Several approaches to graphene nanoribbons exist in the literature. However, in all of them the central part of the molecule is built first and then additional rings are added at the periphery via electrophile induced cyclization or oxidative cyclodehydrogenation. These methods are difficult to apply to the preparation of non-symmetric graphene nanostructures.
Our approach utilizes a different class of starting materials and different chemistry for the formation of six-membered cycles. In our innovative approach, ortho polyyne chains of varying sizes, equipped with different functionalities, are built in a modular fashion using well-characterized and reliable cross-coupling chemistry. In the key step, these systems are then "zipped" up via an efficient cascade of fast and selective radical cyclizations. The selectivity of transformation is achieved via incorporation of a "weak link" - a chemically different functional group which can undergo transformation into a radical center in the presence of multiple alkynes.
Since modular assembly allows each of the peripheral groups to be unique, it will allow preparation of graphene substructures with custom shapes and functionalities.
