ED Sciences Chimiques
Rational Design of Pyrazine-Based Magnetic Materials via a Molecular Building Block Approach
by Katia DUJARRIC (Centre de Recherche Paul Pascal)
The defense will take place at 10h00 - Amphithéâtre Centre de Recherche Paul Pascal UMR 5031 / CNRS-Université de Bordeaux, 115 avenue du Dr Albert Schweitzer, 33600 Pessac, France.
in front of the jury composed of
- Corine MATHONIERE - Professeure des universités - Université de Bordeaux, Centre de Recherche Paul Pascal - Directeur de these
- Dominique LUNEAU - Professeur - Laboratoire des Multimatériaux et Interfaces (UMR 5615), Université Claude Bernard Lyon 1 - Rapporteur
- Leoni BARRIOS MORENO - Professor - Laboratory of Molecular Design (LabMolDesign), University of Barcelona - Examinateur
- Céline PICHON - Chargée de recherche - Laboratoire de Chimie de Coordination (LCC) - UPR 8241 - Rapporteur
- Cécile ZAKRI - Professeure des universités - Université de Bordeaux, Centre de Recherche Paul Pascal - Examinateur
This thesis is devoted to the exploration of different synthetic approaches to rationally prepare systems of different dimensionalities based on the redox-active pyrazine ligand. In particular, a building block approach employing solution chemistry is discussed. Chapter I presents the theoretical definitions of magnetism, electrical conductivity, and X-ray absorption spectroscopy, which are crucial for understanding the experimental results. After that, state-of-the-art molecule-based materials composed of organic radical ligands, which feature high critical temperatures and, for some, conducting properties, are introduced. Additionally, the building block approach and emblematic molecule-based magnetic materials obtained through this synthetic route, ranging from cornerstone systems to modern molecular magnetism systems, are discussed. Chapter II focuses on exploring a building approach that utilizes mononuclear systems as precursors to synthesize and enhance the physical properties of previously reported square Cr-pyrazine two-dimensional networks. Moreover, it examines how this approach can be applied to other metal ions to create new magnetic two-dimensional networks and investigates the effects of these modifications on the resulting physical properties. Chapter III illustrates the use of solution coordination chemistry in the obtention of two new Cr-pyrazine two-dimensional magnetic systems. It highlights the crucial role of the synthetic choice in the design and physical properties of the final compounds. As well, it discusses how the peripheral ligands affect the electronic distribution of the pyrazines within the 2D networks. Finally, Chapter IV explores the use of a mononuclear precursor, introduced in Chapter II, to synthesise four new Cr one-dimensional materials featuring either neutral pyrazines or radical pyrazines. It discusses in particular, the impact of the different peripheral ligands on the redox process of such compounds.
ED Sciences et environnements
Fate and effects of microplastics, nanoplastics and additives resulting from the degradation of fishing gear during their life cycle. Study in the Bay of Biscay
by Edgar DUSACRE (Environnements et Paléoenvironnements Océaniques et Continentaux)
The defense will take place at 14h00 - Amphitéâtre IECB IECB, 2 Rue Robert Escarpit, 33600 Pessac
in front of the jury composed of
- Magalie BAUDRIMONT - Professeure des universités - Université de Bordeaux - Examinateur
- Ika PAUL-PONT - Directrice de recherche - European University Institute of the Sea/Université de Bretagne Occidentale - Examinateur
- Juan Antonio MARIGOMEZ ALLENDE - Professeur des universités - Universidad del Pais Vasco/Euskal Herriko Unibertsitatea - Examinateur
- Mohamed BANNI - Professeur des universités - University of Sousse - Rapporteur
- Lúcia Maria DAS CANDEIAS GUILHERMINO - Professeure des universités - University of Porto - Rapporteur
Fishing activities account for 17% of human consumption of animal proteins and approximately 550 million individuals globally rely for their livelihoods. On the other hand, this sector, could also play a role in marine pollution due to the use of plastic fishing gear (FG). However, scientific studies on how plastic FG contribute to the global oceanic pollution of microplastics (MPs), nanoplastics (NPs) and plastic chemicals were scarce. In this context, operated and lost fishing nets (FNs) in the Southeastern Bay of Biscay were estimated and beached abandoned lost or otherwise discarded fishing gear (ALDFG) were quantified. Then 6 oil-based FNs (1 made of polyethylene-polypropylene (PE-PP) and 5 made of polyamide (PA)) and 2 partially biobased/biodegradable FNs (polybutylene succinate-polybutyrate adipate terephthalate (PBS-PBAT)) were selected to investigate their degradation and toxicity. The degradation of FNs was analyzed through artificial aging in order to quantify the production of MPs, NPs, and plastic chemicals. Then, the effects of leachates were investigated through acute, and subchronic toxicity assays with lethal and sub-lethal endpoints on A. fischeri, T. lutea, A. tonsa and O. latipes. In addition, a comparative study of the toxicity of organic extracts from new FNs and end-of-life (EOL) ones on A. fischeri, the RTL-W1 cell line, and O. latipes was conducted. It was estimated through models that the fishing fleet of the Southeastern Bay of Biscay operated 211 tons of FG in 2023 and lost 6 tons of them. In the same period, it was also estimated that 3 tons of ALDFG were beached. Most of the FG beached were mending pieces coming from trawl and bottom seine repairs (89.8% of the FG in items). The artificial aging (AA) of FNs revealed FN-dependent production of MPs and plastic chemicals. Production of these degradation products tended to increase with AA, although not linearly. Three of the seven FNs studied produced a significant number of fragment MPs after 25 days of AA (1.1x105 MP/g of FN to 6.8x105 MP/g of FN) with a median size of 21.25 µm (min-max: 5 – 430 µm). NPs (< 1 µm) were also identified in the leachates of all FNs. Significant amounts of six heavy metals (Cu, Fe, Pb, Zn, Ni, Ag) were quantified in the leachates. Furthermore, we identified 27 organic compounds. Concerning the comparative toxicity of DMSO extracts of new and EOL FNs, the three species studied were affected by most of the leached products from the FNs. The Bioluminescence inhibition of A. fischery was linked to trace metals. Each of the 4 species exposed to leachates of artificially aged FNs experienced varying degrees of effects. The bioluminescence inhibition of A. fischeri was significantly impacted by most FNs, but more especially by the PBS-PBAT ones. This bioluminescence inhibition was mainly related to the release of trace metals. The density of microalgae cells (T. lutea) was not significantly affected after 72 h of exposure. Most tested FNs significantly disrupted the heart rate and behavior of Japanese Medaka larvae. Alterations in behavior generally increased with FN aging time and was mainly related to the release of organic chemicals. The survival of adult and juvenile copepods was significantly decreased by most of the FNs. The lowest LC50 estimated was caused by one PA FN (1.32±1.14 g/L) and one PBS-PBAT FN (1.55±0.82 g/L). Subchronic exposure of copepods caused significant effects on egg production and hatching success. Globally, these results highlighted that FNs contribute to MP (1.48 ± 1.34 MP/m3 to 2.2 ± 4.76 MPs/m3), NP and plastic chemical pollution of the oceans. Biobased/biodegradable FNs could offer a solution to better manage EOL FG and to reduce ghost fishing when lost, but their current composition needs to be improved to reduce their toxicity.