The molecular orientations and self-assembled arrangements of organic molecules determine the properties of thin films. Here we report the orientational transitions of tin phthalocyanine (SnPc) molecules in the self-assembled structures on Cd(0 0 0 1) surfaces. In the monolayer regime, the low-temperature deposited SnPc molecules form a close-packed phase and ordered arrays of heptamers as well as an ultra-dense-packed monolayer. In particular, all molecules in the close-packed phase are flat-lying, and one seventh of the molecules in the heptamer are tilted, while all molecules in the ultra-dense-packed phase are tilted. These results demonstrate that the specific orientations of SnPc depend on the competition between intermolecular and molecule-substrate interfacial interactions.

中文翻译：

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锡酞菁分子在自组装单层中的取向转变

有机分子的分子取向和自组装排列决定了薄膜的性能。在这里，我们报告锡酞菁（SnPc）分子在Cd（0 0 0 1）表面上的自组装结构中的取向转变。在单层体系中，低温沉积的SnPc分子形成密堆积相和七聚体的有序阵列以及超密堆积的单层。特别地，密堆积相中的所有分子都是平躺的，七聚体中的分子中有七分之一是倾斜的，而超密堆积相中的所有分子都是倾斜的。这些结果表明，SnPc的特定方向取决于分子间和分子-基质界面相互作用之间的竞争。