Carotenoid pigments, ubiquitous in photosynthetic membranes, are essential for the survival of green plants1. Two facets of carotenoid function are recognized in photosynthetic membranes. First, carotenoids prevent the chlorophyll-photosensitized formation of highly destructive singlet oxygen by intercepting the chlorophyll triplet states2-10 and may also scavenge additional singlet oxygen present11,12. Second, carotenoids perform an antenna function by transferring the energy of absorbed light at the singlet excited state level to the chlorophyll system for the execution of photosynthetic work13-16. Nevertheless, the mechanisms by which carotenoids perform these functions are poorly understood. We now report that a unique synthetic carotenoporphyrin I consisting of a carotenoid part covalently linked to a synthetic tetraarylporphyrin successfully mimics both the photophysical functions of carotenoids in photosynthesis. The explanation for this seems to be the close interaction of the carotenoid and porphyrin π-electron systems.
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