Figure 1.
A: Absorption spectra of 2–4 at −78 °C in toluene. B–D: rRaman spectra (413 nm excitation) of 2–4 in toluene at −90 °C: B. 3-16O2 in d8-toluene (solid trace) and 3-18O2 in toluene (dash-dotted trace). C: 2-16O2 in d8-toluene (solid trace) and 2-18O2 in toluene (dash-dotted trace). D: 4-16O2 in d8-toluene (solid trace) and 4-18O2 in d8-toluene (dashed trace). See also Fig S22.