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

• Published in: Coordination chemistry reviews 2007-11, Vol.251 (21), p.2743-2752
• Main Authors: Maeda, Chihiro, Kamada, Taisuke, Aratani, Naoki, Osuka, Atsuhiro
• Format: Article
• Language: English
• Subjects: Chiral recognition; Porphyrin; Self-assembly; Self-sorting
• ISSN: 0010-8545; 1873-3840
• DOI: 10.1016/j.ccr.2007.02.017

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.