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1

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, characterization and Magnetic Studies of Oxamido-Bridged Copper(II)-Iron(III) Heterobinuclear Complexes

Li Y., Zhu C., Yan C., Dou J., Wang D.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 8

1265-1273

EN

Two new oxamido-bridged Cu(II)-Fe(III) heterobinuclear complexes of formulae [Cu(dmoxpn)Fe(bpy)2](ClO4)3 (1) and [Cu(dmoxae)Fe(bpy)2](ClO4)3 (2) have been synthesized, where bpy denotes 2,2_-bipyridine; while dmoxpn and dmoxae represent N,N_-bis[3-(dimethylamino)propyl]oxamido and N,N_-bis[2-(dimethylamino) ethyl]oxamido dianions, respectively. Based on elemental analyses, molar conductivity measurements, IR and electronic spectral studies, it is proposed that the two complexes have oxamido-bridged structures consisting of a copper(II) and an iron(III) ions, which have a square planar environment and a distorted octahedral environment, respectively. The two heterobinuclear complexes 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 = JS S 1 2 2 , giving the exchange integral J = -18.2 cm-1 for (1) and J = -26.5 cm-1 for (2). The results revealed the occurrence of an intramolecular antiferromagnetic interaction between the adjacent iron(III) and copper(II) ions through the oxamido- -bridge within each molecule. The influence of the chelate ring arrangement around the copper( II) in the copper(II)-iron(III) heterobinuclear complexes on magnetic interactions between the metal ions of this kind of complexes is preliminarily discussed.

3

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.

4

Synthesis and Magnetism of Cu(II)-Ln(III)-Cu(II) (Ln+La, Nd, Gd, Tb, Ho, Er) Trinuclear Complexes Bridged by N, N'-Bis[3-dimethylamino)propyl]oxamido

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

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 9

1425-1433

EN

Six new mi-oxamido-bridged copper(II)-lanthanide(III)-copper(II) heterotrinuclear complexes described by the overall formula Cu2(dmoxpn)2Ln(NO3)3 {Ln = La, Nd, Gd, Tb, Ho, Er; dmoxpn = N,N'bis[3-(dimethylamino)propyl]oxamido dianions} have been synthesized and characterized by elemental analyses, molar conductivity measurements, IR and electronic spectral studies. The variable-temperature susceptibility (4.2~300 K), ESR measurements, and studies of the Cu2(dmoxpn)2Gd(NO3)3 complex have revealed that the central gadolinium(III) and terminal copper(II) ions are ferromagnetically coupled with the exchange integral J(Cu-Gd) = +6.85 cm-1, while an antiferromagnetic coupling is detected between the terminal copper(II) ions with J'(Cu-Cu) = -0.27 cm-1, on the basis of the spin Hamiltonian operator [H=-2J(S Cu1.S Gd+S Cu2.Gd)-2J(S Cu1.S Cu2)]. A plausible mechanism for the ferromagnetic coupling between copper(II) and gadolinium( III) is discussed in terms of spin polarization.

5

Synthesis and Magnetic Studies of Copper(II)-Lanthanide(III) Heterobinuclear Complexes Bridged by N,N'-Bis[3-(dimethylamino)propyl]oxamido

Li Y., Yan C., Wu Z., Zhu C.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 1

37-46

EN

Ten new copper(II)-lanthanide(III) heterobinuclear complexes bridged by N,N'-bis[3- (dimethylamino)propyl]oxamido dianions (dmoxpn) and end-capped with 2,2'-bipyridine (bpy), namely, Cu(dmoxpn)Ln(bpy)2(NO3)3 (Ln = La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb), have been synthesized and characterized by elemental analyses, molar conductivity measurements, and spectroscopic (IR, UV, ESR) studies. The Cu(dmoxpn)Gd(bpy)2(NO3)3 complex was further characterized by variable-temperature magnetic susceptibility (4.2~300 K) measurements and the magnetic data have been also used to deduce the indicated heterobinuclear structure. The results derived from least-squares fit of the experimental data have confirmed that the adjacent copper(II) and gadolinium(III) ions through the oxamido-bridge in the complex are ferromagnetically coupled with the exchange integral J(Cu-Gd) = +8.59 cm-1. A plausible mechanism for the ferromagnetic coupling between gadolinium(III) and copper(II) is discussed in terms of spin-polarization.

6

Synthesis and Magnetic Analysis of mi Oxamido-Bridged Cu(II)-Fe(II) Heterodinuclear Complexes

Li Y., Zhang G., Yan C., Dou J., Wang D.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 9

1405-1413

EN

The strategy of "complex as ligand" allowed us to synthesize two new mi-oxamido- bridged heterodinuclear complexes identified as [Cu(bmap)Fe(bpy)2]SO4 (1) and [Cu(bmap)Fe(phen)2]SO4 (2), where bmap represents the N,N'-bis(2-methyl-2-aminopropyl) oxamido dianion; bpy and phen stand for 2,2'-bipyridine and 1,10-phenanthroline, respectively. These complexes are the first examples of copper(II)-iron(II) species bridged by bmap groups. 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 two heterodinuclear 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=-2JS1 . S2-DS2 Z1 , giving the exchange integrals J = -18.9 cm-1 for (1) and J = -20.1 cm-1 for(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 bridging ligand on magnetic interactions between the metal ions of this kind of complexes is also discussed

7

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

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2004

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Vol. 78 / nr 5

635-644

EN

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.

8

Synthesis and Magnetic Analysis of mi-Oxamido-Bridged Copper(II)-Iron(II) Heterodinuclear Complexes

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

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 2

137-145

EN

Five new copper(II)-iron(II) heterodinuclear complexes bridged by the dianion of N,N_-bis[3-(dimethylamino)propyl]oxamido (dmoxpn) and end-capped with 2,2_-bipyridine (bpy); 1,10-phenanthroline (phen); 5-nitro-1,10-phenanthroline (NO2-phen); 5-chloro-1,10-phenanthroline (Cl-phen) or 5-bromo-1,10-phenanthroline (Br-phen); namely [Cu(dmoxpn)FeL2](ClO4)2 (L = bpy, phen, NO2-phen, Cl-phen, Br-phen), have been synthesized and characterized. Based on elemental analyses, magnetic moments (at room temperature), molar conductivity measurements, and spectroscopic studies, extended oxamido-bridged structures consisting of a copper(II) ion and an iron(II) ion, which have a square-planar environment and an octahedral environment, respectively, are proposed for these complexes. The [Cu(dmoxpn)Fe(bpy)2](ClO4)2 (1) and [Cu(dmoxpn)Fe(phen)2](ClO4)2 (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 = 2JS S DS 1 2 Z1 2 Ĺ , giving the exchange integrals J = -15.9 cm-1 for (1) and J = -17.5 cm-1 for (2). These results indicated that the spin coupling between the adjacent copper(II) and iron(II) ions through oxamido-bridge in both complexes (1) and (2) is antiferromagnetic. The influence of methyl (-CH3) substituents in the bridging ligand on magnetic interactions between the metal ions of this kind of complexes is also discussed.

9

Synthesis, Characterization and Magnetic Studies of ž-Oxamido-Bridged Cu(II)-MN(II) Heterobinuclear Complexes

Li Y., Yan C. -W., Yin X.-C.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 1

13-21

EN

Four new ž-oxamido-bridged copper(II)-manganese(II) heterobinuclear complexes described by the overall formula [Cu(dmoxpn)MnL2](ClO4)2, where dmoxpn denotes N,N_-bis[3-(dimethylamino)propyl)]oxamido dianion, L represents 2,2_-bipyridine (bpy); 4,4_-dimethyl-2,2_-bipyridine (Me2-bpy); 5-chloro-1,10-phenanthroline (Cl-phen) or 5-bromo-1,10-phenanthroline (Br-phen), have been synthesized and characterized. Based on elemental analyses, IR and electronic spectra studies and molar conductivity measurements, these complexes are proposed to have oxamido-bridged structures and to consist of the copper(II) ion in a planar environment and the manganese(II) ion in an octahedral environment. The electronic reflectance spectrum indicates the presence of exchange- coupling interaction between bridging copper(II) and manganese(II) ions. The [Cu(dmoxpn)Mn(bpy)2](ClO4)2 complex has been further characterized by variable temperature susceptibility (4.2-300 K) and the observed data were least-square fitted to the susceptibility equation derived from the spin Hamiltonian, _H = -2J _ S1_ S2, giving the exchange integral J = -27.8 cm-1. The results are commensurate with antiferromagnetic interaction between the adjacent manganese(II) and copper(II) ions through the oxamido-bridge within the complex. The influence of structural variation of the bridging ligand on magnetic interactions between the metal ions of this kind of complexes is also discussed.