Spectroscopic Studies on Radicals Produced from Acridine and Acridan in γ-Irradiated Rigid Solutions at −196°C

Dilute solutions of acridine in ethers and amines were frozen at −196°C to a glassy solid and were γ-irradiated. Electrons ejected by ionization are effectively scavenged by acridine to produce acridine anions which are the sole species having an electronic absorption band in the visible region. In alcohol and ester matrices the anion abstracts a proton from the matrix molecule even at −196°C and yields a semiquinone radical equivalent to the species formed by H-atom abstraction at the 9-position of acridan (dihydroacridine). Acridan in γ-irradiated butyl chloride matrix forms acridan cation which has a characteristic absorption band at 500–750 mμ. Detachment of a proton from the acridan cation produces another semiquinone radical identifiable with the species formed by H-atom abstraction at the 10-position of acridan. Both radicals have a similar yet clearly distinguishable absorption band in the visible region.