Bottom up construction of photochemical molecular devices by modular chemistry

Photochemical molecular devices (PMDs) are structurally organized and functionally integrated molecular systems capable to perform useful light-induced functions. The "bottom up" construction of PMDs is an important field of application of modular chemistry. The first step is the design and synthesis of components (modules) having suitable light-related properties (absorption spectrum, excited state lifetime, energy, and redox potentials, etc.). Such modules have then to be assembled in ordered arrays. Ordering does not simply concern the achievement of the desired structure, but also the properties related to the function that the device has to perform In this paper we illustrate the modular aspect of some PMDs which are currently the object of our investigations, namely (i) PMDs based on energy-transfer processes, including dendrimers for light harvesting, and (ii) PMDs based on structural changes (light driven mechanical molecular machines).