Synthèse et propriétés de nouvelles molécules carbo-mères : carbo-quinoïdes et carbo-benzénoïdes

Following numerous illustrations and validations at the fundamental level, the chemistry of carbo-meric molecules was recently directed towards functional targets in terms of application prospects (molecular "carbo-materials'). Such carbon-expanded molecules have indeed recently been shown to exhibit remarkable properties in the areas of single molecule conductivity (SMC) or two-photon absorption efficiency (TPA). The consideration of target of fundamentally "new types" remains necessary in view of the study of new properties as well. The work described in this manuscript focus mainly on results concerning the synthesis of carbo-quinoids and carbo-benzenoids, two types of carbo-meric structures that had not been considered hitherto. The first chapter is a bibliographic summary describing the synthesis and properties of carbo-meric molecules, either aromatic or, more generally, highly pi-conjugated (carbo-benzenes, carbo-cyclohexadienes, carbo-oligoacetylenes...) The second chapter focuses on the complete study of the three regioisomers, "ortho", "para" and "meta" of tetraphenyl-carbo-benzene, the first two representatives having been partly described previously. The third chapter describes the synthesis and study of the first example of carbo-quinoid and its reversible redox transformation to carbo-benzenes, illustrating the "redox pro-aromaticity" of carbo-quinoid with respect to their oxidized carbo-benzenic analogues. The fourth and final chapter is devoted to the synthesis and study of a carbo-benzenoid, carbo-naphthalene, which can be regarded as the smallest condensed polycyclic fragment of alpha-graphyne, a material widely studied at the theoretical level but remaining unknown experimentally to date. The physicochemical and spectroscopic properties of carbo-naphthalene are compared to that of the corresponding monocyclic carbo-benzene, the synthesis of which is also detailed.A la suite de nombreuses illustrations et validations au niveau fondamental, la chimie de molécules carbo-mères s'est récemment orientée vers des cibles fonctionnelles en termes de perspectives d'applications (" carbo-matériaux " moléculaires). C'est ainsi que de telles molécules expansées en carbone ont récemment montré des propriétés remarquables dans les domaines de la conductivité sur molécule unique (SMC) ou de l'absorption à deux photons (TPA). La considération de cibles de types fondamentalement nouveaux " reste cependant nécessaire en préliminaire à l'étude de propriétés nouvelles aussi. Le travail décrit dans ce manuscrit présente essentiellement les résultats concernant la synthèse de carbo-quinoïdes et de carbo-benzénoïdes, deux types de structures carbo-mères qui n'avaient jamais été envisagées expérimentalement auparavant. Le premier chapitre est un résumé bibliographique décrivant notamment la synthèse et les propriétés de molécules carbo-mères aromatiques, et plus généralement hautement pi-conjuguées (carbo-benzènes, carbo-cyclohexadiènes, carbo-oligoacétylènes...) Le second chapitre porte sur l'étude complète des trois régioisomères, " ortho ", " para ", et " meta " du tétraphényl-carbo-benzène, dont les deux premiers représentants avaient été partiellement décrits. Le troisième chapitre décrit la synthèse et l'étude du premier exemple de carbo-quinoïde, ainsi que sa transformation rédox réversible en carbo-benzènes, illustrant ainsi la " pro-aromaticité redox " des carbo-quinoïdes vis-à-vis de leurs analogues oxydés carbo-benzènes. Le quatrième et dernier chapitre est consacré à la synthèse et l'étude d'un carbo-benzénoïde, le carbo-naphtalène, pouvant être considéré comme le plus petit fragment polycyclique condensé d'alpha-graphyne, un matériau largement étudié au niveau théorique mais encore inconnu expérimentalement à ce jour. Les propriétés physico-chimiques et spectroscopiques de carbo-naphtalène sont comparées à celle du carbo-benzène monocyclique correspondant, dont la synthèse est aussi détaillée

Synthesis of Functional Carbo-benzenes with Functional Properties: The C2 Tether Key

International audienceBeyond demonstration of conceptual relevance and synthetic feasibility of aryl/alkyl-substituted representatives, carbo-benzene mols. started to gain prospects of broader impact through the emergence of alkynyl derivs. This is first illustrated by examples of di- and hexaalkynyl- carbo-benzenes, a carbo-naphthalene, a carbo-biphenyl, and two carbo-terphenyls. A focus is then given to dialkynyl derivs. by ref. to the peripherally C 2-extruded parents. In the centrosym. quadrupolar series, the C 2expansion or ethynylogation effect is more particularly considered for 9 H-fluoren-2-yl, tris(O- n-alkyl)pyrogallyl, indol-3-yl, 4-anilinyl, and tetraphenyl- carbo-Ph substituents on the following resp. properties: two-photon absorption, chem. stability, columnar mesogenicity, on-surface photoinduced charge sepn. vssingle-mol. conductance, and redn. potential. Topical results and prospects of application are discussed on the basis of crystallog., spectroscopic, and electrochem. analyses vsDFT-calcd. nuclear and electronic structures. For the sake of the discussion consistency, complementary exptl. and computational results are disclosed in the dianilinyl series. Overall, it is shown that combined advances in strategy, protocols, and substrate scope of acetylenic synthesis remain crucial for the development of yet poorly explored but promising types of mol. materials. 1 Introduction 2 Hexaalkynyl- carbo-benzene 3 ortho-Dialkynyl- carbo-benzene 4 para-Dialkynyl- carbo-benzenes 4.1 Bistrimethylsilylethynyl- carbo-benzene 4.2 Bisfluorenylethynyl- carbo-benzene 4.3 Bistrialkoxyarylethynyl- carbo-benzenes 4.4 Bisindolylethynyl- carbo-benzene 4.5 Bisanilinylethynyl- carbo-benzene 5 Carbo-oligo(phenyleneethynylene)s 6 Conclusions

Reorganization of a photosensitive carbo-benzene layer in a triptych nanocatalyst with enhancement of the photocatalytic hydrogen production from water

International audienceThe preparation of a triptych nanomaterial made of TiO2 nanoparticles as semiconductor, Ag plasmonic nanoparticles and a carbo-benzene macrocyclic molecule as photosensitizer is described, and used to produce hydrogen by photo-reduction of pure deionized water under 2.2 bar argon pressure without any electrical input. Silver nanoparticles (~5 nm) are grafted onto the surface of commercial TiO2 nanoparticles (~23 nm) by a photo-deposition process using an original silver amidinate precursor. The thickness of the photosensitive layer (2 nm), which completes the assembly, plays a crucial role in the efficiency and robustness of the triptych nanocatalyst. Thanks to the organic layer reorganization during the first ~24 h of irradiation, it leads to an enhancement of the hydrogen production rate up to 5 times. The amount of silver and carbo-benzene are optimized, along with the mass concentration of nanocatalyst in water and the pH of the aqueous medium, to allow reaching a hydrogen production rate of 22.1 μmol·h−1·gphotocatalyst−1

Controlled growth of high-density nanoparticles on zinc oxide thin films by photo-deposition

International audienceSince Faraday in the 1850s, gold nanoparticles (AuNPs) have been the subject of growing interest. AuNPs are now commonly used in many applications such as such as sensors, photocatalysis, photovoltaic devices, and biological labeling. The deposition of gold nanoparticles (AuNPs) on zinc oxide films a key step for (photocatalysis)catalysis or photovoltaic applications, still remains difficult to master. The deposition of Au NPs on ZnO films was explored to achieve small AuNPs size and homogeneous shape, high areal density, high purity, and good chemical grafting with the metal oxide film. Among three possible methods to deposit AuNPs on ZnO−spin coating, deposition precipitation with urea and photodeposition (P-D) only P-D achieved good enough results to be useful for most applications. The modified P-D technique developed herein produces homogeneously and dispersed spherical Au NPs (7.5 ± 3 nm in diam.) with a high packing density (3500 ± 10 NPs/μm2). The high density of AuNPs has a direct impact on the activity of photocatalytic reactions. We demonstrate that high densities of Au NPs embedded within ZnO film enhance the production of hydrogen by photo- reduction of water. Furthermore, most of the AuNPs are intercalated into the 25 nm ZnO layer with only 1/5 of their volume emerging out of the metal oxide layer2. While the confinement of nano-objects in small volume remains a great challenge in nanotechnologies in general, the photodeposition process is able to deposit AuNPs on ZnO thin films. This photodeposition process makes it of great interest for many applications needing high purity materials such as photovoltaics, photocatalysis, water purification, or biosensors

Controlled Growth and Grafting of High-Density Au Nanoparticles on Zinc Oxide Thin Films by Photo-Deposition

International audienceThe integration of high-purity nano-objects on substrates remains a great challenge for addressing scaling-up issues in nanotechnology. For instance, grafting gold nanoparticles (NPs) on zinc oxide films, a major step process for catalysis or photovoltaic applications, still remains difficult to master. We report a modified photodeposition (P-D) approach that achieves tight control of the NPs size (7.5 ± 3 nm), shape (spherical), purity, and high areal density (3500 ± 10 NPs/μm 2) on ZnO films. This deposition method is also compatible with large ZnO surface areas. Combining electronic microscopy and X-ray photoelectron spectroscopy measurements, we demonstrate that growth occurs primarily in confined spaces (between the grains of the ZnO film), resulting in gold NPs embedded within the ZnO surface grains thus establishing a unique NPs/surface arrangement. This modified P-D process offers a powerful method to control nanoparticle morphology and areal density and to achieve strong Au interaction with the metal oxide substrate. This work also highlights the key role of ZnO surface morphology to control the NPs density and their size distribution. Furthermore, we experimentally demonstrate an increase of the ZnO photocatalytic activity due to high densities of Au NPs, opening applications for the decontamination of water or the photoreduction of water for hydrogen production

Dispositif de Cellule Solaire Hydrogène intégrant des Matériaux dits Triptyques

National audienceLa photocatalyse, à distinguer de la photo-électro-catalyse, permet de produire de l'hydrogène par photo-réduction de l'eau, tout en s'affranchissant de l'utilisation d'électrodes, d'un courant électrique, ou encore de l'utilisation d'un bain électrochimique. [1] Dans ce cadre, nous avons développé un dispositif de panneau solaire hydrogène (Figure 1a) assurant la transformation de l'eau liquide contenue dans le panneau en hydrogène sans la nécessité d'être raccordé au réseau électrique. [2-3] Le coeur actif du panneau hydrogène est constitué d'un matériau hybride photocatalytique innovant, qualifié de matériau triptyque du fait des trois composants le constituant (Figure 1b) : (1) un film mince semiconducteur de TiO 2 déposé par PVD ; (2) des nanoparticules d'Au ou Ag déposées par un procédé de photo-dépôt; [4] (3) Un film mince photosensible d'une macromolécule de type carbo-benzène (Cbz), présentant des propriétés uniques de conductivité sur molécule unique ( ~100 nS), [5] et d'absorption dans le visible ( = 131 000 L mol-1 cm-1) à max = 493 nm. [6] Nous observons une synergie de ~33% pour le matériau triptyque TiO 2 /Ag/Cbz par rapport à son analogue diptyque TiO 2 /Ag et démontrons qu'un lien entre le métal et le semiconducteur est d'importance primordiale pour exalter les propriétés photocatalytiques dans le cadre de films minces par analogie avec les nanopoudres. [7