XPS studies of charge transfer interactions in some polyphenylacetylene-electron acceptor systems

Abstract

X-ray photoelectron spectroscopy (XPS) studies have been performed on charge transfer complexes of trans-polyphenylacetylene (PPA). The acceptors used included halogens, such as I2 and Br2, and organic electron acceptors, such as 2,3-dichloro-5,6-dichloro-5,6-dicyano-p-benzoquinone (DDQ), chloranil, fluoranil, and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ). Incomplete and relatively weak charge transfer interactions were observed in most of the complexes. These help to account for the relatively low conductivity levels observed in most of the PPA complexes when compared with the corresponding complexes of other conjugated polymers. PPA has also been found to interact with molecular oxygen to some extent in solution. In complexes involving O2, Br2, and fluoranil, XPS data suggest that the charge transfer interaction may have proceeded further than the pure formation of molecular charge transfer complexes.