title: Single-ion magnetic anisotropy and isotropic magnetic couplings in the metal-organic framework Fe2(dobdc).
abstract: The metal-organic framework Fe2(dobdc) (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate), often referred to as Fe-MOF-74, possesses many interesting properties such as a high selectivity in olefin/paraffin separations. This compound contains open-shell Fe(II) ions with open coordination sites which may have large single-ion magnetic anisotropies, as well as isotropic couplings between the nearest and next nearest neighbor magnetic sites. To complement a previous analysis of experimental data made by considering only isotropic couplings [Bloch et al. Science 2012, 335, 1606], the magnitude of the main magnetic interactions are here assessed with quantum chemical calculations performed on a finite size cluster. It is shown that the single-ion anisotropy is governed by same-spin spin-orbit interactions (i.e., weak crystal-field regime), and that this effect is not negligible compared to the nearest neighbor isotropic couplings. Additional magnetic data reveal a metamagnetic behavior at low temperature. This effect can be attributed to various microscopic interactions, and the most probable scenarios are discussed.
authors.affiliation: Department of Chemistry, Supercomputing Institute, and Chemical Theory Center, University of Minnesota, Minneapolis, Minnesota 55455, United States.
authors.forename: Rémi
authors.initials: R
authors.lastname: Maurice
authors.forename: Pragya
authors.initials: P
authors.lastname: Verma
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Zadrozny
authors.forename: Sijie
authors.initials: S
authors.lastname: Luo
authors.forename: Joshua
authors.initials: J
authors.lastname: Borycz
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Long
authors.forename: Donald G
authors.initials: DG
authors.lastname: Truhlar
authors.forename: Laura
authors.initials: L
authors.lastname: Gagliardi
mesh_terms: D016880:Anisotropy; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D060526:Magnetic Fields; D008958:Models, Molecular; D010795:Phthalic Acids / Q000737:chemistry*; D013696:Temperature
chemical_list: D005296:Ferrous Compounds; D007477:Ions; D010795:Phthalic Acids