Porphyrin Nanorings

共轭有机材料因其独特的光学和电子特性而具有重要意义。例如，有机半导体在显示器、柔性晶体管和光伏材料中得到了应用，而双光子染料则用于微加工、生物成像和光信号处理。这一领域在过去20年中取得了巨大的进步，并提供了将基础科学转化为影响日常生活的实际应用的优秀例子。然而，关于有机pi系统的工程和控制仍有许多悬而未决的问题。需要进行基础研究，以支持进一步的长期技术创新。在这个建议中，我们建立了一个新的合成路线环共轭聚合物，基于前体分子的超分子组织。“游标模板”是一种创建分子的新策略，其尺寸可与自上而下的工程技术（如电子束光刻）制造的结构相媲美。介观结构的化学合成通过引入具有原子精度的功能提供了好处。我们将利用这种方法来研究以前未开发的结构空间区域，并产生全新的功能材料。共轭大环或“环烯”自20世纪60年代桑德海默的经典研究以来一直是研究的焦点。大型环烯表现出显著的光电特性，这刺激了该领域活动的复苏。Anderson的团队通过开发模板定向合成6、8或12个卟啉单元的带状纳米结构，直径为2-5纳米，对该领域做出了贡献。该项目将研究这些纳米环的化学和物理性质，并将合成扩展到更大的结构。由于卟啉纳米材料与自然光收集系统的相似性，以及它们有望支持电荷和激发的量子相干输运，因此，本文所针对的卟啉纳米材料本身就具有很大的吸引力。它们还提供了一种新的模型系统，用于探索具有明确形状的介观分子的合成。牛津大学开创的模板程序可能会刺激相关领域的发展，如分子机器和仿生化学，在这些领域，具有复杂功能的大分子的受控合成仍然是未来发展的瓶颈。我们专注于炔连接的金属卟啉低聚物作为测试系统，允许访问新的功能材料。这些材料的合成、结构和功能之间迷人的相互作用激发了这里提出的合作方法。理解分子中能量和电子的流动是许多科学领域的基础。我们将研究具有明确三级结构的纳米级分子线中能量和电荷的离域。传统的环电流只在直径小于2nm的分子中被观察到，然而直径约10nm的半导体环在没有施加电压的情况下表现出持续的环电流。这些量子干涉现象类似于芳香分子的环电流，除了它们随外加磁场而变化（即它们表现出阿哈罗诺夫-玻姆振荡）。我们将研究分子纳米环是否表现出介于小芳香分子和大量子环之间的行为。卟啉纳米结构类似于光收集叶绿素阵列，在光合作用期间将能量汇集到反应中心。我们将探讨它们是否模仿自然光收集阵列的激子行为。最终，这项工作可能会导致太阳能发电材料的改进，或分子螺线管和分裂环谐振器作为光学超材料的功能。

Conjugated organic materials are important because of their unique optical and electronic properties. For example organic semiconductors are finding applications in displays, flexible transistors and photovoltaic materials, while two-photon dyes are used in microfabrication, biological imaging and optical signal processing. This field has advanced tremendously during the past 20 years and provides excellent examples of the translation of fundamental science into practical applications that impact everyday life. However there are many open questions concerning the engineering and control of organic pi-systems. Fundamental studies are required to underpin further long-term technological innovations. In this proposal, we build on a new synthetic route to cyclic conjugated polymers, based on supramolecular organisation of precursor molecules. 'Vernier templating' is a new strategy for creating molecules with dimensions comparable to those of structures made by top-down engineering techniques, such as electron-beam lithography. The chemical synthesis of mesoscopic structures provides benefits through the introduction of functionality with atomic precision. We will exploit this methodology to study a previously unexplored region of structure-space and to generate completely new functional materials.Conjugated macrocycles or 'annulenes' have been a focus of research ever since the classical studies by Sondheimer in the 1960s. Large annulenes exhibit remarkable optoelectronic properties, and this has stimulated a resurgence of activity in the field. Anderson's group has contributed to the area by developing the template-directed synthesis of belt-like nanorings of 6, 8 or 12 porphyrin units, with diameters of 2-5 nm. This project will investigate the chemistry and physics of these nanorings, and extend the synthesis to even larger structures.The porphyrin nanorings targeted here are of great interest in their own right, owing to their similarity to natural light harvesting systems, and because they are expected to support the quantum coherent transport of charge and excitation. They also provide a new model system in which to explore the synthesis of mesoscopic molecules with well defined shapes. The templating procedures pioneered in Oxford are likely to stimulate developments in related fields such as molecular machines and biomimetic chemistry, where the controlled synthesis of large molecules with complex functionality remains a bottleneck for future developments. We focus on alkyne-linked metalloporphyrin oligomers as test systems which allow access to new functional materials. The fascinating interplay between synthesis, structure and function for these materials motivates the collaborative approach proposed here.Understanding the flow of energy and electrons through molecules is fundamental to many areas of science. We will investigating the delocalisation of energy and charge in nano-scale molecular wires with well defined tertiary structures. Conventional ring currents have only been observed in molecules with diameters of less than 2 nm, however semiconductor rings with diameters of about 10 nm exhibit persistent ring currents, in the absence of an applied voltage. These quantum-interference phenomena are analogous to the ring currents of aromatic molecules, except that they vary with the applied magnetic field (i.e. they exhibit Aharonov-Bohm oscillations). We will investigate whether molecular nanorings exhibit behaviour intermediate between those of small aromatic molecules and large quantum rings. Porphyrin nanorings resemble the light harvesting chlorophyll arrays which funnel energy into the reaction centre during photosynthesis. We will explore whether they mimic the excitonic behaviour of natural light harvesting arrays. Ultimately this work may lead to improved materials for solar power generation, or to molecular solenoids and split-ring resonators which function as optical metamaterials.