Koordinationsverbindungen $C_3$- und $C_2$-symmetrischer Liganden mit dreiwertigen Metallionen und Hf(IV)

  • Coordination compounds of $C_3$- and $C_2$-symmetric ligands withtrivalent metal ions and Hf(IV)

Wiederhold, Constanze Bettina; Oppel, Iris Marga (Thesis advisor); Englert, Ulli (Thesis advisor)

Aachen (2020)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2020

Abstract

$C_3$-symmetric, triaminoguanidinium-based ligands with three chelating [ONN]-binding pockets are flexible building blocks for the formation of supramolecular coordination compounds. Some complexes with divalent metal ions are known to date, most of which have high negative total charges. For catalytic applications, positively charged compounds would be advantageous, which is why experiments on charge reversal have already been undertaken. In this work, trivalent metal ions (Y(III), Ga(III) and In(III)) as well as Hf(IV) ions were used and converted with known ligands. The decomposition of the $C_3$-symmetric ligand to a $C_2$-symmetric ligand was observed with Hf(IV). The targeted reproduction of this ligand led to a [2x2]-grid with Hf(IV) and in addition the catalytic oxidation of acetylacetone was observed. A preference of this $C_2$-symmetric ligand over the $C_3$-symmetric ligand could be demonstrated for Y(III) ions. However, the coordination of Y(III) ions is also possible by the $C_3$-symmetric ligands, whereby the coordination sphere of the metal ions is saturated by additional coligands and solvent molecules. The use of Ga(III) ions led to various single- or multi-layered coordination compounds. The formation of these complexes was investigated, whereby an influence of the substituents on the ligands and the bound coligands on the resulting compounds could be determined. In principle, it is possible to build one-, three- and four-layered complexes with different chelating and non-chelating specifically applied coligands. By using sodium ions, several such layered structures can be linked to form a 1D-polymer. Also, the coordination of In(III) ions by the $C_3$-symmetric ligands is possible and leads to comparable two-layered compounds. As coligands Acetylacetonate, acetate and methanolate ions were investigated. Two-layered structures can be combined to a dimer via methanolate ions. In the presence of sodium ions, the linkage to a 1D-polymer is also possible. With a sterically less demanding ligand and without sodium ions, a cyclic coordination oligomer consisting of several two-layered complexes is formed. This has a spherical cavity of 2026 $Å^3$ with a diameter of 15.69(2) Å and is therefore interesting as a host for larger molecules.

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