6 Recent developments in photo- and redox-active dendrimers

Abstract

Dendrimers constitute a fascinating class of monodisperse, highly branched macromolecules which are the object of continuously increasing interest. The possibility of introducing selected chemical units in predetermined sites of the dendritic structure gives rise to the possibility of performing specific functions at the molecular level. The photophysical and electrochemical properties of dendrimers in fluid solution will be reviewed, covering the years 2001–2002, as photons and electrons constitute the most simple means to induce molecular-level functions and to monitor the occurrence of such functions. It will be shown that photochemical and photophysical properties of dendrimers are particularly interesting since (i) cooperation among the photoactive components can allow the dendrimer to perform useful functions such as light harvesting and frequency converting, (ii) changes in the photophysical properties can be exploited for sensing purposes with signal amplification, and (iii) the presence of luminescence signals can offer a valuable handle to better understand the dendritic structure and superstructure. On the other hand, the electrochemical properties of dendrimers are interesting since (iv) redox active units present at the core of a dendrimer can be “encapsulated” by the surrounding branches, thus modulating the electron transfer rate, (v) the presence of multiple equivalent, non-interacting units gives rise to the simultaneous exchange of a large and predetermined number of electrons, and (vi) electroactive units of the same or different types can be placed in topologically equivalent or non-equivalent sites of a dendrimer to obtain specific redox patterns.