Mixed Rubrene Cocrystals Offer Insights into Intermolecular Interactions Influencing Crystal Packing

We report the first examples of mixed cocrystallization in rubrene derivatives. We grew crystals with differing ratios of two previously characterized rubrene derivatives. When crystallized individually, each rubrene derivative packs with a twisted tetracene core in the solid state. In both examples of mixed cocrystallization, the tetracene cores are planar, providing some of the first experimental evidence that intermolecular interactions are a major driving factor for planarization of the tetracene core. Additionally, a larger ratio of the methylated rubrene derivative resulted in a mixed cocrystal displaying a herringbone crystal formation, which is optimal for applications in optoelectronics.