Porphyrin molecular tweezers for fullerenes

Hidemitsu Uno, Mina Furukawa, Akiko Fujimoto, Hiroki Uoyama, Hajime Watanabe, Tetsuo Okujima, Hiroko Yamada, Shigeki Mori, Makoto Kuramoto, Tatsunori Iwamura, Noriyuki Hatae, Fumito Tani, Naoki Komatsu

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Abstract

Facing zinc bisporphyrins connected with diethanoanthracene and diethanonaphthacene (syn-1 and syn-2) are prepared by double [3+1] porphyrin synthesis of tripyrranedicarbaldehyde with syn-5,11-dimethoxy-4,6,10,12- tetrahydro-4,12;6,10-diethanoanthracene[2,3-c;7,8-c′]dipyrrole and syn-4,7,11,14- tetrahydro-4,14;7,11-diethanonaphthacene[2,3-c;8,9-c′] dipyrrole. These bisporphyrins contain large clefts with different sizes capable for complexation with fullerenes such as C60 and C70. These designed syn-oriented bisporphyrins serve as effective and selective molecular tweezers for C70. Binding affinity of the zinc bisporphyrins, namely, syn-1 and syn-2, towards C60 and C 70 in solution is determined by employing UV-vis spectrophotometric technique. Values of binding constants (K) in toluene for the non-covalent complexes of syn-1 with C60 and C70 are estimated to be 3.1(4) × 104 and 5.0(2) × 105 M-1, respectively, and those of syn-2 with C60 and C70 are enumerated to be 2.1(4) × 104 and 1.70(13) × 10 5 M-1, respectively. Binding of C60 and C 70 in the clefts of syn-1 and syn-2 is clearly demonstrated by the crystal structures of C60/syn-1, C70/syn-1, C 60/syn-2, and C70/syn-2 complexes. In the crystal structures with C70, the directions of the long axis of C 70 are found to be quite different: in the case of C 70/syn-1 complex the axis lies perpendicularly to the line connecting two zinc atoms; however, for the C70/syn-2 complex, the axis occupies in-plane to the same line. Both the clefts of syn-1 and syn-2 are induced to fit the included fullerenes by domed out-of-plane distortion of porphyrin rings. Moreover, the bicyclo[2.2.2]octadiene moieties of syn-1 are widened by complexation with the fullerenes, while the same moieties of syn-2 are narrowed by the complexation. Therefore, syn-1 catches the fullerenes at the shallow part of the cleft. On the other hand, syn-2 catches the fullerenes at the bottom part of the cleft. NMR experiments of the complexes in THF-d 8 also support these orientations even in solution.

Original languageEnglish
Pages (from-to)951-963
Number of pages13
JournalJournal of Porphyrins and Phthalocyanines
Volume15
Issue number9-10
DOIs
Publication statusPublished - Jan 1 2011

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

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    Uno, H., Furukawa, M., Fujimoto, A., Uoyama, H., Watanabe, H., Okujima, T., Yamada, H., Mori, S., Kuramoto, M., Iwamura, T., Hatae, N., Tani, F., & Komatsu, N. (2011). Porphyrin molecular tweezers for fullerenes. Journal of Porphyrins and Phthalocyanines, 15(9-10), 951-963. https://doi.org/10.1142/S1088424611003872