Probing stepwise complexation in phenylazomethine dendrimers by a metallo-porphyrin core
Probing stepwise complexation in phenylazomethine dendrimers by a metallo-porphyrin core
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DOI：
10.1021/ja0524797
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发表时间：
2005-10-12
影响因子：
15
通讯作者：
Yamamoto, K
中科院分区：
文献类型：
--
作者：
Imaoka, T;Tanaka, R;Yamamoto, K
合成了一系列以中位取代锌卟啉为核的树枝状苯基甲亚胺（DPA）（DPAGX-ZnP，X = 1-4）。这些树枝状聚合物的结构进行了研究，使用三SEC（三重检测后的大小排阻色谱法），特性粘度分析，TEM（隧道电子显微镜），和分子模拟计算AM 1。结果，观察到单纳米尺度内的球形结构（对于DPAG 4-ZnP，R-h = 22埃）。此外，包封效果的DPA壳在较大的树枝状大分子被确认为基本属性，基于紫外-可见吸收光谱，循环伏安，和H-1 NMR自旋晶格弛豫时间（T-1）。DPAGX-ZnP充当SnCl 2和FeCl 3的多金属离子库。第4代树枝状聚合物（DPAG 4-ZnP）可以在卟啉核周围占据高达60摩尔量的金属络合物。通过紫外-可见滴定法对金属组装反应进行了定量研究，发现从最靠近核的内部亚胺到表面存在逐步的层层络合。锌卟啉的氧化还原行为和荧光也支持了金属离子的分步络合。这些分析表明，精细组装的金属络合物在树枝状大分子结构强烈影响的电子状态的卟啉核心。瞬态吸收测量的结果强烈表明，在亚皮秒的时间尺度上的核心和组装的金属络合物之间的非常快的电子转移。
A series of dendritic phenylazomethines (DPA), which have a meso-substituted zinc porphyrin core (DPAGX-ZnP, X = 1-4), were synthesized. Structural studies of these dendrimers were carried out using Tri-SEC (triple detection after size exclusion chromatography), intrinsic viscosity analysis, TEM (tunneling electron microscopy), and molecular modeling calculations by AM1. As a result, a sphere-like structure within a single-nanometer scale (R-h = 22 angstrom for DPAG4-ZnP) was observed. In addition, encapsulating effects by the DPA shell in the larger dendrimers were confirmed as fundamental properties, based on the UV-vis abosorption spectra, cyclic voltammograms, and H-1 NMR spin-lattice relaxation times (T-1). The DPAGX-ZnP acts as a multi-metal ion reservoir for SnCl2 and FeCl3. The generation-4 dendrimer (DPAG4-ZnP) can take up to 60 molar amounts of metal complexes around the porphyrin core. A quantitative study of the metal assembling reaction by UV-vis titration revealed stepwise layer-by-layer complexations from the inner imines nearest to the core to the surface. The redox behavior and fluorescence of the zinc porphyrin in these metal-assembled clendrimers also support the stepwise complexation of the metal ion. These analyses suggest that the finely assembled metal complexes in a dendrimer architecture strongly affect the electronic status of the porphyrin core. Results from transient absorption measurements strongly indicate a very fast electron transfer on a subpicosecond time scale between the core and assembled metal complexes.