Synthesis, Structure, Adsorption Space and Magnetic Properties of Ni-oxalate Porous Molecular Magnet

We synthesized about sixty metal organic materials. Only three were metal organic frameworks （MOFs）. One of them was a porous molecular magnet （PMM）. For the PMM synthesis Ni was the node, oxalic acid the organic linker and DMF the solvent and shaping molecule. This PMM was studied with DRIFTS, Raman spectrometry, TGA, XRD, adsorption and with a VSM TGA and adsorption data indicated that a microporous material with a pore volume, W = 0.10 ~ 0.01 cm3/g was obtained. The analysis of the XRD profile indicated that it is a layered compound. The DRIFTS, Raman and XRD data revealed that each layer is formed by nickel cations linked by bis-bidentate and bridging-bis-bidentate oxalate ligands and the DMF molecules are perpendicularly linked to the nickel cations to produce stacking. Additionally, the Raman data allowed us to propose that the nickel cations are located in octahedral and pentacoordinated sites as Ni2＋ and Ni3＋. The Pawley fitting of the XRD profiles pointed out that the hydrated sample crystallizes in the P2/m space group. The cell parameters calculated are consistent with the proposed structure. Two different adsorption states showing different adsorption energies, in the physical adsorption range, were observed. The small amount estimated for the dispersive and quadrupole adsorption interaction energies was a confirmation of the proposed layered structure. The VSM study yielded an effective magnetic moment,/J,~= 4.9/~8. This figure is consistent with nickel located in octahedral and pentacoordinated sites as Ni2＋ and Ni3~. We had then obtained a new Ni-oxalic porous molecular magnet （Ni-Ox-PMM）. The significance of this PMM is related to its porosity, that is, during degassing it release water turning into a porous stable structure, showing notable magnetic properties. In this case been porous, it means that the electronic structure of the nickel cations can be manipulated from outside with adsorbed molecules. Thereafter, the material could sense small molecules.