Berrocal José Augusto, Heideman G Henrieke, de Waal Bas F M, Meijer E W, Feringa Ben L
Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, Groningen 9747 AG, The Netherlands.
Institute for Complex Molecular Systems and Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands.
ACS Nano. 2020 Oct 27;14(10):13865-13875. doi: 10.1021/acsnano.0c06274. Epub 2020 Sep 16.
We report two families of naphthalenediimides (NDIs) symmetrically functionalized with discrete carbon chains comprising up to 55 carbon atoms (, = 39, 44, 50, and 55) and their self-assembly at the 1-phenyloctane/highly oriented pyrolytic graphite interface (1-PO/HOPG interface). The compounds differ by the presence or absence of two or three internal double bonds in the carbon chains (unsaturated and saturated , respectively). Combinatorial distributions of geometrical isomers displaying either the - or -configuration at each double bond are obtained for the unsaturated compounds. Analysis of the self-assembled monolayers of equally long unsaturated and saturated by scanning tunneling microscopy (STM) reveal that all tend to form lamellar systems featuring alternating areas of aromatic cores and carbon chains. Extended chain lengths are found to significantly increase disorder in the self-assembled monolayers due to misalignments and enhanced strength of interchain interactions. This phenomenon is antagonized by the local order-inducing effect of the internal double bonds: unsaturated give qualitatively more ordered self-assembled monolayers compared to their saturated counterparts. The use of combinatorial distributions of unsaturated geometrical isomers does not represent a limitation to achieve local order in the self-assembled monolayers. The self-assembly process operates a combinatorial search and selects the geometrical isomer(s) affording the most thermodynamically stable pattern, highlighting the adaptive character of the system. Finally, the antagonistic interplay between the extended carbon chain lengths and the presence of internal double bonds brings to the discovery of the lamellar "phase C" morphology for unsaturated with ≥ 50.
我们报道了两类萘二亚胺（NDIs），它们由含多达55个碳原子的离散碳链（(n = 39)、44、50和55）对称官能化，并研究了它们在1-苯基辛烷/高度取向热解石墨界面（1-PO/HOPG界面）的自组装行为。这些化合物的区别在于碳链中是否存在两个或三个内部双键（分别为不饱和和饱和(n)）。对于不饱和化合物，在每个双键处呈现(E)-或(Z)-构型的几何异构体的组合分布得以获得。通过扫描隧道显微镜（STM）对等长的不饱和和饱和(n)的自组装单分子层进行分析，结果表明所有(n)都倾向于形成具有交替排列的芳香核和碳链区域的层状体系。发现延长链长会由于链间错排和链间相互作用强度增强而显著增加自组装单分子层中的无序度。这种现象因内部双键的局部有序诱导效应而受到抑制：与饱和对应物相比，不饱和(n)形成的自组装单分子层在定性上更有序。使用不饱和(n)几何异构体的组合分布并不妨碍在自组装单分子层中实现局部有序。自组装过程进行了组合搜索，并选择了提供最热力学稳定模式的几何异构体，突出了该体系的适应性特征。最后，延长碳链长度与内部双键的存在之间的拮抗相互作用导致发现了碳链长度(n\geq50)的不饱和(n)的层状“C相”形态。
