Ring rotation polaron

The optical absorption of emeraldine base film, together with selected millisecond photoinduced absorption and long time photoinduced absorption results are shown in Fig. 7. The " steady state (ms) spectrum of emeraldine base has features indicative of both the ring rotation polaron (at 0.9 eV and 2.9 eV) and the ring rotation polaron bound to imine groups (1.4 eV and 2.9 eV) as well as bleaching of the tt-tt band (3.7 eV) [43]. At long times only the trapped polaron is observed [17,27]. 

A model for the effects of electron-lattice coupling via ring rotation on the electronic structure of leucoemeraldine base has been developed [15]. The charge defect states in leucoemeraldine and other phenyl ring-containing polymers, particularly hole polarons, are... 

For instance, poly-p-phenylenes in their doped states manifest high electric conductivity (Shacklette et al. 1980). Banerjee et al. (2007) isolated the hexachloroantimonate of 4" -di(tert-butyl)-p-quaterphenyl cation-radical and studied its x-ray crystal structure. In this cation-radical, 0.8 part of spin density falls to the share of the two central phenyl rings, whereas the two terminal phenyl rings bear only 0.2 part of spin density. Consequently, there is some quinoidal stabilization of the cationic charge or polaron, which is responsible for the high conductivity. As it follows from the theoretical consideration by Bredas et al. (1982), the electronic structure of a lithium-doped quaterphenyl anion-radical also differs in a similar quinoidal distortion. With respect to conformational transition, this means less freedom for rotation of the rings in the ion-radicals of quaterphenyl. This effect was also observed for poly-p-phenylene cation-radical (Sun et al. 2007) and anion-radical of quaterphenyl p-quinone whose C—O bonds were screened by o,o-tert-hutyl groups (Nelsen et al. 2007). 

---