SYNTHESIS AND MAGNETIC-PROPERTIES OF CU(II), NI(II) COMPLEXES BRIDGED BY 4,4'-BIPYRIDINE, PYRAZINE AND IMIDAZOLE

Six-polynuclear complexes bridged by N-heterocycle, of formula [Ni(sala)(2)(4,4'-bipy)](n), [Ni(Et-dtp)(2)(4,4'-bipy)](n), [Cu(acac)(2)(4,4'-bipy)](n),[Cu(TTA)(2)(pyz)](n), [Cu(TTA)(Im)](n) and [Cu(Im)(2)](n), were synthesized and characterized by elemental analysis, IR, MS, ESR and thermogravimetric analysis, Crystal structure analysis has proved that the.complex [Cu(TTA)(2)(pyz)](n) has one-dimensional infinite linear structure. The local coordination geometry around Cu(II)is a distorted octahedron, The variable-temperature magnetic susceptibility determinations show that the magnetic properties of 4,4'-bipyridine and pyrazine bridging complexes obey the Curie-Weiss law. The imidazole complexes have strong antiferromagnetic interactions, the parameters 2J=-75cm(-1) for [Cu(TTA)(Im)](n) and -107cm(-1) for [Cu(Im)(2)](n). Magnetic experimental data are discussed in the relation to the structures of 4,4'-bipyridine, pyrazine and imidazole. It is shown that 4,4'-bipyridine is not a good bridge for propagating a magnetic exchange interaction between metal