Direct current (dc) magnetic susceptibility studies were performed on a polycrystalline sample of 3 over the temperature range T = 2-298 K, in an applied magnetic field B = 0.1 T (Fig. ), where χ = M/B and M is the magnetisation. At 298 K, the χMT value of 37.4 cm 3 mol -1 K is in agreement with the expected value for spin-only contributions to the susceptibility for a [Mn III 4Mn unit (38.25 cm 3 mol - 1 K, g = 2.0). Upon cooling, the χMT product decreases slowly until approximately T = 100 K, wherefrom it decreases more rapidly, reaching a value of 8.6 cm 3 mol -1 K at 2 K. Variable-temperature-variablefield (VTVB) magnetisation data (inset of Fig. , Fig. ) shows M rising slowly with increasing B, reaching a maximum value of M = 17.6 µB at 7 T but without saturating. Both are suggestive of the presence of weak, competing exchange interactions dominated by the antiferromagnetic contributions. The large nuclearity of 3 and the presence of six different exchange interactions prevents a quantitative analysis of the susceptibility and magnetisation data. Previously published Mn complexes of TBC [4] and H8L show that exchange interactions tend to be relatively weak, with JMn(III)-Mn(II) being weakly ferromagnetic, JMn(II)-Mn(II) being weakly antiferromagnetic and JMn(III)-Mn(III) being borderline anti/ferromagnetic. In order to investigate this in more detail, we now turn to theory.