Modern Polymer Spect..

224 4 Vibrcitioiznl Spectroscopy of Intact and Doped Conjugated Polymers
RAMAN SHIFT/cm-' Excitation wavelength is 1064 nin [88]
Figure 4-12. Atomic displacements of inajor vibrational modes
(k = 0) of poly(p-phenylene). (a) 1599 an-' [v2(ng)]; (b) 1295
cm-' [q(ug)];(c) 1226 cm-I [114(a,)]: (d) 776 cm-I [v5(az)]:
(d) (el (f) (e) 1477 c1n-l [1~,0(b,~)]; (f) 991 c1n-l [iy(hlu)][84]
The Raman spectra of the radical anions of PP2 [92, 96, 971, PP3 [70, 981, PP4
[70, 981, PP5 [70] and PP6 [70], and the diaiiions of PP3 [70, 981, PP4 [70, 981, PP5
[70], and PP6 [70] have been reported by several authors. The Raman spectra of the
radical anions (PPnP) and dianions (PPTz~~) in THF solutions are shown in Figures
4-14 and 4-15, respectively. The excitation wavelengths used are rigorously or
nearly resonant with band I1 of the radical anions and band I' of the dianions. The
Raman spectra of the radical anions are similar to each other, and so are the
Rainan spectra of the dianions. However, the two groups of the Raman spectra are
different from each other and from those of neutral 12-oligopheiiyls. These results
suggest that the negative polarons and bipolarons, corresponding respectively to the
radical anions and dianions, can be identified by Raman spectroscopy.
The Ranian spectra of the radical anions in Figure 4-14 show siiiall changes with