Aromatization-based Approaches to Designed Pi Systems with Unusual Structures and Properties

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The top objective of this proposal is to achieve major breakthroughs in the synthesis of aromatic belts (carbon nanobelts), which are not only fascinating molecules in their own right, but may also serve as seeds for the controlled growth of single-walled carbon nanotubes. The pursuit of these highly sought-after materials will be supported by several ongoing and new lines of research, the results of which will underpin the larger goal. At the same time, stand-alone advances in synthetic methodology and strategy (to enable the synthesis of new and increasingly challenging molecular assemblies), and the target-oriented synthesis of designed pi systems with exploitable properties will be achieved. Work with the inverse electron demand Diels-Alder reaction will be directed towards the synthesis of bis(isophthalates), which will ultimately be converted into aromatic "boards" with handles that can be used create a type of cyclophane (bridged aromatic compound) that will be used in one of our approaches to aromatic belts. A new strategy for the rapid construction of heteroaromatic compounds with potentially useful pharmaceutical and optoelectronic properties will be pursued. Our recent advances in the multigram scale synthesis of multifunctional pyrenes (strongly fluorescent polycyclic aromatic hydrocarbons (PAH)) will drive efforts aimed at the development of concise synthetic routes to different types of linear and cyclic arrays of pyrene-based constructs. These compounds are expected to have potential applications as sensors and as luminescent materials. We intend to build on our longstanding expertise in the area of cyclophane chemistry to generate a variety of new cyclophanes, especially those with increasingly large PAHs as the aromatic component. Very large PAHs (nanographenes) have desirable electronic properties, and their incorporation into cyclophanes brings good solubility, which is important for their incorporation into optoelectronic devices. Work in this area will involve both the extension of our existing methodology and the development of new methods and strategies. One such strategy involves growing the aromatic unit while simultaneously shortening the bridge. This will not only provide access to new types of small strained molecules (with unusual chemical and physical properties), but also have the potential to be used iteratively in the synthesis of aromatic belts. Other projects aimed at the synthesis of aromatic belts involve the synthesis of pyrene-based cyclophanes with the appropriate size, shape and functional groups for the construction of macrocyclic systems. Once this have been achieved, different types of chemistry will be applied to sew together the components of the macrocycles and deliver aromatic belts of variable diameter and thickness.