Magnetic characterization, synthesis and crystal structure of a heterodinuclear CuIIGdIII Schiff base complex bridged by the two phenolic oxygen atoms

New Heterotrinuclear CuIILnIIICuII (Ln = Ho, Er) Compounds with the Schiff Base: Syntheses, Structural Characterization, Thermal and Magnetic Properties

New heterotrinuclear complexes with the general formula [Cu₂Ln(H₂L)(HL)(NO₃)₂]·MeOH (Ln = Ho (1), Er (2), H₄L = N,N′-bis(2,3-dihydroxybenzylidene)-1,3-diaminopropane) were synthesized using compartmental Schiff base ligand in conjugation with auxiliary ligands. The compounds were characterized by elemental analysis, ATR-FTIR spectroscopy, X-ray diffraction, TG, DSC, TG-FTIR and XRD analysis. The N₂O₄ salen-type ligand coordinates 3d and 4f metal centers via azomethine nitrogen and phenoxo oxygen atoms, respectively, to form heteropolynuclear complexes having CuO₂Ln cores. In the crystals 1 and 2, two terminal Cu(II) ions are penta-coordinated with a distorted square-pyramidal geometry and a Ln^III ion with trigonal dodecahedral geometry is coordinated by eight oxygen atoms from [Cu^II(H₂L)(NO₃)]⁻ and [Cu^II(HL)(NO₃)]²⁻ units. Compounds 1 and 2 are stable at room temperature. During heating, they decompose in a similar way. In the first decomposition step, they lose solvent molecules. The exothermic decomposition of ligands is connected with emission large amounts of gaseous products e.g., water, nitric oxides, carbon dioxide, carbon monoxide. The final solid products of decomposition 1 and 2 in air are mixtures of CuO and Ho₂O₃/Er₂O₃. The measurements of magnetic susceptibilities and field dependent magnetization indicate the ferromagnetic interaction between Cu^II and Ho^III ions 1.

Ligand-directed assembly of trinuclear and one-dimensional heterotrimetallic CuIILnIIIFeIIIcomplexes: unusual antiferromagnetic CuIIFeIIIcoupling via cyano bridges

Rare phenoxo- and cyano-bridged CuLnFe trinuclear complexes were prepared. The 1D Cu₂DyFe complex displays both single-chain magnetic properties and the intrachain Cu(ii)–Fe(iii) antiferromagnetic coupling.

Octanuclear Zinc(II) and Cobalt(II) Clusters Produced by Cooperative Tetrameric Assembling of Oxime Chelate Ligands

We have synthesized an octanuclear zinc(II) cluster [L4Zn8(H2O)3] by the complexation of 3-hydroxysalamo (H4L) with zinc(II) acetate. The complex crystallizes in the triclinic system, space group P, with unit cell parameters a = 18.233(10) A, b = 20.518(11) A, c = 21.366(11) A, alpha = 98.7557(2) degrees, beta = 99.191(11) degrees, gamma = 108.309(10) degrees, and Z = 4. The crystallographic analysis revealed the S4 symmetrical assembling of four ligands and that the tetrameric complex has three water molecules in an unsymmetrical fashion. Spectroscopic analysis of the complex strongly suggests that the octanuclear cluster also exists in solution and maintains a conformation similar to that in the crystal structure, although exchange of the coordinating water molecules presumably takes place. In addition, the formation process of the octanuclear complex is highly cooperative. A high coordinating ability of the [(salamo)Zn] unit as well as the catecholato2- moieties probably stabilizes the octanuclear assembly and makes the complexation process cooperative. The corresponding octanuclear cobalt(II) cluster [L4Co8(EtOH)3] was prepared in a similar manner. Complex [L4Co8(H2O)2X] (X = H2O or EtOH) was obtained by the recrystallization from chloroform/hexane. The complex crystallizes in the triclinic system, space group P, with unit cell parameters a = 15.2359(10) A, b = 16.9625(12) A, c = 18.9325(13) A, alpha = 101.9710(10) degrees, beta = 105.5410(10) degrees, gamma = 97.1290(10) degrees, and Z = 2. Temperature dependence of magnetic susceptibility showed a continuous decrease in the chi(M)T value with decreasing temperature, suggesting antiferromagnetic interaction among cobalt(II) ions. The magnetic susceptibility above 40 K obeys the Curie-Weiss law with a Weiss constant theta of -39 K and a Curie constant C of 19.7 cm(3) K mol(-1).