Nanostructured polymer duplexes via the covalent casting of 1-dimensional H-bonding motifs: A new strategy for the self-assembly of macromolecular precursors
Nanostructured polymer duplexes via the covalent casting of 1-dimensional H-bonding motifs: A new strategy for the self-assembly of macromolecular precursors
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DOI：
10.1021/ja000777s
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发表时间：
2000-05-24
影响因子：
15
通讯作者：
Krische, MJ
中科院分区：
文献类型：
--
作者：
Archer, EA;Goldberg, NT;Krische, MJ
化学科学发展的一个主要主题在于提高在越来越长的尺度上对物质组织中的选择性问题进行谈判的能力。[1]虽然分子合成已经通过精确控制化学选择性、区域选择性、立体选择性和对映选择性而发展成为一门艺术，但对持久性非共价结合基序的识别和编排正在将合成技术扩展到纳米级，通过在平衡条件下自组装指定的分子组分来构建超分子结构。2沿着这些路线，氢键介导的分子前体自组装代表了逻辑驱动的逆合成和结构均匀形式的纳米级材料的构建的强大策略。然而，大多数非共价聚集体的名义稳定性减损了它们的有用性。为了解决这一缺陷，已经描述了涉及共价捕获离散的非共价超结构3和聚合有组织的超结构4，5的模板导向合成。也可以通过结合位点的预组织和多种结合相互作用的积累来稳定动力学不稳定的系统，从而获得稳健的纳米级组装。6大分子体系非常适合后一种策略，最近人们对制备含有氢键部分的聚合物7以及树枝状大分子8和嵌段共聚物的自组装给予了很大的关注。5a，9，10作为涉及通过大分子前体的自组装来合成纳米结构材料的合成方法的开发的计划的一部分，我们在此报告了关于能够通过一维氢键基序的“共价铸造”形成双链体的合成聚合物链的设计和从头合成的初步研究。排除系统借用自然发生的超结构基序（如，homo-DNA 11），据我们所知，这份报告代表了第一次努力向非天然聚合物双链组装通过股间氢键的作用。[12]通过多个互补结合位点的预组织的协同结合通过减少熵项来增强缔合，所述熵项用于通过受体-底物相互作用形成离散物体。2 e，13为了将该原理应用于一维超结构，例如氢键键合带I，假设可以通过引入共价连接体来实现构成一维超结构的分子的预组织，如部分浇铸的氢键键合带II示意性所示。第二个连接基团的引入完全铸造了氢键带，提供了一个covalentnoncovalent梯形材料，聚合物双链体III（方案1）。雅阁这一策略，我应该包括能够作为一个平台，为后续的阐述III的分子。三氯-1，3，5-三嗪，其经历氯官能度的逐步取代而不过度加成，被证明是合适的。然而，2-氨基-1，3，5-三嗪的H-键合基序未被描述。为此，从四氯化碳中生长2-氨基-4，6-二氯三嗪（1，R）Cl）的晶体。预期的一维氢键基序I表达为
A major theme in the development of the chemical sciences resides in improving the capability to negotiate issues of selectivity in the organization of matter on increasingly greater-length scales. 1 While molecular synthesis has advanced to an art through the precise control of chemo-, regio-, stereo-, and enantioselectivity, the identification and orchestration of persistent noncovalent binding motifs is extending synthetic technology to the nanoscopic regime by allowing the construction of supramolecular architectures through the self-assembly of instructed molecular components under equilibrium conditions. 2 Along these lines, the H-bond-mediated self-assembly of molecular precursors represents a powerful strategy for the logic-driven retrosynthesis and construction of nanoscopic materials in structurally homogeneous form. 2e Nevertheless, the nominal stability of most noncovalent aggregates detracts from their usefulness. To address this deficiency, template-directed syntheses involving the covalent capture of discrete noncovalent superstructures3 and the polymerization of organized assemblies4, 5 have been described. Robust nanoscale assemblies may also be obtained through the stabilization of kinetically labile systems by the preorganization of binding sites and accumulation of multiple binding interactions. 6 Macromolecular systems are well-suited to this latter strategy, and recently much attention has been given to the preparation of polymers incorporating H-bonding moieties7 and the self-assembly of dendritic macromolecules8 and block copolymers. 5a, 9, 10 As part of a program involving the development of synthetic methodologies for the synthesis of nanostructured materials via self-assembly of macromolecular precursors, we herewith report preliminary studies on the design and de novo synthesis of synthetic polymer strands capable of duplex formation through the “covalent casting” of 1-dimensional H-bonding motifs. Excluding systems that borrow from naturally occurring superstructural motifs (eg, homo-DNA11), to the best of our knowledge this report represents the first efforts toward unnatural polymer duplexes assembling through the action of inter-strand H-bonds. 12 Cooperative binding via preorganization of multiple complementary binding sites enhances association through the reduction of entropic terms for the formation of discrete objects through receptor-substrate interactions. 2e, 13 For the application of this principle to 1-dimensional superstructures, such as the H-bonded tape I, it was hypothesized that preorganization of the molecules comprising the 1-dimensional superstructure could be achieved by introduction of a covalent linker as shown schematically for the partially cast H-bonded tape II. Introduction of a second linking group fully casts the H-bonded tape to afford a covalentnoncovalent ladder material, polymer duplex III (Scheme 1).In accord with this strategy, I should be comprised of molecules capable of functioning as a platform for subsequent elaboration to III. Trichloro-1, 3, 5-triazine, which undergoes stepwise substitution of the chloro-functionality without over-addition, proved suitable. However, the H-bonding motif of 2-amino-1, 3, 5-triazines is undescribed. For this reason, crystals of 2-amino-4, 6-dichlorotriazine (1, R) Cl) were grown from carbon tetrachloride. The anticipated 1-dimensional H-bonding motif I was expressed, as