In order to probe the nature and magnitude of the magnetic exchange and anisotropy of the Co II ions further, we now turn to theory (see the computational details in the SI for full details). We have performed DFT calculations on a model of complex 1 (Model 1) based on its ASU, i.e. one [Co moiety plus one linking Co II ion (Fig. ). Based on symmetry and structure there are four unique nearest neighbour magnetic exchange interactions with J values ranging between +1.7 cm -1 ≤ J ≤ +3.8 cm -1 (Table ). The narrow range of ferromagnetic exchange interactions found can be attributed to the similarity of the structural parameters present, including the average Co-µO-Co angles. We have also performed overlap integral calculations using the singly occupied molecular orbitals (SOMOs) of the Co II ions (Fig. ). These help to elucidate the magnitude and sign of magnetic interactions since their magnitude is directly proportional to the magnitude of the antiferromagnetic interaction, i.e. the larger the overlap the larger the antiferromagnetic interaction and vice versa. For 1, there are three intermediate and six small overlap interactions, resulting in a small ferromagnetic interaction overall. Interestingly, replacement of the phenoxide group in Model 1 with a point charge changes the sign of the magnetic interaction from ferromagnetic to antiferromagnetic (4.2 cm -1 to -3.4 cm -1 ), highlighting the importance of this moiety for obtaining ferromagnetic exchange. We have also calculated the next-nearest neighbour exchange mediated via the syn, anti-O-C-O(carboxylate). These are weak and antiferromagnetic, with J < -0.2 cm -1 (Fig. ).