Titania-mediated photoinduced fluorination of nitrone spin traps in acetonitrile (an EPR study)

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 432; p. 114111
• Main Authors: Brezová, Vlasta, Barbieriková, Zuzana, Zalibera, Michal, Lušpai, Karol, Tholtová, Andrea, Dvoranová, Dana
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2022
• Subjects: Acetonitrile; AgBF4; Cyclic voltammetry; EPR spectroscopy; Fluoride; Spectroelectrochemistry; Titanium dioxide; Cyclic voltammetry; Fluoride; Acetonitrile; AgBF4; Titanium dioxide; Spectroelectrochemistry; EPR spectroscopy
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2022.114111

[Display omitted] •TiO2-mediated fluorination of cyclic nitrones in acetonitrile was studied by EPR.•β-Fluorine spin-adducts were found upon UVA exposure of TiO2 containing F– or BF4–.•Ag(I) or Cu(II) ions were used as photoelectrons scavenger in photoactivated TiO2.•The pathways of β-fluorine spin-adduct formation in UVA-exposed TiO2 are discussed. Cyclic nitrone spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and its derivatives were applied in an EPR study of paramagnetic intermediates generated by in situ photoexcitation of TiO2 nanoparticles dispersed in acetonitrile with fluorinated ions. The UVA irradiation of deoxygenated acetonitrile titania suspensions containing the spin traps in the presence of fluoride or tetrafluoroborate, and Ag(I) or Cu(II) as photoelectron acceptors, resulted in the generation of the corresponding fluorine spin-adducts with well-resolved EPR signals. The EPR spectra of β-fluorine spin-adducts of the DMPO analogs, featuring ethoxycarbonyl (EMPO), diethoxyphosphoryl (DEPMPO), or diisopropoxyphosphoryl (DIPPMPO) groups at position 5 of the pyrroline ring, are reported for the first time. The reaction mechanisms leading to the β-fluorine spin-adduct formation in the given photocatalytic system are discussed.