Synthesis of cyclic chlorophyll oligomers

As a new model of photosynthetic light-harvesting antennas, cyclic dimer, trimer, and tetramer of chlorophyllous moieties were prepared by intermolecular transesterification of a hydroxy-methoxycarbonyl-chlorin using 1,3-dichlorotetrabutyl distannoxane as a catalyst. 1H NMR and UV–vis spectra showed that the cyclic oligomers tended to form stacked conformers through intramolecular π–π interactions of the chlorin macrocycles. It was demonstrated that the cyclic trimer could form a complex with fullerenes in CDCl3.