Gold(II) complexes are rare, and their application to the catalysis of chemical transformations is underexplored. The reason is their easy oxidation or reduction to more stable gold(III) or gold(I) complexes, respectively. We explored the thermodynamics of the formation of [AuII (L)(X)]+ complexes (L=ligand, X=halogen) from the corresponding gold(III) precursors and investigated their stability and spectral properties in the IR and visible range in the gas phase. The results show that the best ancillary ligands L for stabilizing gaseous [AuII (L)(X)]+ complexes are bidentate and tridentate ligands with nitrogen donor atoms. The electronic structure and spectral properties of the investigated gold(II) complexes were correlated with quantum chemical calculations. The results show that the molecular and electronic structure of the gold(II) complexes as well as their spectroscopic properties are very similar to those of analogous stable copper(II) complexes.

• Klíčová slova
• density functional calculations, electronic spectroscopy, gold, mass spectrometry, vibrational spectroscopy,
• MeSH
• dusík MeSH
• halogeny MeSH
• kationty MeSH
• krystalografie rentgenová MeSH
• ligandy MeSH
• měď * chemie   MeSH
• teoretické modely MeSH
• zlato * chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• dusík MeSH
• halogeny MeSH
• kationty MeSH
• ligandy MeSH
• měď * MeSH
• zlato * MeSH

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

FeV(O)(OH) species have long been proposed to play a key role in a wide range of biomimetic and enzymatic oxidations, including as intermediates in arene dihydroxylation catalyzed by Rieske oxygenases. However, the inability to accumulate these intermediates in solution has thus far prevented their spectroscopic and chemical characterization. Thus, we use gas-phase ion spectroscopy and reactivity analysis to characterize the highly reactive [FeV(O)(OH)(5tips3tpa)]2+ (32+) complex. The results show that 32+ hydroxylates C-H bonds via a rebound mechanism involving two different ligands at the Fe center and dihydroxylates olefins and arenes. Hence, this study provides a direct evidence of FeV(O)(OH) species in non-heme iron catalysis. Furthermore, the reactivity of 32+ accounts for the unique behavior of Rieske oxygenases. The use of gas-phase ion characterization allows us to address issues related to highly reactive intermediates that other methods are unable to solve in the context of catalysis and enzymology.

• MeSH
• katalýza MeSH
• oxidace-redukce * MeSH
• oxygenasy metabolismus   MeSH
• sloučeniny železa chemie   MeSH
• železo chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• oxygenasy MeSH
• sloučeniny železa MeSH
• železo MeSH