Lescouëzec, et coll.
... used to design
Electro-Active Materials
e.g. switchable thin films for molecular electronic
e.g. intercalation materials for battery
e.g. electrochromism
News
Buqin Xu, Yanling Li & Co.
When the quest for understanding a very interesting behaviour (bistability in a Charge Transfer complex created by pressure) reveals the complex response of molecular switchable materials to pressure application,... and raises new questions.
One of the keep home message On the origin of the cooperativity in Magnetic Switches : SC-XRD at different pressures allows revealing which one of the supramolecular interactions is really efficient in promoting elastic interaction responsible for cooperativity.
More details in J. Chem. Mater. 2024 , 10.1021/acs.chemmater.4c02347
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Yanling Li's Habilitation
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"Molecular nanomagnets
and molecular switches
towards piezo-switchable systems"
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08 Sept. 2022
Discrete A{Fe4Co4} cubic cages were used as model compounds to enlighten the alkali ion role on the photo-induced Electron Transfer. The confrontation of different studies, including original (i) photomagnetic properties in frozen solution (ii) variable temperature CV experiments , allow to correlate the stabilization of the photo-induced metastable state (and the amplitude of Ea) with the overall structural reorganization accompanying the diamagnetic <=> paramagnetic conversion. Smaller alkali ions stabilize the paramagnetic metastable state through the amplitude of the structural reorganization they impulse (horizontal displacement in the E versus S.R. curve) rather than by a thermodynamic stabilization of the metastable state (vertical displacement).
Much more details in J. Am. Chem. Soc., 2022 DOI : 10.1021/jacs.2c03421
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Cs{Fe4Co4} pro-cubes were shown to be stable in DMF solution. By reacting these polylmetallic building units with Tp blocking ligands, molecular cubes readily form. In contrast, the use of Tp-Ar-Tp bridging ligands leads to insoluble polymeric material. While the emectronic state of the molecular cubes can be switched through a photo-induced Fe-Co electron transfer, the polymeric network shows a thermally-induced electron transfer above room-temperature. Interestingly, the electron transfer and the resulting magnetic states of the polymeric material are shown to critically depend on its hydration state, indicating the capability of the material to act as a chemo-sensor.
More in J. Mat. Chem. C , 2021 DOI : 10.1039/D1TC01825F
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The [Fe(C6F5Tp)2] complex is converted through melting and recrystallization at high-T from a kinetic crystal phase (1) showing an extremely gradual spin-crossover to a thermodynamic crystal phase (2) showing a broad hysteretic spin-transition. The uncommon “rounded” hysteresis occurs in a non-cooperative SCO system. It is due to a symmetry-breaking phase transition that is triggered when roughly ca. 50% of the SCO complexes are switched from the low-spin state to the high-spin state or, conversely from the HS state to the LS state.
More in Angew. Chem. Int. Ed. 2021 DOI : 10.1002/anie.202015994
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Cs⊂{Fe4Fe4} cube can be reversibly converted into 9 different redox states in solution. By changing the electric potential, LMCT, MLCT and MMCT transitions can be switched on and off leading to at least 3 very different optical signatures.
Not only that ! The cube is also a MMS, showing a Spin-transition in the neutral form in the solide-state
More in Chem. Commun. 2020 DOI : 10.1039/D0CC04279J
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Yanling Li & Co
The investigated Fe2Co2 square complex shows a Fe(III/II)-Co(II/III) Electron Transfer equilibrium in MeOH solution, with Teq near 0°C. Crystallization at 35°C allows isolating the square in its paramagnetic FeIII-CoII electronic state (see Part I, RSC Adv. 2016 S. De et al.).
Here we showed that application of pressure allows recovering a Fe(III)Co(II) <=> Fe(II)-Co(III) Electron Transfer Transition in the solid-state.
Remarkably, the FeCo shows an unusual p-enhanced hysteresis that allows reaching bistability at room temperature.
More in Angew. Chem. 2020 DOI : 10.1002/anie.202008051
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Amina Benchohra & Co
Many efforts are currently devoted in depositing ultra-thin layers of SCO Molecular Switches onto surfaces. Most of the time, researchers use evaporation methods applied to robust neutral monometallic complexes. Things are more complicated with polymetallic charged complexes that can undergo dissociation, etc... unless you find the good way.
Here we showed with the help of the colleagues from LRS lab (Sorbonne Univ.) that EI allows depositing cubes onto Gold(111)
What's Next ? Probing that the switching properties are preserved, another story...
More in Chem. Commun. 2020 DOI :10.1039/D0CC01906B
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While the switchable properties of the FeCo PBA (first observed by Sato et al in 1996) can be "easily" transferred to discrete molecular systems, things seem much more complicated in the case of the FeMn systems... After some efforts studying cyanide-bridged FeMn systems showing intringuing behaviours, we decided to publish that cube, which shows a fragile transition ascribed to a FeMn electron transfer, together with interesting electrochromic properties ...
More in Angew. Chem. 2020, DOI: 10.1002/anie.201916199
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Juan Jiménez, Akira Sugahara & Co
In the frame of an ANR-JST joined project, we have been investigated the intercalation of cation into cyanido-molecular materials.
In this work Juan and Akira showed that "simple" monodimentional cyanide-bridged complex can reversibly intercalate Li+ ions. Although the material becomes amorphous during the Li intercalation process, crystallinity is recovered once the Li is removed. All the process can be repeated at least 20 times without significant loss of capacity.
More in Chem. Comm. 2018 DOI : 10.1039/C8CC01374H
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