We propose that this discrepancy likely arises from different crystallographic domains or polymorphs in the magnetic data which is necessarily on a bulk polycrystalline sample. The variable temperature crystallographic data on this compound demonstrates that at least two closely related crystallographic polymorphs are accessible which permit different Cr-Cr distances. Therefore, the presence of different crystallites/polymorphs in a bulk sample for variable temperature magnetic susceptibility could feasibly give rise to a mixture of S = 1 and S = 2 species. Our theoretical results demonstrate that some of these molecules should stay in an S = 2 state upon cooling, while others can undergo spin-crossover to an S = 1 state, consistent with the observed magnetic behavior. However, our calculations do not consider the bulk composition of different polymorphs or crystallites. Therefore, it is not surprising that our theoretical calculations on isolated dimers, which unambiguously predict an S = 2 ground state for T > 150 K (and therefore an ideal asymptotic magnetic susceptibility of χT ≈ 3 cm 3 K mol -1 ), imperfectly model the experimental data at high temperatures (see Figure ).