Chiral self-discriminative self-assembling of meso-meso linked diporphyrins

We have explored a variety of self-assembled cyclic porphyrin arrays mainly as biomimetic models of light harvesting antenna in photosynthetic systems. The key reaction is Ag(I)-promoted coupling reaction of 5,15-diaryl zinc(II) porphyrin that provides a meso-meso linked diporphyrin. meso-Pyridine-appended zinc(II) porphyrins M1-M3 and their meso-meso linked dimers D1-D3 assemble spontaneously in non-coordinating solvents into tetrameric porphyrin squares S1-S3 and porphyrin boxes B1-B3, respectively. In the latter case, it has been demonstrated that four molecules of R-diporphyrin assemble into R-box and four molecules of S-diporphyrin assemble into S-box via rigorous homochiral self-sorting process. Efficient excitation energy transfer along these cyclic porphyrin arrays has been revealed by the time-resolved transient absorption and fluorescence measurements. We have also demonstrated that the meso-cinchomeronimide appended Zn(II) porphyrin CIM forms a cyclic trimer, while the corresponding diporphyrins CID exhibit high-fidelity self-sorting assembling to form discrete cyclic trimer, tetramer, and pentamer with large association constants, through perfect discrimination of enantiomeric and conformational differences of the meso-cinchomeronimide substituents. (C) 2007 Elsevier B.V. All rights reserved.