Supramolecular assembly of strongly chemisorbed size-and shape-defined chiral clusters:: S- and R-alanine on Cu(110)
Supramolecular assembly of strongly chemisorbed size-and shape-defined chiral clusters:: S- and R-alanine on Cu(110)
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DOI：
10.1021/la049391b
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发表时间：
2004-08-17
期刊：
影响因子：
3.9
通讯作者：
Raval, R
中科院分区：
文献类型：
--
作者：
Barlow, SM;Louafi, S;Raval, R
用反射吸收红外光谱、低能电子衍射(LEED)和扫描隧道显微镜(STM)研究了手性结构的丙氨酸单分子膜在铜(110)表面的成键和自组装。这种多技术方法使人们能够深入了解手性转移的层次：从单个吸附分子，到大小定义的手性簇，然后到整体手性组装。数据表明，丙氨酸以其阴离子形式，通过电离的羟基团的氧和中性氨基的氮结合到铜表面。重要的是，甲基远离表面，导致直接的手性转移到吸附的丙氨酸分子的足迹中，而S-丙氨酸的局部吸附基序与R-丙氨酸的局部吸附基序是镜像。扫描隧道显微镜显示，S-丙氨酸分子自组织在表面形成由六到八个分子组成的大小确定的手性簇，其间穿插着裸金属的手性通道。在一起，这些簇和通道进一步自组装成手性阵列，在整个表面上保持一个独特的手性结构域。对于R-丙氨酸，也观察到了类似的手性组装，但具有镜像结构。提出了单个团簇的结构模型，并结合LEED数据，构建了S-丙氨酸和R-丙氨酸手性相的整体模型。总体而言，这种吸附体系被发现既具有很强的化学吸附能力，又能够形成广泛的分子间氢键，导致的应力不仅导致分子的手性自组织，还导致散布在结构中的空手性通道和空间的特定自组织，这些空手性通道和空间反过来在宏观长度尺度上手性组装，得到具有全局组织手性的表面。
The bonding and self-assembly of a chirally organized monolayer of alanine on the Cu(110) surface has been investigated using reflection-absorption infrared spectroscopy, low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM). This multitechnique approach has enabled an in-depth understanding of the hierarchy of chirality transfer: from a single adsorbed molecule, to size-defined chiral clusters, and then to an overall chiral assembly. The data have indicated that the alanine is in its anionic form, bound to the copper surface through the oxygens of the ionized earboxylate group and the nitrogen of the neutral amino group. Importantly, the methyl group is held away from the surface, resulting in direct chirality transfer into the footprint of the adsorbed alanine molecules, with the local adsorption motif for S-alanine being the mirror image of that created for R-alanine. STM has shown that S-alanine molecules self-organize to form size-defined chiral clusters of six or eight molecules at the surface, interspersed with chiral channels of bare metal. Together, these clusters and channels further self-assemble into a chiral array with one unique chiral domain sustained across the entire surface. A similar chiral assembly, but with the mirror organization, has been observed for R-alanine. Structural models for the individual clusters are proposed, and in conjunction with LEED data, overall models for these chiral phases of both S- and R-alanine have been constructed. Overall, this adsorption system has been found to be both strongly chemisorbed and capable of extensive intermolecular H-bonding, causing stresses that lead not only to the chiral self-organization of molecules but also to a specific self-organization of the empty chiral channels and spaces that intersperse the structure which, in turn, chirally assemble across macroscopic length scales to give a surface with global organizational chirality.