Model systems for artificial photosynthesis: calix[4]arenes functionalized with chromophoric units for energy and charge transfer

The increasing demand for clean and renewable energy sources has promoted many attempts at mimicking natural photosynthesis through the development of artificial systems able to efficiently absorb solar light and transform it into useful forms of energy. With the aim to elucidate the structure-function relationships in artificial photosynthetic devices and to understand the mechanisms governing the processes of energy transfer and charge separation, in this thesis it is reported the synthesis of calix[4]arenes functionalized with appropriate chromophores, functioning as energy (or electron) donors and acceptors. Based on their spectral properties, three couples of dyes were selected for the study of energy transfer and one couple to investigate charge transfer. The couples of chromophores were linked at the upper rim of cone calix[4]arenes, to obtain bis-chromophoric systems. In particular, the dyads synthesized with the first two couples were designed to give Förster excitation energy transfer, while the bis-chromophoric compound obtained with the third couple was specifically designed to investigate the occurrence of coherent effects in the energy transfer process. Moreover, the first two couples of chromophores were also linked to partial cone calix[4]arenes, in order to study the influence of the chromophore distance and relative orientation on the efficiency of energy transfer. The obtained compounds were characterized by UV-visible absorption and fluorescence spectroscopies. Some selected systems were also investigated via ultrafast transient absorption techniques. Results confirmed that the synthesized bis-chromophoric calix[4]arenes are good model systems for the investigation of energy transfer and charge separation in different interaction regimes.