Tetraazachlorin-Fullerene Conjugates: On-Off Control of Electronic Communication Enabled by Push-Pull Substituents
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- 作者：Takamitsu Fukuda ; Satoshi Masuda ; Nagao Kobayashi
- 刊名：Journal of the American Chemical Society
- 出版年：2007
- 出版时间：May 2, 2007
- 年：2007
- 卷：129
- 期：17
- 页码：5472 - 5479
- 全文大小：539K
- 年卷期：v.129,no.17(May 2, 2007)
- ISSN：1520-5126
文摘
Novel tetraazachlorin (TAC)-fullerene (C60) conjugates (TAC-C60) and their analogues (TAiBC-C60 and TABC-C60 where TAiBC = tetraazaisobacteriochlorin and TABC = tetraazabacteriochlorin) havebeen synthesized by condensing 1,2-dicyanofullerene (1) and phthalonitrile derivatives (2) in the presenceof nickel chloride in quinoline, and fully characterized using mass spectrometry and 1H and 13C NMR. Byarranging the TAC and C60 units at the minimum distance, and taking also into account the molecularsymmetry, the resultant conjugates show on-off electronic communication behavior, depending on thepush-pull properties of the peripheral substituents in the TAC moiety. Consequently, the UV-vis absorptionspectrum of the electron-releasing butyloxy-substituted TAC-C60 (3a) contains an unusual group of threeabsorption bands in the Q-band region (500-900 nm) as a result of a strong electronic communicationbetween the two moieties. On the other hand, the absorption spectrum of the electron-withdrawingbutylsulfonyl-substituted TAC-C60 (3b) comprises a typically normal TAC spectrum with markedly splittwo-peak Q-bands. A similar phenomenon is observed between alkoxy-substituted TAiBC-C60 (4a) andbutylsulfonyl-substituted TAiBC-C60 (4b). This study reveals that the electron-donating or -withdrawingnature of the peripheral substituents on an azachlorin moiety has an important effect on the electronicstructures of our novel azachlorin-C60 conjugates, although the linking carbon atoms are aliphatic sp3carbon atoms which generally do not contribute to aromaticity. The electronic structures of the conjugateshave been investigated in detail using spectroscopic and electrochemical techniques with the aid of DFTcalculations.