ED Sciences Chimiques
Modular Gold Complexes: Synthesis and catalytic properties
by Tiejun LI (Institut des Sciences Moléculaires)
The defense will take place at h00 - Salles de Conférence (3ème EST) Bat A12,Institut des Sciences Moléculaires, UMR CNRS 5255, 351 Cours de la Libération, 33405 Talence, France
in front of the jury composed of
- Brigitte BIBAL - Professeure - Université de Bordeaux - Directeur de these
- Hervé CLAVIER - Directeur de recherche - Aix-Marseille Université - Rapporteur
- Xavier GUINCHARD - Directeur de recherche - Université Paris-Saclay - Rapporteur
- Véronique MICHELET - Professeure - Université Côte d'Azur - Examinateur
- Elizabeth HILLARD - Directrice de recherche - Université de Bordeaux - Examinateur
Over the last decade, homogeneous gold(I) catalysis deeply changed organic synthesis as innovative and highly effective tools. At present, new opportunities in gold chemistry exist by combining gold with diverse functional ligands. Switchable catalysis aims to control the catalytic properties such as reactivity, chemo/regio/enantioselectivity by modulating the catalytic pocket in response to different external stimuli (i.e. light, redox, temperature, ions, molecules). Switchable gold catalysis is an emerging area in this field, offering new chances to explore new types of reactivity and selectivities. To date, most strategies for achieving switchable gold catalysis have focused on light activation, redox stimulus and encapsulation. However, new approaches to control the gold catalysts are still under active development. 9,10-substituted anthracenes can be transformed to their endoperoxide derivatives by [4+2] cycloaddition reactions, in a quantitative and reversible manner (via thermal cycloreversion). The endoperoxides adopt a concave geometry, presenting an opportunity to fine-tune both the steric and electronic properties of a newly designed catalyst. Inspired by this concept, a new family of Buchwald-type phosphine-gold complexes, substituted by anthracene moieties, have been designed. In this Ph. D. thesis, we studied the catalytic reactivity of the two states of catalysts (anthracene and endoperoxide states) by exploring how changes in geometry (from planar anthracene to concave endoperoxide) and electronic (particularly the gold-pi interaction) properties influence the catalytic performances. The project involved the multi-step organic synthesis of three systems of phosphine ligands and the corresponding gold complexes. The stability of the new endoperoxides gold complexes was also carefully evaluated. Finally, three benchmark reactions (hydroamination, hydroarylation and hydration) were conducted to compare the catalytic properties of the Anthracene/endoperoxide gold complexes pairs.
ED Sciences Physiques et de l'Ingénieur
Optomechanical control of a levitated nanoparticle via wavefront shaping
by Mélissa KLEINE (Laboratoire Ondes et Matière d'Aquitaine)
The defense will take place at 14h00 - Salle Gama Bâtiment A33 351 Cours de la libération 33400 Talence
in front of the jury composed of
- Yann LOUYER - Maître de conférences - Université de Bordeaux - Directeur de these
- Jochen FICK - Directeur de recherche - Institut Néel - Rapporteur
- Nicolas BONOD - Directeur de recherche - Institut Fresnel - Rapporteur
- Juliette BILLY - Maîtresse de conférences - Université Paul Sabatier - Toulouse III - Examinateur
- Ivan FAVERO - Directeur de recherche - Laboratoire Matériaux et Phénomènes Quantiques - Examinateur
- Fabio PISTOLESI - Directeur de recherche - Université de Bordeaux - Examinateur
Optical levitation of nanoparticles in vacuum offers a promising experimental platform for investigating fundamental phenomena in thermodynamics and quantum physics. Our trap relies on a tightly focused laser beam, whose intensity gradients exert an optical force that maintains the particle in equilibrium near the focal point. However, traditional configurations, particularly those relying on Gaussian beams, face limitations: trap stability is reduced at low pressure, and laser absorption by the particle leads to heating and quantum decoherence. In this thesis, we develop and implement a robust and reproducible experimental method for optimizing the optomechanical properties of an optical levitation trap. The approach relies on active wavefront modulation of the trapping beam using a Spatial Light Modulator (SLM). After situating our experimental system in an intermediate regime between the Rayleigh and Mie limits, we introduce a multipolar description of optical forces. The experimental setup is then detailed, including the high-numerical-aperture optical trap, the SLM, and the transmission-based homodyne detection system. We implement a feedback protocol that adjusts the wavefront to optimize trap stiffness. The method is evaluated experimentally: for a 125~nm-radius silica particle, a stiffness enhancement by a factor of 2.6 is achieved along the optical axis, compared to a Gaussian beam. We then analyze the performance and limitations of the method, as well as the physical consequences of the optimization. In the underdamped regime, we observe a suppression of motional nonlinearities (Duffing-type effects) and a contraction of the trapping volume. In addition, the non-conservative components of the optical force are significantly reduced. These experimental observations are supported by numerical simulations, which reveal in particular a decrease in the radiation pressure force. Finally, we illustrate the versatility of this method through two specific applications.