d-Orbital orientation in a dimer cobalt complex: link to magnetic properties?

The experimental charge-density distribution of the dinuclear cobalt(II) complex [Co(2)(sym-hmp)(2)](BPh(4))(2)·2H(2)O·2C(3)H(6)O was determined at 100 K. When decreasing the temperature, the magnetic susceptibility of this complex deviates from Curie law because of anti-ferromagnetic exchange interactions, but the susceptibility increases sharply at low temperature (< 20 K). To explain this magnetic behaviour a tilt angle between the Co-atom environments was previously theoretically predicted. The structure and experimental charge density determined in this study show a tilt angle. The calculated value, based on the 100 K experimental d-orbital model, is in agreement with the theoretical one.