Cation ordering from absorption spectra

Fig. 9 (A) Transient absorption spectrum of the cation radical from anthracene (AnH) in CH2C12 at about 35 ps following the 532 nm charge-transfer excitation of the 0s04 complex with 30-ps (FWHM) laser pulse. The inset shows the steady-state spectrum of AnH+- obtained by spectroelectrochemical generation. (B) The decay of the charge-transfer transient by following the absorbance at Amax = 742 nm. The inset shows the first-order plot of the absorbance decay subsequent to the maximum...

In order to measure the absorption spectra, the radical anions were generated electrochemically in the optical path of a spectrophotometer. The absorption spectrum of 3,5-dinitroanisole radical anion (Figure 11, curve c) is very similar to that of the 550-570 nm species produced photochemically. So we believe this species to be the radical anion formed by electron transfer from the nucleophile to the excited 3,5-dinitroanisole and decaying by interaction with its surroundings including the nucleophile radical cation. The behaviour described seems to be rather general for aromatic nitro-compounds since it is observed with a series of these compounds with various nucleophilic reagents. 

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