Exchange interactions in Ti2Cl3- 9 and the magnetic susceptibility tensor

Calculated exchange interactions in Ti²Cl^3- ₉ by the CASSCF method are combined with parametric expressions of metal-centred spin—orbit coupling and Zeeman splittings to predict the temperature dependence of the magnetic susceptibility tensor between 0 and 300 K. The results correctly reproduce the experimental anisotropy at 0 K, the onset of the magnetization and the slope of the susceptibility curve. The discussion confronts the theoretical treatment with existing semi-empirical magnetic models. A ¹A′₁(a × a) → 1E′(a × e) assignment is proposed for the weak absorption feature in the infrared reflectance spectrum.