X-ray photoelectron spectroscopy studies of deprotonated polypyrrole and its complexes

Abstract

Oxidized polypyrrole (PPY) was subjected to deprotonation by 0.5 M NaOH. The interactions of the deprotonated pyrrolylium nitrogens with various protonic acids and organic electron acceptors were studied by X-ray photoelectron spectroscopy (XPS) and were found to be similar to those observed for the imine nitrogens in the emeraldine oxidation state of polyaniline. However, the cyclic acid/base treatments of the deprotonated PPY were not completely reversible. The interactions with the halobenzoquinones, such as o-chloranil, p-chloranil and o-bromanil, resulted in the formation of positively charged nitrogens and the halogen and benzoquinone anions. In the case of interaction with TCNE, cyano anions were involved while interaction with DDQ involved all three types of anions. The charge transfer (CT) behaviour of the deprotonated pyrrolylium nitrogens towards acid protonation, and 'doping' by the organic acceptors, together with the charge neutrality considerations, suggested the presence of localized units positive charge on the pyrrolylium nitrogens. © 1991.