Comments on the structure of copper (II) oxalate: Discussion of X-ray powder diffraction and EXAFS results as a basis for the interpretation of magnetic properties

Some features of the crystal structure of Cu(II) oxalate, which are relevant for the interpretation of unusual magnetic properties of the substance, are discussed. EXAFS and X-ray powder diffraction results described by different authors are compared. The results of both the analytical methods complement each other. The packing of the ribbon-like structural units consisting of Cu²⁺ and (C₂O₄)²⁻ ions is demonstrated. It is shown that the Cu ions are octahedrally coordinated by O atoms (four short and two long Cu-O distances). The environment of a central Cu ion with other Cu ions is discussed in terms of intra- and inter-ribbon distances. In view of the structural characteristics of Cu(II) oxalate it seems to be not justified to disregard the interaction between neighbouring ribbons in the discussion of the magnetic coupling, as done so far.