Imaoka Takane, Tanaka Reiko, Arimoto Sachiko, Sakai Makoto, Fujii Masaaki, Yamamoto Kimihisa
Department of Chemistry, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan.
J Am Chem Soc. 2005 Oct 12;127(40):13896-905. doi: 10.1021/ja0524797.
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 A 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 1H NMR spin-lattice relaxation times (T1). 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 dendrimers 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.
合成了一系列具有中位取代锌卟啉核心的树枝状苯甲亚胺（DPA，DPAGX-ZnP，X = 1 - 4）。使用三检测尺寸排阻色谱法（Tri-SEC）、特性粘度分析、透射电子显微镜（TEM）以及通过AM1进行分子建模计算，对这些树枝状聚合物进行了结构研究。结果观察到在单纳米尺度内的球状结构（DPAG4-ZnP的流体力学半径R(h) = 22 Å）。此外，基于紫外可见吸收光谱、循环伏安图和1H NMR自旋晶格弛豫时间（T1），证实了较大树枝状聚合物中DPA壳的包封效应是其基本性质。DPAGX-ZnP可作为SnCl2和FeCl3的多金属离子储存库。第4代树枝状聚合物（DPAG4-ZnP）在卟啉核心周围最多可容纳60摩尔量的金属配合物。通过紫外可见滴定对金属组装反应进行的定量研究揭示了从最靠近核心的内亚胺到表面的逐层逐步络合。这些金属组装树枝状聚合物中锌卟啉的氧化还原行为和荧光也支持金属离子的逐步络合。这些分析表明，树枝状结构中精细组装的金属配合物强烈影响卟啉核心的电子状态。瞬态吸收测量结果有力地表明，在核心与组装的金属配合物之间，在亚皮秒时间尺度上存在非常快速的电子转移。
