Institute for Complex Molecular Systems and the Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
J Am Chem Soc. 2020 Jul 15;142(28):12400-12408. doi: 10.1021/jacs.0c04962. Epub 2020 Jun 30.
Water is typically considered to be insoluble in alkanes. Recently, however, monomerically dissolved water in alkanes has been shown to dramatically impact the structure of hydrogen-bonded supramolecular polymers. Here, we report that water in methylcyclohexane (MCH) also determines the outcome of combining a Michael reaction with a porphyrin-based supramolecular system. In dry conditions, the components of the reaction do not affect or destabilize the supramolecular polymer, whereas in ambient or wet conditions the polymers are rapidly destabilized. Although spectroscopic investigations show no effect of water on the molecular structure of the supramolecular polymer, light scattering and atomic force microscopy experiments show that water increases the flexibility of the supramolecular polymer and decreases the polymer length. Through a series of titrations, we show that a cooperative interaction, involving the coordination of the amine catalyst to the porphyrin and complexation of the substrates to the flexible polymers invokes the depolymerization of the aggregates. Water crucially stabilizes these cooperative interactions to cause complete depolymerization in humid conditions. Additionally, we show that the humidity-controlled interference in the polymer stability occurs with various substrates, indicating that water may play a ubiquitous role in supramolecular polymerizations in oils. By controlling the amount of water, the influence of a covalent chemical process on noncovalent aggregates can be mediated, which holds great potential to forge a connection between chemical reactivity and supramolecular material structure. Moreover, our findings highlight that understanding cooperative interactions in multicomponent noncovalent systems is crucial to design complex molecular systems.
水通常被认为不溶于烷烃。然而，最近单体溶解在烷烃中的水已被证明会显著影响氢键超分子聚合物的结构。在这里，我们报告说，甲基环己烷（MCH）中的水也决定了迈克尔反应与基于卟啉的超分子体系结合的结果。在干燥条件下，反应的成分不会影响或破坏超分子聚合物，而在环境或潮湿条件下，聚合物会迅速失稳。尽管光谱研究表明水对超分子聚合物的分子结构没有影响，但光散射和原子力显微镜实验表明，水增加了超分子聚合物的灵活性，并降低了聚合物的长度。通过一系列滴定实验，我们表明涉及胺催化剂与卟啉的配位以及底物与柔性聚合物的络合的协同相互作用会引起聚合体的解聚。水至关重要地稳定了这些协同相互作用，导致在潮湿条件下完全解聚。此外，我们表明聚合物稳定性的湿度控制干扰会在各种底物中发生，这表明水可能在油中起超分子聚合的普遍作用。通过控制水的量，可以调节共价化学过程对非共价聚集体的影响，这为在化学反应性和超分子材料结构之间建立联系提供了巨大的潜力。此外，我们的发现强调了理解多组分非共价体系中的协同相互作用对于设计复杂分子体系至关重要。
