Structure and Magnetic Ordering of the Anomalous Layered (2D) Ferrimagnet [NEt4]2MnII3(CN)8 and 3D Bridged-Layered Antiferromagnet [NEt4]MnII3(CN)7 Prussian Blue Analogues

Authors

  • Christopher M. Kareis,

    1. Department of Chemistry, 315 S. 1400 E. RM 2124, University of Utah, Salt Lake City, Utah 84112-0850 (USA)
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  • Dr. Jae-Hyuk Her,

    1. Department of Physics & Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (USA)
    2. Current address: GE Global Research, 1 Research Circle, Niskayuna, NY 12309 (USA)
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  • Prof. Peter W. Stephens,

    Corresponding author
    1. Department of Physics & Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (USA)
    • Department of Physics & Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (USA)
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  • Dr. Joshua G. Moore,

    1. Department of Chemistry, 315 S. 1400 E. RM 2124, University of Utah, Salt Lake City, Utah 84112-0850 (USA)
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  • Prof. Joel S. Miller

    Corresponding author
    1. Department of Chemistry, 315 S. 1400 E. RM 2124, University of Utah, Salt Lake City, Utah 84112-0850 (USA)
    • Department of Chemistry, 315 S. 1400 E. RM 2124, University of Utah, Salt Lake City, Utah 84112-0850 (USA)
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Abstract

The reaction of MnII and [NEt4]CN leads to the isolation of solvated [NEt4]Mn3(CN)7 (1) and [NEt4]2Mn3(CN)8 (2), which have hexagonal unit cells [1: Requation imagem, a=8.0738(1), c=29.086(1) Å; 2: Pequation imagem1, a=7.9992(3), c=14.014(1) Å] rather than the face centered cubic lattice that is typical of Prussian blue structured materials. The formula units of both 1 and 2 are composed of one low- and two high-spin MnII ions. Each low-spin, octahedral [MnII(CN)6]4− bonds to six high-spin tetrahedral MnII ions through the N atoms, and each of the tetrahedral MnII ions are bound to three low-spin octahedral [MnII(CN)6]4− moieties. For 2, the fourth cyanide on the tetrahedral MnII site is C bound and is terminal. In contrast, it is orientationally disordered and bridges two tetrahedral MnII centers for 1 forming an extended 3D network structure. The layers of octahedra are separated by 14.01 Å (c axis) for 2, and 9.70 Å (c/3) for 1. The [NEt4]+ cations and solvent are disordered and reside between the layers. Both 1 and 2 possess antiferromagnetic superexchange coupling between each low-spin (S=1/2) octahedral MnII site and two high-spin (S=5/2) tetrahedral MnII sites within a layer. Analogue 2 orders as a ferrimagnet at 27(±1) K with a coercive field and remanent magnetization of 1140 Oe and 22 800 emuOe mol−1, respectively, and the magnetization approaches saturation of 49 800 emuOe mol−1 at 90 000 Oe. In contrast, the bonding via bridging cyanides between the ferrimagnetic layers leads to antiferromagnetic coupling, and 3D structured 1 has a different magnetic behavior to 2. Thus, 1 is a Prussian blue analogue with an antiferromagnetic ground state [Tc=27 K from d(χT)/dT].

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