Electrochemically controlled layer-by-layer deposition of metal-cluster molecular multilayers on gold
Electrochemically controlled layer-by-layer deposition of metal-cluster molecular multilayers on gold
复制标题
DOI：
10.1002/anie.200351334
复制
发表时间：
2003-01-01
影响因子：
16.6
通讯作者：
Sasaki, Y
中科院分区：
文献类型：
--
作者：
Abe, M;Michi, T;Sasaki, Y
我们的合成方法概述于图1中，详细程序提供于实验部分中。在该方法中，我们使用三核钌配合物[Ru 3（μ3-O）（μ-CH 3COO）6（bpy）2（CO）]（1，bpy= 4，4о-bipyridine;图1）[6]作为分子构建块。1的Ru 3核心形式上包含两个RuIII位点和一个RuII位点，其中CO配体占据后者的位置。[7，8]已知这类分子簇在溶液中具有明确的氧化还原过程，并且末端配体置换的特征由Ru 3（μ3-O）簇核心的氧化还原状态精确控制。[9]为了构建分子多层膜，我们如前所述在Au（111）电极[10]上制备了CO结合的Ru 3络合物的密堆积自组装膜（图1a）。[11]当所连接的RuII中心被电化学氧化为RuIII时，末端CO被消除，并且形成图1b中所示的含有动力学不稳定水分子的单层（步骤1）。[11]将图1b中所示的单层浸入1的溶液中，导致1通过单个RuIII-N（bpy）键与单层结合位点配位，得到图1c中所示的CO封端的双层（步骤2）。通过交替重复界面反应（步骤1和2），我们成功制备了多达五层的分子多层膜（图1）。已经表征的bpy-和吡嗪-桥接的延伸结构[12-14]与我们的多层膜中预期的分子结构相关。由于“CO-结合”和“CO-游离”簇分子之间的氧化还原电位显著不同，[7，8]通过循环伏安法定量评估表面物质。在图2a-f中描绘了在Au电极上依次制备的具有和不具有CO的单层、双层和三层的一系列循环伏安图（CV）。如前所述，[11]紧密堆积的CO封端的单层（表面覆盖率r = 1.4 × 10 - 10 mol cm-2）导致
Our synthetic approach is outlined in Figure 1 and the detailed procedures are provided in the Experimental Section. In the approach, we use a trinuclear ruthenium complex [Ru3 (μ3-O)(μ-CH3COO) 6 (bpy) 2 (CO)](1, bpy= 4, 4о-bipyridine; Figure 1)[6] as a molecular building block. The Ru3 core of 1 formally contains two RuIII sites and one RuII site, in which the CO ligand occupies the latter position.[7, 8] This class of molecular clusters is known to have well-defined redox processes in solution, and the character of the terminalligand displacement is precisely controlled by the redox state of the core of the Ru3 (μ3-O) cluster.[9] With the aim of constructing molecular multilayers, we prepared close-packed SAMs of a CO-bound Ru3 complex on an Au (111) electrode [10](Figure1a) as described previously.[11] The terminal CO is eliminated when the attached RuII center is electrochemically oxidized to RuIII, and the monolayer containing a kinetically-labile water molecule shown in Figure 1b is formed (step 1).[11] Immersion of the monolayers shown in Figure 1b into a solution of 1 results in the coordination of 1 to the monolayer binding site through a single RuIIIÀN (bpy) bond to afford CO-terminated bilayers shown in Figure 1c (step 2). We have successfully prepared molecular multilayers up to five layers, by repeating interfacial reactions (steps 1 and 2) alternately (Figure 1). The bpy-and pyrazine-bridged extended structures that have been characterized [12–14] are relevant to the expected molecular structures in our multilayers.Cyclic voltammetry was used to follow the multilayerformation processes. As the redox potentials are substantially different between the “CO-bound” and “CO-free” cluster molecules,[7, 8] the surface species were quantitatively evaluated by cyclic voltammetry. A series of cyclic voltammograms (CVs) obtained for the monolayers, bilayers, and trilayers with and without CO, which were sequentially prepared on an Au electrode are depicted in Figure2a–f. As established previously,[11] the close packed CO-terminated monolayers (the surface coverage Γ= 1.4 10À10 mol cmÀ2) result in a