Acta Crystallographica Section A

Foundations of Crystallography

Volume 60, Part 5 (September 2004)

Acta Cryst. (2004). A60, 382-389 [doi:10.1107/S010876730401699X]

Synchrotron charge-density studies in materials chemistry: 16 K X-ray charge density of a new magnetic metal-organic framework material, [Mn₂(C₈H₄O₄)₂(C₃H₇NO)₂]

R. D. Poulsen, A. Bentien, T. Graber and B. B. Iversen

Abstract: A new magnetic metal-organic framework material, [Mn₂(C₈OH₄₄)₂(C₃H₇NO)₂], has been synthesized. The structure consists of chains of carboxylate-bridged Mn atoms interconnected with acid linkers, giving much larger interchain than intrachain MnMn distances. Magnetic susceptibility data fitted to a Curie-Weiss law give [Theta] = -5.7 K and a total magnetic moment of 5.96 µ_B. The heat capacity provides no evidence of magnetic ordering down to 2 K. The X-ray charge density was determined from multipole modeling of 16 (1) K single-crystal synchrotron-radiation data. The structural surroundings of the two unique Mn centers are different, but orbital population analysis reveals close to single electron occupation in all 3d orbitals of both Mn sites, in agreement with the magnetic susceptibility measurements. Bader topological analysis shows the presence of direct chemical MnMn interactions only in two out of three intrachain contacts, which suggests a `broken' chain. The topological measures and approximate energy densities at the metal-ligand bond critical points ( [bold rho] , [bold nabla] ², G, V and H) indicate ionic interactions. Formal electron counting suggests mixed-valence Mn sites, but this hypothesis is not supported by the Bader atomic charges [q(Mn) = +2.035 and +2.031].

Online 26 August 2004


	PDF file (100.1 kbytes) Topological properties, bond angles around Mn, DTA and TGA graphs

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Acta Crystallographica Section A

Foundations of Crystallography

Volume 60, Part 5 (September 2004)

Synchrotron charge-density studies in materials chemistry: 16 K X-ray charge density of a new magnetic metal-organic framework material, [Mn2(C8H4O4)2(C3H7NO)2]

R. D. Poulsen, A. Bentien, T. Graber and B. B. Iversen

Synchrotron charge-density studies in materials chemistry: 16 K X-ray charge density of a new magnetic metal-organic framework material, [Mn₂(C₈H₄O₄)₂(C₃H₇NO)₂]