Takayuki MIYAMAE, Daisuke YOSHIMURA (Nagoya Univ.), Hisao ISHII, Yukio OUCHI (Nagoya Univ.), Takafumi MIYAZAKI (Toyama Univ.), Tsuneaki KOIKE (Mitsui Petrochem. Inductries LTD), Takakazu YAMAMOTO (Tokyo Inst. Tech.), Yukiko MURAMATSU (Tokyo Inst. Tech.), Hideki ETORI (Tokyo Inst. Tech.), Tsukasa MARUYAMA (Tokyo Inst. Tech.) and Kazuhiko SEKI (Nagoya Univ.)
[Synth. Met. 84, 939 (1997)]
Ultraviolet Photoelectron Spectra were measured using synchrotron radiation for four kinds of (pi)-conjugated polymers, poly(pyridine-2,5-diyl)[Ppy], poly(2,2'-bipyridine-5,5'-diyl)[Pbpy], poly(2-methylantraquinone-1,4-diyl)[P(2Me-1,4-AQ)], and poly-(antraquinone-1,5-diyl)[P(1,5-AQ)], which exhibit n-type electrically conducting polymers. The spectra were analyzed with MO calculations of the oligomers. Upon potassium doping of Pbpy, two new states, which can be assigned to bipolaron bands, appeared in the originally empty energy gap. While Ppy shows similar gap states, it requires higher dopant concentration to create bipolaron bands than in the case of K-doped Pbpy. Ppy shows a weak coordinating ability toward the alkaline-metal than in the case of Pbpy, because of the mainly head-to-tail structure of Ppy. The UPS spectra of K-doped P(2Me-1,4-AQ) and K-doped P(1,5-AQ) also shows similar gap states. The changes in electronic structure of these polymers are discussed based on the conformational difference between these polymers.