Expansion of a Discrete [3 × 3] Mn9 Metallogrid to a µ-Carboxylato-Bridged Polymeric {Mn11}n Assembly

Compounds based on the [3 × 3] nonamanganese(II) square grid motif and featuring additional manganese(II) ions linked to the grid core were isolated through a strict self-assembly approach. Extended tritopic picolinic dihydrazide ligands were used, which contain terminal ester groups and differ in the R substituent on the para position of the central pyridine ring (H2L1, R = OCH3; H2L2, R = H). Upon reaction with Mn(OAc)2·4H2O, the ligand H2L1 undergoes hydrolysis and spontaneous self-assembly to afford [Mn10(L1′)6(H2O)5][Mn(H2O)6]2·11H2O, where a pentaaquomanganese(II) unit is connected to one of the terminal carboxylate functions of the grid through a Mn–O bond. The same reaction carried out with H2L2 affords an unprecedented 2D polymeric structure [Mn11(L2′)6(H2O)8][Mn(H2O)6]·24H2O, in which each nonamanganese grid is connected to its four neighbors through tetraaquomanganese(II) centers, again linked to the carboxylate functions. The two compounds also contain [Mn(H2O)6]2+ complexes in the lattice. These metallogrid-based compounds, for which DC magnetic data were collected and analysed in detail, emphasize the rich binding affinity and bridging versatility of the used ligands, which provide access to both discrete complexes and extended polymeric assemblies.