Catalysis with Molecular Nanoreactors: Dendrimers and other Highly Branched Macromolecules

分子纳米反应器催化：树枝状聚合物和其他高度支化的大分子

• 批准号: 0317514
• 负责人: Jean M. J. Frechet
• 金额: $ 45.6万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0317514&HistoricalAwards=false
• 关键词: Catalysis; Molecular; Nanoreactors; Dendrimers; other

During the last few decades, tremendous progress has been made in the field of catalysis in part due to its important role in the economically and ecologically sound production of fine chemicals and pharmaceuticals. Research in the field of catalysis is typically divided into two areas, namely homogenous and heterogeneous. While the former offers the unique advantage of well-defined catalytic sites that can systematically be optimized, the latter is of great industrial importance due to the inherent retention of the catalysts, which facilitates product separation. In recent years, functional polymers carrying catalytically active sites have emerged that combine the advantages of both homogeneous and heterogeneous catalysis. In particular, polymeric macromolecules with a highly branched, globular architectures, such as dendrimers, have shown promise for application as true nanoscale "molecular reactors" to affect specific chemical tranformations withing a well-controlled environment. A research program utilizing dendritic and other highly branched polymer architectures for the design of new catalyst systems is proposed. In each instance, a reactive functionality with catalytic activity is placed at the core or the interior of a globular dendritic structure so that the unique properties offered by dendritic encapsulation may be fully realized. Dendritic encapsulation, can afford several advantages such as: (i) reactive species essential for catalysis are isolated from each other preventing mutal deactivation; (ii) the reactivity of the catalytic site can be tuned, either directly at the catalytic site, or via its surrounding microenvironment; (iii) the catalyst solubility can be altered by peripheral modification; (iv) the microenviroment of the catalytic site my provide not only enhanced activity but also additional functions such as transport of substrate and product; (v) the potential for positive cooperative interactions between multiple catalytically active subunits. Such properties, resulting from dendritic encapsulation, are frequently found in natural enzymatic systems and are employed to high efficacy, but they generally cannot be incorporated simultaneouly in classical artificial homogeneous or heterogeneous catalysts. The knowldege to be gelaned from the proposed investigations will have two-fold importance, both to further increase our understanding of the fundamental principles regarding catalysis with a specialized and somewhat unusual class of synthetic polymers and to uncover leads for development of superior, fully synthetic, catalysts that rival naturally occurring enzymes. This impact of this research will be felt not only on the production of chemical and pharmaceutical products but also in our environment as better, more effective, ecologically friendly, and recyclable catalysts will be discovered. In one possible implementation, a series of dendrimer catalysts may be used to carry out multistep tranformations in a single medium in much the same way as several enzymes carry out complex tranformations in succession within the same overall environment.

在过去的几十年里，催化领域取得了巨大的进展，部分原因是它在精细化学品和药物的经济和生态无害生产中发挥了重要作用。 催化领域的研究通常分为两个领域，即均相和非均相。 虽然前者提供了可以系统地优化的明确定义的催化位点的独特优势，但由于催化剂的固有保留，后者具有很大的工业重要性，这有助于产物分离。 近年来，联合收割机均相和多相催化的优点，出现了携带催化活性位点的功能聚合物。 特别是，具有高度支化的球形结构的聚合物大分子，如树枝状聚合物，已经显示出作为真正的纳米级“分子反应器”的应用前景，以在良好控制的环境中影响特定的化学转化。 提出了一个利用树枝状和其他高度支化的聚合物结构设计新的催化剂体系的研究计划。 在每种情况下，将具有催化活性的反应性官能团置于球状树枝状结构的核心或内部，使得可以完全实现树枝状封装所提供的独特性质。 树枝状包封可以提供几个优点，例如：（i）催化所必需的反应性物种彼此隔离，防止相互失活;（ii）催化位点的反应性可以直接在催化位点处或通过其周围的微环境进行调节;（iii）催化剂溶解度可以通过外围修饰来改变;（iv）催化位点的微环境不仅可以提供增强的活性，而且还可以提供额外的功能，例如底物和产物的运输;（v）多个催化活性亚基之间的积极合作相互作用的潜力。 这种特性，从树枝状封装，经常发现在天然酶系统，并采用高效率，但它们通常不能掺入经典的人工均相或非均相催化剂。 从拟议的研究中得到的知识将具有双重重要性，既可以进一步增加我们对有关特殊的和有点不寻常的一类合成聚合物催化的基本原理的理解，又可以揭示开发可与天然酶相媲美的上级、全合成催化剂的线索。 这项研究的影响不仅会影响到化学和医药产品的生产，而且会影响到我们的环境，因为我们将发现更好、更有效、更环保和可回收的催化剂。 在一种可能的实施方式中，可以使用一系列树枝状聚合物催化剂在单一介质中进行多步转化，其方式与几种酶在相同的总体环境中连续进行复杂转化的方式大致相同。