We report a detailed study of electron transfer in aromatic systems that have been suggested by Tour as basic elements for assembling simple molecular circuits. We simulated the behavior of electrons in response to an external perturbation by means of the Gaussian 98 quantum chemical package, and we carried out calculations for isolated molecules, consisting of an anionic system made up of two benzene rings bonded by an "insulator" methylene group. When point charges creating an external forcing field are placed close enough to one of the aromatic rings, a strongly nonlinear behavior is observed for the location of the highest energy electron, as a consequence of the presence of the methylene group acting as a barrier. Quantitative results on such a behavior are reported here for the first time.