The rational design of new emergent materials is a novel synthetic challenge for materials and inorganic chemists, as their discovery and understanding of their properties promises to revolutionize our understanding of phenomenon such as high temperature superconductivity. A promising platform to explore for this purpose are metal-organic frameworks (MOFs), due to their inherent high-degree of chemical tunability relative to the traditional solid state materials that have been previously investigated in this field. Towards this goal, we describe the synthesis and magnetic characterization of a new 2,5-dihydroxy-1,4-benzoquinone based MOF, (NMe2H2)3.5Ga2(C6O4Cl2)3 (1) which features radical-based electronic spins on the sites of a kagomé lattice, a lattice of corner-sharing equilaterl triangles that is known to engender exotic electronic properties. Vibrational and electronic spectroscopies in combination with magnetic susceptibility measurements reveal 1 hosts mixed valency between the radical-bearing trianionic and diamagnetic tetraanionic oxidation states of the ligand, forming a partially occupied kagomé lattice. We find that gallium mediates ferromagnetic coupling between spins, creating a ferromagnetic kagomé lattice. By modulation of the interlayer spacing via post-synthetic cation metathesis of 1 to (NMe4)3.5Ga2(C6O4Cl2)3 (2) and (NEt4)3.5Ga2(C6O4Cl2)3 (3), we determined the nature of the magnetic coupling between neighboring planes is antiferromagnetic as the magnetic moment increases with increasing layer separation. This combination of magnetic exchange interactions nominates these materials to host topological phenomena.

Synthetic investigation of competing magnetic interactions in 2D metal-organic frameworks

2019 Fall National Meeting

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