Quantification of Interactions in Per- and Polyfluorinated Organic Substances

• Applicant: Professor Dr. Hermann A. Wegner
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544142612

Fluorinated organic compounds are ubiquitous in our daily lives, such as Teflon as a non-stick coating for cookware. Recently, however, the negative environmental and human health impacts of per- and oligofluorinated alkyl substances (PFAS) have brought this class of compounds into a different focus. Therefore, a deep understanding of the special “fluorine effect” on the molecular level is the basis to design new materials using, and replacing, fluorine to create new functions. In recent years, the importance of low energy molecular level contacts has been recognized and addressed, for example, in the DFG Priority Program SPP 1807 "Control of London Dispersion Interactions in Molecular Chemistry". Within this framework, we have developed the azobenzene switch as an effective tool for quantifying London dispersion interactions. The ease of synthesis and functionalization of azobenzenes, as well as the subsequent quantification of interactions by UV-Vis spectroscopy, distinguish this tool from other molecular scales. In this proposal, we will apply the azobenzene tool to study systematically fluorine interactions in organic compounds. For this purpose, fluorinated chains are attached to the azobenzene core in meta-position. By varying the position of fluorine atoms, degree of fluorination and branching, detailed information on F–F, C-H–F as well as F–π-system interactions will be obtained. In addition, the effect of different solvents is tested. The study is supported by detailed calculations. The use of a combination of the CREST (Conformer-Rotamer Ensemble Sampling Tool) and CENSO (Commandline ENergetic SOrting of Conformer Rotamer Ensembles) method will reflect the crucial aspect of conformation in fluorinated compounds.

• DFG Programme: Research Grants