In order to function as a single-molecule magnet (SMM), a molecule must have a combination of a large spin ground state (S) and large and negative magnetoanisotropy. The synthesis of such molecules is difficult and relies on the self-assembly of metal ions with organic bridging ligands. This paper discusses the synthesis, structures and initial magnetic properties of three new manganese carboxylate clusters: one octanuclear and two enneanuclear clusters which feature new topologies of metal ions and demonstrate how simple changes in geometry can alter the magnetic properties of a cluster.