Designing light harvesting antennas by luminescent dendrimers

Dendrimers are well defined, tree-like macromolecules, with a high degree of order and the possibility to contain selected chemical units in predetermined sites of their structure. Nowadays it is possible to design and synthesize dendrimers containing a variety of chromophoric groups organized in the dimensions of time, energy, and space so as to obtain efficient light-harvesting devices that can be useful for solar energy conversion, as well as for other purposes. In order to design the pattern and maximize the efficiency of light harvesting it is necessary to take into account not only the absorption and emission spectra of the various chromophoric units, but also their redox properties in the ground and excited states since dissipative photoinduced electron transfer processes can compete with energy transfer. Luminescence intensity measurements, both steady state and time dependent, fluorescence anisotropy, and transient absorption spectra are the techniques commonly used in this field. In this paper we discuss some paradigmatic cases including: (i) light harvesting within dendritic structures; (ii) light harvesting by molecules or ions hosted inside the dendritic structure; (iii) light harvesting in systems resulting from association of dendrimers with other large molecules.