Abstract
We have synthesized zinc 3^1^‐hydroxychlorins 1–4 possessing a methoxycarbonyl group at the 13‐position by modifying naturally occurring chlorophyll‐a. Synthetic zinc chlorins 1–4 have three specific substituents, namely 3^1^‐OH, central Zn and 13‐C=O moieties, along the Qy axis, and 1–3 self‐aggregate in an aqueous medium containing Triton X‐100, as do natural bacteriochlorophylls in the main light‐harvesting antennas (chlorosome) of green photosynthetic bacteria. The 13‐methoxycarbonyl group in 1–3 is a prerequisite for such self‐aggregation, while the other methoxycarbonyl groups at the 15^1^‐ and/or 17^2^‐positions are not. This indicates that such a linear situation of these substituents is significant for chlorosomal self‐aggregation of chlorophyllous pigments and also that the 13‐methoxycarbonyl group is an alternative to the 13‐keto‐carbonyl group in natural pigments. Furthermore, the resulting oligomers of 1–3 have fluorescence emission peaks at less than 700 nm, which are considerably more blue‐shifted than previously prepared self‐aggregates of chlorins possessing the 13‐keto‐carbonyl group fixed onto an exo five‐membered ring, and are a new class of artificial light‐harvesting systems. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)