Multiple cation insertion into a polyaromatic hydrocarbon guided by data and computation

We report the synthesis, structural characterization and magnetic properties of K₃coronene, and demonstrate a computational screening workflow designed to accelerate the discovery of metal intercalated polycyclic aromatic hydrocarbon (PAH), a class of materials of interest following reports of superconductivity, but lacking demonstrated and understood characterised material compositions. Coronene is identified as a suitable PAH candidate from a library of PAHs for potassium intercalation by computational screening of their electronic structure and of the void space in their crystal structures, targeting LUMO similarity to C₆₀ and the availability of suitable sites to accommodate inserted cations. Convex hull calculations with energies from crystal structure prediction based on ion insertion into the identified void space of coronene suggest that the x = 3 composition in K _x coronene is stable at 0 K, reinforcing the suitability of coronone for experimental investigation. Exploration of reaction conditions and compositions revealed that the mild reducing agent KH allows formation of K₃coronene. The structure of K₃coronene solved from synchrotron powder X-ray diffraction features extensive reorientation and associated disorder of coronene molecules compared with the parent pristine host. This is driven by K⁺ intercalation and occupation of sites both within and between the coronene stacks that are partially retained from the parent structure. This disruption of the host structure is greater when three cations are inserted per coronene than in reported metal PAH structures where the maximum ratio of cations to PAH is 2. Superconductivity is not observed, contrary to previous reports on K _x coronene. The expected localised moment response of coronene^3- is suppressed, which may be associated with the combination of extensive disorder and close coronene^3--coronene^3- contacts.