Digital Processing and Communication with Molecular Switches

The tremendous pace in the development of information technology is rapidly approaching a limit. Alternative materials and operating principles for the elaboration and communication of data in electronic circuits and optical networks must be identified. Organic molecules are promising candidates for the realization of future digital processors. Their attractive features are the miniaturized dimensions and the high degree of control on molecular design possible in chemical synthesis. Indeed, nanostructures with engineered properties and specific functions can be assembled relying on the power of organic synthesis. In particular, certain molecules can be designed to switch from one state to another, when addressed with chemical, electrical, or optical stimulations, and to produce a detectable signal in response to these transformations. Binary data can be encoded on the input stimulations and output signals employing logic conventions and assumptions similar to those ruling digital electronics. Thus, binary inputs can be transduced into binary outputs relying on molecular switches. Following these design principles, the three basic logic operations (AND, NOT, and OR) and more complex logic functions (EOR, INH, NOR, XNOR, and XOR) have been reproduced already at the molecular level. Presently, these simple “molecular processors” are far from any practical application. However, these encouraging results demonstrate already that chemical systems can process binary data with designed logic protocols. Further fundamental studies on the various facets of this emerging area will reveal if and how molecular switches can become the basic components of future logic devices. After all, chemical computers are available already. We all carry one in our head!