Magnetic nanosystems
Axis 5. Redox-active magnetic molecules
Talal Mallah, Nathalie Bridonneau, François Lambert
PhD students: Dr. Yiting Wang, Dr. Aristide Colin, Solène Delaporte
Collaborations:
- Nicolas Suaud, Nathalie Guihéry, Hélène Bolvin (études théoriques, Laboratoire de Chimie et Physique Quantiques, Toulouse)
- Laurent Maron, Ganping Wang, Thayalan Rajeshkumar (TD-DFT, LPCNO, INSA Toulouse)
- Shin Ichi Ohkoshi (Ohkoshi Laboratory, Université de Tokyo, Japon)
Related publications:
- Y. Wang, F. Lambert, E. Rivière, R. Guillot, C. Herrero, A. Tissot, Z. Halime, T. Mallah,
Chemical Communication, 55, 12336-12339, 2019 - N. Suaud,
A. Colin, M. Bouammali, T. Mallah, N. Guihéry,
Chem. Eur. J. 2023, e202302256. https://doi.org/10.1002/chem.202302256 - A Trinuclear Co(II) Complex Based on the Tris-dioxolene Triphenylene Non Innocent Bridge: Complementary Redox, Magnetic Behavior and Theoretical Calculations
-
Aristide Colin, Yiting Wang, François Lambert, Nathalie Bridonneau*, Nicolas Suaud*, Régis Guillot, Eric Rivière, Zakaria Halime, Nathalie Guihéry, Shin-ichi Ohkoshi, Talal Mallah*
Magnetochemistry 2024, 10(12), 102; https://doi.org/10.3390/magnetochemistry10120102 -
Solvatochromism and Redox Multi-Switch in a Trinuclear Cobalt(II) Complex
Solène Delaporte, Nathalie Bridonneau, François Lambert, Régis Guillot, Nicolas Suaud, Nathalie Guihéry, Ganping Wang, Thayalan Rajeshkumar, Laurent Maron, Talal Mallah
Chemistry – A European Journal 2025 DOI 10.1002/chem.202501455.
This work focuses on the rational design of magnetic systems (qubits, molecule-magnets) based on transition metals with the aim of controlling interactions between metal ions using a central redox active ligand. We use a central ligand that has three positions available for complexation, each of which can switch between three redox states: quinone/semiquinone/cathecol. We have isolated a trinuclear [Ni3] complex in which all Ni(II) ions are pentacoordinated and the central ligand is in the {sq-sq-sq} state. Cyclic voltammetry shows four reversible monoelectron waves (three in reduction, one in oxidation), which defines five potentially accessible redox states for this complex. Spectroelectrochemical measurements allowed the characterization of these states, and we were able to isolate and characterize the first oxidized {sq-sq-q} and reduced {sq-sq-cat} states in the solid state (powders or crystals).
Electron paramagnetic resonance (EPR) and SQUID magnetometry measurements show that the magnetic interaction between spin carriers is influenced by the electronic state of the central ligand. Obtaining crystal structures allows us to precisely define the presence and location of radicals which is not the same in the different redox states, and thus to rationalize the observed magnetic behavior. Additionally, ab initio calculations provide information on the electronic structure of the studied species. Specifically, the properties of the central redox active ligand are examined and help explain the experimentally observed properties of the complexes. We are currently trying to understand and rationalize the reciprocal interaction between the redox-active ligand, the nature of the metallic center (Ni, Co), and the influence of the external ligand. Overall, this redox-active magnetic system is rich and opens the way to a possible switching of different magnetic systems (qbit, valence tautomerism, molecule-magnet).
Solvatochromism and redox activity in a trinuclear cobalt complex
A trinuclear cobalt(II) complex incorporating the redox-active hexahydroxytriphenylene ligand (HHTP) is reported. The complex can be isolated in two different electronic states, enabled by its remarkable solvatochromic behaviour. Electrochemical studies revealed an extended redox-activity compared to parent compounds, with six reversible one-electron processes. These electronic properties arise from the ligand field tuning of the Co(II) centers through the Me3TPA (tris(6-methyl-2-pyridylmethyl)amine) capping ligand. The ability of stabilizing multiple redox states, combined with reversible magnetic and optical changes, makes this complex appealing for molecular electronics and switchable materials. These findings also illustrate how fine tuning of the metallic centre environment can enhance the electronic properties of such polynuclear complexes.
