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2 Polish Journal of Chemistry

2 2004

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Synthesis and Magnetic Studies of Copper(II)-Iron(II) Heterodinuclear Complexes with N,N'-Bis[2-dimethylamino)ethyloxamido Dianion as Ligand

Li Y., Yan C., Lou J., Zhu C.

Polish Journal of Chemistry

2004

Vol. 78 / nr 5

635-644

Three new copper(II)-iron(II) heterodinuclear complexes bridged by the dianions of N,N_-bis[2-(dimethylamino)ethyl]oxamido (dmoxae) and end-capped with 2,2_-bipyridine (bpy); 1,10-phenanthroline (phen) or 5-nitro-1,10-phenanthroline (NO2phen); namely [Cu(dmoxae)Fe(bpy)2]SO4 (1), [Cu(dmoxae)Fe(phen)2]SO4 (2) and [Cu(dmoxae)Fe(NO2phen)2]SO4 (3), have been synthesized and characterized. The three dinuclear complexes have not yet been isolated in crystalline form suitable for X-ray structure analysis, but based on elemental analyses, IR and electronic spectra studies, magnetic moments at room-temperature and molar conductivity measurements, these complexes are proposed to have an extended oxamido-bridged structure consisting of planar copper(II) and octahedral iron(II) ions. The [Cu(dmoxae)Fe(bpy)2]SO4 (1) and [Cu(dmoxae)Fe(phen)2]SO4 (2) complexes have been further characterized by variable temperature magnetic susceptibility (4.2~300 K) and the observed data were least-squares fitted to the susceptibility equation derived from the spin Hamiltonian including single-ion zero-field interaction for the iron(II) ion, _H =-2J_S1_ _ S2 - D_SZ1 2 , giving the exchange integrals J = -20.9 cm-_ for (1) and J = -22.7 cm-1for (2). These results indicated that the spin coupling between the adjacent copper(II) and iron(II) ions through the oxamido-bridge in both complexes (1) and (2) is antiferromagnetic. The influence of methyl substituents in the amine groups of the bridging ligand and the relative stability of the chelate ring arrangement around the copper(II) on magnetic interactions between the metal ions of this kind of complexes is also discussed.

Antiferromagnetically Coupled Chromium(III)-Chromium(III) Binuclear Complexes with Tris(oxalato)chromate(III)

Li Y., Lou J., Yan C.

Polish Journal of Chemistry

2004

Vol. 78 / nr 6

761-769

Three new binuclear chromium(III) complexes bridged by tris(oxalato)chromate(III), [Cr(ox)3]3- and end-capped with 2,2_-bipyridine (bpy); 4,4_-dimethyl-2,2_-bipyridine (Me2bpy) or 5-methyl-1,10-phenanthroline (Mephen), have been synthesized and characterized, namely [Cr2(ox)3(bpy)2] (1), [Cr2(ox)3(Me2bpy)2] (2) and [Cr2(ox)3(Mephen)2] (3). At present, the three complexes have not yet been isolated in crystalline form, suitable for X-ray structure analysis, but based on elemental analyses, molar conductance and magnetic moments of room-temperature measurements, and spectroscopic studies, extended ox-bridged structures consisting of two chromium(III) ions, each in an octahedral environment are proposed for these complexes. The complexes [Cr2(ox)3(bpy)2] (1) and [Cr2(ox)3(Me2bpy)2] (2) were further characterized by variable temperature magnetic susceptibility (4.2~300 K) measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, H_ = 2JS_ ĹS_ 1 2, giving the exchange integrals J = -9.73 cm-1 for (1) and J = -5.29 cm-1 for (2). This result indicates the presence of weak antiferromagnetic spin-exchange interaction between the metal ions within each molecule. The influence of the methyl substituents in the terminal ligand on magnetic interactions between the metals is also discussed.