Efficiency of π-π tunneling in [2]rotaxane molecular electronic switches

We perform large-scale density functional and matrix Green's function calculations, and study the coherent charge tunneling properties of molecular electronic devices based on the central part of [2]rotaxane molecules. We extract molecular core regions from realistic monolayer configurations with folded molecular structures and sandwich them between Au(111) electrodes to form device models. We show that the electrical switching behavior can be observed within the π-π stacked serial arrangement of redox-active components in the [2]rotaxane monolayer as with the parallel arrangement in the [2]catenane case. We thus demonstrate the effectiveness of the π-π electron tunneling and the universality of the switching mechanism based on the energetic movement of frontier orbitals accompanying the conformational switching. In addition, via considering the energetic ordering of highest-occupied molecular orbital (HOMO) and HOMO-1 levels that originated from tetrathiafulvalene and dioxynaphthalene in several ground-state conformation device models, we show that the molecule-electrode configurations critically affect the device functionality.