Fullerene-Terminated Dendritic Multiporphyrin Arrays: “Dendrimer Effects” on Photoinduced Charge Separation

✍ Scribed by Myung-Seok Choi; Takuzo Aida; Hongxia Luo; Yasuyuki Araki; Osamu Ito

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 164 KB
• Volume: 115
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/ange.200351460

✦ Synopsis

The development of light-harvesting antenna molecules for visible photons is one of the important subjects in the basic issue of solar-energy conversion in natural photosynthesis and also to their potential applications to molecular electronics. [1] Recently, we reported light-harvesting dendritic zinc porphyrin arrays which can efficiently capture visible photons and channel the excitation energy to the focal core. [2,3] This observation prompted us to integrate such dendritic dye molecules as light-harvesting antennas into electron-transfer relay systems. Here we report the molecular design and photoinduced electron-transfer properties of a series of fullerene-terminated dendritic zinc-porphyrin arrays nP Zn -C 60 (Scheme 1). [4] Covalently linked porphyrin-C 60 dyads (P-C 60 ) have attracted a great deal of attention as novel photoinduced electron-transfer units, [5][6][7] in which the chargeseparated (CS) state (PC + -C CÀ 60 ), which results from electron transfer from the porphyrin moiety to C 60 , can take advantage of the low reorganization energy of C 60 . Thus, the present study featuring C 60 -terminated multiporphyrin arrays nP Zn -C 60 can make use of the well-established photochemistry of covalently linked porphyrin-C 60 dyads. Herein, we highlight a unique effect of a large dendritic array (7P Zn ) on the lifetime of the CS state.

The arrays nP Zn -C 60 (n = 1, 3, and 7) were synthesized from hydroxy-terminated zinc-porphyrin dendrons (nP Zn -OH) and a carboxylic acid appended C 60 derivative (C 60 -CO 2 H), by using azodicarboxylic acid diethyl ester as a condensation agent, and unambiguously characterized by