Manipulating the dynamic processes of nanographenes, from conformational flipping to supramolecular dimerization, is essential for gaining precise control over their properties and functions. In this study, a nanographene with two fused carbaporphyrin units (HBC2P) was synthesized by introducing dipyrromethene units into opposite bay areas of hexa-peri-hexabenzocoronene (HBC). HBC2P has a flexible monolithic skeleton, with a backbone length exceeding 1.8 nm. Its two conformations, referred to as "boat-shaped" and "chair-shaped," were individually achieved by selecting a suitable solvent. Notably, HBC2P forms a stable bilayer structure with two "boat-shaped" monomers arranged back-to-back in the polar solvents. Moreover, its flexible structure can be fixed by metal coordination, where the hollow ribbon-like nanographene is transformed into a planar metallized nanographene after the insertion of two Cu(III) ions. This metallization modulates the assembly behavior and terminates the dimerization behavior observed in the free-base form. This work provides a unique example of a nanographene that is fully tunable in its monomeric and dimeric forms, forms a stable bilayer in polar solvents, and has an assembly behavior that can be tuned further through metalation. The clarification of the structure-photophysical property relationships of such a dynamic nanographene offers guiding principles for the rational design of molecular bilayer graphenes and related π-conjugated systems with both tailored structures and tailored properties.
He et al. (Mon,) studied this question.