All the Co II ions in 1 are in distorted octahedral geometries (Table ), with previous magnetostructural studies suggesting such ions would possess large easy-plane anisotropy. Ab initio NEVPT2 calculations on each Co II ion in 1 confirms this, with values in the range +41.2 ≤ D ≤ +87.1 cm -1 . The dominant contribution to D arises from the dxz/yz  dxy electronic transition (Table , Fig. ). Positive axial zero-field splitting can be attributed to electronic transitions between orbitals with different mL levels and the magnitude correlated to the energy separation between the orbitals involved in the electronic transition (Table , Fig. ).