XPS STUDIES OF CHARGE-TRANSFER INTERACTIONS IN SOME PYRIDINE - ORGANIC-ACCEPTOR COMPLEXES

Complexes resulting from charge-transfer (CT) interactions between pyridine and some organic electron acceptors, such as tetrachloro-o-benzoquinone (o-chloranil), tetrabromo-o-benzoquinone (o-bromanil), tetrafluoro-p-benzo-quinone (p-fluoranil), tetracyanoethylene (TCNE) and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), are characterized by X-ray photoelectron spectroscopy (XPS). A 1:1 complex is obtained for the pyridine: o-chloranil and pyridine: TCNE complexes, while a 2:1 stoichiometry is observed for the remaining pyridine: acceptor complexes. Except in the case of the pyridine: TCNE complex, all CT interactions proceed further than the pure formation of molecular complexes and result in the formation of new adducts. The mechanisms of interaction between the pyridinium nitrogens and the various functional groups of the acceptors are revealed by XPS. Chemical structures are also proposed for the resulting complexes. © 1990 Taylor & Francis Ltd.