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Compounds Comprising Lanthanide Clusters and Their Potential as Molecular Magnets: Synthesis, Structure and Magnetic Properties
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The purpose of this research is to synthesize new compounds containing lanthanides. Using slow diffusion crystallization methods and solid-state synthetic techniques, different families of compounds comprising lanthanides were synthesized and characterized by X-ray diffraction methods. Magnetic susceptibility measurements were also employed to characterize a new zirconium compound and to study the magnetic behavior of a family of isostructural reduced lanthanide-bromide clusters. Four different families of compounds were synthesized by slow diffusion using trinuclear lanthanide complexes supported by TDCI (1,3,5-tris(dimethylamino)-1,3,5- trideoxy-cis-inositol), [Ln3 (TDCI)2 (H2O)]6]^3+, and metallocyanates as linkers. The combination of [Cr(CN)6]^3– and trinuclear complexes having the lanthanide ions Gd^3+, Tb^3+ and Dy^3+ results in a family of compounds that features 1D-chains. [Fe (CN)6]^3– couple with trinuclear complexes containing Gd^3+ - Er^3+ yields a family of compounds featuring 2D-networks. Using [Co(CN)6 ]^3–, a new family of compounds characterized by 1D-chains is obtained when the trinuclear cluster has the lanthanide ions Ho^3+, Er^3+ and Y^3+. The last family of compounds was discovered when utilizing tetracyanometallates, [M(CN)4]^2– (M = Ni, Pd and Pt); this new family of compounds is composed of two trinuclear complexes and three linker units. The solid-state synthesis using lanthanide bromides resulted in clusters with the Y6 I10Ru-type structure, Ln6Br10Co (Ln = Gd, Tb and Er) and Tb6Br10Ni. Magnetic susceptibility of the Ln6Br10Co compounds, with 17e^– per cluster, revealed that these compounds exhibit intracluster ferromagnetic coupling while the compound Tb6Br10Ni, with 18e^– closed-shell configuration, does not. The encapsulation of C resulted in three new isostructural compounds adopting the form of Gd10C4Cl18, Ln10Br18 (C2)2 (Ln = Gd, Ho and Y). A new reduced zirconium compound, [Zr6MnI12]4[MnI4]3, was obtained by solid state synthesis. This new compound has Mn atoms in two different environments, as interstitial and in tetrahedral cavities, and has three axial iodides. These features are not known for other zirconium-cluster compounds or the lanthanides. Computational methods were employed to obtain the energies and the frontier molecular orbitals of three different spin patterns of a dinuclear gadolinium complex. The involvement of the f-orbitals of the gadolinium ions help to understand the observed magnetic behavior. A structural optimization of Zr6MnI12 was also performed using DFT methods, and a reasonable structure and its frontier orbitals were obtained. In conclusion, the lanthanides have shown to be very versatile in the synthesis of new compounds. Using slow diffusion crystallization, we synthesized four different families of compounds having trinuclear lanthanide complexes and metallocyanates; by solid-state synthetic methods, we obtained reduced lanthanide clusters and a new reduced zirconium iodide compound, which were characterized by X-ray diffraction methods and magnetic susceptibility measurements. In addition, computation methods were employed to find the energies of different spin patterns and molecular frontier orbitals that helps us to better understand the bonding in lanthanide based compounds.
Escobedo Cruz, Francisco Vidal (2016). Compounds Comprising Lanthanide Clusters and Their Potential as Molecular Magnets: Synthesis, Structure and Magnetic Properties. Doctoral dissertation, Texas A & M University. Available electronically from