Tailoring Non-Innocence in a Family of 2D Coordination Solids

Metal-organic frameworks (MOFs) and their non-porous analogues, coordination solids, constitute a new class of materials with highly multifaceted physical and chemical properties and virtually unlimited possibilities for synthetic modification and tuning. The realization of magnetic MOFs has been hampered by the large spatial separation between spin-carriers leading to magnetic order setting in at only low temperatures. A particularly attractive approach to magnetic MOFs is rooted in the use of radical ligands as spacers between paramagnetic metal ions, which alleviates the inter-metallic distance issue and have resulted in materials featuring extremely strong super-exchange interactions. Unfortunately, relatively few isolatable radical ligands possess the stability to allow their incorporation into MOF structures. An interesting approach to realize otherwise elusive radical ligands consists in the use of highly reducible metal ions, that will reduce even ligands considered wholly redox-inactive. We recently reported a quadratic, 2D coordination solid, CrCl₂(pyrazine)₂, that features Cr(III) and a partially reduced ligand scaffold, ensuing strong magnetic Cr(III)-radical exchange interactions [1].
In this talk, recent progress in the development of metal-organic solids with extremely strong magnetic exchange interactions will be presented. Focussing on a family of isostructural, quadratic 2D coordination solids, MX₂(pyrazine)₂, we show (1) how the occurrence of redox events between the metal ion, M, and the pyrazine ligand may be controlled by chemical tuning and external stimuli, and (2) how the macroscopic materials properties (magnetic, conductive, optical) relate to the redox state of the coordination solid.

1) K. S. Pedersen, P. Perlepe, M. L. Aubrey, D. N. Woodruff, S. E. Reyes-Lillo, A. Reinholdt, L. Voigt, Z. Li, K. Borup, M. Rouzieres, D. Samohvalov, F. Wilhelm, A. Rogalev, J. B. Neaton, J. R. Long, R. Clérac, Nat. Chem. 2018, 10, 1056.