Structure and magnetic ordering of the anomalous layered (2D) ferrimagnet [NEt4]2Mn(II)3(CN)8 and 3D bridged-layered antiferromagnet [NEt4]Mn(II)3(CN)7 Prussian blue analogues.
Chemistry
; 18(30): 9281-8, 2012 Jul 23.
Article
em En
| MEDLINE
| ID: mdl-22714821
ABSTRACT
The reaction of Mn(II) and [NEt(4)]CN leads to the isolation of solvated [NEt(4)]Mn(3)(CN)(7) (1) and [NEt(4)](2) Mn(3)(CN)(8) (2), which have hexagonal unit cells [1 R3m, a = 8.0738(1), c = 29.086(1)â
Å; 2 P3m1, a = 7.9992(3), c = 14.014(1)â
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 Mn(II) ions. Each low-spin, octahedral [Mn(II)(CN)(6)](4-) bonds to six high-spin tetrahedral Mn(II) ions through the Nâ
atoms, and each of the tetrahedral Mn(II) ions are bound to three low-spin octahedral [Mn(II)(CN)(6)](4-) moieties. For 2, the fourth cyanide on the tetrahedral Mn(II) site is Câ
bound and is terminal. In contrast, it is orientationally disordered and bridges two tetrahedral Mn(II) centers for 1 forming an extended 3D network structure. The layers of octahedra are separated by 14.01â
Å (câ
axis) for 2, and 9.70â
Å (c/3) for 1. The [NEt(4)](+) 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 Mn(II) site and two high-spin (S = 5/2) tetrahedral Mn(II) sites within a layer. Analogue 2 orders as a ferrimagnet at 27(±1)â
K with a coercive field and remanent magnetization of 1140â
Oe and 22,800â
emuOe mol(-1), respectively, and the magnetization approaches saturation of 49,800â
emuOe mol(-1) at 90,000â
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 [T(c) = 27â
K from d(χT)/dT].
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Ano de publicação:
2012
Tipo de documento:
Article