Polarized absorption spectra of radical ions of some azanaphthalenes and biphenyls in stretched polymer films

Abstract

The stretched polymer film technique combined with -γ-irradiation has been employed to measure the polarized absorption (linear dichroism) spectra of radical anions of quinoline, isoquinoline, quinoxaline, phthalazine, phenylpyridine, 4,4′-bipyridyl, and 2,2′-bipyridyl. Profiles of polarized absorption spectra of all the radical anions are similar to those of the parent naphthalene or biphenyl radical anions. Those of radical cations of isoquinoline and 2,2′-bipyridyl are also similar to those of radical cations of their parent molecules. Quinoxaline radical cations, however, show quite a different spectrum from that of naphthalene radical cations; a long vibrational structure with ca. 550 cm−1 intervals was observed and peaks of these vibrational bands were polarized parallel to the molecular short-axis or normal to the molecular plane.