Unusual ferromagnetic couplings in single end-to-end azide-bridged cobalt(II) and nickel(II) chain systems

Chang Seop Hong, Ja Eung Koo, Sang Kil Son, Yoon Sup Lee, Yaung Soo Kim, Youngkyu Do

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138 Citations (Scopus)

Abstract

Two new one-dimensional single azide-bridged metal(II) compounds [{M(5-methylpyrazole) 4(N 3)} n](ClO 4) n(H 2O) n [M = Co (1a), Ni (2a)] were prepared by treating an M II ion with stoichiometric amount of sodium azide in the presence of four equivalents of the 3(5)-methylpyrazole ligand. The isostructural compounds 1a and 2a crystallize in the monoclinic space group P2 1/n. The azide bridging ligands have a unique end-to-end coordination mode that brings two neighboring metal centers into a cis-position with respect to the azide unit to form single end-to-end azide-bridged cobalt(II) and nickel(II) chains. The two neighboring metal atoms at inversion centers adopt octahedral environments with four equatorial 3(5)-methylpyrazole ligands and two axial azide bridges. Two adjacent equatorial least-squares planes form dihedral angles of 60.5° and 60.6° for Co and Ni, respectively. In addition, the metalazide-metal units form large M-N 3-M torsion angles, which are magnetically important geometrical parameters, of 71.6° for M = Co and 75.7° for M = Ni. It should also be noted that the M-N-N angles associated with end-to-end azide group, another magnetically important structural parameter, fall into the experimentally observed range of 120-140° as 128.3(3) and 147.8(3)° for cobalt species and 128.4(2) and 146.1(3)° for nickel species; these values deviate from the theoretical value of around 164° at which the incidental orthogonality is achieved under the torsion angle of 0°. The compounds 1a and 2a have unique magnetic properties of ferromagnetism, zero-field splitting, and spin canting. The MO calculations indicate that the quasi-orthogonality between the magnetic orbitals of metal ions and the p atomic orbitals of the bridging azide is possible in the observed structures and leads to the ferromagnetism. The spin canting related to the perturbation of ferromagnetism arises from the magnetic anisotropy and antisymmetric interactions judged by the structural parameters of the zero-field splitting and the tilted MN 4 planes in a chain. The enhancement of magnetic interactions was accomplished by dehydrating the chain compounds to afford two soft magnets with critical temperature T c and coercive field of 2 K and 35 G for 1b and 2.3 K and 20 G for 2b, respectively.

Original languageEnglish
Pages (from-to)4243-4252
Number of pages10
JournalChemistry - A European Journal
Volume7
Issue number19
DOIs
Publication statusPublished - 2001 Oct 1
Externally publishedYes

Fingerprint

Azides
Cobalt
Nickel
Metals
Ferromagnetism
Ligands
Torsional stress
Ions
Sodium Azide
Magnets
Magnetic anisotropy
Anisotropy
Dihedral angle
Least-Squares Analysis
Metal ions
Magnetic properties
Atoms
Temperature

Keywords

  • Azide
  • Cobalt
  • Magnetic properties
  • Nickel
  • Spin canting

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Unusual ferromagnetic couplings in single end-to-end azide-bridged cobalt(II) and nickel(II) chain systems. / Hong, Chang Seop; Koo, Ja Eung; Son, Sang Kil; Lee, Yoon Sup; Kim, Yaung Soo; Do, Youngkyu.

In: Chemistry - A European Journal, Vol. 7, No. 19, 01.10.2001, p. 4243-4252.

Research output: Contribution to journalArticle

Hong, Chang Seop ; Koo, Ja Eung ; Son, Sang Kil ; Lee, Yoon Sup ; Kim, Yaung Soo ; Do, Youngkyu. / Unusual ferromagnetic couplings in single end-to-end azide-bridged cobalt(II) and nickel(II) chain systems. In: Chemistry - A European Journal. 2001 ; Vol. 7, No. 19. pp. 4243-4252.
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T1 - Unusual ferromagnetic couplings in single end-to-end azide-bridged cobalt(II) and nickel(II) chain systems

AU - Hong, Chang Seop

AU - Koo, Ja Eung

AU - Son, Sang Kil

AU - Lee, Yoon Sup

AU - Kim, Yaung Soo

AU - Do, Youngkyu

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N2 - Two new one-dimensional single azide-bridged metal(II) compounds [{M(5-methylpyrazole) 4(N 3)} n](ClO 4) n(H 2O) n [M = Co (1a), Ni (2a)] were prepared by treating an M II ion with stoichiometric amount of sodium azide in the presence of four equivalents of the 3(5)-methylpyrazole ligand. The isostructural compounds 1a and 2a crystallize in the monoclinic space group P2 1/n. The azide bridging ligands have a unique end-to-end coordination mode that brings two neighboring metal centers into a cis-position with respect to the azide unit to form single end-to-end azide-bridged cobalt(II) and nickel(II) chains. The two neighboring metal atoms at inversion centers adopt octahedral environments with four equatorial 3(5)-methylpyrazole ligands and two axial azide bridges. Two adjacent equatorial least-squares planes form dihedral angles of 60.5° and 60.6° for Co and Ni, respectively. In addition, the metalazide-metal units form large M-N 3-M torsion angles, which are magnetically important geometrical parameters, of 71.6° for M = Co and 75.7° for M = Ni. It should also be noted that the M-N-N angles associated with end-to-end azide group, another magnetically important structural parameter, fall into the experimentally observed range of 120-140° as 128.3(3) and 147.8(3)° for cobalt species and 128.4(2) and 146.1(3)° for nickel species; these values deviate from the theoretical value of around 164° at which the incidental orthogonality is achieved under the torsion angle of 0°. The compounds 1a and 2a have unique magnetic properties of ferromagnetism, zero-field splitting, and spin canting. The MO calculations indicate that the quasi-orthogonality between the magnetic orbitals of metal ions and the p atomic orbitals of the bridging azide is possible in the observed structures and leads to the ferromagnetism. The spin canting related to the perturbation of ferromagnetism arises from the magnetic anisotropy and antisymmetric interactions judged by the structural parameters of the zero-field splitting and the tilted MN 4 planes in a chain. The enhancement of magnetic interactions was accomplished by dehydrating the chain compounds to afford two soft magnets with critical temperature T c and coercive field of 2 K and 35 G for 1b and 2.3 K and 20 G for 2b, respectively.

AB - Two new one-dimensional single azide-bridged metal(II) compounds [{M(5-methylpyrazole) 4(N 3)} n](ClO 4) n(H 2O) n [M = Co (1a), Ni (2a)] were prepared by treating an M II ion with stoichiometric amount of sodium azide in the presence of four equivalents of the 3(5)-methylpyrazole ligand. The isostructural compounds 1a and 2a crystallize in the monoclinic space group P2 1/n. The azide bridging ligands have a unique end-to-end coordination mode that brings two neighboring metal centers into a cis-position with respect to the azide unit to form single end-to-end azide-bridged cobalt(II) and nickel(II) chains. The two neighboring metal atoms at inversion centers adopt octahedral environments with four equatorial 3(5)-methylpyrazole ligands and two axial azide bridges. Two adjacent equatorial least-squares planes form dihedral angles of 60.5° and 60.6° for Co and Ni, respectively. In addition, the metalazide-metal units form large M-N 3-M torsion angles, which are magnetically important geometrical parameters, of 71.6° for M = Co and 75.7° for M = Ni. It should also be noted that the M-N-N angles associated with end-to-end azide group, another magnetically important structural parameter, fall into the experimentally observed range of 120-140° as 128.3(3) and 147.8(3)° for cobalt species and 128.4(2) and 146.1(3)° for nickel species; these values deviate from the theoretical value of around 164° at which the incidental orthogonality is achieved under the torsion angle of 0°. The compounds 1a and 2a have unique magnetic properties of ferromagnetism, zero-field splitting, and spin canting. The MO calculations indicate that the quasi-orthogonality between the magnetic orbitals of metal ions and the p atomic orbitals of the bridging azide is possible in the observed structures and leads to the ferromagnetism. The spin canting related to the perturbation of ferromagnetism arises from the magnetic anisotropy and antisymmetric interactions judged by the structural parameters of the zero-field splitting and the tilted MN 4 planes in a chain. The enhancement of magnetic interactions was accomplished by dehydrating the chain compounds to afford two soft magnets with critical temperature T c and coercive field of 2 K and 35 G for 1b and 2.3 K and 20 G for 2b, respectively.

KW - Azide

KW - Cobalt

KW - Magnetic properties

KW - Nickel

KW - Spin canting

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