SYNTHESIS AND OPTICAL-PROPERTIES OF CONFORMATIONALLY CONSTRAINED TRIMERIC AND PENTAMERIC PORPHYRIN ARRAYS

Synthesis, UV-visible absorption, and fluorescence emission properties are presented for the trimeric and pentameric porphyrins bridged by rigid aromatic spacers (m- or p-phenylene, anthracene-1, 8-diyl, etc.). The synthetic method utilized here is based on the previously reported synthesis of 5, 15-diaryloctaalkylporphyrins, with several important improvements. The new method can be generally utilized for preparation of conformationally constrained oligomeric porphyrins sequentially linked with aromatic spacers. The Soret absorption bands of anthracene-linked series were blue shifted, while those of p-phenylene series were split, which can be explained in terms of the exciton coupling theory. The relative fluorescence intensity was observed to decrease for higher oligomers. These porphyrin oligomers will be useful for synthetic model studies on photosynthetic charge separation. © 1990, American Chemical Society. All rights reserved.