Crystal Structure of a Peculiar Polycyclic Aromatic Hydrocarbon Determined by 3D Electron Diffraction

Recently, 7,16-di-tert-butyl-5,14-bis(4-(tert-butyl)phenyl)dibenzo[a,m]rubicene has been reported as a polycyclic aromatic hydrocarbon synthesized through a peculiar Scholl reaction and exhibited promising properties for optical and electronic applications. This compound has been previously crystallized as a solvate, but the presence of disordered solvent molecules has hampered a complete elucidation of its crystal structure. Here we present a novel solvent-free crystal phase of the molecule solved ab initio by 3D electron diffraction (3D ED) from micrometric single crystals. The kinematically and dynamically refined structure has been further corroborated by powder X-ray diffraction and energy minimization calculations, confirming the accuracy of the results achieved by 3D ED. This work discusses the relevance of the crystal structure obtained for possible technological applications and demonstrates the overall significance of 3D ED for the structural determination of challenging small molecules.