The complementation of Resonance Raman, Raman Polarization data, and far infrared spectroscopy was used to determine the nature of the iodine moiety in iodine-doped poly(phenyl)acetylene. For the molar concentration range of iodine/polymer of 1 to 5, the predominant iodine entity in the iodine-doped conductive polymer appears to be I5−.
John R. Ferraro, Kathleen Martin, Anita Furlani, and Maria Vittoria Russo, "Vibrational Spectroscopy of Iodine-doped Poly(phenyl)acetylene," Appl. Spectrosc. 38, 267-270 (1984)