Design of metal-complex magnets. Syntheses and magnetic properties of mixed-metal assemblies [NBu{sub 4}[MCr(ox){sub 3}]]{sub x} (NBu{sub 4}{sup +} = Tetra(n-butyl)ammonium ion; ox{sup 2-} = oxalate ion; M = Mn{sup 2+}, Fe{sup 2+}, Co{sup 2+}, Ni{sup 2+}, Cu{sup 2+}, Zn{sup 2+})
- Kyushu Univ., Fukuoka (Japan); and others
The reaction of K{sub 3}[Cr(ox){sub 3}]{center_dot}3H{sub 2}O, a metal(II) salt, and tetra(n-butyl)ammonium bromide in the molar ratio of 1:1:1.5 in water at room temperature afforded a series of mixed-metal assemblies with the formula [NBu{sub 4}[MC(ox){sub 3}]]{sub x} (M = Mn{sup 2+} (1), Fe{sup 2+} (2), Co{sup 2+} (3), Ni{sup 2+} (4), Cu{sup 2+} (5), Zn{sup 2+} 6)). The compounds are designed so as to assume a three-dimensional structure consisting of alternately arrayed Cr(III) and M(II) ions due to the D{sub 3} symmetry of the building block [Cr(ox){sub 3}]{sup 3-}. The magnetic susceptibility data of 1-5 above ca. 20 K obey the Curie-Weiss law with positive Weiss constants, and upon lowering the temperature, the effective magnetic moments increase gradually in the 300-20 K range and abruptly below ca. 20 K. The temperature dependences of magnetizations studied under a weak applied field (1 G) showed a magnetic phase transition at T{sub c} = 6, 12, 10, 14, and 7 K for 1, 2, 3, 4, and 5, respectively. Field dependences on the magnetization up to 7.5 T have been studied at 4.2 K using a pulsed magnet and the saturation magnetization values per formula M{sub s} were compatible with M{sub s} = Ng{Beta}(S{sub Cr} + S{sub M} (M{sub s}/N{Beta} = 7.74, 6.71, 5.94, 4.94, 3.83, and 2.79 for 1, 2, 3, 4, 5, and 6, respectively). Hysteresis loops have been obtained at 5 K, where the remnant magnetizations are 1500, 4100, 3000, 1200, and 1500 cm{sup 3} mol{sup -1} G and the coercive fields are 20, 320, 80, 160, and 30 G for 1, 2, 3, 4, and 5, respectively. 27 refs., 6 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 223955
- Journal Information:
- Journal of the American Chemical Society, Vol. 114, Issue 18; Other Information: PBD: 26 Aug 1992
- Country of Publication:
- United States
- Language:
- English
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