Magnetic ordering of YBa2(Cu1−x Fe x )3O7

The Mössbauer spectra of YBa₂(Cu_1?x Fe _x )₃O₇ at room temperature show several doublets attributed to Fe in Cu(1) sites with different oxygen configurations. Here we present a systematic study performed at 4.2 K forx=0.005, 0.01, 0.03, 0.05, 0.10, 0.15. To obtain information about the magnetic ordered state two samples, withx=0.005 andx=0.15, have been studied at 4.2 K underB _ext=5 T. The Mössbauer spectra indicate that the iron moments are polarized forx=0.005, while in the ordered state (x=0.15) they have an antiferromagnetic or spin-glass-like arrangement with high anisotropy.     

Magnetic order in LaEuSrCuO studied [2pt] by Fe Mössbauer spectroscopy

⁵⁷Fe M?ssbauer effect studies of La_1.65Eu_0.20Sr_0.15CuO₄ doped with 0.5 at% ⁵⁷Fe performed in the temperature region 300 K > T > 4.2 K give an onset temperature for magnetic ordering of K. This temperature practically is the same as that found in Nd doped La_2-xSr_xCuO₄. It indicates that the magnetic ordering temperature in the LTT phase of rare earth (RE) doped La_2-xSr_xCuO₄ is independent of the RE moment. The direction of the ⁵⁷Fe magnetic moment in the magnetically ordered state is within the CuO₂ plane, while it has been found to be parallel to the c-axis in Nd doped La_2-xSr_xCuO₄. Received: 23 June 1998 / Accepted: 14 July 1998     

Bis(μ‐acetato‐κ3O,O′:O′)bis[bis(acetato‐κ2O,O′)diaquadysprosium(III)] tetrahydrate

The title compound, [Dy₂(C₂H₃O₂)₆(H₂O)₄]·4H₂O, crystallizes in the form of dimeric units related by an inversion centre. Each cation is nine‐coordinate, binding to two water mol­ecules and three acetate groups, two of which are bidentate and the third tridentate. This last acetate group acts as a bridge between neighbouring metal atoms, leading to an intradimer Dy?Dy separation of 4.170 (1) Å.     

Carboxylate-bridged copper(II)-lanthanide(III) complexes [(Cu(3)Ln(2)(oda)(6)(H(2)O)(6)).12H(2)O](n)(Ln = Dy,Ho, Er,Y; oda = oxydiacetate)

The hydrothermal reaction of Ln(2)O(3) (Ln = Dy and Ho), Cu(OAc)(2).2H(2)O, and oxydiacetic acid in the approximate mole ratio of 1:3:8 resulted in the formation of two new members of the isostructural series of polymers formulated as [(Cu(3)Ln(2)(oda)(6)(H(2)O)(6)).12H(2)O](n), crystallizing in the hexagonal crystal system, space group P6/mcc (No. 192). Temperature-dependent magnetic susceptibilities and EPR spectra are reported for the heterometallic compounds Cu-Dy 1, Cu-Ho 2, Cu-Er 3, and Cu-Y 4. The results are discussed in terms of the structure of the compounds, the electronic properties of the lanthanide ions, and the exchange interactions between the magnetic ions.     

Bis(1,10‐phenanthroline)(thio­sulfato)­manganese(II) methanol solvate and catena‐poly­[[di­aqua(2,9‐di­methyl‐1,10‐phenanthroline)­manganese(II)]‐μ‐thio­sulfato]

The structure of bis(1,10‐phenanthroline‐κ²N,N′)(thio­sulfato‐κ²O:S)­manganese(II) methanol solvate, [Mn(S₂O₃)(C₁₂H₈N₂)₂]·CH₃OH, is made up of Mn²⁺ centers coordinated to two bidentate phenanthroline (phen) groups and an S,O‐chelating thio­sulfate anion, forming monomeric entities. The structure of catena‐poly­[[di­aqua(2,9‐di­methyl‐1,10‐phen­anthro­line‐κ²N,N′)­manganese(II)]‐μ‐thio­sulfato‐κ²O:S], [Mn(S₂O₃)(C₁₄H₁₂N₂)(H₂O)₂]_n, is polymeric, consisting of Mn(dmph)(H₂O)₂ units (dmph is 2,9‐di­methyl‐1,10‐phenanthroline) linked by thio­sulfate anions acting in an S,O‐chelating manner.     

Two nickel complexes stabilized by nitrate counter‐ions

Two new nickel nitrates, di­aqua­bis(3,4,7,8‐tetra­methyl‐1,10‐phenanthroline‐κ²N,N′)­nickel(II) dinitrate methanol solvate, [Ni(C₁₆H₁₆N₂)₂(H₂O)₂](NO₃)₂·CH₄O, (I), and tri­aqua­[2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine‐κ³N¹,N²,N⁶]nickel(II) di­ni­trate trihydrate, [Ni(C₁₈H₁₂N₆)(H₂O)₃](NO₃)₂·3H₂O, (II), are reported. In both structures, the cation is octahedrally coordinated, to two bidentate 3,4,7,8‐tetra­methyl‐1,10‐phenanthroline (tmp) and two water mol­ecules in (I), and to one tridentate 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine (tpt) and three water mol­ecules in (II). Both structures are stabilized by extensive hydrogen‐bonding interactions.     

A unique tautomer of 1‐n‐hexyl‐3‐phenyl‐1H‐pyrazol‐5‐ol

In the title compound, C₁₅H₂₀N₂O, the bond distances and angles are consistent with the presence of the hydroxy tautomer. This tautomer was unambiguously determined by the clear presence of a H atom bonded to oxygen, as well as the total absence of any residual electron density around the N atom in the heterocycle, thus precluding any possibility of desmotropism.     

Three oxo complexes with a tetra­nuclear [Cu4(μ2‐Cl)6(μ4‐O)] unit

The three title compounds, namely 4‐phenyl‐1H‐imidazolium hexa‐μ₂‐chloro‐chloro‐μ₄‐oxo‐tris­(4‐phenyl‐1H‐imidazole‐κN¹)­tetra­copper(II) monohydrate, (C₉H₉N₂)[Cu₄Cl₇O(C₉H₈N₂)₃]·H₂O, hexa‐μ₂‐chloro‐μ₄‐oxo‐tetra­kis­(pyridine N‐oxide‐κO)tetra­copper(II), [Cu₄Cl₆O(C₅H₅NO)₄], and hexa‐μ₂‐chloro‐tetra­kis(2‐methyl‐1H‐imidazole‐κN¹)‐μ₄‐oxo‐tetra­copper(II) methanol trisolvate, [Cu₄Cl₆O(C₄H₆N₂)₄]·3CH₄O, exhibit the same Cu₄OCl₆ framework, where the O atom at the centre of an almost regular tetra­hedron bridges four copper cations at the corners. This group is in turn surrounded by a Cl₆ octa­hedron, leading to a rather globular species. This special arrangement of the Cu^II cations results in a diversity of magnetic behaviours.