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Synthesis and Antiaromatic Properties of Highly Planar Dithiaamethyrin |
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| Authors: | Dr. Yoshihiro Ishimaru Naoyuki Shimoyama Dr. Takashi Fujihara Keigo Watanabe Prof. Dr. Jun‐ichiro Setsune |
| Affiliation: | 1. Division of Material Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo‐ohkubo, Sakura‐ku, Saitama, Saitama, 3388570 (Japan), Fax: (+81)?48‐8583537;2. Research and Development Bureau, Comprehensive Analysis Center for Science, Saitama University, 255 Shimo‐ohkubo, Sakura‐ku, Saitama, Saitama, 3388570 (Japan);3. Department of Chemistry, Graduate School of Science, Kobe University, 1‐1 Rokkodai‐cho, Nada‐ku, Kobe, 6578501 (Japan) |
| Abstract: | 2,5‐Bis(4‐propyl‐2‐pyrrolyl)thiophene was reacted with aryl aldehydes to afford large porphyrinoids; [24]dithiaamethyrin(1.0.0.1.0.0) and [36]trithianonaphyrin(1.0.0.1.0.0.1.0.0). X‐ray crystallography of the dithiaamethyrin revealed a highly planar ring structure with mean plane deviation (MPD) value of 0.053 Å. A large positive NICS(0) value (+13.9 ppm) calculated for this planar 24π system unambiguously indicates an antiaromatic character that is consistent with a remarkably low field 1H chemical shift of the inner NH proton at 24.0 ppm. The magnitude of the paratropic ring current effect in the 24π amethyrin framework in the free base form and the diprotonated form was discussed on the basis of the MPD value and the NICS value. The present dithiaamethyrin is much more strongly antiaromatic than the dodecaalkylamethyrin in their free base forms, but the order inversed in their diprotonated forms. |
| Keywords: | antiaromaticity aromaticity mean plane deviation planarity porphyrinoids |