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Hexadentate N,N,N’,N’-tetrapyrazolyl alkyl diamine metal complexes as scaffolds for bimetallic systems by Corentin POCHET -
Vendredi 29 août 2025 à 10h00 - Auditoire LAVO51 - Bâtiment Lavoisier - Place Louis Pasteur, 1 - 1348 Louvain-la-Neuve -
Multielectron transformations are essential in the catalytic activity of many rare transition metals such as palladium-based catalysts. However, transposing this chemistry to more accessible and sustainable metals remains challenging as such elements tend to favor single-electron transfer. To overcome this limitation, placing two redox-active metal partners in close proximity can promote cooperative two-electron processes.
Cooperativity is a key concept in chemistry, whereby multiple components work together to achieve a specific function. It can manifest in various forms, ranging from the formation of stable supramolecular entities to multisite catalysis. In particular, redox cooperativity refers to the facilitated transfer of multiple electrons involving several redox-active partners, i.e., multielectron transformations. When these partners are metal centers, efficient electronic communication between them is crucial. Such communication requires the metals to be held within the same ligand framework, allowing for direct orbital overlap or electronic coupling.
Tetrapyrazole-based ligands represents a new class of ditopic hexadentate scaffolds, offering a tunable second coordination sphere through accessible N–H protons. Their ability to reversibly switch from pyrazole to pyrazolate donors allows control over metal redox properties and binding modes, paving the way for the formation of bimetallic complexes and the investigation of metal-metal redox cooperativity.
In this work, eight ligands were synthesized and used to prepare 32 Co, Ni, Cu, and Zn complexes. The modularity of the scaffold was explored through linker length, substituent effects, and partial substitution by pyridine rings. Spectroscopic and electrochemical studies highlighted their potential for anion recognition and redox activity.
One bimetallic complex was structurally characterized, and evidence from solution studies suggests the formation of related species. While redox cooperativity between two metal centers could not be demonstrated experimentally, the results underscore the relevance of ligand design in stabilizing reactive metal pairs.
Future efforts should focus on fine-tuning the steric and electronic properties of the ligand to improve metal pairing and redox compatibility, with promising perspectives for bimetallic catalysis and cooperative reactivity.
Jury members :
Prof. Michael Singleton (UCLouvain) (Supervisor)
Prof. Yann Garcia (UCLouvain) (Chairperson)
Prof. Olivier Riant (UCLouvain) (Secretary)
Prof. Guillaume Berionni (UNamur)
Prof. Frédéric Avenier (Université Paris-Saclay)
Pay attention : the public defense of Corentin POCHET will also take place in the form of a videoconference
