Two-dimensional magnetic coordination polymers: tuning the surface and the magnetic properties.

Magnetic two-dimensional (2D) materials have emerged recently with examples of inorganic monolayers like antiferromagnets (FePS₃) [Nano Letters 16, 7433, 2016; 2D Materials 3, 031009, 2016] and highly unstable ferromagnets such as CrI₃ [Nature 546, 270, 2017] or Fe₃GeTe₂ [Nature Materials 17, 778. 2018].
To overcome the present unstabilities of 2D magnetic materials, we take advantage of layered molecular magnets since, thanks to the chemical design, it is feasible to bring new magnetic scenarios as well as to overcome the present unstabilities of 2D magnetic materials. Here [Nature Chemistry 10, 1001, 2018 and unpublished data] we present a pre-synthetic method based on coordination chemistry that affords the isolation of crystalline molecular monolayers. The concept is illustrated using layered coordination polymers formed by reacting various benzimidazole derivatives with ferrocene. By the election of the proper ligand and the metal source, it is possible to tune the surface properties as well as the magnetism. Moreover, the magnetic order of the flakes is probed by its integration into membranes. Therefore, these new 2D molecular materials are exceptional candidates for studying the magnetism in the 2D limit, as well as for developing membranes for selective molecular sensing.