Magnetic Anisotropy of a Tri-anionic Complex

The trivalent chromium tri-oxalate complex, {Cr⁺³[(C₂O₄) ^-2]₃}^-3 is known to exist as a tri-anion in water. Such systems are difficult to describe with standard DFT due to the fact the HOMO level of the complex solute is pushed to higher energies than the LUMO levels of the H₂O solvent. The mismatch in the solute/solvent Fermi-levels causes charge transfer from the tri-anion to the water as shown in earlier work. However, the spin of the solute complex is not affected by the unphysical charge transfer. The generalized gradient approximation gives a magnetic anisotropy for the isolated and solvated tri-anion Cr⁺³[(C₂O₄) ^-2]₃}^-3 (H₂O)₂₄ of 0.83 and 0.82 Kelvin respectively. These values of magnetic anisotropy agree with 0.89 Kelvin (0.619 cm^-1), which is derived from measurement [1], and imply that the oxalates lose electrons. In this paper results on the electronic and magnetic structure of the tri-anionic complex in water are presented with and without a self-interaction corrected method as a function of cluster size.

[1] Morgunov, Mushenok, Aldoshin, Yur’eva, Shilov, and Tanimoto, J. Solid State Chem. 182, 1424-1429 (2009).