State Key Laboratory of Physical Chemistry of Solid Surfaces, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, Fujian, China.
Phys Chem Chem Phys. 2012 Oct 5;14(37):12919-29. doi: 10.1039/c2cp41502j.
We propose that aromatic nitro and amine compounds undergo photochemical reductive and oxidative coupling, respectively, to specifically produce azobenzene derivatives which exhibit characteristic Raman signals related to the azo group. A photoinduced charge transfer model is presented to explain the transformations observed in para-substituted ArNO(2) and ArNH(2) on nanostructured silver due to the surface plasmon resonance effect. Theoretical calculations show that the initial reaction takes place through excitation of an electron from the filled level of silver to the lowest unoccupied molecular orbital (LUMO) of an adsorbed ArNO(2) molecule, and from the highest occupied molecular orbital (HOMO) of an adsorbed ArNH(2) molecule to the unoccupied level of silver, during irradiation with visible light. The para-substituted ArNO(2)(-)˙ and ArNH(2)(+)˙ surface species react further to produce the azobenzene derivatives. Our results may provide a new strategy for the syntheses of aromatic azo dyes from aromatic nitro and amine compounds based on the use of nanostructured silver as a catalyst.
我们提出，芳香族硝基和胺化合物分别经历光化学还原和氧化偶联，以特异性地产生具有与偶氮基团相关的特征拉曼信号的偶氮苯衍生物。提出了光致电荷转移模型来解释在纳米结构银上由于表面等离子体共振效应而观察到的对取代的 ArNO(2) 和 ArNH(2) 的转化。理论计算表明，初始反应是通过用光照射从填充的银能级激发电子到吸附的 ArNO(2)分子的最低未占据分子轨道 (LUMO)，以及从吸附的 ArNH(2)分子的最高占据分子轨道 (HOMO)激发到银的未占据能级来进行的。进一步反应，对位取代的 ArNO(2)(-)˙和 ArNH(2)(+)˙表面物种反应生成偶氮苯衍生物。我们的结果可能为基于使用纳米结构银作为催化剂从芳香族硝基和胺化合物合成芳香族偶氮染料提供了一种新策略。
