Structure and Reactivity of Shape-Shifting Molecules

The structure of chemical compounds plays a deciding role in promoting or hindering microscopic processes that shape our natural environment and promote molecular transformations important for technology and biochemistry. Many of these molecules can take different structural forms, which are commonly called isomers. In a significant number of applications and in natural processes such as solar energy, information technology and plant metabolism, structural transformations of specific isomers can act as a driving force. Therefore, it is of high relevance to unravel the structural differences between these molecules, as well as finding the reason for their respective stabilities. Moreover, from a technological point of view it is crucial to find ways to efficiently separate single isomers and study the effect of external impulses on their shape and reactivity. The proposal entitled Structure and Reactivity of Shape-Shifting Molecules aims for a detailed understanding of the way in which light radiation, heat and collisions affect the shape of chemical compounds at a microscopic level, as well as for a precise insight on their inherent structural properties. This shall be achieved by combining gas-phase techniques that are capable of separating molecular isomers with laser and collision experiments that can induce structural transformations in these preselected molecules. The first part focuses on understanding the way in which external actions can induce and stabilize conformational changes in molecules of technological relevance. The target of the second part is the investigation of the structural properties of compounds whose shape has a strong impact on the evolution of our chemical universe. The third part of this project, embedded in my return phase to Innsbruck, will be devoted to study specific bending and torsional motions of the above-mentioned species, thereby applying the gained knowledge on molecular spectroscopy during the previous years. The Methods Section describes the experimental arrangement that will be employed and anticipates a new method that extends the capability of the current machine to study the specific reactivity of distinct isomers by preselecting and controlling them in an ion trap. By unravelling in which way and under which conditions chemical species change their structural arrangement, a fundamental insight into the chemistry of complex natural environments can be achieved. In addition, these investigations can steer technological improvements towards a better selectivity, control and efficiency of devices that use shape-shifting molecules as microscopic motors for their operation.

Molecules that change their shape in response to external actions such as light or collisions play a key role in many natural realms. Further, the operation of many modern technological devices is based on purpose-synthesized shape-shifting species. The goal of the present research project was to design and implement laboratory methods to separate isomers - molecules with the same mass but different structural arrangement- and study their fundamental structure and photochemical behaviour at a molecular level and in the absence of environmental disruptions. The research project consisted of two main subunits. In a first project, a homebuilt apparatus combining isomer separation and laser activation was used to investigate light-driven transformations in biologically and technologically relevant molecules, as well as the competition between such transformations and other photochemical processes. During this project, multiple chemical systems ranging from fluorescent proteins to synthetic azobenzenes were investigated. The second project was devoted to the design and construction of a worldwide unique apparatus that should combine isomer separation with molecular trapping and structural elucidation at ultracold conditions. This project included design and construction of a new modular instrument combing a laser ablation source, several ion mobility stages, a quadrupole mass section, a cryogenic ion trap and a time-of flight mass spectrometer. This combination is unique and makes this instrument one of the most multifaceted and sophisticated of its kind. The development of such powerful technology can represent a crucial step towards establishing isomer specific studies as an important analysis dimension in conventional mass spectrometry that ultimately shall drastically improve the quality and detail of molecular characterization.