The fascinating vision of molecular nanotechnology lies in the use of single molecules as machines or devices and the controlled assembly of molecular matter at the nanometer scale (nanomanufacturing). The possibility to manipulate and control things on a small scale was first introduced by Richard Feynman in his famous 1959 speech “There’s plenty of room at the bottom”. Resulting applications, like electronic circuits, sensors or nano-machines, would, due to their small dimensions, open the door to completely new technologies, with advantages in cost, operation speed (efficiency) and power dissipation. In contrast to top-down approaches (e.g. by improving lithographic techniques), the use of molecules reveals several important advantages: 1. Molecules have nano-scale dimensions by nature: Thus, the use of single molecules automatically leads to structural dimensions at the atomic scale. The top-down miniaturization of existing applications and devices requires fundamental improvements of conventional fabrication techniques, which are limited. 2. Molecular recognition: Intermolecular interactions can be used to grow molecular nanostructures. Molecules are known to self-organize according to their chemical properties and to self-assemble in topologies that reflect the interactions between them. By controlling the chemistry of the involved molecules, various structures of different size and shapes can be produced. 3. Capabilities of organic chemistry: By choosing the structure and composition of a molecule, chemical synthesis can be used to produce molecules of precisely defined properties. 4. Functions: Molecules can have specific functions, for instance switching between different states (of characteristic optical, magnetic and electronic properties). In fact, the latter is a fundamental concept in nature, where many molecules have multiple stable isomers.
