Grant: Discovery Grants Program - Individual

Polycyclic aromatic hydrocarbons (PAH) constitute a large class of organic molecules with numerous sub-classes. PAHs find application in a broad range of settings (chemical sensors, molecular wires, spintronics, light-emitting diodes, photovoltaic devices, field-effect transistors, etc.) owing mainly to the optical and electronic properties arising from the p systems. The electronic and optical properties of PAHs are heavily influenced by the architecture of the PAH, which means that there is great scope for the tailoring of properties. The most prevalent challenge in gaining access to large PAHs is poor solubility, which emerges even in relatively small-sized PAHs and poses problems during synthesis and processing. The standard solution to this problem is to employ multiple large alkyl or alkoxy solubilizing groups on the edges of the PAH. This comes with major disadvantages: 1) the mass of the solubilizing groups can significantly outweigh that of the functional p system and this limits device performance, and 2) the presence of the solubilizing groups severely limits or even rules out performing chemistry at the edges, which means that growing the PAH by synthetic means is out of the question. In contrast, incorporating a large PAH into a [n]cyclophane (one composed of just one aromatic system and one bridge) leads to greatly enhanced solubility using just a handful of aliphatic atoms that occupy only two of the edge positions. The long-term goal of this research is to develop robust synthetic methodologies and synthetic strategies that enable the synthesis of series of [n]cyclophanes with large PAHs that are both soluble and largely free of solubilizing groups on the edges. The main approach is to use series of [n]cyclophanes with a small PAH (especially pyrene) as starting points for the synthesis of series of [n]cyclophanes with larger PAHs by applying a variety of p-extension methods, including our own recently-developed strategy, contractive annulation. As described in Part A of the proposal, this will be fueled by the development of new, concise and scalable synthetic routes that will ensure an abundant supply of [n](2,7)pyrenophanes. Part B deals with the development of more concise and efficient ways to implement the contractive annulation strategy and its use in the synthesis of a range of molecules with highly unusual structures. In Part C contains details of how the chemistry from Parts A and B may be used to approach the synthesis of the most ambitious targets - different types of carbon nanobelts.  Although the motivation of our research is not to optimize specific properties for specific applications, we are cognizant of what properties may have potential for exploitation.  Accordingly, we will seize opportunities as they arise to develop suitable collaborations with groups focused on applications.