RRS characterization of selected oligomers of polyaniline in situ spectroelectrochemical study

Electrochemical, optical and vibrational properties of two oligomeric model compounds of emeraldine salt (ES), the only electrically conducting form of polyaniline, in nonaqueous solution are studied. The phenyl-end-capped dimer and tetramer of leucoemeraldine base are electrochemically oxidized in acetonitrile solution and the electrogenerated species are investigated using spectrophotometry and Resonance Raman Scattering (RRS). In situ resonance Raman study of the oligomers reveals the appearance of the Vibrational bands characteristic of the semiquinoid units, and in particular of the CN bond intermediate between the single and double CN bonds which are strongly resonantly enhanced with a red excitation line. The vibrational assignments of the fundamental modes of the electrogenerated species are reported and compared with those of the corresponding polymeric form. Our Raman results provide very interesting information not only about the vibrational properties of emeraldine salt but also about its electronic configuration. (C) 1999 Elsevier Science Ltd. All rights reserved.