Rigid molecular tripod with an adamantane framework and thiol legs. Synthesis and observation of an ordered monolayer on Au(111)
Rigid molecular tripod with an adamantane framework and thiol legs. Synthesis and observation of an ordered monolayer on Au(111)
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DOI：
10.1021/jo051863j
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发表时间：
2006-02-17
影响因子：
3.6
通讯作者：
Komatsu, K
中科院分区：
文献类型：
--
作者：
Kitagawa, T;Idomoto, Y;Komatsu, K
合成了金刚烷骨架的三个桥头位置含有CH2SH基团和第四个桥头位置含有卤素基团的三脚架状三硫醇1-3，并在原子平坦的Au(111)表面制备了自组装单分子膜。偏振调制红外反射吸收光谱证实了三脚架的三点化学吸附，没有S-H伸缩带。1的SAM的扫描隧道显微镜显示吸附分子呈六方排列，晶格常数为8.7埃。提出了一种单向的、从头到尾的1阵列，它允许相邻分子的接近，是一种合理的二维晶体模型，其中吸附的硫原子形成了准(根3 x根3)R30度晶格。1的SAM的电化学还原脱附电荷与预期的表面覆盖率一致，而2和3的SAM的电荷略少(约70%)。在SAM为1的情况下观察到的大的负还原峰电位表明该三脚架被三个硫原子紧密锚定。
Tripod-shaped trithiols 1-3, containing CH2SH groups at the three bridgehead positions of the adamantane framework and a halogen-containing group [Br (1), p-BrC6H4 (2), or p-IC6H4 (3)] at the fourth bridgehead, were synthesized, and self-assembled monolayers (SAMs) were prepared on atomically flat Au(111) surfaces. The three-point chemisorption of these tripods was confirmed by polarization modulation infrared reflection absorption spectroscopy, which showed the absence of a S-H stretching band. Scanning tunneling microscopy of the SAM of 1 exhibited a hexagonal arrangement of the adsorbed molecule with a lattice constant of 8.7 angstrom. A unidirectionally oriented, head-to-tail array of 1, which allows the close approach of neighboring molecules, is proposed as a reasonable model of the two-dimensional crystal, where the adsorbed sulfur atoms form a quasi-(root 3 x root 3)R30 degrees lattice. The charge of the electrochemical reductive desorption of the SAM of 1 was in good agreement with the expected surface coverage, while the SAMs of 2 and 3 showed somewhat less (ca. 70%) charge. The large negative reduction peak potentials, observed for the SAM of 1, are taken to indicate a tight anchoring of this tripod by three sulfur atoms.