. Two-photon microscopy is exploited to monitor the polymer blending before and after reprocessing.

International audience; Eucalyptus Kraft lignin was blended in various proportions with two different types of polyethylene (PE) (low-density polyethylene and post-consumer recycled [PCR]), with or without compatibilizer (PE-glycidyl methacrylate [GMA] or PE-2-hydroxyethyl methyl acrylate copolymers). Materials prepared by injection molding or extrusion casting were characterized for their thermal, antioxidant, antibacterial and mechanical properties. In addition, the photopermeability was assessed, as this property is specifically relevant to mulching applications. The use of compatibilizers enhanced the antioxidant properties which reached more than 3 h oxidation induction time when lignin was present at 20 wt% and beyond. Good antibacterial properties were obtained on Gram-positive bacteria when using PE-GMA as compatibilizer. The photopermeability of the materials was also reduced, reaching a transmittance lower than 5% throughout the whole measurement range (200-800 nm) in PCR. However, higher lignin contents led to a more brittle material and the overall processability of the material became more difficult, features that were not improved by compatibilizers. These materials are promising candidates for mulching film application, especially with PCR which still lacks high-volume market applications.

Diastereomeric doubly bridged biphenyl azepines, atropos at 20 degrees C and tropos at 80 degrees C, are precursors to effective iminium organocatalysts that are employed in the enantioselective epoxidation of prochiral olefins (up to 85% ee).

Homologous biphenyl and (diastereomeric) binaphthyl tertiary azepines and quaternary iminium salts were prepared from (S)- and (R)-3,3-dimethylbutan-2-amine. Both the amines and iminium ions behave as effective catalysts for the enantioselective epoxidation of unfunctionalized olefins (ee up to 87%).

The reaction of racemic orthomercurated (η6-arene)tricarbonylchromium complexes with bis[(?6-cymene)ruthenium(II)dichloride] affords the corresponding dinuclear (Cr,Ru) products with moderate yields, which have been satisfactorily characterized by X-ray diffraction analysis. The synthesis of nonracemic orthomercurated (η6-arene)tricarbonylchromium complexes has been attempted starting from enantio-enriched homo- and heteroleptic Pd(II) bischelated complexes. Both enantiomers of ortho-mercurated 2-[tricarbonyl(?6-phenyl)chromium]pyridine have been synthesized by reaction of a heteroleptic Pd(II) bischelated with HgCl2. The two mercury(II) complexes were also submitted to a transmetalation reaction with bis[(?6-cymene)ruthenium(II)dichloride] and yielded the corresponding nonracemic (Cr, Ru) products, with enantiomeric excesses ranging from 82 to 89% as suggested by 1H NMR analyses in the presence of BINPHAT anion.

Triphosphonate cavitand, 3 i PO, has been designed for the recognition of ammonium in solution. This Letter presents a study of the selective guest–host recognition between Acetylcholine and Choline ions, ACh + and Ch + , and the host. We are able to observe that the ACh + ion replaces the Ch + ion in the 3 i PO-Ch + complexes with a concomitant exchange/substitution constant of 7 × 10 4 M −1 . Conversely a replacement of the ACh + ions by the Ch + ions in the 3 i PO-ACh + complexes has been also observed with a concomitant exchange constant of 5.8 × 10 3 M −1 . The structure of the 3 i PO-ACh + complex is determined by single crystal X-ray crystallography.

International audience; Inherently chiral phosphonatocavitands with various bridging moieties at their wide rim were synthesized. Optical resolution by chiral HPLC was performed with cavitand 8 to afford enantiopure compounds (+)-8 and (−)-8. The molecular structures of hosts 8 and 12 were determined by X-ray diffraction. The host properties were investigated by 1H and 31P NMR spectroscopy. The phosphonatocavitands form inclusion complexes with chiral ammonium neurotransmitters, some presenting enantioselectivity towards the right or left-handed host enantiomers.

International audience; ABii diphosphonatocavitands self-assemble in chloroform solution to form dimeric molecular capsules. The molecular capsules can incarcerate an N-methylpyridinium or N-methylpicolinium guest. We have demonstrated that the supramolecular assembly acts as a molecular rotor as a result of the restricted motion of the guest inside the molecular cavity. In the solid state, X-ray diffraction analysis of the free host showed that two cavitands interact through strong hydrogen bonds to give the supramolecular self-assembled capsule. The solid-state structure of the N-methylpicolinium complex is comparable to that of the free host and indicates that the guest is not a prerequisite for the formation of the capsule. DOSY NMR studies provided a definitive argument for the formation of the free and complexed supramolecular capsule in CDCl3 solution. In solution, the tumbling of the N-methylpyridinium and N-methylpicolinium guests about the equatorial axes of the host can be frozen and differs by the respective energy barriers, with the larger picolinium substrate having a larger value (ΔG⧧ = 69.7 kJ mol−1) than the shorter pyridinium guest (ΔG⧧ = 44.8 kJ mol−1). This behavior corresponds to the restricted rotation of a rotator in a supramolecular rotor.

International audience; An inherently chiral ABii diphosphonato cavitand (±)-4 bearing a single quinoxaline bridging moiety was synthesized and resolved by chiral HPLC. Its chiroptical properties were investigated and VCD experiments allowed the determination of its absolute configuration. Distinguishable diastereomeric complexes in solution with l-adrenaline were observed by 1H and 31P NMR together with a noticeable enantio-discrimination at 253 K (dr ∼2:1) in favor of the dextrorotatory cavitand (+)-4.

Three tricyclic diquats with an eight-membered ring were prepared and shown to be the first configurationally stable derivatives of their kind. Resolution was achieved by using chiral hexacoordinated phosphorus BINPHAT and TRISPHAT anions. The diquat cations were obtained in high diastereo- and enantiomeric purity (ee>96 % in most cases). X-ray diffraction analysis coupled with circular dichroism (CD) measurements allowed a precise determination of the relative and absolute configuration of the salts. The barriers to racemization of these compounds were calculated by using CD time-course measurements at different temperatures, affording Delta G? values above 25 kcal mol-1. Derivatives 4 a, 4 b, and 4 c are the first eight-membered-ring derivatives with only three ring constraints to be resolved. This manuscript also reports the first procedure to remove TRISPHAT anions after diastereomeric separation.

Several novel chiral iminium TRISPHAT [tris(tetrachlorobenzenediolato)phosphate(V)] salts combining a diphenylazepinium core, chiral exocyclic appendages, and lipophilic counterions have been prepared and tested in biphasic enantioselective olefin epoxidation conditions. Interestingly, the iminium salts derived from commercially available (S)- or (R)-1,2,2-trimethylpropylamine can display efficiency similar to those made from L-acetonamine. Variable-temperature NMR spectroscopy (VT-NMR) and circular dichroism (CD) experiments were performed in search of a correlation between good enantioselectivity in the products and high diastereomeric control of the biphenyl axial chirality of the catalysts.

Herein is reported an experimental and theoretical study of the circular dichroism properties of TRISPHAT (1) anion. ECD analysis of the [tetramethylammonium][Δ-1] salt confirms the absolute configuration assignment obtained through X-ray crystallographic analysis of the parent cinchonidium salt. The structure, infrared, and vibrational circular dichroism (VCD) spectra derived from density functional theory (DFT) calculations are compared with experimental data.

Enantiopure (diastereomeric) doubly bridged biphenyl azepines prepared from (S)-3,3-dimethylbutan-2-amine and (S)-1-phenylpropylamine can be – as a function of the exocyclic side chain – either effective catalysts for the enantioselective epoxidation of unfunctionalized olefins or no catalysts at all. In the case of the (S)-1-phenylpropylamine derivative, an unwanted and unexpected Cope elimination derails the catalytic reactivity which can, however, be recovered by the addition of NBS prior to that of the substrate and other reagents.