Synthese einer Chlorin-Fulleren-Dyade mittels Diels-Alder-Reaktion zur Untersuchung der lichtinduzierten Elektronenübertragung

Abstract

The aim of this work was the synthesis of a photosynthetic model system. This model gives the possibility to study the ground process of photosynthesis: the so called photo-induced electron transfer (PET). This process is based on the intramolecular light induced charge separation. The model is built using an electron donor and an electron acceptor. The electron donor used in this case was a chlorin, a derivative of chlorophyll. Fullerene C60, which has been used very successfully in the recent years, was chosen as the electron acceptor. The synthesis of a chlorin with two ester-groups in an anellated norbornan ring was based on a total synthetic model pathway using the tricycle of A, B, C rings, and a new ring D, a pyrrole bearing a norbornan ring. The synthesis of this new ring was developed in this work.The ester-groups of the chlorin were reduced to alcohol and transformed to a selenium ether compound. After oxidation of the selenium atoms, the phenylseleniumoxide groups were eliminated, giving a diene-group. This chlorin with the diene-group reacted with fullerene by means of a Diels-Alder reaction to attain to the chlorin-fullerene-dyad.The previous studies of the photophysical properties of the chlorin-fulleren-dyad showed, through the UV-Spectrum, that there are no interactions between donor and acceptor in the relaxed state. In different analyses from fluorescense spectra, it was verified that the emission of the dyad diminishes almost completely, compared with the chlorin without fullerene, a fact that indicates a possible intramolecular electron transference.