Synthesis and study of new magnetic hybrid materials : Toward liquid crystal systems – MagnLC

In the field of liquid crystals, the incorporation of metal ions into the mesogenic objects has received great interest in recent decades. This intense research activity was firstly motivated by the possibility to orient more easily the mesophases under a magnetic field. Therefore, the strategy used, consists to functionalize the mesogenic molecules by coordinating groups in order to bind the metal ion. In the fields of molecular materials, the approach for imparting mesomorphic properties to the systems is somehow the reverse to the one used in liquid crystal field. Indeed, the applied strategy consists to modify the organic part of molecular objects by functions known to induce liquid-crystal phases. In the project, we use this second approach to develop new magnetic hybrids with liquid-crystal properties.

In this project, we develop magnetic hybrids starting from well-known molecular systems which belong to the families of single-molecule magnets, spin crossover compounds or electron transfer systems. Notably, we work on the dodecanuclear complex [Mn12O12(OAc)16(H2O)4] which is probably the most famous and studied single-molecule magnet. By exchanging the sixteen acetate ligands by mesogenic ligands, we obtained new magnetic hybrids that self-organize into interesting cubic or smectic mesophases. Currently, we are working on new functionalization in order to induce new mesomorphic behaviors such as nematic or columnar phases.
We also work on spin crossover systems such as the coordination polymer [Fe(RTrz)3](A)2 (with RTrz = 4-substituent-1,2,4-triazole; A = monovalent anion). We have previously shown that these materials can self-organize as gels or liquid crystals. We are now applying new ligand design strategies to enhance the mesogenic and magnetic properties of these materials.

For the rest of the project, we plan to continue our work on the design of magnetic hybrids based on [Mn12O12(RCOO)16(H2O)4] and [Fe(RTrz)3](A)2 systems. We also project to extent our studies to additional magnetic materials including spin crossover complexes and electron transfer compounds.

Two papers are in preparation for publication in peer-reviewed journals

The aim of the MagnLC project is to develop and study molecular magnetic materials with liquid crystalline properties. During the last decades, molecular magnetic materials have received much interest for their original physical properties and their potential applications. Indeed, these compounds can exhibit uncommon or previously unknown magnetic properties compared with traditional inorganic materials. These properties include spin crossover, photomagnetism, single-molecule magnets or single-chain magnets behaviors. Thus, these magnetic objects have been proposed as potential candidates for novel applications, including for data storage devices that offer prospect for reducing the size of magnetic storage units to the nanometer scale or the molecular level. Although these properties and their potential may be realized, it is often difficult to transition to the next step that involves fabrication of the materials into a functioning device. It is now appropriate to direct research efforts towards the organization of these kinds of compounds onto technologically sustainable systems for future applications. An interesting approach is to use self-organization of the matter in fluid systems such as gels or liquid crystals. The MagnLC project takes place in this emerging field. We plan to develop and study new magnetic hybrid materials obtained from well-known molecular magnetic compounds, which will be chemically modified in order to induce mesogenic properties. This strategy will be applied to several interesting compounds including single-molecule magnets (in particular the dodecanuclear complex [Mn12O12(OAc)16(H2O)4]) and spin crossover compounds like the linear coordination polymer [Fe(RTrz)3](A)2 (with RTrz = 4-substitued-1,2,4-triazole; A = monovalent anion) and the mononuclear complex [Fe(bpy)2(X)2] (with bpy = 2,2-bipyridine, X = monovalent anion). All these systems possess physical properties and potential, which have already been highlighted through numerous studies. This work will allow for significant enhancement of these magnetic materials and an important advance in this emerging research field.

This basic interdisciplinary research project will be conducted at the Centre de Recherche Paul Pascal (CRPP, CNRS, UPR-8641) in the Magnetic Molecular Materials group (M3) which offers an ideal environment in terms of facilities and scientific expertise for carrying out such research.