On the Rational Synthesis of Stable Trimetallic Alkoxide Frameworks

The growing field of materials science and ever-increasing need of new materials and their applications especially on the nano scale necessitates rational concepts for their controlled processing. The demand for multimetallic oxide ceramics containing three or more different metals, requires a versatile precursor class capable of implementation in common liquid or gas phase processes to obtain multimetallic ceramics as powders and films.

This thesis gives novel insights into the chemistry of targeted trimetallic alkoxide construction. A series of new trimetallic alkoxide compounds were synthesized using the nonaisopropoxodimetallate unit {M2(OiPr)9}- based on tetravalent Ti, Zr, Hf, and Ce centers as the fundamental building block. Successive chelation of different alkoxometallates were used to access multimetallic precursors of diverse composition including metals of different ionic radii or oxidation states. The new compounds were thoroughly examined by elemental analysis, NMR spectroscopy and mass spectrometry. In addition, single crystal X-ray diffractions of trimetallic compounds provided further detailed information how to achieve stable multimetallic frameworks. The combination of applied analyses enabled the disclosure of unusual structural and physical features for these new compounds. Most notably, for the first time gas phase stable trimetallic isopropoxide fragments were observed, which represent a significant step towards the chemical vapor deposition of quaternary oxides.

The crucial insight acquired in this study by comprehensive investigations on different metal combinations was used to develop and elaborate general concepts for the rational construction of trimetallic assemblies. Each metal location in the trimetallic alkoxide framework contributes a different function to the overall stability of the final arrangements and only the proper synergetic interplay of fulfilled requirements enables the expansion of bi- to trimetallic alkoxides.