Kinetic dispersion in redox-active dithiocarbamate monolayers.
Kinetic dispersion in redox-active dithiocarbamate monolayers.
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DOI：
10.1021/la902839r
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发表时间：
2010-02-16
期刊：
影响因子：
--
通讯作者：
Meade TJ
中科院分区：
文献类型：
--
作者：
Eckermann AL;Shaw JA;Meade TJ
二硫代氨基甲酸酯是分子电子学中重要的金结合基团。双链烷烃有两个链烷分支，在一个锚定点连接，具有双齿共振结构。二叔胺和CS2在原位形成，并迅速吸附在金表面。利用二茂铁二烷基二硫代氨基甲酸酯（Fc dtc）与稀释剂dtc在金电极上的共吸附，制备了电活性自组装膜（eSAMs）。使用短链和长链烷烃（分别为11和16个亚甲基），并引入极性酯基。循环伏安法（CV）表明该电化学反应是准可逆的。在高表面覆盖度，峰分离和全宽在半最大Fc dtc偏离理论值，并类似于在高表面覆盖度的金上的二茂铁烷硫醇。重要的是，这些特征在低Fc dtc表面覆盖率下不改变，如对二茂铁烷硫醇所观察到的。二茂铁二叔丁基化合物被用来标记单层缺陷位点，并证明表面结合的二叔丁基化合物与溶液二叔丁基化合物的交换。最后，使用塔菲尔图和交流伏安法分析了电子转移速率。这两种技术的结果是一致的动力学分散人口的氧化还原位点。稀释剂链的长度似乎对电子转移速率的分布有影响，可能是因为eSAM结构。这项工作表明，在结构上，Fc dtc eSAMs与金上的烷硫醇SAMs根本不同。
Dithiocarbamates (dtcs) have been implicated as important gold-binding groups in molecular electronics. Dtcs have two alkane branches connected at a single anchoring point that has a bidentate resonance structure. Forming readily in situ by the combination of secondary amines and CS2, dtcs adsorb quickly onto gold surfaces. Electroactive self-assembled monolayers (eSAMs) were prepared by the coadsorption of ferrocene dialkyldithiocarbamates (Fc dtcs) with diluent dtcs on gold electrodes. Short and long alkane chains were used (11 and 16 methylene groups, respectively), and a polar ester group was incorporated. Cyclic voltammetry (CV) shows that the electrochemistry is quasi-reversible. At high surface coverage, the peak separations and full widths at half-maximum for Fc dtcs deviate from theoretical values and are analogous to that of ferrocene alkane thiols on gold at high surface coverage. Importantly, these features do not change at low Fc dtc surface coverage as observed for ferrocene alkane thiols. Ferrocene dtcs were used to label monolayer defect sites and to demonstrate the exchange of surface-bound dtcs with solution dtcs. Finally, the rate of electron transfer was analyzed using Tafel plots and ac voltammetric methods. The results for both techniques are consistent with a kinetically disperse population of redox sites. The length of the diluent alkane chain appears to have an effect on the distribution of electron-transfer rates, likely because of the eSAM structure. This work indicates that structurally, Fc dtc eSAMs are fundamentally different from alkane thiol SAMs on gold.
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