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Herein, we report the effect of protonation on the electronic properties and the conductivity of a soluble derivative of polyazomethine, poly(1,4-(2,5-bisoctyloxy phenylene­methylidynenitrilo)-1,4-phenylene­nitrilomethylidyne), BOO-PPI. Following protonation, a marked change in electronic structure occurs, as evidenced by a bathochromic shift in visible absorption and the appearance of a broad absorption in the infrared coupled with new infrared active vibrational modes, signaling the appearance of a new electronic state. In other conjugated polymers, such features usually evidence the formation of mobile polarons on the polymer chain, leading to an increase in electrical conductivity. Surprisingly, BOO-PPI protonation does not lead to such an increase. Protonation also does not result in an electron spin resonance signal. We propose a model for protonation inducing a charged state on the polymer chain with strongly limited delocalization accounting for the lack of the electron spin resonance signal and the missing conductivity. To our knowledge, this is the first time that spectral features usually corresponding to mobile charges in organic materials do not correspond to an actual change in conductivity.

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Raman scattering measurements in the tetragonal CdSAs, single crystals are carried out a t temperatures of 300 and 77 K. The spectra obtained are interpreted in terms of phonon-electron and electron-electron interactions. The features in the low-frequency interval are due to contributions from phonon and single particle scattering. The electronic RS involving intra-and interband excitations is dominant a t frequencies higher than 80 cm-l. The resonant enhancement of the band a t 300 cm-l arises from the incident light frequency being in the vicinity of El -C4.La diffusion Raman dans les mono-cristaux de C%As, quadratique a &tit BtudiBe Q 300 et 77 K. Les spectres Raman obtenus sont interprBt6s en termes des interactions un phonon-electron etBlectron-6lectron. Des spectres en region de basses frkquences sont attribuks Q la diffusion It un phonon et It une particule. Cependant la diffusion Raman faisant intervenir des excitations Blectroniques intra-et interbandes est dominant aux frhquences au-dessus de 80 cm-l. Une croissance resonante d'une bande Q 300 cm-l resulte du voisinage des Bnergies de raie incidente et un seuil d'excitation El -E4.

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