Laura Finazzi

Mass spectrometry (MS) has established itself as a cornerstone technique in many scientific fields thanks to its high selectivity and sensitivity. However, its biggest limitation is the inability to directly probe molecular structure. Information about a species’ molecular structure can only be inferred indirectly through the molecular formula and fragmentation patterns, as MS data does not provide any information about the spatial connectivity or configuration of atoms.

Infrared ion spectroscopy (IRIS) merges the structural insights of infrared spectroscopy with the high sensitivity and selectivity of mass spectrometry (MS), enabling the characterization of mass-selected ions of interest. This thesis provides an introductory overview of the various iterations and technological advancements of IRIS, highlighting its versatility across diverse scientific domains. We demonstrate this broad applicability in this thesis by addressing various research questions pertaining to distinct fields, with the experimental findings organized into three parts.

Part I describes the application of IRIS to the determination of protonation sites of gas-phase systems which present multiple competing basic sites. We demonstrate the potential of IRIS employing aromatic amines as model systems, not only solely from a standpoint of protomer identification but also to get insight into the pathways of proton migration and their implications when ion mobility separation is applied to these systems.

Part II explores the application of IRIS in the elucidation of MS/MS fragment ions structures of steroidal hormones. In biochemical investigations, tandem MS is typically used for the detection and quantification of steroidal hormones by monitoring diagnostic fragment ion structures, but identification of their precise molecular structures is often challenging. A better understanding of the MS/MS fragmentation chemistry may aid in a better classification and identification of the hormones. Here, we show that IRIS is a successful methodology for identifying steroidal hormones fragment structures.

Part III explores the application of IRIS in the study of ionized fullerenes. Since the discovery of C60, fullerenes and their analogues have been hypothesized to exist in interstellar and circumstellar environments. Building on our group’s previous research into protonated fullerenes, we present new IR spectral data revealing the accurate position of the single CH-stretch band in protonated C60 and C70, which may serve as a diagnostic astronomical marker for these species. Furthermore, we present new IR spectra for a set of anionic fullerenes - as they are good electron acceptors and are predicted to be present in planetary nebulae.