Azobenzene Photoisomerization under High External Pressures: Testing the Strength of a Light-Activated Molecular Muscle

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• 作者：Thomas A. Singleton ; Kevin S. Ramsay ; Mirela M. Barsan ; Ian S. Butler ; Christopher J. Barrett
• 刊名：The Journal of Physical Chemistry B
• 出版年：2012
• 出版时间：August 16, 2012
• 年：2012
• 卷：116
• 期：32
• 页码：9860-9865
• 全文大小：278K
• 年卷期：v.116,no.32(August 16, 2012)
• ISSN：1520-5207

文摘

The photoinduced isomerization and thermal back relaxation of an azobenzene-functionalized polymer poly(disperse red 1 acrylate) were investigated at increasing external pressures up to 1.5 GPa inside a diamond-anvil spectroscopic cell. The thermal cis鈥搕rans isomerization was monitored by laser pump鈥損robe spectroscopy, which demonstrated an increase in the half-life of the isomerization process with increasing pressure. Additionally, the cis content of the photostationary state gradually decreased as a function of pressure, with complete arrest of the trans鈥揷is photoisomerization above 1.5 GPa. The fact that the photoswitching behavior however could still be observed beyond 1 GPa is remarkable and is effectively a measure of the strength of the azobenzene chromophore as an artificial muscle. The changes in the Raman shifts of both trans- and cis-azobenzene were also investigated from ambient pressure up to 4 GPa, and no discontinuities were observed in the pressure vs wavenumber plots indicating no change in phase. The cis鈥搕rans photoisomerization of azobenzene was shown however to still be inducible at all the pressures investigated, confirming the suitability of these molecules for high-efficiency light actuation.