For full details of the computational methodology, see the SI. Analysis of the structures of 3 and 4 reveals a total of six different exchange interactions (J1-6), as shown in Figure . The magnitude and sign of the DFT calculated exchange constants is provided in Table , alongside pertinent structural information describing the bond distances and angles in each pairwise interaction. In each case the sign and magnitude of the J values obtained can be easily explained via magneto-structural correlations previously published for O-bridged Mn II/III complexes, and are in close agreement with those calculated for a mixed-valent [Mn III 2Mn cage published by Milios and co-workers. For complex 3, the J values are all found to be weakly antiferromagnetic (-0.2 ≤ J ≤ -4.8 cm -1 ), with J1 the strongest and J5 the weakest. J1 is mediated between the two central Mn II ions via two µ3-OH bridges, with (short) Mn-O/Mn-Mn distances of 1.99/3.00 Å and (relatively acute) Mn-O-Mn of angles of 97.7°. The J2-J5 interactions are more weakly antiferromagnetic than J1 due to the larger Mn-O-Mn angles and larger Mn-O/Mn-Mn distances present. The value of J6, bridged by a single Mn III -µOR-Mn II unit is comparable to that of J1 due to the large Mn-O-Mnangle (116.0°). Magneto-structural correlation of such units predict antiferromagnetic exchange in the range of ~5 cm -1 . Based on these J values complex 3 has an S = 2 ground state (Fig. ).