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

Journal Article · Sat Mar 10 00:00:00 EST 2012 · Journal of Materials Science and Engineering. A

OSTI ID:1336265

Rios-Ramos, Agustín ^[1]; Rivera-Maldonado, Christymarie ^[1]; Garcia-Acosta, Geidy Ines ^[1]; Lozano-Paulino, Cesar Manuel ^[1]; Fierro-Mercado, Pedro Manuel ^[2]; Fuentes-Cobas, Luis ^[3]; Roque-Malherbe, Rolando Marcos ^[1]

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1. Univ. of Turabo, Gurabo (Puerto Rico). Inst. for Physical Chemical Applied Research
2. Univ. of Puerto Rico, Mayaguez (Puerto Rico). Dept. of Chemistry
3. Advanced Materials Research Center, Chihuahua (Mexico)

Here, 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. Furthermore, 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, μ_eff= 4.9 μ_B. Our 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.

• Research Organization: Univ. of Turabo, Gurabo (Puerto Rico)
• Sponsoring Organization: USDOE; National Science Foundation (NSF)
• Grant/Contract Number: NA0000672; CHE-0959334
• OSTI ID: 1336265
• Journal Information: Journal of Materials Science and Engineering. A, Vol. 2012, Issue 3; ISSN 2161-6213
• Publisher: David Publishing
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Metal organic frameworks
oxalic acid
nickel
adsorption
magnetisms