Work

Non-classical disproportionation revealed by photo-chemically induced dynamic nuclear polarization NMR

Year: 2021

Type: article

Abstract: . Photo-chemically induced dynamic nuclear polarization (photo-CIDNP) was used to observe the light-induced disproportionation reaction of 6,7,8-trimethyllumazine starting out from its triplet state to generate a pair of radicals comprising a one-electron-reduced and a one-electron oxidized species. Our evidence is based on the measurement of two marker proton hyperfine couplings, Aiso(H(6α)) and Aiso(H(8α)), which we correlated to predictions from density functional theory. The ratio of these two hyperfine couplings is reversed in the oxidized and the reduced radical species. Observation of the dismutation reaction is facilitated by the exceptional C–H acidity of the methyl group at position 7 of 6,7,8-trimethyllumazine and the slow proton exchange associated with it, which leads to NMR-distinguishable anionic (TML–) and neutral (TMLH) protonation forms.

Source: Magnetic Resonance

DOI: 10.5194/mr-2-281-2021

Authors: Jakob Wörner, Jing Chen, Adelbert Bacher, Stefan Weber

Institutions: University of Freiburg, Technical University of Munich

Language: English

Topic: Advanced NMR Techniques and Applications

Subfield: Spectroscopy

Field: Chemistry

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,015

Funders: Deutsche Forschungsgemeinschaft, Albert-Ludwigs-Universität Freiburg, China Scholarship Council, Université de Fribourg