Polytopic picolinic hydrazone ligands show a remarkable ability to direct self-assembly reactions with transition metal ions to produce square µ-O bridged [nxn] spin-coupled grids (n = 2,3) in high yield. Cu₄ [2x2] and Cu₉ [3x3] examples exhibit overall ferromagnetic behavior, while antiferromagnetic exchange prevails with other metals.¹ The ground state spin of Mn(II)₉ [3x3] grids can be modulated by site specific oxidation of Mn(II) to Mn(III), or heterometal substitution at certain grid sites leading to ferrimagnetic behaviour, and high spin ground states in some cases. Ligand modifications with large heterocyclic end groups (L1) lead to rectangular Mn₉ grids with both µ-O and µ-N-N bridges. Homometallic Mn₉ systems and heterometallic Mn/Cu, Mn/Zn and Mn/Ni mixed metal grids will be discussed. Extended tetratopic and pentatopic ligands have increased coordination capacity, and lead to linear spiral antiferromagnetic Mn₄ chains (L2), and antiferromagnetic square Mn₁₆ [4x4] (L3), and Mn₂₅ [5x5] (L4) grids. Structures, magnetic and electronic properties and surface studies will be discussed, with a view to using such systems in a nanoscale device capacity. 1. L.K. Thompson et al, Coord. Chem. Rev. 2005, 249, 2677.