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Résumé: Developed in the 1980s, dendrimer chemistry has opened up new perspectives in fields as diverse as catalysis, molecular electronics and artificial photosynthesis.[1] Surprisingly, however, magnetic dendrimers are not common in the literature due to puzzling difficulties in their synthesis and characterization.[2] In this context, the design of such multimetallic and monodisperse starburst architectures, endowed with magnetic properties, is therefore a real challenge.[3]
Following a supramolecular “complex as ligand” approach, we succeeded in this challenge by carrying out the synthesis, characterization (including X-Ray diffraction) and study of magnetic dendrimers. Our synthetic strategy essentially relies on (i) oxalate-based coordination chemistry as the core of the architecture and (ii) trinuclear complexes, LnCo2 for the branches (with Ln a lanthanide and Co, the Klaui ligand) that feature single-molecule magnet properties. The combination of these two building blocks allows us to obtain supramolecular and dendritic assemblies.
The versatility of this approach makes it possible to anticipate the properties according to the choice of metal cations involved in the structure (single molecule magnets or giant spin values, etc.). Thus we obtained hetero-tri-metallic magnetic dendrimers, MLn3Co6 and ZrLn4Co8 (with M=Co or Cr, and Ln=La, Tb, Dy, Er, …) fully characterized by X-ray diffraction.[3] The magnetic properties are in good agreement with the expected theoretical models. This type of compound could be of great interest for applications in information storage or magnetic refrigeration.
References :
[1] Astruc, D; Boisselier, E; Ornelas, C; Chem. Rev. 2010, 110 (4), 1857-1959.
[2] Racja, A; Wongsriratanakul, J ; Racja, S; Cerny, R; Angew. Chem. Int. Ed. 1998, 37 (9), 1229-1232.
[3] Suzana, I; Pécou, C; Forté, J; ; Rupf, S; Rousset, E; Rahman, A; Klemke, B; Von Barbeleden, J; Pillet, S; Marvaud, V; Malischewski, M, manuscript in preparation
