Syntheses, crystal structures, and magnetic properties of Mn–Nb and Co–Nb cyanido-bridged bimetallic assemblies

• Published in: Inorganica Chimica Acta Vol. 425; pp. 92 - 99
• Main Authors: Imoto, Kenta, Takemura, Miho, Nakabayashi, Koji, Miyamoto, Yasuto, Komori-Orisaku, Keiko, Ohkoshi, Shin-ichi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.01.2015
• Subjects: 3D network; Large coercive field; Magnetic anisotropy; Molecular-based magnet; Octacyanidoniobate; 3D network; Large coercive field; Magnetic anisotropy; Octacyanidoniobate; Molecular-based magnet
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2014.10.001

Cyanido-bridged Mn–Nb and Co–Nb bimetal assemblies, MnII2[NbIV(CN)8]·(L)2·nH2O (1: L=5-aminopyrimidine, n=5; 2: L=5-methylpyrimidine, n=4), and CoII2[NbIV(CN)8]·(4-pyridinealdoxime)8·2H2O (3) are synthesized. 1 and 2 have isomorphic three-dimensional (3D) cyanido-bridged network composed of a square antiprism Nb sites, showing ferrimagnetism with Curie temperatures (TC) of 32 and 34K, respectively, due to the antiferromagnetic coupling between MnII (S=5/2) and NbIV (S=1/2) through the CN groups. 3 has a 3D cyanido-bridged network composed of a dodecahedral Nb site and axially distorted Co site, exhibiting ferromagnetism with a TC of 18K. Magnetization versus rotation angle of single crystal reveals that 3 has a large coercive field of 15000Oe as crystal is oriented to a-axis, which is due to the strong magnetic anisotropy on distorted CoII. [Display omitted] •MnII–[NbIV(CN)8] (1, 2) and CoII–[NbIV(CN)8] (3) assemblies are synthesized.•Coordination geometries of Nb are square antiprism (1, 2) and dodecahedron (3).•3 exhibits large coercive field of 15000Oe.•Magnetic interaction is affected by the population of 2p orbital on N atoms.•A large coercivity of 3 is suggested to be due to single-ion anisotropy of CoII. We report three-dimensional (3D) cyanido-bridged Mn–Nb and Co–Nb bimetal assemblies, MnII2[NbIV(CN)8]·(L)2·nH2O (1: L=5-aminopyrimidine, n=5; 2: L=5-methylpyrimidine, n=4), and CoII2[NbIV(CN)8] (4-pyridinealdoxime)8·2H2O (3). The single-crystal X-ray structural analyses show that 1 and 2 consist of isomorphic 3D cyanido-bridged network (monoclinic, P21/n) composed of square antiprism Nb sites and distorted octahedral Mn sites. Both 1 and 2 show ferrimagnetism with Curie temperatures (TC) of 32 and 34K, respectively, which is caused by the antiferromagnetic superexchange interaction between MnII (S=5/2) and NbIV (S=1/2) through the CN groups. 3 has a 3D cyanido-bridged network (tetragonal, I41/a) composed of a dodecahedral Nb site and axially distorted pseudo-octahedral Co site. This compound shows ferromagnetic ordering with a TC of 18K. Magnetization versus rotation angle of single crystal reveals that 3 has a large coercive field of 15000Oe as crystal is oriented to a-axis, which is due to the strong magnetic anisotropy on distorted CoII.