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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Photoinduced Electron-Transfer within Free Base and Zinc Porphyrin Containing Poly(Amide) Dendrimers
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Photoinduced Electron-Transfer within Free Base and Zinc Porphyrin Containing Poly(Amide) Dendrimers

机译：含聚（酰胺）树枝状聚合物的游离碱和卟啉锌中的光诱导电子转移

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摘要

The synthesis and photophysical characterization of a series of free base and zinc porphyrin containing, Newkome-type dendrimers terminated with anthraquinone groups (FbP-G_a-AQ_n and AnP-G_a-AQ_n) and ethyl groups (FbP-G_a-Et_n and ZnP-G_a-Et_n) are described. These dendrimers were designed for use as mimics of the photosynthetic reaction center. Red-shifts in the absorption spectra, particularly in the anthraquinone-terminated series, were interpreted as resulting from backfolding of the dendrimer branches. Dendrimers FbP-G_a-AQ_n were shown to exhibit substantial quenching (58—75%) of the porphyrin fluorescence as measured against the analogous ethyl-terminated dendrimers (FbP-G_a-Et_n) in steady-state fluorescence experiments. The zinc porphyrin containing dendrimers ZnP-G_a-AQ_n exhibited nearly complete quenching (96—99.5%) of the porphyrin fluorescence. An intramolecular electron-transfer m.schanism is proposed for the substantial decrease in fluorescence in both series of dendrimers. Time-resolved fluorescence experiments for FbP-G_a-AQ_n were fit to 2-3 exponentials and indicated that multiple orientations of the porphyrin and anthraquinone groups contribute to the electron-transfer event. These results were in good agreement with the steady-state fluorescence results. From the time-resolved fluorescence data, the electron-transfer rate constants were calculated, indicating krr values in the range of 3.77 x 10~7 s~(-1) to 2.28 x 10~8 s~(-1) that were dependent upon both dendrimer generation number and solvent. Similar experiments on ZnP-G_a-AQ_n also indicated that multiple zinc porphyrin anthraquinone conformations were likely responsible for the electron-transfer. Dramatic differences between the steady-state and time-resolved fluorescence data in the zinc porphyrin dendrimers were interpreted in terms of ligation of the terminal anthraquinone groups with the zinc porphyrin that results in either a nonemissive state or an ultrafast electron-transfer.
机译：一系列以蒽醌基团（FbP-G_a-AQ_n和AnP-G_a-AQ_n）和乙基（FbP-G_a-Et_n和ZnP-G_a -Et_n）。这些树状聚合物被设计用作光合作用反应中心的模拟物。吸收光谱中的红移，特别是蒽醌封端的红移，被解释为是由于树枝状大分子分支的反向折叠造成的。在稳态荧光实验中，相对于类似的乙基封端的树枝状大分子（FbP-G_a-Et_n）测量，树枝状大分子FbP-G_a-AQ_n显示出卟啉荧光的基本猝灭（58-75％）。含锌卟啉的树枝状聚合物ZnP-G_a-AQ_n表现出几乎完全的淬灭（96-99.5％）的卟啉荧光。提出了分子内电子转移机制以用于两个系列树状聚合物中荧光的显着降低。 FbP-G_a-AQ_n的时间分辨荧光实验适合2-3个指数，并表明卟啉和蒽醌基团的多个方向有助于电子转移。这些结果与稳态荧光结果非常吻合。根据时间分辨的荧光数据，计算出电子传递速率常数，表明krr值在3.77 x 10〜7 s〜（-1）至2.28 x 10〜8 s〜（-1）范围内。树枝状大分子的生成数和溶剂。在ZnP-G_a-AQ_n上进行的类似实验也表明，多个卟啉锌蒽醌构象可能是电子转移的原因。锌卟啉树状大分子的稳态和时间分辨荧光数据之间的显着差异是通过末端蒽醌基团与锌卟啉锌的连接来解释的，这导致了非发射态或超快电子转移。

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