The Carbon Factory: A laboratory for the chemistry of carbon-rich systems

在采用摩尔定律概念的过程中，半导体行业通过提供巨大的计算能力，为40年来的社会增长提供了保障。国际半导体技术路线图为研究人员提供了维持这种增长所需的短期和长期研究目标。2007年版的路线图预测，元件的几何缩放将在10 - 15年内达到固态的极限，并强调需要开发固态/分子混合器件。尽管对自上而下方法消亡的预测并不新鲜，但值得注意的是，在可预见的未来，半导体行业将支持混合器件架构（即分子结构集成在CMOS器件内的器件）作为目标。为了应对这些挑战，需要对电子如何在分子结构内部被操纵和在分子结构周围转移有一个坚定的理解，以及如何将这样的系统固定在半导体表面上是必要的。我们对分子内电子转移的大部分理解源于对线性化合物M(a)-B-M(b)的研究，其中两个位点M(a)和M(b)除了电荷状态外在各方面都相同，它们通过一些桥接结构连接在一起。在过去的40年里，这些混合价化合物的分子内电子转移的基本原理已经被系统地绘制出来。随着地点M(a)和M(b)与桥梁b之间相互作用的重要性被清楚地识别出来。共轭富碳桥在M(a)和M(b)位点之间具有强耦合相互作用的混合价体系的构建中特别有用。线性碳桥混合价化合物中容易的电子转移过程引起了人们对电子器件应用中分子尺度线等系统的极大兴趣。然而，可以合理地认为，分子尺寸的电线是不够的，如果要实现优于传统固态器件的真正优势，必须将更高级别的功能纳入分子组件。从设计晶体管类分子电子元件和分子开关的分子材料的角度来看，二维和三维分子系统中的电荷转移概念引起了人们的关注，其中一个位点的状态可以影响其他位点之间相互作用的性质。多位点混价配合物已被提出作为构建基于量子元胞自动机（QCA）的逻辑门和记忆单元的元件。尽管支链（例如X形和Y形）混合价体系的概念简单，但事实证明，制备一个支链配体核是困难的，它允许多个（两个以上）远程位点之间的强电子耦合，并且对这些系统中的电荷转移机制知之甚少。与线性M(a)-B-M(b)系统相比，具有两个以上氧化还原位点的混合价系统，为了方便起见，这里称为多位点，没有很好地表示，通常仅限于线性阵列M(a)-B-M(b)-B-M(c)。本提案旨在开发与支链碳基桥接配体和多位点混合价化合物相关的合成化学，研究这些二维共轭化合物中的电子转移，以及这些配合物可以附着在半导体表面的机制。此外，本文还介绍了一些研究项目，这些项目将开辟新的研究领域，包括：长累积烯的化学性质、富碳有机金属在富勒烯和碳纳米管合成中的作用、由氧化还原活性介质组成的盘状液晶以及振动耦合在电子转移反应中的作用。

In adopting the concept of Moore's Law , the semiconductor industry has underwritten 40 years of societal growth through the provision of immense computing power. The International Technology Roadmap for Semiconductors informs researchers of short and long-term research targets necessary to maintain this growth. The 2007 edition of the roadmap predicts geometric scaling of components will reach the limits of the solid state in 10 - 15 years, and highlights the need to develop hybrid solid-state / molecule devices. Although forecasts of the demise of the top down approach are not new, it is remarkable to see the semiconductor industry endorse hybrid device architectures (i.e. those in which molecular structures are integrated within a CMOS device) as targets within the foreseeable future. To meet these challenges, a firm understanding of how an electron can be manipulated within and transferred around a molecular structure will be required, and how such systems can be immobilised onto semiconductor surfaces will be required.Much of our understanding of intramolecular electron transfer originates from studies of linear compounds M(a)-B-M(b) in which two sites, M(a) and M(b) identical in every respect except charge state, are linked by some bridging structure, B. The fundamental principles of intramolecular electron transfer in these mixed valence compounds have been systematically mapped over the last 40 years, with the importance of the interactions between the sites M(a) and M(b) and the bridge B being clearly identified. Conjugated carbon-rich bridges have been identified as being particularly useful in the construction of mixed-valence systems with strong coupling interactions between the M(a) and M(b) sites.The facile electron transfer processes in linear, carbon-bridged mixed-valence compounds have led to significant interest in such systems as molecular-scale wires in electronic device applications. However, it could be reasonably argued that a molecular-sized wire is not sufficient, and higher-level function must be incorporated into the molecular component if true advantages over conventional solid state devices are to be realised. The concepts of charge-transfer in 2-D and 3-D molecular systems have attracted attention from the point of view of designing molecular materials for transistor-like molecular electronic components and molecular switches in which the state of one site can influence the nature of the interactions between the others. Multi-site mixed-valence complexes have been proposed as elements for the construction of quantum cellular automata (QCA)-based logic gates and memory cells. Despite the conceptual simplicity of branched (e.g. X and Y shaped) mixed-valence systems, it has proven difficult to prepare a branched ligand core that permits strong electronic coupling between multiple (more than two) remote sites, and relatively little is known about the mechanisms of charge transfer in these systems. In contrast to linear M(a)-B-M(b) systems, mixed valence systems featuring more than two redox sites, termed here multi-site for convenience, are not well-represented, and generally limited to linear arrays M(a)-B-M(b)-B-M(c). This proposal sets out to develop the synthetic chemistry associated with branched carbon-based bridging ligands and multi-site mixed-valence compounds, studies of electron-transfer within these 2-D conjugated compounds, and mechanisms through which these complexes can be attached to semi-conductor surfaces. A number of aside projects are also described, which initiate new lines of investigation in the chemistry of the longer cumulenes, the role of carbon-rich organometallics in the synthesis of fullerenes and carbon nanotubes, discotic liquid crystals comprised of redox-active mesogens and the role of vibrational coupling on electron-transfer reactions.