Uniform π-System Alignment in Thin Films of Template-Grown Dicarbonitrile-Oligophenyls
Uniform π-System Alignment in Thin Films of Template-Grown Dicarbonitrile-Oligophenyls
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DOI：
10.1002/adfm.201001940
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发表时间：
2011-05-10
影响因子：
19
通讯作者：
Barth, Johannes V.
中科院分区：
文献类型：
--
作者：
Klappenberger, Florian;Kuehne, Dirk;Barth, Johannes V.
利用X射线结构分析、低温扫描隧道显微镜和近边X射线吸收精细结构谱等方法研究了二腈-对低聚苯基化合物的有序性和构象性质。功能化变体的包装不同于它们在技术上感兴趣的对位低聚苯基对应物，无论是在体晶相还是在超高真空条件下在Ag（111）表面上通过有机分子束外延（OMBE）生长的薄膜中。在晶相中，构象取决于苯环的数目n，在室温和180 K下，n = 4时，构象呈现螺旋状结构。对于OMBE生长的薄膜，整个系列获得相同类型的构象，其特征在于交替扭曲的苯环，类似于纯oligophenyl物种。然而，对于所有测试的分子，分子参考平面的取向在整个膜内是均匀的，并且与表面平面一致。这与没有腈基的苯基主链所采用的人字形排序形成对比。我们的研究结果表明，如何与扩展的共轭电子系统的部分的官能化可以帮助提高技术相关的有机薄膜的结构均匀性。
The ordering and conformational properties of dicarbonitrile-para-oligophenyls are studied with complementary methods, namely X-ray structure analysis, low-temperature scanning tunneling microscopy, and near-edge X-ray absorption fine-structure spectroscopy. The packing of the functionalized variants differs from their technologically interesting para-oligophenyl counterparts, both in the bulk crystal phase and in thin films grown by organic molecular beam epitaxy (OMBE) under ultra-high vacuum conditions on the Ag(111) surface. In the crystal phase, the conformation depends on the number n of phenyl rings, exhibiting an intriguing screw-like structure in the case of n = 4 at room temperature as well as at 180 K. For OMBE-grown thin films, the whole series acquires the same type of conformation, characterized by alternately twisted phenyl rings, similar to the pure oligophenyl species. However, for all tested molecules, the orientation of the molecular reference plane is uniform within the entire film and coincides with the surface plane. This contrasts with the herringbone ordering adopted by the phenyl backbones without the carbonitrile groups. Our results demonstrate how the functionalization of moieties with extended conjugated electron systems can help to improve the structural homogeneity in technologically relevant organic thin films.