Synthèse et étude de cages moléculaires photo-modulables et génération de nano-cristaux d'or par photo-catalyse supramoléculaire

Les objectifs de cette thèse sont articulés autour de deux axes principaux : la synthèse et l étude de cages moléculaires photo-modulables, et la génération de nano-cristaux d or par photo-catalyse supramoléculaire. Ces deux thématiques sont reliées entre elles par l exploitation des propriétés photophysiques et photochimiques d un motif commun, le 9,10-diphénylanthracène (DPA). Dans un premier temps, de nouvelles architectures tridimensionnelles photo-modulables de type cage moléculaire ont été conçues et étudiées. En présence d oxygène, l irradiation directe ou sensibilisée du DPA permet de former réversiblement le dérivé endoperoxyde et ainsi moduler les propriétés de complexation de la cage. Les différentes stratégies de synthèse mises en place reposent sur l exploitation conjuguée de la réactivité de la 2,4,6-trichloro-1,3,5-triazine, et de réactions de chimie click (métathèse des oléfines, cycloaddition de Huisgen). L étude et la modulation des propriétés des reconnaissances ont été effectuées sur des sels de cations alcalins (sodium et césium) et suivies par émission de fluorescence et spectroscopie d absorption UV-visible. Les résultats obtenus avec deux cages possédant des constantes d'associations élevées (logK = 8,7 pour le cation sodium) montrent une augmentation de la constante d association d un facteur 10 et 20 pour respectivement le sodium et le césium entre la forme DPA et la forme endoperoxyde. Dans un second temps, des photocatalyseurs supramoléculaires basés sur le chromophore DPA ont été étudiés en vue de la synthèse de nano-cristaux d or nus. L association du chromophore avec des thioéthers permet de former un complexe en phase organique par extraction de sels d or(III) depuis une phase aqueuse. L irradiation à 400nm permet la réduction de l or(III) par transfert d énergie depuis le 9,10-diphénylanthracène. Les atomes d or sont ensuite relargués en phase aqueuse pour former des nano-cristaux nus qui ont pu être caractérisés par MET, XPS, AFM et DLS. Par ailleurs, ce procédé est catalytique dans le toluène et un système de réduction en flux continu a été mis au point permettant un turnover moyen de 150.The goals of this thesis are organized around two major axes: the synthesis and study of photo-gated molecular cages, and the generation of gold nanocrystals by supramolecular photocatalysis. These two themes are connected by the use of the photochemical and photophysical properties of a common chromophore, 9,10-diphenylanthracene (DPA). Three-dimensional photo-gated cage-like architectures were designed and synthesized. Various synthetic strategies based on the combined use of the 2,4,6-trichloro-1,3,5-triazine unit and "click" chemistry reactions (olefin metathesis, Huisgen cycloaddition) were employed for the synthesis. In the presence of oxygen, sensitized or direct irradiation of the DPA chromophore forms the corresponding endoperoxide derivative, thereby modulating the binding properties of the cage. The study and the modulation of the recognition properties were performed on various alkali metal cations and a strong binding of sodium and cesium was evidenced by fluorescence emission and UV-visible absorption spectroscopy. The cages investigated possessed high association constants towards sodium and cesium cations (logK = 8.7 for the sodium cation) which could be reversibly increased by a factor 10 and 20 for sodium and cesium, respectively, upon formation of the endoperoxide. Supramolecular photocatalysis of gold(III) reduction based on the DPA chromophore was also studied for the preparation of uncapped gold nanocrystals. The combination of the DPA chromophore with thioether chains allows the formation of a complex in the organic phase by extraction of gold(III) chloride from an aqueous phase. Irradiation at 400 nm enables the reduction gold(III) by energy transfer from the 9,10-diphenylanthracene followed by oxidation of the solvent. The gold atoms are subsequently released in the aqueous phase to form uncapped nanocrystals characterized using TEM, XPS, AFM, and DLS techniques. Furthermore, the process is catalytic in toluene, where a continuous flow reactor was developed. The latter allowed an average catalytic turnover of 150 to be determined.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

SYNTHESE ET PROPRIETES COMPLEXANTES DE PHOSPHACAVITANDS FONCTIONNALISES

LYON-ENS Sciences (693872304) / SudocSudocFranceF

Ring-opening polymerization of lactones using supramolecular organocatalysts under simple conditions

Ring-opening polymerizations of delta-valerolactone (delta-VL) and epsilon-caprolactone (epsilon-CL) were catalyzed by a metal-free system composed of two H-bonding components, a phenol derivative to activate the monomer, and DBU, which enhanced the nucleophilicity of the initiator and the propagating chain. Compared to other H-bonding systems for the ROP of lactones, phenol + DBU catalysts had the practical advantages of being commercially available and inexpensive, efficient at room temperature and under simple experimental conditions that avoid drying of reactants and the use of a glove-box. In addition, the obtained polyesters had a narrow dispersion of molar masses which were controlled by the concentration ratio of monomer versus initiator. Moreover, the initiation of the polymerization by DBU and residual water molecules (despite no specific drying of reagents) was shown to be very minor under the experimental conditions. No initiation by the phenol catalysts was observed. Block copolyesters PVL-PLA and PCL-PLA were also prepared using these conditions

Ring Opening Polymerization of DL-Lactide Using A Supramolecular Sulfonamide - Tertiary Amine Organocatalytic System

Sulfonamides are common ligands for organometallic catalysis in the Ring Opening Polymerization (ROP) of cyclic esters. In our quest for original Hydrogen-bonding catalytic systems, our goal was to use a sulfonamide derivative as an electrophilic activator of DL-lactide in partnership with a tertiary amine, as a nucleophilic activator of the initiator and growing polymer chain. Several sulfonamides were synthesized and tested in the ROP of DL-lactide. The impact of sulfonamide substituents was analyzed to better understand the H-bonds involved in the process

Photoreduction of Thioether Gold(III) Complexes: Mechanistic Insight and Homogeneous Catalysis

International audienc

Activation of carbonyl bonds by quaternary ammoniums and a (Na+:crown-ether) complex: investigation of the ring-opening polymerization of cyclic esters

Quaternary ammoniums associated with bis(trifluoromethane) sulfonimide (NTf2) or tetrakis[3,5-bis-(trifluoromethyl)phenyl]borate (BARF) counterions were readily prepared from commercially available tertiary amine, amidine, guanidine and pyridine. As predicted by molecular modelling, these ammonium salts proved to be efficient multiple H-bond donor catalysts in the ring-opening polymerization of cyclic esters (lactide, delta-valerolactone and epsilon-caprolactone). In addition, a sodium(I) complex of [15-c-5] crown-ether paired with NTf2 or BARF was shown to activate the cyclic monomers through a cation-dipole interaction. These simple and non-protonated ionic structures appeared as attractive alternative organocatalysts to classical H-bond donors for the activation of carbonyl bonds

Supramolecular Photocatalyst for the Reduction of Au(III) to Au(I) and High-Turnover Generation of Gold Nanocrystals

International audienceWe report a photocatalyst composed of a diphenylanthracene core appended with two lipophilic thioether side-chains that binds gold(III) chloride. Upon excitation using visible light, the AuIII ions are smoothly reduced to AuI which, in the presence of water, lead to the formation of crystalline gold nanoparticles of 20–50 nm diameter that are devoid of sulfur-containing capping agents. Ultrafast transient absorption spectroscopy shows that the anthracene excited state is quenched with a rate k = 3.5 × 1010 s–1, assigned to intramolecular energy transfer to the bound gold ions, which then oxidizes the solvent to produce an intermediate low-valency gold(I) species. In the absence of water, the latter is stable and can be used as a homogeneous AuI catalyst. When employed in a biphasic reactor, the photocatalyst shows average turnover numbers of 150 atoms of AuIII reduced to Au0 per molecule of photocatalyst

Phenols and Tertiary Amines: An Amazingly Simple Hydrogen-Bonding Organocatalytic System Promoting Ring Opening Polymerization

International audienceA simple and easily available organocatalytic system was developed for the polymerization of lactide. In partnership with tertiary amines, phenol derivatives were demonstrated to be excellent single H-bonding catalysts with high conversion within 24 h. In particular, ortho-, meta- and meta,meta'-trifluoromethylphenols revealed an amazing capacity for triggering the controlled ring opening polymerization (ROP) of lactide, through a fitted hydrogen-bond with the monomer