XPS STUDIES OF CHARGE-TRANSFER INTERACTIONS IN SOME POLY(N-VINYLCARBAZOLE) ACCEPTOR COMPLEXES

The charge transfer (CT) interactions between poly(N-vinylcarbazole) (PVK) the various electron acceptors such as tetrachloro-o-benzoquinone (o-chloranil), tetrachloro-p-benzoquinone (p-chloranil), tetrabromo-o-benzoquinone (o-bromanil), tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 2,4,7-trinitrofluoranone (TNF), I2 and Br2, have been investigated by X-ray photoelectron spectroscopy (XPS). The interactions involving halobenzoquinones, DDQ, I2, and Br2 resulted in the partial localization of negative charges on the halogen sites; for that involving TCNE, the negative charges were found to be partially localized on the cyano group. The CT interaction involving Br2 progressed beyond the mere formation of molecular complex. Most of the iodine was removed from the PVK-I2 complex under the ultra-high vacuum environment. In all cases, the partial negative charges on the acceptors were counter-balanced by the positively charged carbazole nitrogens. For the PVK-TNF complexes, which are excellent photoconductors, no charge localization was discernible from the XPS results.