Classification of novel thiazole compounds for sensitizing Ru–polypyridine complexes for artificial light harvesting

A systematic study of the Förster resonance energy transfer (FRET) efficiency between thiazole dyes and a ruthenium–polypyridine complex is presented. While ruthenium–polypyridines are conventionally used in artificial light harvesting systems as primary electron donors, their application suffers from rather low extinction coefficients in the visible spectral range and an absorption gap between the ππ⁎ transitions of the ligands and the MLCT transitions. In this paper it is shown how thiazoles might help to circumvent theses issues. The absorption and emission spectra of the thiazole can be synthetically adjusted to fall into the absorption gap of the Ru dye and to efficiently overlap with the 1MLCT absorption of the complex, respectively. Thereby, the thiazoles might serve as antenna structures to funnel energy to the Ru-polypyridine unit, which finally can act as a photoactivated primary electron donor. Systematic investigations of the Förster radii of representative thiazole Ru-polypyridine dye pairs corroborate this potential quantitatively.