[M(N3)2(H2O)2]⋅(bpeado): Unusual Antiferromagnetic Heisenberg Chain (M=Mn) and Ferromagnetic Ising Chain (M=Co) with Large Coercivity and Magnetic Relaxation (bpeado=1,2-Bis(4-pyridyl)ethane-N,N′-dioxide)

Authors

  • Hao-Ling Sun Dr.,

    1. Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (PR China), Fax: (+86) 10-6275-1708
    2. Department of Chemistry, Beijing Normal University, Beijing 100875 (PR China)
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  • Zhe-Ming Wang Prof. Dr.,

    1. Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (PR China), Fax: (+86) 10-6275-1708
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  • Song Gao Prof. Dr.

    1. Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (PR China), Fax: (+86) 10-6275-1708
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Abstract

Contrasting magnetic properties: Two isostructural metal-azido magnetic chains embedded in 3D threefold interpenetrated H-bonded frameworks and separated by a long bpeado spacer have been assembled (see figure). Incorporation of Mn2+ displays a rarely observed antiferromagnetic Heisenberg chain, while incorporation of Co2+ displays a ferromagnetic Ising chain.

original image

We present here the structures and magnetism of two isostructural magnetic metal-azido chain compounds of the type [M(N3)2(H2O)2]⋅(bpeado) (1, M=Mn; 2, M=Co; bpeado=1,2-bis(4-pyridyl)ethane-N,N′-dioxide), prepared by utilizing the long spacer bpeado. The structure is composed of [M(N3)2(H2O)2]n metal-azido chains, in which metal ions are bridged by two end-on azido ligands, and the chains are further supported by H-bonding interactions between the coordination water of the chain and the lattice bpeado in a three-dimensional (3D) threefold interpenetrated H-bonded framework. Within the structure, the metal-azido chains are separated quite well. Investigation of the magnetic properties has revealed that the Mn compound 1 is an isotropic Heisenberg chain with unusual antiferromagnetic coupling between the Mn2+ ions linked by double end-on azide anions. The Co compound 2 shows a strong anisotropic Ising-type ferromagnetic chain within the material. Detailed magnetic studies on both polycrystalline and single-crystal samples of 2 have revealed a large coercivity of up to 37.5 kOe (along the crystallographic b-axis), multi-magnetic transitions, and single-chain-magnet-like magnetic relaxation behavior.

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