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1 2003

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Antiferromagnetically Coupled Binuclear Chromium(III) Complexes Through mi-Isophthalato-Bridge

Li Y., Yan C. -W., Guan H. -S.

Polish Journal of Chemistry

2003

Vol. 77 / nr 8

953-959

Three new _-isophthalato-bridged binuclear chromium(III) complexes were synthesized and characterized, namely [Cr2(IPHTA)(Me2bpy)4](NO3)4 (1), [Cr2(IPHTA)(Me2phen)4](NO3)4 (2) and [Cr2(IPHTA)(Cl-phen)4](NO3)4 (3), where IPHTA represents the isophthalate dianions; Me2bpy, Me2phen and Cl-phen stand for 4,4_-dimethyl-2,2_-bipyridine; 2,9-dimethyl-1,10-phenanthroline and 5-chloro- 1,10-phenanthroline, respectively. 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 IPHTA-bridged structures consisting of two chromium( III) ions, each in an octahedral environment are proposed for these complexes. The complexes [Cr2(IPHTA)(Me2bpy)4](NO3)4 (1) and [Cr2(IPHTA)(Me2phen)4](NO3)4 (2) were further characterized by variable temperature magnetic susceptibility (4~300 K) measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, _ _ _ H JS S = Ĺ 2 1 2, giving the exchange integrals J = -1.27 cm-1 for (1) and J = -2.19 cm-1 for (2). This result indicates the presence of weak antiferromagnetic spin-exchange interaction between the metal ions within each molecule.