Molecular memory and processing devices in solution and on surfaces

Molecular mechanical and supramolecular systems have been with us for some time, but the means for their programmed control have often been lacking. I n order to construct useful nanomechanical devices, the structures need not only to have a mechanical function, but this function needs to be addressa ble. Ideally a nanomechanical system will be 'programmed' for a particular task, that is, it will be sensitive to its environment and contain the proc essing ability to act appropriately without external control at every step of its operation. Here, we review the developing methods for the integratio n and interfacing of molecular mechanical components and the solutions that have been found for performing information functions (memory, processing) on a molecular scale. Fundamental units such as photochromic, redox, fluore scent and supramolecular moieties are introduced and their combination into multicomponent covalent or supramolecular systems is discussed. The immobi lization of molecular devices on surfaces is given special attention, along with methods for the transduction and amplification of output signals from the devices.