Graphene related magnetic materials: micromechanical exfoliation of 2D layered magnets based on bimetallic anilate complexes with inserted [FeIII(acac2-trien)]+ and [FeIII(sal2-trien)]+ molecules

Abstract

The syntheses, structures and magnetic properties of the coordination compounds of formula [Fe^III(acac₂-trien)][Mn^IICr^III(Cl₂ An)₃]·(CH₃CN)₂ (1), [Fe^III(acac₂-trien)][Mn^IICr^III(Br₂An)₃]·(CH₃CN)₂ (2) and [Ga^III(acac₂-trien)][Mn^IICr^III(Br₂An)₃]·(CH₃CN)₂ (3) are reported. They exhibit a 2D anionic network formed by Mn(II) and Cr(III) ions linked through anilate ligands, while the [Fe^III(acac₂-trien)]⁺ or [Ga^III(acac₂-trien)]⁺ charge-compensating cations are placed inside the hexagonal channels of the 2D network, instead of being inserted in the interlamellar spacing. Thus, these crystals are formed by hybrid layers assembled through van der Waals interactions. The magnetic properties indicate that these compounds behave as magnets exhibiting a long-range ferrimagnetic ordering at ca. 11 K, while the inserted Fe(III) cations remain in the high-spin state. As for graphene, these layered materials can be exfoliated in atomically-thin layers with heights down to 2 nm by using the well-known Scotch tape method. Hence, this micromechanical procedure provides a suitable way to isolate ultrathin layers of this kind of graphene related magnetic materials. Interestingly, this method can also be successfully used to exfoliate the 2D anilate-based compound [Fe^III(sal₂-trien)][Mn^IICr^III(Cl₂An)₃]·solv (4), which exhibits the typical alternated cation/anion layered structure. This result shows that the micromechanical exfoliation method, which has been extensively used for exfoliating van der Waals layered solids, can also be useful for exfoliating layered coordination compounds, even when they are formed by ionic components.