Spin crossover
= Spin crossover
<Spin crossover> interconverts electronic states with different total <spin>, often in response to <temperature>. For octahedral <iron>(II), $t_{2g}^4e_g^2$ and $t_{2g}^6$ correspond to $S=2$ and $S=0$. Removing <electrons> from <metal>–ligand antibonding $e_g$ orbitals shortens bonds in the low-<spin> state. Crystal packing and <hydrogen bonds> can affect transition temperatures.