To catch and understand excited-state proton transfer intermediates

• Applicants: Professor Dr. Gregor Jung; Dr. Jose Luis Perez Lustres
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559282314

Proton transfer is one of the most elemental chemical reactions. Despite, knowledge about the various reaction stages and intermediates is incomplete, as consequence of the ultrafast timescales involved and strong spectral congestion. This proposal addresses excited-state proton transfer with photostable pyranine-based photoacids, which undergo proton transfer to hydrogen-bonded phosphine oxide bases. In continuation of previous work, we now use bisphosphine oxides as complex ligands where the primary ESPT is followed by another proton hopping event. A rich combination of femtosecond time resolved and steady-state spectroscopic methods aims to disentangle the reaction mechanism, that is to estimate activation parameters of the elemental steps and to disclose the time-evolving structure of the intermediates. To this aim, temperature and solvent properties are varied. The latter tune rate and extent of the reaction and are thus an important instrument to trap intermediates. Thereby, the most complete picture of proton transfer in condensed phase is advanced, paving the way for polarity probes at single molecular level.

• DFG Programme: Research Grants