Coordination polymers: from uranium(IV) and thorium(IV) to non-uranyl U(V) and U(VI)

This thesis explores the diverse chemistry of thorium and uranium coordination polymers, focusing on actinides in +4 and +5 oxidation states, and their reactivity with various ligands. While uranium predominantly exists as the uranyl cation [UO2]2+ in the +6 oxidation state, it also naturally occurs in oxidation states +4 and +5 due to geochemical and biological processes. Understanding those oxidation states is critical for modelling uranium's environmental behaviour. This research addresses gaps in the study of uranium(IV) coordination chemistry, particularly with polytopic carboxylate ligands and other environmentally relevant linkers such as catechols, and phenols. It presents novel findings on the synthesis and characterization of 2D and 3D uranium(IV) coordination polymers based on tritopic carboxylic acids, including an examination of the effects of various reaction conditions on their structures (temperature, solvent, pH, modulation). Coordination polymers based on nitrogen-rich tricarboxylic acids were studied as well. Post-synthetic modifications through the crystal-to-crystal transformations are also explored. Additionally, the first examples of crystallographically characterized uranium(IV) coordination polymers with phenolate-based ligands are reported herein. Such ligands are underrepresented in the field of metal-organic coordination polymers but are largely used in the molecular chemistry of uranium(III). Their potential in stabilizing uranium(III) coordination polymers is evaluated. A unique class of catecholate-based networks was synthesized to support three distinct oxidation states of uranium: U(IV), U(V), and U(VI). This work offers new insights into the fundamental chemistry of actinide-based coordination polymers, which serve as a model of possible uranium transformation pathways in nature.