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Spin Crossover in 2D and 3D Networks with 4-R-1,2,4-Triazole Ligands: Insights to Multistep Transitions by Xiaochun LI -
Jeudi 27 novembre 2025 à 14h00 - Auditoire LAVO51 - Bâtiment Lavoisier - Place Louis Pasteur, 1 - 1348 Louvain-la-Neuve -
This dissertation investigates Fe(II) spin crossover (SCO) materials, emphasizing the structural characteristics and spin-transition behaviors of two- and three-dimensional coordination polymers constructed from 1,2,4-triazole ligands. As reversible molecular switches responsive to external stimuli, SCO compounds offer significant potential for smart functional materials, chemical sensing, and molecular information storage. However, the mechanisms governing multistep spin transitions are highly intricate, arising from the interplay among crystal structure, supramolecular interactions, and lattice flexibility. Systematic structure-property correlations for such systems therefore remain limited. A series of Fe(II) coordination frameworks with diverse dimensionalities, topologies, and cooperative features were developed by modulating counteranions, lattice solvents, and supramolecular forces. The results demonstrate that the steric profile and charge distribution of counteranions profoundly influence lattice elasticity and the transmission of cooperative interactions. Meanwhile, the introduction or removal of lattice solvent molecules adjusts the framework rigidity, reshaping the energetic balance between spin states and tuning the overall cooperativity. Furthermore, supramolecular contacts, including hydrogen bonding, π-π stacking, and metal-affinity interactions, give rise to anisotropic lattice strain fields that facilitate the stabilization of multiple intermediate spin states. These structural insights deepen the understanding of multistep spin transitions in high-dimensional Fe(II) SCO materials and enrich the family of triazole-based SCO frameworks. They also provide useful guidelines for designing programmable and multi-stimuli-responsive molecular spin-functional materials with promising prospects for applications in smart devices, sensing technologies, and molecular information storage systems.
Jury members :
Prof. Yann Garcia (UCLouvain) (Supervisor)
Prof. Arnaud Delcorte (UCLouvain) (Chairperson)
Prof. Michael Singleton (UCLouvain) (Secretary)
Prof. Pascal Gehring (UCLouvain)
Prof. Yves Gossuin (Université de Mons)
Dr. Mariusz Jozef Wolff (Universität Wien)
Pay attention : the public defense of Xiaochun LI will also take place in the form of a videoconference
