Supramolecular Chemistry of Charged Curved Polyaromatic Species

Recent achievements in experimental and theoretical chemistry of reduced corannulene and sumanene (two smallest prototypic fragments of fullerene, so-called buckybowls) revealed a tendency of highly reduced curved polyaromatic molecules to form sandwich-like aggregates. The latter contain five or six alkali metals as electrostatic “glue” between two bowls in their convex-convex orientation and show remarkable stability in solution. Then, it was found that step-by-step replacement of small lithium by potassium or larger alkali metals leads to a so-called “clamshell” effect resulting in occupation by lithium cation of the last available site: the space between two 5-membered rings. Subsequent theoretical investigations revealed that this lithium center shows unprecedentedly a large chemical shift of ~-25ppm, further confirmed by experiment.

This provides experimentalists with a unique tool, which allows one to precisely control the formation of such supramolecular aggregates. The same strategy, applied to sumanene, resulted in formation of similar type of sandwich-like aggregates, but with higher M:C ratio (M – alkali metal), which makes them even more promising candidates for building blocks for the creation of batteries with extremely high capacity. In this talk, we show how modern theoretical/computational chemistry can help and guide experimentalists and present the results of a very successful combination of theory and experiment, which made possible all recent achievements in the field. Moreover, recent theoretical predictions of complete encapsulation of metal cation between two endo-surfaces of buckybowls were successfully realized in experiment, leading to the discovery of the new type of sandwich-like supramolecular assemblies. This opens the way to new materials and possible applications.