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Conducting Anilate-Based Mixed-Valence Fe(II)Fe(III) Coordination Polymer: Smallpolaron Hopping Model for Oxalate-Type Fe(II)Fe(III) 2D Networks

S. Sahadevan, A. Abhervé, N. Monni, C. Sáenz de Pipaón, J. R. Galan-Mascaros, J. Waerenborgh, B. Vieira, P. Auban-Senzier, S. Pillet, E. Bendeif, P. Alemany, E. Canadell, M.L. Mercuri, N. Avarvari.
J. Am. Chem. Soc., 140 (2018) 12611-12621.

Crystal structure for the coordination polymer highlighting the FeIIFeIII(anilate)3 layers and the directions of electric conductivity and magnetic ordering. The potential energy surface at the right-hand side corresponds to the small-polaron hopping, shown schematically in the top and bottom parts of the figure.

In this work, we report on a multidisciplinar study of the electric and magnetic properties of an interesting coordination polymer formed by iron with the anilate ligand. Our measures show that it is indeed a mixed valence Fe(II)-Fe(III) compound with an unusually high electric conductivity. To answer the question about the origin of this unexpected conductivity we propose a small-polaron hopping model that, in combination with simple quantum chemical calculations for an Fe(anilate)3 monomer, is able to explain why the conductivity should be much higher than in analogous compounds with oxalate or squarate anions.