Single Crystal Growth of π‑Conjugated Large Molecules without Solubilizing Alkyl Chains via the Naphthalene Flux Method

Single-crystal growth of organic materials is crucial to study the charge transport mechanism and performance limits as transistors due to a few defects, no grain boundary, and the accurate molecular packing structure. This article reports the “naphthalene flux method” to grow single crystals of extensive π-conjugated molecules without solubilizing alkyl chains. Single crystals of seven molecules with π-conjugated systems could be obtained due to their reasonable solubility in molten naphthalene. The crystal quality of the single crystals grown by the naphthalene flux method was good enough to determine the crystal structure by X-ray diffraction. A packing motif for each material was assigned by the π° parameter, and its assignments were successful without exception. It was demonstrated that the π° parameter was still valid even for molecules containing aromatic nitrogen and sulfur atoms.