An XPS study on the coordination mode of organic R-COO- ligands to metal centers

Abstract

ABSTRACT: This thesis is within the context of surface science, more specifically in the context of the structure of coordination compounds at the surface of materials, this is in order to unravel the mechanism of interfacial interactions between the surface atomic lattices and their surroundings. These interactions can be modified and tuned by surface functionalization, for example one of the most commonly used functional groups at the surface of materials are the metal carboxylates due to their versatility in the way that they can binded to the surface, which can change the surface properties. For this reason, they are of prime interest in hot topics such solar cells, catalysis and nanoengineering. Customary techniques like XRD and FTIR which are used to perform structural analysis are sensible to the bulk structure, but they provide poor information about the surface; on the contrary, XPS senses fundamentally the chemical environment and the behavior of surface atoms. In this work, we aim to employ XPS as an alternative technique to elucidate the coordination mode in transition metal carboxylates, by using several metal acetates as model compounds. Specifically, we show how the chemical shifts observed in the C1s and O1s signals of metal carboxylate in the XPS spectrum can be used to distinguish between common binding modes of metal carboxylates. All the conclusions presented in this work are supported by structural data obtained from X-Ray Powder Diffraction.