Flavin-based catalysts are photoactive in the visible range which makes them useful in biology and chemistry. Herein, we present electrospray-ionization mass-spectrometry detection of short-lived intermediates in photooxidation of toluene catalysed by flavinium ions (Fl+ ). Previous studies have shown that photoexcited flavins react with aromates by proton-coupled electron transfer (PCET) on the microsecond time scale. For Fl+ , PCET leads to FlH.+ with the H-atom bound to the N5 position. We show that the reaction continues by coupling between FlH.+ and hydroperoxy or benzylperoxy radicals at the C4a position of FlH.+ . These results demonstrate that the N5-blocking effect reported for alkylated flavins is also active after PCET in these photocatalytic reactions. Structures of all intermediates were fully characterised by isotopic labelling and by photodissociation spectroscopy. These tools provide a new way to study reaction intermediates in the sub-second time range.

• Klíčová slova
• flavin, ion spectroscopy, mass spectrometry, peroxy intermediates, photooxidation,
• MeSH
• flaviny chemie   MeSH
• hmotnostní spektrometrie s elektrosprejovou ionizací MeSH
• katalýza MeSH
• lasery polovodičové * MeSH
• oxidace-redukce MeSH
• peroxid vodíku chemie   MeSH
• protony MeSH
• transport elektronů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• flaviny MeSH
• peroxid vodíku MeSH
• protony MeSH