Exploiting chirality in mechanically interlocked molecules for new applications in nanotechnology

在科学（1）和J. Am. Chem. Soc. (2)Leigh小组已经表明，分子结由于其良好限定的空腔和良好表达的手性而具有有希望的催化性能。（1，2）特别是五叶结，由于多重氢键和库仑相互作用的组合结果，对卤素阴离子显示出非常强的亲和力，其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金属离子来变构地打开和关闭，所述金属离子以使人联想到酶中的变构控制的方式模板化空腔形成。（1）本项目的目标是制备一系列含有光氧化还原活性Ir（III）中心的分子结，以取代以前使用的第一行过渡金属中心。（1，4）铱中心将发挥双重作用：首先，Ir（III）的相对惰性允许起始材料作为单一对映体分离。(5)由于所需的对称性的圆形螺旋，使用对映体纯的Ir（III）配合物应导致立体选择性合成的结前体。其次，环化的Ir（III）配合物轴承联吡啶辅助配体是有据可查的有效的可见光光氧化还原催化剂。(6)By将光氧化还原活性组分掺入单手螺旋物中，我们的目标是实现立体选择性双重光氧化还原/阴离子结合催化。例如，四氢异喹啉的两步亲核攻击可以通过光氧化还原催化剂和对映选择性氢键供体催化剂的组合混合物来促进。(7)该过程可以使用Ir（III）结在一锅程序中实现。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防止系统充当阴离子结合催化剂，而光氧化还原性质将不受影响。添加Fe（II）以模板化空腔将允许阴离子结合但淬灭光氧化还原过程。最后，Zn（II）的加入应该允许光氧化还原和阴离子结合催化同时工作，该项目旨在合并一系列重要和新兴的领域，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，并严格控制立体化学和区域化学，使人联想到生物系统。分子结是一个新兴的领域，具有广阔的应用前景。化学拓扑学提供了一个迄今为止尚未开发的策略，以保持分子的连接性，同时改变功能。利用化学拓扑学改变反应途径的任何进展都将处于该领域的最前沿。虽然光氧化还原催化作为一种绿色和温和的合成方法的使用正在迅速增加，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将是对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来微调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。该项目旨在联合收割机的一系列新兴技术，创造新的和令人兴奋的功能催化剂，为未来的应用。1. V. Marcos et.例如，Science 2016，352，1555-1559.2. G.吉尔-拉米雷斯等例如，J. Am. 2016，138，13159-13162.3. J. - F. Ayme et.例如，J. Am. 2015，137，9812-9815.4. D. A. Leigh，et.例如，2014，6，978-982.5。O. Chepelin et.例如，J. Am. 2012，134，19334-19337.6. C. K. Prier et.例如，2013，113，5322-5363.7。G. Bergonzini et.例如，化学科学2014年，第5期，第1 -60页

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