Infrared and Raman studies of the radical anion of α,ω-diphenyl-1,3,5,7,9-decapentaene as a model compound in polyacetylene

The FT-infrared (IR) and Raman spectra of the radical anion of α,ω-diphenyl-1,3,5,7,9-decapentaene (DP10−), a polyene molecule with five conjugated CC bonds, were observed in vacuum condition. The IR absorption spectrum for ionic species of polyene molecule was observed for the first time in the experimental method. The CC stretching band of IR absorption has the weak at 1591–1603 cm−1, while the Raman band has the two intense peaks at 1533 and 1574 cm−1. In IR absorption, the in-plane CH bending has the several strong bands between 1448 and 1551 cm−1, whereas the Raman has a strong band used as a marker of negatively charged polyene at 1272 cm−1. The origin of IR and Raman spectra of DP10− is discussed in terms of a polaron model compound in polyacetylene.