Exploiting chirality in mechanically interlocked molecules for new applications in nanotechnology

利用机械互锁分子的手性实现纳米技术的新应用

• 批准号: 2279459
• 金额: --
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2279459
• 关键词: Exploiting; chirality; mechanically; interlocked; molecules

In pioneering publications in Science(1) and J. Am. Chem. Soc.(2) molecular knots have been shown by the Leigh group to have promising catalytic properties due to their well-defined cavities and well-expressed chirality.(1,2) Pentafoil knots, in particular, show very strong affinities for halide anions as a combined result of the multiple hydrogen bond and coulombic interactions that can be utilised for anion binding catalysis.(3) Furthermore, the catalytic activity can be allosterically switched on and off by the addition or removal of metal ions that template the cavity formation in a manner reminiscent of allosteric control in enzymes.(1)This project will aim to prepare a range of molecular knots that contain photoredox-active Ir(III) centres in place of the previously used first row transition metal centres.(1,4 )The iridium centres will play a dual role: Firstly, the relative inertness of Ir(III) allows the isolation of the starting materials as single enantiomers.(5) Due to the required symmetry of the circular helicates, the use of an enantiopure Ir(III) complex should result in the stereoselective synthesis of the knot precursor. Secondly, cyclometallated Ir(III) complexes bearing a bipyridine ancillary ligand are well documented as effective visible light photoredox catalysts.(6)By incorporating photoredox active components into a helicate of single-handedness we aim to achieve stereoselective dual photoredox/anion binding catalysis. As an example, the two step nucleophilic attack of tetrahydroisoquinolines can be promoted by a combined mixture of a photoredox catalyst and an enantioselective hydrogen bond donor catalyst.(7) This process could be achieved in a one pot procedure using Ir(III) knots. We propose controlling the reaction via allosteric interactions using different metal ions as signalling systems. The removal of first row transition metal ions will prevent the system from acting as an anion binding catalyst whilst the photoredox properties will be unaffected. The addition of Fe(II) to template the cavity will allow anion binding but quench the photoredox process. Finally, the addition of Zn(II) should allow both photoredox and anion binding catalysis to work in tandem.This project aims to merge a range of important and emerging areas including molecular knots, photoredox catalysis and switchable catalysis to provide systems capable of catalysing reaction pathways with strict control over both the stereochemistry and regiochemistry in a manner reminiscent of biological systems. Molecular knots are an emerging field with promising potential for switchable catalysis. Chemical topology provides a to date untapped strategy for retaining molecular connectivity whilst altering function. Any progress in using chemical topology to alter reaction pathways would be at the forefront of the field. Whilst the use of photoredox catalysis as a green and mild synthetic method is rapidly on the rise, stereoselective photoredox processes are still in their infancy. Any enantioselectivity achieved using photoredox catalysis would be a significant addition to the current state-of-the-art. Nature is able to finely tune the reaction rate of many complex pathways via allosteric interactions with a wide range of different signalling molecules. The ability to alter synthetic reaction pathways opens the possibility of creating smart systems capable of responding to different stimuli. This project aims to combine a range of emerging technologies to create new and exciting functional catalysts for future applications.1. V. Marcos et. al., Science 2016, 352, 1555-1559.2. G. Gil-Ramirez et. al., J. Am. Chem. Soc. 2016, 138, 13159-13162.3. J.-F. Ayme et. al., J. Am. Chem. Soc. 2015, 137, 9812-9815.4. D. A. Leigh, et. al., Nat. Chem. 2014, 6, 978-982.5. O. Chepelin et. al., J. Am. Chem. Soc. 2012, 134, 19334-19337.6. C. K. Prier et. al., Chem. Rev. 2013, 113, 5322-5363.7. G. Bergonzini et. al., Chem. Sci. 2014, 5,1-60

在科学(1)和J. Am.的开创性出版物。化学。Soc。(2) Leigh基团表明分子结具有良好的空腔和良好的手性，具有很好的催化性能。特别是（1,2）Pentafoil结，对卤化物阴离子表现出很强的亲和力，这是多重氢键和库仑相互作用的综合结果，可用于阴离子结合催化。(3)此外，催化活性可以通过添加或去除模板空腔形成的金属离子来开启和关闭，这与酶的变构控制类似。(1)本项目旨在制备一系列含有光氧化还原活性Ir（III）中心的分子结，以取代先前使用的第一排过渡金属中心。（1,4）铱中心将发挥双重作用：首先，Ir（III）的相对惰性允许将起始材料分离为单个对映体。(5)由于所要求的圆螺旋的对称性，使用对映纯Ir（III）配合物应导致结前驱体的立体选择性合成。其次，含联吡啶辅助配体的环金属化Ir（III）配合物是有效的可见光光氧化还原催化剂。(6)通过将光氧化还原活性成分加入到单手性螺旋结构中，我们的目标是实现立体选择性双光氧化还原/阴离子结合催化。例如，光氧化还原催化剂和对映选择性氢键给体催化剂的组合混合物可以促进四氢异喹啉的两步亲核攻击。(7)该过程可以在使用Ir（III）结的一锅程序中实现。我们建议使用不同的金属离子作为信号系统，通过变构相互作用来控制反应。第一行过渡金属离子的去除将阻止系统作为阴离子结合催化剂，而光氧化还原性能将不受影响。在模板腔中添加铁（II）将允许阴离子结合，但会抑制光氧化还原过程。最后，锌（II）的加入应该允许光氧化还原和阴离子结合催化协同工作。该项目旨在融合一系列重要的新兴领域，包括分子结、光氧化还原催化和可切换催化，以提供能够催化反应途径的系统，严格控制立体化学和区域化学，使人想起生物系统。分子结是一个新兴的领域，具有广阔的潜力，可切换催化。化学拓扑学为在改变功能的同时保持分子连通性提供了迄今尚未开发的策略。使用化学拓扑结构改变反应途径的任何进展都将处于该领域的前沿。虽然光氧化还原催化作为一种绿色和温和的合成方法正在迅速兴起，但立体选择性光氧化还原过程仍处于起步阶段。使用光氧化还原催化实现的任何对映体选择性都将是当前最先进技术的重要补充。大自然能够通过与各种不同信号分子的变构相互作用，精细地调节许多复杂途径的反应速率。改变合成反应途径的能力开启了创造能够对不同刺激做出反应的智能系统的可能性。该项目旨在结合一系列新兴技术，为未来的应用创造新的、令人兴奋的功能催化剂。《科学通报》，2016,35(2):1555-1559.2。G. Gil-Ramirez等，J. Am。化学。系统工程学报，2016,38(1):13159-13162.3。肯尼迪。艾梅等人，j。化学。学报，2015,37,9812-9815.4。D. A. Leigh，等人，化学学报，2014,6,978-982.5。O. Chepelin等人，J. Am。化学。社会科学学报，2012,34(4):19334-19337.6。C. K. Prier等人，化学。中国生物医学工程学报，2013,33(3):522 -5363.7。G. Bergonzini等人，化学。科学通报，2014,(5):1-6