Synthesis of a double-stranded spiroborate helicate bearing stilbene units and its photoresponsive behaviour

HPC resources of CINES and of IDRIS under the allocations 2013-[x2013080649] made by GENCI (Grand Equipement National de Calcul Intensif)International audienceA novel spiroborate-based double-stranded helicate bearing photoresponsive cis-stilbene units in the middle (cis-3) was successfully synthesised from the corresponding cis-stilbene-bound tetraphenol strand in the presence of NaBH4, whereas the tetraphenol strands with a trans-stilbene or trans-azobenzene unit did not form such a double-stranded helicate. The 1H NMR and NOESY experiments revealed that cis-3 adopted contracted (cis-3C) and extended (cis-3E) forms under equilibrium in CD3CN at 25 °C. The contracted cis-3C that accommodated a Na+ ion in the center showed an almost reversible extension and contraction motion by removal and addition of a Na+ ion. The cis-to-trans photoisomerisation of the extended cis-3E with UV light (295 nm) further induced an extension of the helicate, producing a mixture of cis,trans-3E and trans-3E helicates at the photostationary state. However, trans-to-cis photoisomerisation of the trans-mixtures using UV light (360 nm) was irreversible in this system and produced the photooxidated aldehyde species (trans-4), resulting from the photo-cleavage of the trans-stilbene moieties of the trans-3E

The application of capillary electrophoresis and mass spectrometry to clinical and environmental problems

Using capillary electrophoresis (CE) as a separation technique has allowed analytes, previously difficult to separate by standard methods because they did not conform to requirements for GC or HPLC, to be separated with speed and great efficiency. The only requirements for CE analysis are that the sample is soluble in a liquid matrix and that analytes are present as positive or negative ions whilst in this matrix. This technique has been used here to analyse both clinical and environmental samples, some as cations and others boron-containing complexes as anions. Samples were analysed using a combination of CE alone, mass spectrometry alone and also coupled capillary electrophoresis/electrospray mass spectrometry (CE/ES). Clinically orientated analytes, dipeptides in urine and acylcamitines from blood spots were examined and peaks detected directly via uv absorbance. The environmental samples analysed included those which contained chromophoric or non-chromophoric herbicides as well as those containing diisocyanates. Analytes were either detected in their native form as with the dipeptides and chromophoric herbicides, or more typically after derivatisation to improve their absorbance characteristics. The exception was the non-chromophoric herbicides which were detected via indirect uv. CE was an experimental technique for the analysis of all these compounds, except for the dipeptides, all the others having originally been analysed using HPLC or GC methods. In each case an evaluation of the CE method was performed to determine the suitability of the method. By analysing standards in each case, it was possible to confirm that the technique was suitable for qualitative and quantitative analysis of each class of compound. CE proved to be a viable technique for the separation of all classes of compound dealt with in this thesis. However the method could not be relied upon to confirm the identity of these analytes by their migration time alone. To identify the analytes, experiments were carried out to couple CE with a mass spectrometer. Two techniques of mass spectrometry were used within this thesis, fast atom bombardment and electrospray but only electrospray ionisation mass spectrometry was used to couple to capillary electrophoresis and was the only mass spectrometric technique used to analyse clinical and environmental samples. CE instruments were successfully coupled to an electrospray mass spectrometer which then became the detector. Mass/charge ratio measurements were obtained for each analyte used and these allowed the unambiguous identification of each analyte. Other work involved using CE, ES and FAI3 mass spectrometry, to develop a new technique to detect diol containing compounds. This involved complexing the diol with a boron-containing acid to produce an anion which could then be detected using ES and FAB mass spectrometric methods. This work was viewed as a possible technique for the detection of diol containing lipids found within some body fluids

Synthesis and Biological Activity of Arylspiroborate Salts Derived from Caffeic Acid Phenethyl Ester

Two novel boron compounds containing caffeic acid phenethyl ester (CAPE) derivatives have been prepared and characterized fully. These new compounds and CAPE have been investigated for potential antioxidant and antimicrobial properties and their ability to inhibit 5-lipoxygenase and whether chelation to boron improves their biological activity. Sodium salt 4 was generally more active than ammonium salt 5 in the biological assays and surpassed the radical scavenging ability of CAPE. Compounds 4 and 5 were more active than CAPE and Zileuton in human polymorphonuclear leukocytes. These results clearly show the effectiveness of the synthesized salts as transporter of CAPE

Chirality in molecular conductors from enantiopure or racemic coordination complexes

There has been growing interest in recent years in the synthesis of multifunctional materials that exhibit both chirality and electrical conductivity. These materials can exhibit electrical magnetochiral anisotropy (eMChA) or the chirality induced spin selectivity (CISS) effect. Several families of chiral tetrathiafulvalene (TTF)-based donor molecules have been successfully used with acceptors or simple anions to prepare chiral molecular conductors. Chiral materials have also been obtained by employing racemic or enantiopure counter anions with chiral or achiral TTF donors. Most recently, enantiopure molecular conductors of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene (BDH-TTP) have been obtained through chiral induction from a racemic mixture of a coordination complex, which provides the anion. This Frontier article provides an overview of chiral molecular conductors and a summary of progress to date. It highlights future perspectives on how chirality can be introduced into molecular conductors by employing enantiopure or racemic coordination complexes, which also have the potential to introduce magnetism into the multifunctional material

Scope of enantioselective reduction of imines with trichlorosilane

Herein, we report the results of research continuing previous successI in the field of enantioselective organocatalytic reduction of imines with trichlorosilane. Syntheses of various precursors (ketones) and substrates (imines) for the reduction reaction and their reduction following the protocol (Scheme A1) are described in this thesis. 1. Aromatic heterocycles containing nitrogen – good yields of the reduced product (68-85 %), the enantioselectivity depended on steric bulk in proximity to the nitrogen, steric bulk improved the enantioselectivity (up to 78 % ee), probably due to thwarting the coordination of the nitrogen to HSiCl3. 2. Aromatic heterocycles containing sulfur – sulfur in the ring was tolerated well (89 % ee). 3. Aromatic heterocycles containing oxygen – generally good yields (62-90 %), dependence on position isomer was observed: furan-2-yl-derived substrates were reduced in moderate enantioselectivity (45-85 % ee), possibly due to the problem of coordination; in contrast, furan-3-yl derivatives were reduced in good enantioselectivity (77-91 % ee). 4. Non-heterocyclic aromatic or aliphatic – good yields (62-98 %) but varied enantiomeric excess (10-97 %). The high enantioselectivity values (76-97 % ee) were for substrates with significant contrast of the steric hindrance of the groups next to the reaction centre. Furthermore, an example of practical utilisation of the method is presented. Naturally occurring alkaloid N-acetylcolchinol was synthesised in 9 steps and overall 8 % yield (Scheme A2). The stereogenic centre was introduced using our method and afforded the desired enantioenriched amine in 96 % ee

Emäskatalysoitu aryylialdehydien ja valiinista johdettujen boroksatsolidonien kondensaatio

Imines are an important group of compounds for many chemical reactions in organic chemistry, mostly as electrophiles. In nature, imines are important for the transamination reaction. N-B bonds are interesting because they can be thought of as an analogy to a C-C bond. However, unlike a C-C bond, the N-B bond is polarized. Imines and N-B bond-containing compounds both have similar potentials as pharmaceuticals. Both of these groups can have antibacterial, antifungal and anticancer effects. The N-B bond focused on in this thesis is formed when an amino acid reacts with a boron compound to form a hetero ring structure known as a boroxazolidone. In this master’s thesis, the imine condensation between aldehydes and boroxazolidones, and the N-B bond were studied. Boroxazolidones with differing substituents at the boron were prepared from the corresponding triethylammonium tetra-arylborates (TEATABs) and (L)-valine. These were then reacted with different aryl aldehydes in the presence of a base as a catalyst to afford the corresponding imines. The general procedures for preparing the TEATABs, the boroxazolidones and imines had already been established in prior projects in the laboratory. Two Lewis bases, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and sodium methoxide (NaOMe), were found to produce the most simple ketimine and aldimine respectively in good yields and without side products. However, the aldimine is very labile and reverts easily to its starting materials. When testing other aldehydes with TBD, it was found that the yields range from 63 to 0 %, in this general order depending on the aldehyde’s substituents: halogen-substituted > electron withdrawing but non-halogen-substituted > electron donating. 4-Methoxybenzaldehyde was an exception to this because it produced a decent yield. Five different boroxazolidones were prepared from the corresponding TEATABs. The effect of the boroxazolidones’ substituents at boron had a lesser effect on the imine yield than the aldehydes’ substituents. Difluoro- and methyl-substituted boroxazolidones produced good yields but the 4-methoxy-substituted boroxazolidone produced a much lower yield

Controlled synthesis of Ru nanoparticle covalent assemblies and their catalytic application

This research work focuses on the preparation of Ru nanoparticle (NP) covalent assemblies stabilized by different functional molecules, and the study of structure/activity relationships for catalytic hydrogenation reactions. Chapter 1 reviews the metal NP covalent assemblies according to the synthesis strategies and their application in catalysis. Chapter 2 described the preparation of three-dimension (3D) Ru NP covalent assemblies characterized by: i) well-defined nanometricsized Ru NP stabilized by functionalized adamantane, bis-adamantane and diamantane ligands, and ii) a tunable interparticle distance. The coordination chemistry with amine and carboxylic acid ligands towards the Ru NP surface was investigated. In the case of carboxylic acid ligands it was shown that Ru species formed during the NP assembly are able to partially decarbonylate carboxylic acid ligands at room temperature. The mechanism of this reaction was elucidated by DFT. Chapter 3 detailed the use of other molecular building blocks for Ru NP assembly formation. We showed that the use of tricarboxylic-hexyloxy triphenylene ligand leads to the formation of twodimensional (2D) Ru NP assemblies with homogeneous interparticle distance and NP size. Additionally, 3D Ru NP assemblies were prepared with 9, 10-dicarboxylic anthracene and a hexaadduct functionalized C60 fullerene. In Chapter 4 we studied the catalytic performances of the Ru NP networks in various reactions. All these materials constitute an interesting set to investigate the structural and electronic effects in heterogeneous catalysis. In the selective hydrogenation of phenyl acetylene, the assemblies are active, reaching good selectivity towards styrene. Especially, we demonstrated that confinement and electronic effects are occurring and that Ru NP interparticle distance affects the catalyst activity, whereas electronic effects mainly govern the catalyst selectivity. The stability of the Ru NP assembly is finally discusse

Foldaxanes (pseudorotaxanes hélicoïdaux auto-assemblés)

L'auto-assemblage dynamique est une méthode puissante pour accéder à des édifices moléculaires fonctionnels complexes. Son application à la construction de moteurs moléculaires par le biais de la maîtrise des échelles de temps ouvre la voie à des générations de nano-machines de plus en plus sophistiquées pouvant spontanément renouveler leurs composants ou les changer pour d'autres. La première partie de ce manuscrit est axée sur le design d hélices d oligoamides aromatiques qui peuvent s enrouler le long d un axe et glisser rapidement le long de celui-ci avant de se dérouler. Le second volet de cette thèse est consacré à la mise en évidence d un mouvement qui est caractérisé pour la première fois à l échelle moléculaire: le vissage. Le dernier axe de recherche développé dans ce manuscrit concerne la mise en évidence d un intermédiaire cinétique de type foldaxane se transformant progressivement en un complexe hôte-invité 2:2 thermodynamiquement stable.Dynamic self-assembly is a powerful method for fabricating complex, functional molecular structures. Its application to the construction of molecular motors through the control of timescales paves the way for new generations of nano-machines, in which sophisticated components can be spontaneously renewed or changed by others. The first part of this thesis focuses on the design of aromatic oligoamides that can slowly wind along an axis and shuttle along it before unfolding. The second chapter is devoted to the detection of a movement that is characterized for the first time at the molecular level: the screwing motion. The last line of research developed in this manuscript concerns the identification of a long-lived kinetic supramolecular by-product based on foldaxane architecture, which gradually transforms into a thermodynamically favored 2:2 host-guest complex.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF