Synthesis, Structures, and Magnetic Properties of Face-Sharing Heterodinuclear Ni(II)−Ln(III) (Ln = Eu, Gd, Tb, Dy) Complexes

Heterodinuclear [(NiIIL)LnIII(hfac)2(EtOH)] (H3L = 1,1,1-tris[(salicylideneamino)methyl]ethane; Ln = Eu, Gd, Tb, and Dy; hfac = hexafluoroacetylacetonate) complexes (1·Ln) were prepared by treating [Ni(H1.5L)]Cl0.5 (1) with [Ln(hfac)3(H2O)2] and triethylamine in ethanol (1:1:1). All 1·Ln complexes (1·Eu, 1·Gd, 1·Tb, and 1·Dy) crystallized in the triclinic space group P1̅ (No. 2) with Z = 2 with very similar structures. Each complex is a face-sharing dinuclear molecule. The NiII ion is coordinated by the L3− ligand in a N3O3 coordination sphere, and the three phenolate oxygen atoms coordinate to an LnIII ion as bridging atoms. The LnIII ion is eight-coordinate, with four oxygen atoms of two hfac−’s, three phenolate oxygen atoms of L3−, and one ethanol oxygen atom coordinated. Temperature-dependent magnetic susceptibility and field-dependent magnetization measurements showed a ferromagnetic interaction between NiII and GdIII in 1·Gd. The NiII−LnIII magnetic interactions in 1·Eu, 1·Tb, and 1·Dy were evaluated by comparing their magnetic susceptibilities with those of the isostructural ZnII−LnIII complexes, [(ZnL)Ln(hfac)2(EtOH)] (2·Ln) containing a diamagnetic ZnII ion. A ferromagnetic interaction was indicated in 1·Tb and 1·Dy, while the interaction between NiII and EuIII was negligible in 1·Eu. The magnetic behaviors of 1·Dy and 2·Dy were analyzed theoretically to give insight into the sublevel structures of the DyIII ion and its coupling with NiII. Frequency dependence in the ac susceptibility signals was observed in 1·Dy

Synthesis, Structures, and Magnetic Properties of Face-Sharing Heterodinuclear Ni(II)−Ln(III) (Ln = Eu, Gd, Tb, Dy) Complexes

Heterodinuclear [(NiIIL)LnIII(hfac)2(EtOH)] (H3L = 1,1,1-tris[(salicylideneamino)methyl]ethane; Ln = Eu, Gd, Tb, and Dy; hfac = hexafluoroacetylacetonate) complexes (1·Ln) were prepared by treating [Ni(H1.5L)]Cl0.5 (1) with [Ln(hfac)3(H2O)2] and triethylamine in ethanol (1:1:1). All 1·Ln complexes (1·Eu, 1·Gd, 1·Tb, and 1·Dy) crystallized in the triclinic space group P1̅ (No. 2) with Z = 2 with very similar structures. Each complex is a face-sharing dinuclear molecule. The NiII ion is coordinated by the L3− ligand in a N3O3 coordination sphere, and the three phenolate oxygen atoms coordinate to an LnIII ion as bridging atoms. The LnIII ion is eight-coordinate, with four oxygen atoms of two hfac−’s, three phenolate oxygen atoms of L3−, and one ethanol oxygen atom coordinated. Temperature-dependent magnetic susceptibility and field-dependent magnetization measurements showed a ferromagnetic interaction between NiII and GdIII in 1·Gd. The NiII−LnIII magnetic interactions in 1·Eu, 1·Tb, and 1·Dy were evaluated by comparing their magnetic susceptibilities with those of the isostructural ZnII−LnIII complexes, [(ZnL)Ln(hfac)2(EtOH)] (2·Ln) containing a diamagnetic ZnII ion. A ferromagnetic interaction was indicated in 1·Tb and 1·Dy, while the interaction between NiII and EuIII was negligible in 1·Eu. The magnetic behaviors of 1·Dy and 2·Dy were analyzed theoretically to give insight into the sublevel structures of the DyIII ion and its coupling with NiII. Frequency dependence in the ac susceptibility signals was observed in 1·Dy

Magnetic Interactions in Cu^II−Ln^III Cyclic Tetranuclear Complexes: Is It Possible to Explain the Occurrence of SMM Behavior in Cu^II−Tb^III and Cu^II−Dy^III Complexes?

An extensive series of tetranuclear CuII2LnIII2 complexes [CuIILLnIII(hfac)2]2 (with LnIII being all lanthanide(III) ions except for the radioactive PmIII) has been prepared in order to investigate the nature of the CuII−LnIII magnetic interactions and to try to answer the following question:  What makes the CuII2TbIII2 and CuII2DyIII2 complexes single molecule magnets while the other complexes are not? All the complexes within this series possess a similar cyclic tetranuclear structure, in which the CuII and LnIII ions are arrayed alternately via bridges of ligand complex (CuIIL). Regular SQUID magnetometry measurements have been performed on the series. The temperature-dependent magnetic susceptibilities from 2 to 300 K and the field-dependent magnetizations from 0 to 5 T at 2 K have been measured for the CuII2LnIII2 and NiII2LnIII2 complexes, with the NiII2LnIII2 complex containing diamagnetic NiII ions being used as a reference for the evaluation of the CuII−LnIII magnetic interactions. These measurements have revealed that the interactions between CuII and LnIII ions are very weakly antiferromagnetic if Ln = Ce, Nd, Sm, Yb, ferromagnetic if Ln = Gd, Tb, Dy, Ho, Er, Tm, and negligible if Ln = La, Eu, Pr, Lu. With the same goal of better understanding the evolution of the intramolecular magnetic interactions, X-ray magnetic circular dichroism (XMCD) has also been measured on CuII2TbIII2, CuII2DyIII2, and NiII2TbIII2 complexes, either at the L- and M-edges of the metal ions or at the K-edge of the N and O atoms. Last, the CuII2TbIII2 complex exhibiting SMM behavior has received a closer examination of its low temperature magnetic properties down to 0.1 K. These particular measurements have revealed the unusual very slow setting-up of a 3D order below 0.6 K

Magnetic Interactions in Cu^II−Ln^III Cyclic Tetranuclear Complexes: Is It Possible to Explain the Occurrence of SMM Behavior in Cu^II−Tb^III and Cu^II−Dy^III Complexes?

An extensive series of tetranuclear CuII2LnIII2 complexes [CuIILLnIII(hfac)2]2 (with LnIII being all lanthanide(III) ions except for the radioactive PmIII) has been prepared in order to investigate the nature of the CuII−LnIII magnetic interactions and to try to answer the following question:  What makes the CuII2TbIII2 and CuII2DyIII2 complexes single molecule magnets while the other complexes are not? All the complexes within this series possess a similar cyclic tetranuclear structure, in which the CuII and LnIII ions are arrayed alternately via bridges of ligand complex (CuIIL). Regular SQUID magnetometry measurements have been performed on the series. The temperature-dependent magnetic susceptibilities from 2 to 300 K and the field-dependent magnetizations from 0 to 5 T at 2 K have been measured for the CuII2LnIII2 and NiII2LnIII2 complexes, with the NiII2LnIII2 complex containing diamagnetic NiII ions being used as a reference for the evaluation of the CuII−LnIII magnetic interactions. These measurements have revealed that the interactions between CuII and LnIII ions are very weakly antiferromagnetic if Ln = Ce, Nd, Sm, Yb, ferromagnetic if Ln = Gd, Tb, Dy, Ho, Er, Tm, and negligible if Ln = La, Eu, Pr, Lu. With the same goal of better understanding the evolution of the intramolecular magnetic interactions, X-ray magnetic circular dichroism (XMCD) has also been measured on CuII2TbIII2, CuII2DyIII2, and NiII2TbIII2 complexes, either at the L- and M-edges of the metal ions or at the K-edge of the N and O atoms. Last, the CuII2TbIII2 complex exhibiting SMM behavior has received a closer examination of its low temperature magnetic properties down to 0.1 K. These particular measurements have revealed the unusual very slow setting-up of a 3D order below 0.6 K