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ISBN 9783843942850

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978-3-8439-4285-0, Reihe Anorganische Chemie

Aida Raauf
Heterobimetallic Lanthanide and Actinide Alkoxides as Single-Source Precursors for the Development of Nanomaterials

305 Seiten, Dissertation Universität Köln (2019), Softcover, A5

Zusammenfassung / Abstract

This PhD thesis contains new findings on the synthesis of lanthanide and actinide alkoxides. The synthesis of homo- and heteroleptic bimetallic lanthanide alkoxides [LnM(L)m(OR)nsolv] and their structural investigations upon alteration of the ionic radii and the valence states of the metal centers is described. Furthermore, the role of the steric profile of the employed alkoxo ligand and the presence of donor ligands in the coordination sphere is discussed. Despite the presumed ionic nature of Ln-O and An-O bonds, such mixed-ligand complexes offer strikingly good volatility, which makes them potential single-source precursors for gas phase deposition of binary and ternary oxide phases. For the first time thin films of pyrochlore Nd2Sn2O7 could be deposited via liquid and gas phase, by using [NdSn(OtBu)5py] and [NdSn(L)(OtBu)4], respectively, as a molecular source. The sols prepared from mixed-metal Nd-Sn compounds were successfully electrospun to obtain single-phase Nd2Sn2O7 nanofibers. The photocatalytic and sensing properties of the prepared pyrochlore materials were investigated. The bilayered (Nd2Sn2O7//Fe2O3) photoanode exhibited a significant enhancement in photoelectrochemical (PEC) performance. Furthermore, the gas sensing measurement of Nd2Sn2O7 single layer showed a high selectivity towards hydrogen. In the next step, the properties of novel heterometallic actinide(IV, V, VI) alkoxides ([AnM(OR)n] and [UO2M2(OR)(OAc)]2) were investigated. The reaction of a trivalent uranium compound with bivalent tin derivatives was investigated which allowed the isolation of the first monomeric pentavalent uranium tert-butoxide [U(OtBu)5py]. In a new synthetic strategy the Lewis basicity of the Sn(II) compound [Sn{N(SiMe3)2}2] was exploited to reduce uranyl groups (O=UVI=O) that delivered pentavalent uranyl-free compounds [U(OtBu)5(OAc)]2 in a facile reaction.