MOLECULAR ORIENTATION EFFECTS ON THE RATES OF HETEROGENEOUS ELECTRON TRANSFER OF UNSYMMETRIC DENDRIMERS
MOLECULAR ORIENTATION EFFECTS ON THE RATES OF HETEROGENEOUS ELECTRON TRANSFER OF UNSYMMETRIC DENDRIMERS
复制标题
分子取向对不对称树枝状聚合物异质电子转移速率的影响
DOI：
10.1021/ja991628g
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发表时间：
1999
影响因子：
15
通讯作者：
A. Kaifer
中科院分区：
文献类型：
--
作者：
Yun Wang;C. Cardona;A. Kaifer
氧化还原蛋白通常具有不对称定位的辅基，并且部分地埋在蛋白质的多肽骨架中。在电化学实验中，蛋白质在电极表面的界面取向影响着非均相电子转移反应的有效速率。[1]细胞色素c为这些现象提供了一个极好而清楚的例子。2在这次交流中，我们描述了类似的取向依赖性，异质et率涉及，第一次，完全合成的氧化还原活性系统。在这些树枝状聚合物系统中的异质ET的界面取向和速率可以通过pH值的变化可逆地控制。我们以前曾报道的制备和电化学的树枝状大分子含有一个单一的二茂铁亚基定位不对称的“偏离中心”的树枝状大分子结构。3这些树枝状聚合物中外围叔丁基酯的水解产生相应的水溶性羧酸树枝状聚合物1-3（参见支持信息）。根据pH滴定数据，我们发现这些树枝状聚合物中羧酸的pKa在4.5-6的范围内（支持信息）。因此，在pH g 7下，化合物1-3完全电离并具有多个负电荷。这些电荷可用于在电极-溶液界面处定向树枝状聚合物。
Redox proteins often have their prosthetic groups unsymmetrically located and partially buried in the protein’s polypeptide backbone. In electrochemical experiments, the interfacial orientation of the protein near the electrode surface influences the effective rates of the heterogeneous electron transfer (et) reactions. 1 Cytochrome c affords an excellent and clear example of these phenomena. 2 In this communication, we describe similar orientation-dependent, heterogeneous et rates involving, for the first time, fully synthetic redox active systems. Interfacial orientations and rates of heterogeneous et in these dendrimer systems can be reversibly controlled through pH changes. We have previously reported the preparation and electrochemistry of dendrimers containing a single ferrocene subunit positioned unsymmetrically “off center” in the dendrimer structure. 3 Hydrolysis of the peripheral tert-butyl esters in these dendrimers yields the corresponding water-soluble, carboxylic acid dendrimers 1-3 (see Supporting Information). From pH titration data we have found that the pKa of the carboxylic acids in these dendrimers is in the range 4.5-6 (Supporting Information). Therefore, at pH g 7 compounds 1-3 are fully ionized and have multiple negative charges. These charges can be utilized to orient the dendrimers at the electrode-solution interface.