High sensitivityresonator

EPR measurements were performed using
a CW X-band EMXplus spectrometer with a PremiumX microwave bridge
and a high-sensitivity resonator (Bruker, Germany). The EPR spectra
were registered at 100 kHz modulation and a microwave power of 5 mW
at room temperature. An NMR teslameter (Bruker, Germany) was used
for precise g value determination. For in
situ EPR spectroelectrochemical experiments, a three-electrode
EPR flat cell was used. A laminated gold mesh (Goodfellow, U.K.) as
the working electrode, an AgCl-coated silver wire as the pseudoreference
electrode, and a platinum wire as the counter electrode were used
in spectroelectrochemical experiments. The 0.1 M [N(Bu)₄][B(C₆F₅)₄] in THF (anhydrous, ≥99.9%,
inhibitor-free, Sigma-Aldrich) was used as the supporting electrolyte.
Cell assembling and the measurements were performed under an inert
(nitrogen) atmosphere. In the spin-trapping experiments, dimethylformamide
(DMF, anhydrous, ≥99.8%, Sigma-Aldrich) solutions were bubbled
with air, oxygen, or nitrogen for 2 h. 50 mM spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO, ≥99.0% (GC), Dojindo, Japan) and 1.5
mM ferrocene compound were added to the solution one after another.