Conformational Molecular Rectifiers

Alessandro Troisi, Mark A. Ratner

One of the goals of the emerging field of molecular electronics (ME) is the realization of molecular scale rectifiers, switches, or transistors coupled one another via metallic wiring.1,2 The extension of conventional electronics approaches requires that the molecular device is rigid, with functions entirely determined by electronic structure. With several remarkable exceptions,3 most current experiments in ME are focused on rigid molecules, with molecular motions generally regarded as unwanted complications.

Conformational motions driven by the electric field might lead a molecular junction to exhibit switching behavior.

Controllable dynamical stereochemistry breaks the analogy that sees the molecule only as the ultimately miniaturized “material” for electronics, and thereby opens many interesting mechanistic and device possibilities.

In this papper, the researchers presented two examples of conformational molecular rectifiers.

One of them was a benzenethiol meta-substituted with the cyanomethyl group that can be easily chemisorbed on a gold surface. The next figure shows how the conformation can change with the change of the potential applied.

Another simple example is shown in the next figure, here we can see that again, by changing the polarization. This effect is due to a change in the relative erngies of the orbital conformation, that allow the molecule to change according to the most stable conformation formed by the symmetry on the molecular orbitals, specially over the delocalized π electrons.

 It is clear, from these two examples, that one essential condition for viable CMRs is the possibility to control the molecule orientation at the interface.