AbstractA family of 36‐armed dendrimers containing six internal amino groups was synthesized and used to incorporate polyoxometalates (POMs) into their structures by ionic bonding. Allyl‐terminated dendrimer 17 (with oxidizable end groups) and methylphenyl‐terminated dendrimer 18 (with non‐oxidizable end groups) were used for these studies. It was found that the electrostatic incorporation of the tri‐anionic POM [PO4WO(O2)2}4]3− into the methylphenyl‐terminated dendrimer 18, in an acidic medium, leads to the dendritic POM hybrid 19, bearing two POM units in its structure. In contrast, attempts to encapsulate POMs into allyl‐terminated dendrimer 17 gave unsatisfactory results. Indeed, the epoxidation kinetics of the 36‐olefinic terminated dendrimer 17 was too slow, and the expected 36‐epoxy‐dendritic POM framework 20 was not obtained. Lengthening the reaction up to six hours led to the decomposition of POM species. The solubility in organic solvents of the dendritic POM hybrid 19, combined with its NMR and infrared data, indicate that POM units are clearly connected to the dendritic structure. The catalytic performance of this hybrid material in the oxidation of cyclooctene shows that the properties of POM are retained. The POM‐encapsulated dendrimer 19 was found to be an effective catalyst in the oxidation of cyclooctene.
摘要 合成了一系列含有六个内部
氨基的 36 臂树枝状聚合物,并通过离子键将聚
氧化金属(POM)结合到其结构中。这些研究使用了烯丙基封端树枝状聚合物 17(具有可氧化端基)和甲基苯基封端树枝状聚合物 18(具有不可氧化端基)。研究发现,在酸性介质中,将三阴离子 POM [PO4WO(O2)2}4]3- 静电掺入甲基苯基封端树枝状聚合物 18 中,可产生树枝状 POM 混合物 19,其结构中含有两个 POM 单元。相比之下,将 POM 包入烯丙基封端树枝状聚合物 17 的尝试结果并不令人满意。事实上,36-烯烃端树枝状聚合物 17 的环氧化动力学太慢,因此没有得到预期的 36-环氧树枝状 POM 框架 20。将反应时间延长至 6 小时会导致 POM 物质分解。树枝状 POM 混合物 19 在有机溶剂中的溶解度以及核磁共振和红外数据表明,POM 单元与树枝状结构明显相连。这种杂化材料在
氧化环辛烯过程中的催化性能表明,它保留了 POM 的特性。研究发现,POM 包裹的树枝状聚合物 19 在环
辛烯的氧化过程中是一种有效的催化剂。