Nanographene Metallaprisms: Structure, Stimulated Transformation, and Emission Enhancement

Nanographenes are inclined to assemble into stacked columnar structures that are stabilized by pi-pi interactions, whereas other supramolecular structures of nanographenes, such as prisms and cages, are rarely investigated. Herein, a diazananographene was synthesized, and then assembled with a coordination unit, thereby producing a triangular metallaprism. After adding C-60 or C-70, the triangular metallaprism was transformed into a square tetramer, which encapsulated a pair of C-60 or C-70 molecules. The formed host-guest complex demonstrated efficient energy transfer from the diazananographene shell to the C-60 cores. The emission intensity of the capsulated C-60 was enhanced remarkably, compared with free C-60, due to an increased quantum yield and optical absorption coefficient. This work demonstrates the versatility of nanographene-based supramolecular architectures beyond columnar stacking and their ability to enhance the emission of otherwise non-emissive fullerene.