Surface-Induced Modification of Supported Late Transition Metal Complexes

Detta är en avhandling från Division of Synchrotron Radiation Research, Department of Physics, Faculty of Science, Lund University

Sammanfattning: The work presented in this thesis addresses the investigation of the electronic, magnetic, and structural properties of late transition metal complexes supported on various surfaces. The research is aimed at studying the interaction between the molecules and the support, together with the intermolecular interaction. This knowledge is essential e.g. for the development of organic molecule-based devices and the creation of active and stable catalysts. In this work, the modification of the electronic states of the iron phthalocyanine (FePc) complex induced by a Cu(111) surface was extensively investigated. These studies were motivated by the role that phthalocyanines play in charge injection devices and molecular electronics. The analysis revealed a non-isotropic charge transfer from the surface, which arises from the rehybridisation of molecular and metal electronic states and results in the breaking of the perfect fourfold symmetry of the molecule. In addition, I demonstrate a surface-driven thermal modification of the electronic and structural properties of the phthalocyanine molecules when deposited on Cu(111) support. This knowledge is essential because a thermal evaporation of adsorbates is the most common preparation technique for the creation of molecular monolayers. This technique is widely used for commercial purposes such as the creation of molecular switches and data storage devices. The FePc molecule is also quite unique due to the similarity of its structural and magnetic properties to that of the reactive site in haemoproteine, a molecule known to perform the activation, storage, and transport of molecular oxygen. Therefore, I also investigated FePc as a synthetic model of the iron porphyrine in the haem reactive site. This investigation revealed that despite its structural similarity to haem, the molecule interacts with molecular oxygen only as a result of the stronger electronic coupling of the FePc molecules to the surface. These studies can help to obtain a better understanding of mechanisms of the haem-oxygen interaction. Motivated by the success in the development and mass production of green and affordable surface-supported transition metal complex catalysts, this thesis incorporates the full characterisation of two new N-heterocyclic carbene palladium complexes anchored to a silica surface. The study is aimed at providing a comprehensive knowledge about stability, surface orientation, and catalytic activity of late transition metal complexes at surfaces for heterogeneous catalysis, as opposed to the more commonly used homogeneous catalysis in inorganic chemistry. In summary, the strength of this thesis lies in the provision of a comprehensive overview of the interaction and surface-driven modifications of supported transition metal complexes on various surfaces and new insight into the magnetic and electronic properties of single molecules, monolayer, and multilayers.