New methods of collection and interpretation in photoelectron spectroscopy: Applications to metallocenes

Abstract

The use of ultraviolet photoelectron spectroscopy (UPS) to probe bonding and electronic structure in organometallic molecules is explored by development of new techniques for obtaining and interpreting valence ionizations in photoelectron spectra. Methods used in this work include understanding molecular functional group cross sections, determining communication between groups separated by alkane chains and the development of a new method of obtaining high quality UPS of surface-bound species. Our understanding of orbital mixing and the behavior of atomic orbitals in molecules is probed by investigation of a series of molecules containing functional groups separated by an alkane chain. The communication between functional endgroups is probed by varying the length of the alkane chain separating them. An investigation of these systems by variable photon energy photoelectron spectroscopy is presented and discussed. Molecules containing long (>10) alkane chains are described as models for gas-phase "solvation". Metallocene-terminated alkanethiol monolayers are prepared and analyzed as the first-ever method of obtaining high quality photoelectron spectroscopy organometallics in the condensed phase. The UPS of ferrocene and osmocene terminated monolayers are presented, showing that self-assembled monolayer technology can be successfully adapted to a method of producing UPS spectra of non-volatile molecules. Due to the unique environment of the metallocene, these terminated alkanethiol monolayers also act as an effective system to probe the effects of solvation on electronic structure and electron ionizations.