Theoretical investigation of the photophysics of light-harvesting molecular systems and supramolecular photocatalysts for hydrogen generation

  • In the last decades, several propositions have been made by the scientists to find a solution to the global energy crisis, searching for sources of energy that are renewable, clean and cheap. In this respect, a promising source of energy is sunlight. In nature, plants have the unique ability to convert sunlight into chemical energy by means of photosynthesis. By mimicking the principles of natural photosynthesis, two basic possibilities can be followed: i) the conversion of solar energy by light-harvesting devices into electric energy, this is usually realized using so-called dye-sensitized solar cells, and ii) the generation of high-energy compounds such as molecular hydrogen by means of artificial photosynthesis, this is widely considered based on so-called supramolecular photocatalysts. The latter are large molecules consisting of a photoactive center that absorbs light and a catalytic center, where hydrogen is generated. The photoactive and catalytic centers are interlinked by an electron relay that stores electrons and allows electron transfer between both units (see figure).

    In the group of dr hab. Julien Guthmuller, the fundamental photophysical and photochemical properties and processes in light-harvesting molecular systems are investigated by means of computational and theoretical approaches. In particular, the structures, energies and properties of the molecular excited states are predicted using quantum chemistry methods. The electron transfer rates are determined in order to unravel the relaxation pathways leading to charge separation or charge recombination. Additionally, spectroscopic properties, for example absorption, emission and resonance Raman spectra, are simulated to provide interpretation of experimental results.

    The knowledge gained by these studies improves the understanding of the fundamental processes related to light-harvesting and electron transfer in such systems, and will help in the design of new photocatalysts and light-harvesting molecules having desired properties.

    This research is financed by the National Science Centre (NCN).

    Example of a supramolecular photocatalyst (S. Rau et al. Angew. Chem. Int. Ed. 45 (2006) 6215)