Kitagawa Toshikazu, Matsubara Hiroaki, Okazaki Takao, Komatsu Koichi
Department of Chemistry for Materials, Graduate School of Engineering, Mie University, Tsu, Mie 514-8507, Japan.
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Molecules. 2014 Sep 24;19(9):15298-313. doi: 10.3390/molecules190915298.
Self-assembled monolayers (SAMs) of tripod-shaped trithiols, consisting of an adamantane core with three CH2SH legs and a bithiophene group, were prepared on a Au(111) surface. Adsorption in a tripod-like fashion was supported by polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS) of the SAMs, which indicated the absence of free SH groups. Cyclic voltammetry showed an irreversible cathodic wave due to reductive desorption. The SAM also showed an anodic wave due to the single-electron oxidation of the bithiophene moiety without concomitant desorption of the molecules. Although oxidation was irreversible in the absence of a protecting group, it became reversible with the introduction of a terminal phenyl group. The charge of the oxidation was one-third that of the reductive desorption, confirming a three-point adsorption. The surface coverage was ca. 50% of that expected for the anti bithiophene conformation, which suggested that an increase in the surface area per molecule had been caused by the presence of an energetically high-lying syn conformer. In accordance with this, the line shape of the oxidation wave suggested an electrostatic repulsive interaction between neighboring molecules.
由带有三条CH2SH支链和一个联噻吩基团的金刚烷核心组成的三脚架状三硫醇自组装单分子层（SAMs）在Au(111)表面制备而成。SAMs的偏振调制红外反射吸收光谱（PM-IRRAS）支持了其以三脚架状的方式吸附，这表明不存在游离的SH基团。循环伏安法显示由于还原脱附而产生不可逆的阴极波。该SAMs还由于联噻吩部分的单电子氧化而显示出阳极波，且分子没有伴随脱附。尽管在没有保护基团的情况下氧化是不可逆的，但随着末端苯基的引入，氧化变得可逆。氧化电荷是还原脱附电荷的三分之一，证实了三点吸附。表面覆盖率约为反式联噻吩构象预期值的50%，这表明每个分子的表面积增加是由能量较高的顺式构象的存在引起的。据此，氧化波的线形表明相邻分子之间存在静电排斥相互作用。
