Figure 4. Infrared spectra probing the localization of the two one-electron oxidations of the reduced model [1].

a–d, Titration of ${\text{FcBAr}}_4^{\mathrm{F}}$ into a CH₂Cl₂ solution of 1 monitored by solution IR spectroscopy: [1] (a), [1] + 1 equiv. ${\text{FcBAr}}_4^{\mathrm{F}}$ (b), [1] + 1.5 equiv. ${\text{FcBAr}}_4^{\mathrm{F}}$ (c), [1] + 2 equiv. ${\text{FcBAr}}_4^{\mathrm{F}}$ (d). On conversion of [1]⁺ to [1]²⁺, an isosbestic point is observed at 1,969 cm⁻¹.