Abstract: Four novel cobalt(Ⅱ) complexes have been synthesized and characterized,namely[Co₂(4Br-PHTH)(L)₄](ClO₄)₂(L denotes 1,10-phenanthroline(phen)(1),5-nitro-1,10-phenanthroline(NO₂-phen) (2),2,2'-bipyridyl(bpy)(3) and 4,4'-dimethyl-2,2'-bipyridyl(Me₂bpy)(4),respectively),where 4Br-PHTH is the tetrabromophthalate anion. Based on IR,elemental analysis and conductivity measurements,these complexes are proposed to have extended tetrabromophthalato-bridged structure consisting of two cobalt ions in which each cobalt(Ⅱ) ion has a distorted octahedral environment.The temperature dependence of the magnetic susceptibility for all the complexes were measured over the range 75～300 K and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator(H=-2JS₁·S₂),giving the exchange integral J=-0.87 cm^-1,J=-0.84cm^-1(2),J=-0.82 cm^-1(3) and J=-0.85 cm^-1(4).These results indicate the existence of weak antiferromagnetic spin exchange interaction between the metal ions.

Key words: binuclear complex, Co(Ⅱ)-Co(Ⅱ), antiferromagnetic interaction