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1

Synthesis, Spectral and Antiferromagnetic Interaction in Oxalato-Bridged Linear TRinuclear Oxovanadium(IV) Complexes

Li Y., Yan C., Guan H.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 2

187-194

EN

Three new linear trinuclear oxovanadium(IV) complexes bridged by oxalato (ox) and end-capped with 2,2_-bipyridine (bpy); 1,10-phenanthroline (phen) or 5-nitro-1,10- phenanthroline (NO2phen); respectively, namely [(VO)3(ox)2(bpy)2]SO4 (1), [(VO)3(ox)2(phen)2]SO4 (2) and [(VO)3(ox)2(NO2phen)2]SO4 (3), have been synthesized and characterized by elemental analyses, molar conductivity, magnetic measurements, IR, ESR and electronic spectral studies. It is proposed that these complexes have extended ox-bridged structures, consisting of three oxovanadium(IV) ions, each in a distorted square-pyramidal environment. Variable-temperature magnetic susceptibility measurements (4.2~300 K) of the complexes (1) and (2) revealed the occurrence of an intramolecular antiferromagnetic interaction between the oxovanadium(IV) ions through the oxalato-bridge within each molecule. The magnetic data have been also used to deduce the indicated structure. On the basis of spin Hamiltonian operator, _ _ _ H = 2J(S S S_ S_ ) 1 2 2 3 Ĺ + Ĺ , the magnetic analyses were carried out for the two trinuclear complexes and the spin-coupling constants (J) were evaluated as -9.85 cm-1 for (1) and -10.16 cm-1 for (2).

2

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.

3

Synthesis and Magnetic Properties of mi-Oxalato-Bridged Cu(II)-Fe(III)-Cu(II) Heterotrinuclear Complexes

Wang H. D., Li Y. -T., Yan C. -W., Zeng X.-C.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 5

637-644

EN

Three new _-oxalato-bridged copper(II)-iron(III)-copper(II) heterotrinuclear complexes described by the overall formula [Cu2Fe(ox)3L2]ClO4, where ox represents the oxalato dianions and L stands for 5-phenyl-1,10-phenanthroline (Ph-phen), 4,7-diphenyl- 1,10-phenanthroline (Ph2-phen) or 5-chloro-1,10-phenanthroline (Cl-phen), have been synthesized and characterized by elemental analyses, molar conductivity and magnetic moment (at room-temperature) measurements, IR and electronic spectral studies. It is proposed that these complexes have extended ox-bridged structures, consisting of two copper(II) and an iron(III) ions, in which the central iron(III) ion has an octahedral environment and the end capped two copper(II) ions have a square-planar environment. The variable-temperature susceptibilities of [Cu2Fe(ox)3(Ph-phen)2]ClO4 complex were measured and studied in the 4.2~300 K range. The least-squares fit of the experimental susceptibility based on the spin Hamiltonian operator, _ _ _ H = JS S 1 2 _ _ 2 , yielded J = -9.89 cm-1. The magnetic coupling parameter is consistent with an antiferromagnetic exchange interaction between the copper(II) and iron(III) ions through the oxalato-bridge in the complex.

4

Syntesis and Ferromagnetic Interaction in Oxalato-Bridged Copper(II)-Chromium(III)-Copper(II) Heterotrinuclear Complexes

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

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 12

1655-1663

5

Synthesis, Characterization and Magnetic Properties of mi-Oxalato-Bridged Binuclear Iron(III) Complexes

Li Y. T., Yan C. W., Zhang Y. H.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 12

1825-1831

EN

Four new oxalato-bridged iron(FII)-iron(III) binuclear complexes have been synthesized and characterized, namely [Fe2(ox)jL2], where ox represents the oxalato dianions; L stands for 2,9-dimethyl-1,10-phenanthroline (Mc2-phen); 4,7-diphenyl-1,10-phenanthroline o:'"o (Ph2-phen); diaminoethane (en) or l ,3-diaminopropane (pn), respectively. Based on elemental analyses, molar conductivity and magnetic moment (at room-temperature) measurements, IR and electronic spectral studies, these complexes arę proposed to have extended ox-bridged structure consisting of two iron(IIl) ions, each in an octahedral environment. The variab!e-teinperature susceptibilities of [Fe2(ox)](Me2-phen)2] (1) and [Fe2(ox))(Ph2-phen)j] (2) complexes were measured and studied in the 4.2-300 K range. The magnetic coupling parameter is consistent with an antiferromagnetic exchange in-teraction between the iron(FFI) ions through the oxalato-bridged in both complexes (1) and (2). Based on the spin Hamiltonian operator, H = 2JS i -S 2, the exchange parameters (J) were evaluated as -4.85 cm"' for (I) and J = -6.39 crrf' for (2).