Through-bond charge-transfer interaction in N-(p-methoxyphenylalkyl)pyridinium ions

Abstract

Intramolecular charge-transfer absorption is observed for a series of molecules containing the p-methoxyphenyl group as an electron donor and the 4-methoxycarbonylpyridinium group as an electron acceptor separated by a saturated carbon–carbon bond. The appearance of this absorption even in rigid model systems, where donor and acceptor are spatially far apart, is used as evidence for the through-bond character of the charge-transfer interaction. A simple theoretical model is shown to predict qualitatively the dependence of the charge-transfer absorption intensity on the dihedral angle defined by donor, acceptor, and the interconnecting carbon–carbon bond.