Multilayer stacks of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) show promise for applications in functional devices such as organic photovoltaics and field-effect transistors, but, although nanometre-sized PAHs—often referred to as nanographenes—have been well investigated as single-layer molecules, their multilayer counterparts remain rather unexplored. Here we show the assembly of a C 64 nanographene derivative (comprising a planar core decorated with four meta -terphenyl–imide moieties at its periphery) into multilayer stacks with smaller PAHs ranging from naphthalene to ovalene and hexabenzocoronene. The functionalized C 64 nanographene serves as a ditopic host that can accommodate a smaller PAH on either side of its planar core, in cavities delimited by its bulky imide substituents. Bilayers and trilayers (that is, complexes with 1:1 and 1:2 host:guest ratios, respectively) were observed in solution, and dimers of these complexes as well as multilayer compounds were isolated in the solid state. Quantum-chemical calculations indicate that dispersion forces are the main stabilizing factor for these complexes. Nanometre-sized polyaromatic hydrocarbons (nanographenes) have been largely explored as single-layer systems. Now a C 64 nanographene comprising a planar core decorated with four terphenyl–imide moieties at its periphery has been shown to assemble with coronene to form bi- and trilayer host–guest complexes in solution, as well as tetra-, hexa- and multilayer stacks in the crystalline state.