Manuel Mosquera González, M. Carmen Ríos Rodríguez, M. Flor Rodríguez Prieto
Proton-transfer reactions are very important in Chemistry and Biology. Even though their empirical study began with the origin of chemistry, their detailed mechanism is still unknown. The proton movement in water has been a topic of study and controversy for years and the phenomenon is far from being understood. Proton transfer is also a crucial step in many biochemical processes. Recent investigations are aimed at unravelling their complex operating mechanism, which includes the proton-relay systems in enzymes, ionic channels and membrane proteins (the so-called proton wires).
Research on the dynamics and mechanism of proton transfer processes is driven by basic questions in the area of acid-base chemistry and by puzzling mechanistic questions in the areas of proton transport across biological membranes or across the proton-exchange membranes of fuel cells, considered as the main "green" alternatives to current combustion engines.
The objective of our research is to progress on the knowledge about the medium influence on the dynamics of proton-transfer reactions with the aim of improving both the comprehension of the reaction in condensed media and the understanding of the structure and dynamics of the medium in which the reaction takes place and of the nature of the interactions with the reacting species.
The study of photoinduced proton-transfer reactions is a powerful approach to investigate the dynamics of proton-transfer processes. Molecules bearing acid or basic groups may experience drastic changes in their acid-base properties upon electronic excitation. For these molecules, absorption of light triggers proton transfer reactions whose dynamics can be studied on ultrafast time scales with spectroscopic techniques. By measuring transient absorption and time-resolved fluorescence, we were able to show that the intrinsic rate of proton transfer from a strong acid to the solvent is controlled by solvation (J. Am. Chem. Soc. 2007), and that the process takes place in steps (J. Phys. Chem. B 2013 and J. Phys. Chem. Lett. 2014).
