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

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 generate a pair radicals comprising one-electron reduced and oxidized species. Our evidence is based on measurement two marker proton hyperfine couplings, Aiso(H(6α)) Aiso(H(8α)), which we correlated predictions density functional theory. The ratio these couplings reversed in radical Observation dismutation facilitated by exceptional C–H acidity methyl group at position 7 slow exchange associated with it, leads NMR-distinguishable anionic (TML−) neutral (TMLH) protonation forms.