Synthesis of 7,8‐Dehydropurpurin Dimers and Their Conversion into Conformationally Constrained β‐to‐β Vinylene‐Bridged Porphyrin Dimers |
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Authors: | Norihito Fukui Prof. Dr. Hideki Yorimitsu Dr. Jong Min Lim Prof. Dr. Dongho Kim Prof. Dr. Atsuhiro Osuka |
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Affiliation: | 1. Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo‐ku, Kyoto 606‐8502 (Japan);2. ACT‐C (Japan) Science and Technology Agency (Japan);3. Spectroscopy Laboratory for Functional π‐Electronic Systems and Department of Chemistry, Yonsei University, Seoul 120‐749 (Korea) |
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Abstract: | 7,8‐Dehydropurpurin has attracted much attention owing to the dual 18π‐ and 20π‐electron circuits in its macrocyclic conjugation. The two‐fold Pd‐catalyzed [3+2] annulation of meso‐bromoporphyrin with 1,4‐diphenylbutadiyne furnished 7,8‐dehydropurpurin dimers. The 8a,8a‐linked dimer displays a red‐shifted and enhanced absorption band in the NIR region and a small electrochemical HOMO–LUMO band gap as a consequence of efficient conjugation between the two coplanar 7,8‐dehydropurpurin units. Treatment of this dimer with N‐bromosuccinimide in chloroform and ethanol gave β‐to‐β vinylene‐bridged porphyrin dimers. Owing to the highly constrained conformations, these dimers exhibit perturbed absorption spectra, small Stokes shifts, and high fluorescence quantum yields. |
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Keywords: | 7,8‐dehydropurpurin conjugation dimerization porphyrinoids |
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