Module 4 – Molecular Electronics

Molecular Electronics combines Nanoelectronics and Nanoelectrooptics with Synthetic Supramolecular Chemistry. All projects within the module are strongly interrelated. They cover the following topics:

• molecular wires
• transport properties and networks of molecular junctions
• optical properties and electron spectroscopy of single molecules
• chemical synthesis of novel conjugated molecules for electrooptical applications

By studying single supramolecular structures and the way they conduct current, we can learn a great deal about the way electrons flow through molecules and about single-molecule functions.

The rational design and preparation of molecular (nano-) systems are the challenges of modern synthetic chemistry. As a consequence of the intense interest in this field, the synthetic methodologies are nowadays prepared to approach a variety of nano-sized molecular systems with specific functionalities. Such tailored molecules are used within this NCCR project in:

• surface assembling studies (STM imaging and spectroscopy)
• optical studies
• single-molecule experiments (single-molecule electrical transport)
• studies of assembled networks.

Theory is going to address fundamental aspects of molecular charge transport.

A selection of key questions are:

Can we find molecular switches and memory elements that have a high on-off ratio and that can be built from molecules in a reliable and reproducible way? Is it possible to achieve a large transmission probability approaching unity in molecules? Is it possible to go beyond single molecule junctions and to build networks of junctions with a multitude of embedded functions?

Possible mechanisms for reversible molecular switches. (a) Electrochemically controlled desorbtion of an anchoring group (triangle). This can be envisioned for molecules with two distinct anchoring groups, e.g.: z.B. -SH (●) und –CN (▶). (b) Electrochemically induced switching. The controlled charging of a redox active unit can induce a conductance change. (c) Light-induced switching. UV light will drive the system from open to closed, while visible light will drive the transition from closed to open.

Redox switchable TTF derivative.

Light-switchable 1,2-bis-(3-thienyl)ethane derivative.