Highly Efficient Reversible Z-E Photoisomerization of a Bridged Azobenzene with Visible Light through Resolved S1(nπ*) Absorption Bands
Highly Efficient Reversible Z-E Photoisomerization of a Bridged Azobenzene with Visible Light through Resolved S1(nπ*) Absorption Bands
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DOI：
10.1021/ja906547d
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发表时间：
2009-11-04
影响因子：
15
通讯作者：
Temps, Friedrich
中科院分区：
文献类型：
--
作者：
Siewertsen, Ron;Neumann, Hendrikje;Temps, Friedrich
利用紫外维斯吸收光谱定量研究了强约束桥联偶氮苯衍生物5，6-二氢二苯并[c，g][1，2]二氮杂环辛四烯（1）的（Z）和（E）异构体在正己烷溶液中的可逆Z-E光开关性质。与正常偶氮苯（AB）相比，1具有良好分离的S-1（n π *）吸收带，峰值在λ（Z）= 404 nm和λ（E）= 490 nm处。使用λ = 385 nm的光，发现1 Z可以以非常高的效率（Gamma = 92 +/-3%）切换到1 E。相反，使用λ = 520 nm的光，1 E可以切换回1 Z，产率接近100%。测得的量子产率为Phi（Z -> E）= 72 +/-4%和Phi（E -> Z）= 50 +/-10%。（E）异构体的热寿命在28.5 ℃下为4.5 +/- 0.1 h。所观察到的光致变色和光开关性能的I是更有利的比那些正常AB，使我们的标题化合物作为一个有趣的应用程序，特别是在低温下的分子光开关一个有前途的候选人。烯键桥的严格约束显然不阻碍而是有利于Z-E光异构化反应。
The reversible Z-E photoswitching properties of the (Z) and (E) isomers of the severely constrained bridged azobenzene derivative 5,6-dihydrodibenzo[c,g][1,2]diazocine (1) were investigated quantitatively by UV/vis absorption spectroscopy in solution in n-hexane. In contrast to normal azobenzene (AB), 1 has well separated S-1(n pi*) absorption bands, peaking at lambda(Z) = 404 nm and lambda(E) = 490 nm. Using Light at lambda = 385 nm, it was found that 1Z can be switched to 1E with very high efficiency, Gamma = 92 +/- 3%. Conversely, 1E can be switched back to 1Z using light at lambda = 520 nm with similar to 100% yield. The measured quantum yields are Phi(Z -> E) = 72 +/- 4% and Phi(E -> Z) = 50 +/- 10%. The thermal lifetime of the (E) isomer is 4.5 +/- 0.1 h at 28.5 degrees C. The observed photochromic and photoswitching properties of I are much more favorable than those for normal AB, making our title compound a promising candidate for interesting applications as a molecular photoswitch especially at low temperatures. The severe constraints by the ethylenic bridge apparently do not hinder but favor the Z-E photoisomerization reactions.