非手性的酞菁铜分子在Bi(111)表面上的手性特征

利用低温扫描隧道显微镜（LT-STM）研究了酞菁铜（CuPc）分子在Bi（111）表面上的吸附和手性自组装结构。由于较弱的分子-衬底相互作用，我们发现在液氮温度（78 K）下吸附在Bi（111）表面上的单个CuPc分子围绕着分子中心发生旋转，直到遇到其他分子形成团簇为止。随着分子覆盖度的增加，CuPc分子形成了自组装分子单层。高分辨STM图表明，非手性的CuPc分子出现了手性特征：两个相对的酞菁基团发生了弯曲。当覆盖度超过一个分子层，酞菁铜分子的吸附取向由“平躺”转变到“站立”姿态。我们认为，酞菁铜分子的手性起源是由两种因素共同导致的结果：一种是分子-衬底之间的非对称电荷转移，另一种是相邻分子间的非对称性的范德华力作用。

Chiral Features of the Achiral Copper Phthalocyanine on a Bi(111) Surface

The adsorption and chiral features of a self-assembled CuPc monolayer on a semi-metallic Bi(111) surface have been evaluated using the low temperature scanning tunneling microscopy (LT-STM). Under low coverage conditions, the individual CuPc molecules rotated around the molecular center at 78 K until they interacted with other molecule to form clusters, because of the relatively weak interfacial interactions between the CuPc molecules and the Bi(111) surface. As the level of molecular coverage increased, the CuPc molecules self-assembled into two-dimensional domains with each molecule exhibiting chiral features. Beyond one monolayer, the CuPc molecules underwent an orientational transition from a flat-lying to a standing-up configuration. The chiral features of the CuPc molecules were attributed to the combined effect of asymmetric charge transfer between the CuPc molecules and the Bi(111) substrate and the formation of asymmetric intermolecular van der Waals interactions.