Electrocatalytic Z → E Isomerization of Azobenzenes
Electrocatalytic Z → E Isomerization of Azobenzenes
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DOI：
10.1021/jacs.6b10822
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发表时间：
2017-01-11
影响因子：
15
通讯作者：
Hecht, Stefan
中科院分区：
文献类型：
--
作者：
Goulet-Hanssens, Alexis;Utecht, Manuel;Hecht, Stefan
合成了一系列偶氮苯，研究了其E、Z异构体的电化学还原行为。我们的研究结果表明，自由基阴离子的Z异构体是能够迅速异构化到相应的E配置的对应物与显着增强的速率相比，中性物种。由于随后电子从形成的E自由基阴离子转移到中性Z起始材料，整体转变在电子中具有催化作用;即，亚化学计量量的还原物质可使整个混合物异构化。这种途径大大提高了（光）开关的效率，同时也允许人们达到光稳态组合物，不限于个别偶氮苯异构体的光谱分离和它们的量子产率。此外，用光电子转移剂激活这种自由基异构化途径允许我们通过由相同波长的光触发反向异构化方向（Z -> E）来超越偶氮苯物质的固有性质，这通常触发E -> Z异构化。我们报告的行为似乎是一般的，这意味着光开关的亚稳异构体可以异构化到更稳定的催化还原后，允许优化偶氮苯开关在新的和间接的方式。
A variety of azobenzenes were synthesized to study the behavior of their E and Z isomers upon electrochemical reduction. Our results show that the radical anion of the Z isomer is able to rapidly isomerize to the corresponding E configured counterpart with a dramatically enhanced rate as compared to the neutral species. Due to a subsequent electron transfer from the formed E radical anion to the neutral Z starting material the overall transformation is catalytic in electrons; i.e., a substoichiometric amount of reduced species can isomerize the entire mixture. This pathway greatly increases the efficiency of (photo)switching while also allowing one to reach photostationary state compositions that are not restricted to the spectral separation of the individual azobenzene isomers and their quantum yields. In addition, activating this radical isomerization pathway with photoelectron transfer agents allows us to override the intrinsic properties of an azobenzene species by triggering the reverse isomerization direction (Z -> E) by the same wavelength of light, which normally triggers E -> Z isomerization. The behavior we report appears to be general, implying that the metastable isomer of a photoswitch can be isomerized to the more stable one catalytically upon reduction, permitting the optimization of azobenzene switching in new as well as indirect ways.