Building-block synthesis of porphyrin light-harvesting arrays

Abstract

Photosynthetic organisms employ light-harvesting complexes to capture dilute sunlight and funnel energy to the reaction centers. Light-harvesting complexes are remarkable in achieving efficient energy migration among hundreds of pigments with avoidance of non-energy transfer quenching processes. In this communication we report a convergent strategy for preparing rigid, soluble arrays of covalently-linked porphyrins in various metalation states. The strategy employs readily available tetraarylporphyrins as modular building blocks. The porphyrins bear peripheral iodo or ethynyl groups and are facially-encumbered to suppress aggregation. The free base or metalloporphyrins are then joined via homogeneous Pd-mediated coupling reactions under basic conditions to give a desired assembly. We believe that this building-block approach provides an ideal route to model light-harvesting compounds. 10 refs., 1 fig.