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PhotoSwitchable Chain Magnet – PhotoSCM

PhotoSwitchable Chain Magnet

This project is developped in the M3 (“magnetic Molecular Materials”) group of the CRPP (Centre de Recherche Paul Pascal) located at Pessac. It also involves a strong collaboration with the “molecular science “ group of the ICMCB (Institut de Chimie de la Matière Condensée de Bordeaux). The project consists in the preparation and characterizations of photo-switchable single-chain magnets, made of the one-dimensional assemblies of Single Molecule Magnets (SMM) and photomagnetic building blocks.

New photoswitchable materials for data-storage

This work will contribute to the wide research on multifunctional memories at the nanoscopic scale. The aim is to prepare photoswitchable chain magnets that combine photoswitchability with slow relaxation of the magnetization.<br />To obtain photoswitchable single-chain magnets, single molecule magnets (SMMs) will be linked by (i) spin-crossover complexes (ii) electron transfer pairs. At low temperature and before irradiation, the SMM will not interact, separated by diamagnetic building blocks. Under light irradiation, the photomagnetic builging blocks reach the paramagnetic state, which will create interactions between SMMs and should induce a SCM behaviour. Strong work will be devoted to the preparation of the chains made from spin crossover complexes and SMMs that keep the physical properties of the constitutive building-blocks. Moreover, a major challenge will concern the synthesis of solution stable electron transfer pairs that present a photomagnetic effect at the solid state, still unreported by now. Then, the association of the electron transfer pairs with SMM will also be an issue, because it will imply the formation of heterotrimetallic compounds, which is not trivial.

For the preparation of one-dimensional compounds made of the association of SMM and spin-crossover complexes, the molecules [Fe(LN5)(CN)2].H2O and [Fe(LN3O2)(CN)2].H2O will be prepared first because they display two cyanide groups in axial positions allowing the bridging of two SMMs and favoring a priori a one-dimensional assembly. Then, their ability to be connected to cyclic metallo-ligands with labile axial ligands will be tested and the photomagnetic properties of these complexes integrated in a coordination network at the solid state will be studied. The complexes will be then coordinated to robust SMMs that possess a high ground spin state and two labile axial ligands, and complete photomagnetic and magnetic properties of such coordination network will be measured.
The synthesis of FeIII-CN-CoII photomagnetic pairs will be achieved from the association of a Co(II) complex, in which the metallic cation is coordinated to a pentadentate ligand to let only one labile position, and a Fe(III) complex with at least 3 cyanide groups that permits the coordination to the Co(II) and the future integration of the pair in a chain of SMMs. The nature of the ligands will be chosen judiciously to promote a thermally activated electron transfer from the Co(II) to the Fe(III). Photomagnetic properties of these pairs at the solid state will be checked, and their stability in solution before coordinating them to metallo-ligands and SMMs.

The synthesis of the two spin-crossover systems [Fe(LN5)(CN)2].H2O and [Fe(LN3O2)(CN)2].H2O have been carried out following the synthesis reported. ). First, their ability of connecting mononuclear paramagnetic complexes via their cyanide group is explored. In this respect, some paramagnetic complexes based on H2acacen ligand and possessing labile axial ligands has been synthesized and characterized. First attempts in order to connect such mononuclear paramagnetic compounds with the previously synthesized photomagnetic building blocks have been tried. Even no crystal structures have been obtained so far, some evidences of the connection of paramagnetic mononuclear compounds [Cu(acacen)] with the spin-crossover photoswitchable units have been shown by infrared spectroscopy.
Moreover, the synthesis of the electron transfer dinuclear complex [(Tp)FeIII(CN)3CoII(PY5Me2)](OTf) ·2DMF that successfully present a photomagnetic effect at the solid state was achieved as part of the project. The synthesis of a Co(II) complex with a unique coordination site, based on the pentadentate ligand 2,6-bis(bis(2-pyridyl)-méthyl,méthyl-methyl)pyridine (PY5Me2)2 permitted the preparation of a FeIII-CN-CoII pair by reaction with the complex [FeIII(Tp)(CN)3] (Tp = trispyrazolylborate, OTf = trifluoromethylsulfonate). After drying, the compound presents a thermally and photo- induced electron transfer, showing remarkable magnetic and photomagnetic properties.

To study the electron transfer phenomenon at the local scale on the [(Tp)FeIII(CN)3CoII(PY5Me2)](OTf) pairs, X-ray magnetic circular dichroism are in progress, as part of a collaboration with Marie-Anne Arrio, Philippe Sainctavit et Sadaf Jafri (IMPMC, Paris VI).
The influence of the counteranion in the physical properties of the pairs is also considered and the pair [(Tp)FeIII(CN)3CoII(PY5Me2)](PF6).2DMF prepared from KPF6 is under investigation.
Most of future work will be dedicated to the synthesis of a panel of SMMs, the preparation based on SMMs and the photomagnetic units know available and the study of their magnetic properties.

A cyanido-bridged dinuclear Fe/Co complex mimicing the switchable properties of Prussian Blue analogues, Evangelia Koumousi, Ie-Rang Jeon, Pierre Dechambenoit, Florence Volatron, Danny Woodruf, Xiao Jia, Qian Gao, Dong Feng Li, Corine Mathonière, Rodolphe Clérac, J. Am. Chem. Soc., in preparation

This project will be conducted by the young scientist Florence Volatron in the M3 (“magnetic Molecular Materials”) group of the CRPP (Centre de Recherche Paul Pascal) located at Pessac. It will also involve a strong collaboration with the “molecular science “ group of the ICMCB (Institut de Chimie de la Matière Condensée de Bordeaux). The project consists in the preparation and characterizations of photo-switchable single-chain magnets, made of the one-dimensional assemblies of Single Molecule Magnets (SMM) and photomagnetic building blocks. The main properties intended are (i) a slow relaxation of the magnetization, characteristic of a SMM or a Single Chain Magnet (SCM) behavior, which can confer a magnetic bistability to the system (ii) a photo-control of this magnetic bistability. This work will contribute to the wide research on multifunctional memories at the nanoscopic scale.
The present proposal relies on the research conducted by R. Clérac in the CRPP for the last ten years on the study of SCM and SMM assemblies in extended networks. It is also motivated by the recent work of R. Clérac and C. Mathonière on the detection of a photomagnetic effect on finite objects, ie molecules containing a limited number of electron transfer pairs.
To obtain photoswitchable single-chain magnets, SMM will be linked by (i) spin-crossover complexes (ii) electron transfer pairs. The second point is particularly ambitious since it implies first the synthesis of the photomagnetic bimetallic complexes and personnel staff will be needed to help in the synthesis and physical characterization of the pairs as well as the chains made of the association of these dinuclear complexes with SMM.
The expertise of the candidate in organic synthesis and physical chemistry, as well as the intellectual and geographical proximities of the CRPP and the ICMCB groups will permit to carry through the project.

Project coordination

Florence Volatron (Centre de Recherche Paul Pascal) – florence.volatron@upmc.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

CRPP Centre de Recherche Paul Pascal

Help of the ANR 353,000 euros
Beginning and duration of the scientific project: April 2013 - 30 Months

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