Self-assembled polymetallic square grids ([2 x 2] M4, [3 x 3] M-9) and trigonal bipyramidal clusters (M-5) - structural and magnetic properties

New self-assembled grids and clusters are reported, with square [ 2 x 2] M-4 ( M = Mn(II)(4), Cu( II)(4)), trigonal-bipyramidal Mn( II)(5), and square [3 x 3] M-9 ( M = Mn( II), Cu( II)) examples. These are based on a series of ditopic and tritopic hydrazone ligands involving pyridine, pyrimidine and imidazole end groups. In all cases the metal centres are bridged by hydrazone oxygen atoms with large (> 125 degrees) bridge angles, leading to antiferromagnetic exchange for all the Mn systems (J = -2 to -5 cm(-1)), which results in S = 0 (Mn-4), and S = 5/2 (Mn-5, Mn-9) ground states. The copper systems have a 90 degrees alternation of the Jahn - Teller axes within the Cu-4 and Cu-8 grid rings (Cu-9), which leads to magnetic orbital orthogonality, and dominant ferromagnetic coupling. For the Cu-9 grid antiferromagnetic exchange between the ring and the central copper leads to a S = 7/2 ground state, while for the Cu-4 grids S = 4/2 ground states are observed. The magnetic data have been treated using isotropic exchange models in the cases of the Cu-4 and Cu-9 grids, and the Mn5 clusters. However due to the enormity of a fully isotropic calculation a simplified model is used for the Mn-9 grid, in which the outer Mn-8 ring is treated as the equivalent of an isolated magnetic chain, with no coupling to the central metal ion.