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Updated: May 16, 2026

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
Published on: February 10, 2020
Ultrafast two-dimensional infrared spectroscopy resolves the conformational change of an Evans auxiliary induced by
Andreas T Messmer1, Sabrina Steinwand, Katharina M Lippert
1Institute of Biophysics, Johann Wolfgang von Goethe University, Max-von-Laue-Strasse 1, 60438 Frankfurt, Germany.
Abstract:
Structure determination of reactive species is a key step in understanding reaction mechanisms. We demonstrate the application of polarization-dependent two-dimensional infrared spectroscopy (P2D-IR) as a powerful tool combining structure resolution with ultrafast time resolution. We apply this technique to investigate the substrate-catalyst complexes in a Lewis acid catalyzed Diels-Alder reaction. Using Mg(ClO(4))(2) as a Lewis acid, we found that an additional complex besides the chelate typically postulated as reactive species forms. Experimental access to this new species leads to a deeper understanding of the observed selectivities for the Diels-Alder reaction catalyzed by Lewis acids. Our findings are supported by density functional computations at the M06/6-31+G(d,p) level, including solvent corrections.
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