Freiburg 2024 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 3: Novel Spectroscopies

MO 3.1: Vortrag

Montag, 11. März 2024, 17:00–17:15, HS 1015

Two-Dimensional IR Spectroscopy of Bifunctional Vibrational Probes — •Claudia Gräve, Stefan Flesch, Luis Ignacio Domenianni, Jörg Lindner, and Peter Vöhringer — Universität Bonn, Wegelerstr. 12, 53115 Bonn, Germany

The nitrile group is a superb vibrational probe for the dynamics of biomolecular systems.^[1] Unfortunately, it exhibits a relatively small transition dipole moment, which causes sensitivity issues in IR-spectroscopic studies.

Here, we study the vibrational dynamics of small organic nitriles featuring an azide residue, which can later be utilized for protein incorporation. The two nitriles studied here are 4-azidobenzonitrile (N3-C6H4-CN) and 3-(4-azidophenyl)propiolonitrile (N3-C6H4-CC-CN).

We report on the linear Fourier-transform infrared spectra, as well as on the femtosecond pump-probe and 2DIR spectroscopy. The linear spectra in the azide and nitrile stretching region are highly complex due to Fermi resonances involving the N3-fundamental. Furthermore, the 2DIR spectra reveal the detailed vibrational energy flows between the azide and the nitrile groups separated by the phenyl ring. Finally, coherent oscillations resulting from impulsive excitation of the Fermi multiplets were observed by means of pump-probe measurements. Our results suggest that propiolonitrile is a superior vibrational probe as compared to the bare CN.
Literature:

[1] H. Kim and M. Cho, Chem. Rev. 2013, 113, 5817-5847.

Keywords: 2DIR spectroscopy; pump-probe spectroscopy