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Synthesis and Ferromagnetic Interaction in Oxamido-Bridged Copper(II)-Chromium(III) Heterotetranuclear Complexes

Wang S., Li Y., Yan C.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 8

1327-1336

EN

Two new mi-oxamido-bridged copper(II)-chromium(III) heterotetranuclear complexes formulated as [Cu3 (dmoxae)3Cr](ClO4 )3 (1) and [Cu3(dmoxpn)3Cr](ClO4)3 (2), where dmoxae and dmoxpn represent N,N'-bis[2-(dimethylamino)ethyl]oxamido and N,N'-bis[3-(dimethylamino)propyl]oxamido dianions, respectively, have been synthesized and characterized by the elemental analyses, spectroscopic (IR, UV, ESR) studies, magnetic moments (at room-temperature) and by molar conductivity measurements. It is proposed that these complexes have oxamido-bridged structures consisting of three copper( II) ions and a chromium(III) ion, in which the chromium(III) ion has an octahedral environment and the three copper(II) ions have a square-planar environment. The two heterotetranuclear complexes were further characterized by variable-temperature magnetization (3~300 K) measurements and the magnetic data have been used to deduce the indicated heterotetranuclear structure. The results derived from least-squares fit of the experimental data have confirmed that the operation of a ferromagnetic interaction between the adjacent copper(II) and chromium(III) ions occurs through the oxamidobridge within each molecule. On the basis of the spin Hamiltonian operator, H= - 2J(S cu . S cr + S cu2 . S cr + S cu2 . S cr ), the magnetic analyses were carried out for the two copper(II)-chromium(III) heterotetranuclear complexes and the spin-coupling constants (J)were evaluated as +9.28 cm-1 for (1) and+9.63 cm-1 for (2). The influence of the symmetry of the magnetic orbitals on the nature of the magnetic interaction between the paramagnetic centers is preliminary discussed.

2

Synthesis and Magnetism of Ferromagnetically Coupled {Cu II 3 Cr III] Heterotetranuclear Complexes with N,N'-Bis(aminoalkyl)oxamidatocopper(II)

Li Y., Yan C., Xu G., Zhang G., Sun W.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 9

1415-1424

EN

The strategy of "complex as ligand" allowed us to synthesize two new _-oxamido- bridged copper(II)-chromium(III) heterotetranuclear complexes formulated as [Cu3(oxae)3Cr](ClO4)3 (1) and [Cu3(oxpn)3Cr](ClO4)3 (2), where oxae and oxpn represent N,N_-bis(2-aminoethyl)oxamido and N,N_-bis(3-aminopropyl)oxamido dianions, respectively. Based on elemental analyses, molar conductivity and magnetic moment (room-temperature) measurements, IR, ESR and electronic spectral studies, these complexes are proposed to have oxamido-bridged structures consisting of three copper(II) ions and a chromium(III) ion, in which the chromium(III) ion has an octahedral environment and the three copper(II) ions have a square-planar environment. The two heterotetranuclear complexes were further characterized by variable-temperature magnetic susceptibility (3~300 K) measurements and the magnetic data have been used to deduce the indicated heterotetranuclear structure. The results derived from least-squares fit of the experimental data have confirmed the ferromagnetic interaction between the adjacent copper(II) and chromium(III) ions through the oxamido-bridge within each molecule. On the basis of the spin Hamiltonian operator, H=-2J(S Cu1 . S Cr+S Cu2 . S Cr + S Cu3 . S cr) , the magnetic analyses were carried out for the two copper(II)-chromium(III) heterotetranuclear complexes and the spin-coupling constants (J) were evaluated as +13.98 cm-1 for (1) and +12.65 cm-1 for (2). The results indicate that the bridging oxamido should be able to transmit ferromagnetic interaction in the strict orthogonality [Cu3 IICrIII] system. The influence of the symmetry of the magnetic orbitals on the nature of the magnetic interaction between the paramagnetic centers is preliminarily discussed.

3

Synthesis of Ferromagnetic Cu3IICrIII-Type Heterotetranuclear Complexesv with Oxalato Bridges

Li Y., Yan C., Guan H.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 1

9-18

EN

Three new _-oxalato-bridgedCu3 IICrIII-type heterotetranuclear complexes have been synthesized and identified as: [Cu3Cr(ox)3(phen)3](ClO4)3 (1), [Cu3Cr(ox)3(Me2phen)3](ClO4)3 (2) and [Cu3Cr(ox)3(NO2phen)3](ClO4)3 (3), where ox represents the oxalato dianions; phen, Me2phen and NO2phen represent 1,10-phenanthroline; 2,9-dimethyl-1,10-phenanthroline or 5-nitro-1,10-phenanthroline respectively. These complexes are the first examples of [Cu3 IICrIII] species bridged by oxalato groups. The three complexes have not yet been isolated in crystalline form suitable for X-ray structure analysis, but based on elemental analyses, molar conductivity and magnetic moment (at room-temperature) measurements, IR, ESR and electronic spectral studies, these complexes are proposed to have oxalato-bridged structure consisting of three copper(II) ions and a chromium(III) ion, in which the chromium(III) ion has an octahedral environment, and the three copper(II) ions have a square-planar environment.Variable temperature magnetic susceptibility (4.2~300 K) measurements and studies of the complexes (1) and (2) revealed the occurrence of an intramolecular ferromagnetic interaction between the copper(II) and chromium(III) ions through the oxalato-bridge within each molecule. The magnetic data have been also used to deduce the indicated _-oxalato-bridged [Cu3 IICrIII] tetranuclear structure. On the basis of the spin Hamiltonian operator,_ _ _ _ _ _ _ H= 2J(S S S S S S Cu1 Cr Cu2 Cr Cu3 Cr Ĺ + Ĺ + Ĺ ), the magnetic analyses were carried out for the two CuII-CrIII heterotetranuclear complexes and the spin-coupling constants (J) were evaluated as +10.97 cm-1 for (1) and +9.28 cm-1 for (2), indicating that the bridging oxalato would be able to transmit ferromagnetic interaction in the strict orthogonality [Cu3 IICrIII] tetranuclear system.

4

Synthesis, Characterization and magnetic Properties of Copper(II)-Iron(III) heterotetranuclear Complexes Bridged by Tris(oxalato)ferrate(III)

Yan C., Li Y., Zhu C.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 5

653-661

EN

The strategy of "complex as ligand" allowed us to synthesize three new _-oxalatobridged heterotetranuclear complexes identified as [Cu3Fe(ox)3(Me2bpy)3](ClO4)3 (1), [Cu3Fe(ox)3(Me2phen)3](ClO4)3 (2) and [Cu3Fe(ox)3(phen)3](ClO4)3 (3), where ox represents the oxalato dianions; Me2bpy, Me2phen and phen stand for 4,4_-dimethyl- 2,2_-bipyridine, 2,9-dimethyl-1,10-phenanthroline or 1,10-phenanthroline, respectively. These complexes are the first examples of [Cu3 IIFeIII] species bridged by oxalato groups. Based on elemental analyses, molar conductivity and magnetic moment (at room-temperature) measurements, IR, ESR and electronic spectral studies, these complexes are proposed to have oxalato-bridged structure consisting of three copper(II) ions and an iron(III) ion, in which the iron(III) ion has an octahedral environment, and the three copper(II) ions have a square-planar environment. The complexes (1) and (2) were further characterized by variable-temperature magnetic susceptibility (4.2~300 K) measurements and the observed data were simulated by the equation based on the spin Hamiltonian operator, _ _ _ _ _ _ _ H= 2J(S S S S S S Cu1 Fe Cu2 Fe Cu3 Fe Ĺ + Ĺ + Ĺ ), giving the exchange integrals J = -9.15 cm-1 for (1) and J = -8.79 cm-1 for (2). The results indicate the presence of an antiferromagnetic spin-exchange interaction between the copper(II) and iron(III) ions through the oxalato-bridge in both complexes (1) and (2).

5

Synthesis and Magnetic Studies of [Cu3IILnIII] Heterotetranuclear Complexes with N,N’- Bis(3-amino-2,2-dimethylpropyl)oxamidocopper (II)

Li Y. T., Yan C. W., Wang H. L.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 12

1817-1824

EN

Eleven newoxamido-bridged Cu"Ln"'-type (Ln = La, Ce, Pr.Nd, Sm, Eu, Gd, Tb, Ho, Er, Yb) heterotetranuclear complexes, namely Cu3(Me2Oxpn)3Ln(NOj)3, where Me2oxpn denotesN,N'-bis(3-amino-2,2-dimethylpropyl)oxamido dianion, have been synthesized and characterized by elemental analyses, molar conducti vity measurements, and spectro-scopic (IR, UV, ESR) studies. Cryomagnetic measurements (4.2~300 K) and studies of Cu3(Me2oxpn)jGd(NO3)3 complex have revealed that the gadolinium(Ill) and copper(II) ions arę ferromagnetically coupled with the exchang_e integraj J = +3.88 cm'1, on the basis of the spin Hamiltonian operator [H = -2J(S, o S" + S: o S" + Sj o S,>)].