Figure 2. Characterization of 2.

(a) Ultraviolet–visible spectral changes observed upon photoirradiation (>420 nm) of a deaerated solution of 1 (black line: 1.0 mM) in acetone/H₂O (v/v=1/1) with [Ru^II(bpy)₃]²⁺ (0.050 mM) and Na₂S₂O₈ (10 mM) at −25 °C. Inset shows the time course monitored at 625 nm due to the formation 2. (b) Ultraviolet–visible spectral changes observed upon addition of PhIO (3 equiv.) to a solution of 1 (blue line; 2.0 mM) in the presence of HOTf (CF₃SO₃H, 1.2 equiv.) in acetone at −40 °C. Inset shows the time course monitored at 625 nm during the conversion of 3 (black bold line) to 2 (red line). (c) CSI-TOF MS spectrum of 2. Peak at m/z=466.1 corresponds to [(13-TMC)Co(O)(CF₃SO₃)]⁺ (calculated m/z=466.1). Insets show the observed isotope distribution patterns for 2-¹⁶O at m/z=466.1 (left panel) and 2-¹⁸O at m/z=468.1 (right panel). (d) Resonance Raman spectra of 2-¹⁶O (black line) and 2-¹⁸O (red line) obtained upon excitation at 413.1 nm in acetone at −40 °C. Blue line shows the difference between two spectra of 2-¹⁶O and 2-¹⁸O. The peaks marked with asterisks (*) originate from the solvent.