Hannover 2020 – scientific programme
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MO: Fachverband Molekülphysik
MO 16: Femtosecond Spectroscopy II
MO 16.4: Talk
Thursday, March 12, 2020, 14:45–15:00, f102
Signatures of halogen-bond interactions in time-resolved fluorescence spectroscopy — •Bastian Geissler1, Sarah Khani2, Elric Engelage3, Christof Haettig3, Stefan Huber3, and Patrick Nuernberger1 — 1Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93040 Regensburg — 2Center for Theoretical Chemistry, Ruhr-Universität Bochum, 44780 Bochum — 3Organische Chemie I, Ruhr-Universität Bochum, 44780 Bochum
The formation of non-covalent halogen bonds between a halogenated organic compound and a Lewis base in solution is an active field of research with relevance to various chemical reactions and biological processes. However, the complex spectroscopic behavior of such mixtures and the assignment of (transient) spectroscopic signatures to halogen-bond formation in solution are still rather unexplored.
In this contribution, we focus on benzoimidazolium derivatives serving as halogen bond donors and pyridine derivatives as Lewis base acceptors dissolved in acetonitrile. We identify the impact of additional counterions [OTf]- and [BArF4]- on the fluorescence properties of these donor-acceptor pairs. In addition to ultrafast transient absorption measurements, we perform time-resolved fluorescence streak imaging studies to scrutinize halogen bonding and competing complex formations. Whereas transient absorption indicates an ultrafast reversible halogen-bond cleavage upon illumination, the fluorescence studies additionally reveal new insights concerning the role of complexation with [OTf]- and [BArF4]-.