Inorganic Chemistry III and North Bavarian NMR Center, University of Bayreuth, Universitätsstraße 30, 95447, Bayreuth, Germany.
Macromolecular Chemistry and Bavarian Polymer Institute, University of Bayreuth, Universitätsstraße 30, 95447, Bayreuth, Germany.
Chemphyschem. 2021 Dec 13;22(24):2585-2593. doi: 10.1002/cphc.202100597. Epub 2021 Nov 8.
Benzene bisamides are promising building blocks for supramolecular nano-objects. Their functionality depends on morphology and surface properties. However, a direct link between surface properties and molecular structure itself is missing for this material class. Here, we investigate this interplay for two series of 1,4-benzene bisamides with symmetric and asymmetric peripheral substitution. We elucidated the crystal structures, determined the nano-object morphologies and derived the wetting behaviour of the preferentially exposed surfaces. The crystal structures were solved by combining single-crystal and powder X-ray diffraction, solid-state NMR spectroscopy and computational modelling. Bulky side groups, here t-butyl groups, serve as a structure-directing motif into a packing pattern, which favours the formation of thin platelets. The use of slim peripheral groups on both sides, in our case linear perfluorinated, alkyl chains, self-assemble the benzene bisamides into a second packing pattern which leads to ribbon-like nano-objects. For both packing types, the preferentially exposed surfaces consist of the ends of the peripheral groups. Asymmetric substitution with bulky and slim groups leads to an ordered alternating arrangement of the groups exposed to the surface. This allows the hydrophobicity of the surfaces to be gradually altered. We thus identified two leitmotifs for molecular packings of benzene bisamides providing the missing link between the molecular structure, the anisotropic morphologies and adjustable surface properties of the supramolecular nano-objects.
苯甲脒是超分子纳米物体的有前途的构建模块。它们的功能取决于形态和表面性能。然而，对于这种材料类别，其表面性能与分子结构本身之间缺少直接联系。在这里，我们研究了具有对称和不对称外围取代基的两个系列的 1,4-苯甲脒之间的这种相互作用。我们阐明了晶体结构，确定了纳米物体的形态，并推导出优先暴露表面的润湿行为。通过单晶和粉末 X 射线衍射、固态 NMR 光谱和计算建模相结合来解决晶体结构。在这里，体积庞大的侧基，如叔丁基，作为一种结构导向的 motif，有利于形成薄的薄片。在我们的情况下，使用两侧的细长外围基团，即线性全氟化烷基链，将苯甲脒自组装成另一种包装模式，从而形成带状纳米物体。对于这两种包装类型，优先暴露的表面由外围基团的末端组成。带有大体积和细长基团的不对称取代导致暴露于表面的基团的有序交替排列。这使得表面的疏水性可以逐渐改变。因此，我们确定了苯甲脒分子堆积的两个主题，从而在分子结构、各向异性形态和超分子纳米物体的可调表面性能之间建立了缺失的联系。
