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Molecular gauge blocks for building on the nanoscale

机译：用于纳米级构建的分子规模块

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Molecular gauge blocks, based on 1-7, 9-11 paraxylene rings, have been synthesized as part of a homologous series of oligoparaxylenes (OPXs) with a view to providing a molecular tool box for the construction of nano architectures-such as spheres, cages, capsules, metal-organic frameworks (MOFs), metal-organic polyhedrons (MOPs) and covalent-organic frameworks (COFs), to name but a few-of well-defined sizes and shapes. Twisting between the planes of contiguous paraxylene rings is generated by the steric hindrance associated with the methyl groups and leads to the existence of soluble molecular gauge blocks without the need, at least in the case of the lower homologues, to introduce long aliphatic side chains onto the phenylene rings in the molecules. Although soluble molecular gauge blocks with up to seven consecutive benzenoid rings have been prepared employing repeating paraxylene units, in the case of the higher homologues it becomes necessary to introduce hexyl groups instead of methyl groups onto selected phenylene rings to maintain solubility. A hexyl-doped compound with seven substituted phenylene rings was found to be an organogelator, exhibiting thermally reversible gelation and a critical gelation concentration of 10 mM in dimethyl sulfoxide. Furthermore, control over the morphology of a series of hexyl-doped OPXs to give microfibers, microaggregates, or nanofibers, was observed as a function of their lengths according to images obtained by scanning electron microscopy. The modular syntheses of the paraphenylene derivatives rely heavily on Suzuki-Miyaura cross-coupling reactions. The lack of π-π conjugation in these derivatives that is responsible for their enhanced solubilities was corroborated by UV/Vis and fluorescent spectroscopy. In one particular series of model OPXs, dynamic ~1H NMR spectroscopy was used to probe the stereochemical consequences of having from one up to five axes of chirality present in the same molecule. The Losanitsch sequence for the compounds with 1-3 chiral axes was established, and a contemporary mathematical way was found to describe the sequence. The development of the ways and means to make molecular gauge building blocks will have positive repercussions on the control of nanostructures in general. Their incorporation into extended structures with the MOF-74 topology provides an excellent demonstration of the potential usefulness of these molecular gauge blocks. Walking along a fine line: The synthesis and characterization of a series of high-aspect-ratio oligoparaxylenes as molecular gauge blocks are reported. The lengths of the molecules range from 10 ? for the shortest member of the series with two phenylene rings up to 50 ? for the longest member with eleven phenylene units (see figure). Minimalistic design criteria led to a walk along a fine line between keeping the molecules slender, yet also rendering them soluble.
机译：合成了基于1-7、9-11对二甲苯环的分子规嵌段，作为低聚对二甲苯（OPX）同源系列的一部分，目的是为构建纳米结构（例如球体）提供分子工具箱，笼子，胶囊，金属有机骨架（MOF），金属有机多面体（MOP）和共价有机骨架（COF），仅举几个定义明确的尺寸和形状。对位二甲苯​​环平面之间的扭曲是由与甲基相关的位阻引起的，并导致存在可溶性分子规嵌段，至少在较低的同系物的情况下，不需要将长的脂族侧链引入分子中的亚苯基环。尽管已经使用重复的对二甲苯单元制备了具有多达七个连续的苯环的可溶性分子规嵌段，但是在较高的同系物的情况下，有必要在选择的亚苯基环上引入己基而不是甲基来保持溶解度。发现具有七个取代的亚苯基环的己基掺杂化合物是有机胶凝剂，在二甲基亚砜中表现出热可逆凝胶化和10 mM的临界凝胶化浓度。此外，根据通过扫描电子显微镜获得的图像，观察到对一系列己基掺杂的OPX的形态的控制随其长度而变化，从而得到微纤维，微聚集体或纳米纤维。对苯撑衍生物的模块合成在很大程度上依赖于Suzuki-Miyaura交叉偶联反应。 UV / Vis和荧光光谱法证实了这些衍生物中缺乏π-π共轭，这导致它们的溶解度提高。在一系列特殊的模型OPX中，动态〜1H NMR光谱用于探测同一分子中存在一个至五个手性轴的立体化学结果。建立了具有1-3个手性轴的化合物的Losanitsch序列，并发现了一种当代数学方法来描述该序列。通常，制造分子规构件的方法和手段的发展将对控制纳米结构产生积极的影响。将它们结合到具有MOF-74拓扑结构的扩展结构中，可以很好地证明这些分子规模块的潜在用途。沿着一条细线走：报告了一系列高纵横比的低聚对二甲苯作为分子规嵌段的合成和表征。分子的长度范围从10？该系列中最短的一个，带有两个亚苯基环，最高达50？对于具有11个亚苯基单元的最长成员（见图）。极简的设计标准导致在保持分子细长和使分子可溶之间走过一条细线。

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