engleski

Magnetic and structural properties of [Ta_6Cl_12(CH_3OH)_6]Br_3 and [Ta_6Cl_12(CH_3OH)_6]Br_3&middot ; ; 4H_2O

In most magnetic molecular clusters studied in the literature, localized moments of metal ions are coupled by superexchange interactions via ligand entities which are parts of molecular clusters. There is a limited number of studies where magnetic behaviour arises from unfilled molecular orbitals delocalized over the entire metal cores of molecular metal clusters [J. Sinzing et al., Phys. Rev. Lett. 81 (1998) 3211]. This type of magnetism is present in compounds with paramagnetic hexanuclear tantalum halide clusters. Temperature dependent magnetic susceptibility measurements for the compound [Ta_6Cl_12(CH_3OH)_6]Br_3 (I) and temperature dependent magnetic susceptibility anisotropy measurements for the compound [Ta_6Cl_12(CH_3OH)_6]Br_3&middot ; ; 4H_2O (II) can be interpreted as Bonner-Fisher one-dimensional model of interacting magnetic centres [J. C. Bonner, M. E. Fisher, Phys. Rev. A, 135 (1964) 640]. Structural data for compounds (I) and (II) are available from the literature [N. Brničević et al., Inorg. Chem. 31 (1992) 3294]. Compound (I) crystallizes in space group, a = b = 19.127 (4) &Aring ; ; , c = 8.565 (1) &Aring ; ; , and compound (II) in C2/m space group, a = 12.187 (14) &Aring ; ; , b = 15.793 (4) &Aring ; ; , c = 9.182 (6) &Aring ; ; , β = 99.05 (3)o. Magnetic measurements will be discussed in view of the structural data with special attention to the crystallographic origin of anisotropy for compound (II).

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