Azobenzene-functionalized N-heterocyclic carbenes as photochromic ligands in silver(i) and gold(i) complexes
作者:Manuel Kaiser、Sebastian P. Leitner、Christa Hirtenlehner、Manuela List、Alexander Gerisch、Uwe Monkowius
DOI:10.1039/c3dt51565f
日期:——
The reaction of meta- and para-bromomethylene-azobenzenes with 1-methyl-imidazole yields the respective meta-/para-functionalized azobenzenes tagged with an imidazolium group. Similar reactions of ortho- and para-bromo-azobenzene with imidazole and successive quaternation with benzylbromide give the analogues, with an imidazolium group in ortho/para substituted azobenzenes. With the exception of the ortho derivative, all imidazolium salts could be transformed into their respective silver(I) complexes by reaction with Ag2O. Transmetallation of these silver(I) complexes with (Me2S)AuCl gives the azobenzene-containing complexes (NHC)AuCl. Two of these formed crystals suitable for X-ray diffraction, which revealed the typical linear coordination geometry of the NHC–Au–Cl moiety. All gold complexes feature E→Z photo-isomerisation upon irradiation with UV light. The thermal back reaction to the E-isomers is relatively slow and comparable to that of other azobenzene compounds.
间位和对位溴亚甲基偶氮苯与1-甲基咪唑反应,分别生成带有咪唑鎓基团的间位/对位功能化偶氮苯。类似地,邻位和对位溴偶氮苯与咪唑反应,随后与苄基溴进行季铵化,得到邻位/对位取代的偶氮苯同类物,其中含有咪唑鎓基团。除了邻位衍生物外,所有咪唑鎓盐均可通过与Ag2O反应转化为相应的银(I)配合物。这些银(I)配合物与(Me2S)AuCl进行金属转移反应,得到含有偶氮苯的配合物(NHC)AuCl。其中两种形成了适用于X射线衍射的晶体,结果显示了典型的NHC-Au-Cl部分的直线型配位几何结构。所有金配合物在紫外光照射下均表现出E→Z光异构化现象。热反向反应回到E异构体的速度相对较慢,与其他偶氮苯化合物相当。