Tb₂, Dy₂, and Zn₂Dy₄ Complexes Showing the Unusual Versatility of a Hydrazone Ligand toward Lanthanoid Ions: a Structural and Magnetic Study

Abstract

Three dinuclear complexes, [Tb(Hdaps)(CHOH)(HO)](Cl) (TbCl), [Dy(Hdaps)(Cl)(CHOH)(HO)]Cl (DyCl), and [Dy(Hdaps)(HO)](CFSO) (DyCFSO), as well as the heterohexanuclear compound [ZnDy(daps)(Hdaps)(Cl)(OH)(CHOH)(HO)] (ZnDy) (Hdaps: 2,6-bis(1-salicyloylhydrazonoethyl)pyridine), which crystallize with different lattice molecules, show their hexa- or heptadentate hydrazone ligands acting with hitherto unknown μ-κ:κ, μ-κ:κ:κ, μ-κ:κ:κ:κ, or μ-κ:κ:κ:κ bridging modes. The single X-ray crystal structures of the dinuclear complexes show nine-coordinated N O environments for lanthanoid atoms in TbCl and DyCFSO, with distorted geometries, between spherical capped square antiprism and muffin-like, while the dysprosium atoms in DyCl are eight-coordinated, with distorted triangular dodecahedron geometries. In the case of ZnDy, both eight-coordinated, O and O Cl, as well as nine-coordinated N O environments coexist in the crystal structure, with biaugmented trigonal prism, triangular dodecahedron, and muffin-like pseudogeometries. The magnetic study of all the complexes shows that none of the pure samples behaves as a single molecular magnet (SMM) and that the quantum tunnel cannot be removed by dilution of any of the dinuclear complexes, but except in diluted [YDy(Hdaps)(Cl)(HO)]Cl (DyCl@Y), behaves as a weak field induced SMM. The heterohexanuclear ZnDy complex also lacks slow relaxation of the magnetization.

Attainment of Pentagonal-Bipyramidal Ln^III Complexes from a planar pentadentate ligand

“…The infrared spectra of the compounds show two intense bands at ca. and 1520 cm -1 , which can be assigned to the amide I [ν(C=O)] and the amide II [(NH) + ν(C=N)] vibrations, respectively [5,[11][12][13]. These bands experience significant negative shifts ranging from 30 to cm -1 with respect to free H4daps, what is consistent with the coordination of both carbonyl and both imine groups to the metal centers [5,[10][11][12][13].…”

“…In the pseudo pentagonal bipyramid, the angles around the metal ion differ from the ideal values of 180 and 72°, the main distortion arising from the O-Dy-O angle of the equatorial plane (98.94(18)° for DyH2daps and 93.36(19)° for ErH2daps). In spite of this, all the distances and angles are within their normal range [10,13,15], but it should be noted that the Dy-Npyridine distance is a bit shorter than in related Et3NH[Dy(H2daps)Cl2] [10], and that the Cl-Dy-Cl angle is notably less deviated from 180 in DyH2daps (171.44(9)°) than in Et3NH[Dy(H2daps)Cl2] (166.32(6)°), showing that the cationic counterion could have an important influence in the structural parameters of the anionic complex. This may be related with the N-H•••Cl interaction between the Et3NH + cation and one of the chloride ligands.…”

“…and 1520 cm -1 , which can be assigned to the amide I [ν(C=O)] and the amide II [(NH) + ν(C=N)] vibrations, respectively [5,[11][12][13]. These bands experience significant negative shifts ranging from 30 to cm -1 with respect to free H4daps, what is consistent with the coordination of both carbonyl and both imine groups to the metal centers [5,[10][11][12][13]. The spectra also show the presence of a quite broad band centered at about 3360 cm -1 , which can be assigned to OH vibrations, in agreement with the non-deprotonation of the phenolic groups.…”

Attainment of Pentagonal-Bipyramidal LnIII Complexes from a Planar Pentadentate Ligand

“…1590 and 1520 cm -1 , which can be assigned to the amide I [ν(C=O)] and the amide II [δ(NH) + ν(C=N)] vibrations, respectively [5,[11][12][13]. These bands experience significant negative shifts ranging from 30 to 65 cm -1 with respect to free H4daps, which is consistent with the coordination of both carbonyl and both imine groups to the metal centers [5,[10][11][12][13]. The spectra also show the presence of a fairly broad band centered at about 3360 cm −1 , which can be assigned to OH vibrations, in agreement with the non-deprotonation of the phenolic groups.…”

“…In the pseudo pentagonal-bipyramid, the angles around the metal ion differ from the ideal values of 180 and 72°, the main distortion arising from the O-Dy-O angle of the equatorial plane (98.94(18)° for DyH2daps and 93.36(19)° for ErH2daps). In spite of this, all the distances and angles are within their normal range [10,13,15], but it should be noted that the Dy-Npyridine distance is a bit shorter than in the related Et3NH[Dy(H2daps)Cl2] [10], and that the Cl-Dy-Cl angle is notably less deviated from 180 in DyH2daps (171.44(9)°) than in Et3NH[Dy(H2daps)Cl2] (166.32(6)°), showing that the cationic counterion could have an important influence on the structural parameters of the anionic complex. This may be related with the N-H•••Cl interaction between the Et3NH + cation and one of the chloride ligands.…”