To further support the relative sign and magnitude of the exchange interactions obtained experimentally, we have performed DFT calculations on both dimeric and trimeric models derived from the full structure of 1 (Figures ; see ESI for computational details). This affords Jring = +4.1 cm -1 and Jcap = -30.1 cm -1 for the dimeric model, and Jring = +2.1 cm -1 and Jcap = -30.4 cm -1 for the trimeric model. We have also performed overlap integral calculations between the singly occupied molecular orbitals of the Fe III ions. These suggest three moderate magnetic orbital overlaps for Jring resulting in small ferromagnetic interactions (Table , Figure ), and one strong and ten moderate magnetic orbital overlaps for Jcap leading to strong antiferromagnetic interactions (Table , Figure ). Spin density analysis indicates the presence of a strong spin delocalization mechanism, as seen previously for other polymetallic iron complexes (Figure ). 20 In conclusion, the simple reaction between anhydrous FeBr3 and MeO-py results in the formation of an cluster whose metallic skeleton conforms to a hexagonal bipyramid, and whose metaloxygen core is related to the mineral magnetite. Magnetic measurements reveal antiferromagnetic exchange between the two capping tetrahedral Fe III ions and the six ring octahedral Fe III ions leading to an S = 10 ground state. The ease of synthesis and the striking structural similarity of [Fe8] to other molecular iron oxides such as [Fe13], [Fe17], [Fe30] and [Fe34] suggests that many more such species with much larger nuclearities remain undiscovered.