Infrared absorption spectra of naphthalene and anthracene anion-radicals

The infrared spectra of naphthalene and anthracene anion-radicals and their completely deuterated analogs have been studied. The most intense bands have been assigned, and it has been shown that the frequencies of the bending and stretching vibrations of the ring and the C-H (D) bond are less than the corresponding frequencies for the hydrocarbons. The decrease in the frequencies has been attributed to the fact that the unpaired electron of the anionradical, present in an antibonding orbital, decreases the force constants of the bonds; this is analogous to an excited state of the hydrocarbon molecule. A product rule has been proposed for the anion-radicals and their original hydrocarbons.