On the intimate relation of proton transfer and molecular complexation

In this Thesis, we study molecular-scale proton-transfer reactions and physical chemistry. Chapter 1 introduces the research themes, while Chapters 2 and 3 provide a description of the theoretical and experimental backgrounds. In Chapter 4, we use time-resolved vibrational spectroscopy, to trigger and observe the aqueous proton-transfer dynamics between the strong base actinoquinol and the weak acid succinimide. We find that such reactions are much slower, and mechanistically very different from previously studied strong acid – weak base systems. In Chapter 5, we follow up with a temperature-dependent study of the same reaction. We build a model that accounts for reverse and forward reactions, and connect those with the observable, ‘net’ reaction rates and activation barriers. We find that the energy penalty associated with the formation of intermediate complexes plays a significant role. In Chapter 6, we study the effect of metal ions. We find that metal ions accelerate proton-uptake, but inhibit subsequent hydroxide-release. In Chapter 7, we use vibrational sum-frequency generation spectroscopy, to study the interfacial orientation of the neurotransmitter glycine. We find that this orientation is determined by an interplay of interfacial electric fields and specific interactions with surfactant monolayers. In Chapter 8 we study how anions impact the self-assembly of cationic surfactant monolayers. We find that the surface potential is a major barrier to adsorption. We observe that adding bicarbonate anions to solutions of ammonium-based surfactants leads to full surface coverage under bio/marine relevant bicarbonate concentrations, and infer that efficient interfacial pair-formation is likely neutralizing the surface potential.