Search Results (4)

A new cobalt(III) complex with a pentadentate Schiff base was synthesized using a reaction of 2,2′-{(2-hydroxypropane-1,3-diyl)bis(nitriloeth-1-yl-1-ylidene)}diphenol (H₃L) and cobalt(II) acetate in a methanolic solution. This synthesis resulted in the isolation of dinuclear compound [Co^III₂L₂] (1), which was characterized using elemental analyses and XRF, FTIR, and TG/DSC techniques. The molecular structure of the complex was confirmed using single-crystal X-ray diffraction. The structure of 1 consists of a centrosymmetric dimer in which two crystallographically equivalent cobalt(III) ions are bridged by two alkoxido oxygen atoms. In addition, each metal center is coordinated by two Schiff bases. Full article

The search for mononuclear lanthanoid-based single-ion magnets (SIMs) has increased the interest in some coordination environments with low coordination numbers, in combination with an axial symmetry, as they could maximize the anisotropy of complexes of oblate lanthanoid ions, such as dysprosium(III). In this sense, the pentagonal–bipyramid geometry can have ground-state doublets with perfect axiality, and therefore such complexes can be good candidates for SIMs. In our particular case, we have used a well-known open planar pentadentate chelating Schiff base ligand as 2,6-bis(1-salicyloylhydrazonoethyl)pyridine) (H₄daps) for the synthesis of air-stable pentagonal–bipyramidal Ln^III complexes (these being Ln: Dy and Er, oblate and prolate, respectively), in order to compare their structures. Thus, the reaction of H₄daps with (CH₃)₄NOH·5H₂O and the corresponding LnCl₃·hexahydrate has yielded heptacoordinate [(CH₃)₄N][Ln^III(H₂daps)Cl₂] complexes, where the tetramethylammonium cation is acting as the counterion of pentagonal–bipyramidal Ln^III complexes, which are bearing two chloride atoms in apical positions. As both complexes could be crystallized as single crystals, we can compare their crystal structures, as well as with some other related complexes in the literature, which contain different counterions, trying to see their influence on other properties of the compounds, such as their magnetic behavior. Full article

A series of five neutral mononuclear lanthanide complexes [Ln(HL)(L)] (Ln = Dy³⁺, Ho³⁺ Er³⁺ and Tb³⁺) with rigid pentadentate N₃O₂-type Schiff base ligands, H₂L^H (1-Dy, 3-Ho, 4-Er and 6-Tb complexes) or H₂L^OCH3, (2-Dy complex) has been synthesized by reaction of two equivalents of 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))dibenzohydrazine (H₂L^H, [H₂DAPBH]) or 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))di-4-methoxybenzohydrazine (H₂L^OCH3, [H₂DAPMBH]) with common lanthanide salts. The terbium complex [Tb(L^H)(NO₃)(H₂O)₂](DME)₂ (5-Tb) with one ligand H₂L^H was also obtained and characterized. Single crystal X-ray analysis shows that complexes 1–4 have the composition {[Ln³⁺(HL)⁻(L)²⁻] solv} and similar molecular structures. In all the compounds, the central Ln³⁺ ion is chelated by two interlocked pentadentate ligands resulting in the coordination number of ten. Each lanthanide ion is coordinated by six nitrogen atoms and four oxygen atoms of the two N₃O₂ chelating groups forming together a distorted bicapped square antiprismatic polyhedron N₆O₄ with two capping pyridyl N atoms in the apical positions. The ac magnetic measurements reveal field-induced single-molecule magnet (SMM) behavior of the two dysprosium complexes (with barriers of U_eff = 29 K at 800 Oe in 1-Dy and U_eff = 70 K at 300 Oe in 2-Dy) and erbium complex (U_eff = 87 K at 1500 Oe in 4-Er); complex 3-Ho with a non-Kramers Ho³⁺ ion is SMM-silent. Although 2-Dy differs from 1-Dy only by a distant methoxy-group in the phenyl ring of the ligand, their dynamic magnetic properties are markedly different. This feature can be due to the difference in long-range contributions (beyond the first coordination sphere) to the crystal-field (CF) potential of 4f electrons of Dy³⁺ ion that affects magnetic characteristics of the ground and excited CF states. Magnetic behavior and the electronic structure of Ln³⁺ ions of 1–4 complexes are analyzed in terms of CF calculations. Full article

The manuscript described the synthesis and characterization of the new [Cd(BDMPT)₂](ClO₄)₂; 1 and [Cd₂(MBPT)₂(H₂O)₂Cl](ClO₄)₃.4H₂O; 2 s-triazine pincer-type complexes, where BDMPT and MBPT are 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine and 2-methoxy-4,6-bis(2-(pyridin-2-ylmsethylene)hydrazinyl)-1,3,5-triazine respectively. The synthesized complexes were characterized using Fourier-transform infrared spectroscopy (FTIR), ¹H and ¹³C NMR spectroscopy, and the single-crystal X-ray diffraction technique. The homoleptic mononuclear complex (1) contains a hexa-coordinated Cd(II) center with two tridentate N-pincer ligand (BDMPT) with a highly distorted octahedral coordination environment located as an intermediate case between the octahedron and trigonal prism. The heteroleptic dinuclear complex (2) contains two hepta-coordinated Cd(II) coordination spheres where each Cd(II) is coordinated with one pentadentate pincer N-chelate (MBPT), one water, and one bridged chloride ligand connecting the two metal ions. The different intermolecular interactions in the studied complexes were quantified using Hirshfeld analysis. Their thermal stabilities and FTIR spectra were compared with the corresponding free ligands. The strength and nature of Cd–N, Cd–O, and Cd–Cl coordination interactions were discussed in light of atoms in molecules calculations (AIM). The M(II)–BDMPT and M(II)–MBPT interaction energies revealed that such sterically hindered ligands have higher affinity toward large-size metal ions (M = Cd) compared to smaller ones (M = Ni or Mn). Full article