Novel porphyrins and chlorins that self-assemble in nonpolar solvents in a manner similar to that of the bacteriochlorophylls c, d, and e have been synthesized by a common protective group approach. The supramolecular assemblies have broad and red-shifted absorption spectra in comparison to those of the monomeric building blocks. The presence of a carbonyl group in conjugation with the tetrapyrrolic macrocycle produces green colors both in the free bases and in their zinc complexes, which, after self-assembly, are thus perfect artificial mimics of the chlorosomal antennas encountered in green photosynthetic bacteria. Enantiopure building blocks produce large helical aggregates with M or P helicity determined by the chirality of the 1-hydroxyethyl substituent. It is demonstrated that the groups essential for self-or-
IntroductionThe ubiquitous green color of light-harvesting apparata is encountered in (bacterio)chlorophyll-based photosynthetic organisms. In conjunction with other pigments, such as carotenoids, the light absorption characteristics, which include broad wavelength ranges and high extinction coefficients, have been optimized during evolution in order to ensure conversion of light into biochemical energy by adaptation to different habitats. Thus, bacteria that live under the water surface at depths of over 50 m have evolved antenna systems different to those of bacteria or algae living at the surface, and these differ in turn from terrestrial plants in their light-harvesting systems. While the last, more highly evolved, of these species have developed protein complexes to bind chromophores, in the early green photosynthetic bacteria, due to the pressures of synthetic and genetic economy, self-assembly of bacteriochlorophylls c, d, and e (Figure 1) is used. [1,2] This much simpler architectural construct, which is fully functional, is worth mimicking [a] Forschungszentrum Karlsruhe,