Polymorphs and Pseudopolymorphs of <i>N</i>,<i>N</i>-Di(<i>n</i>-butyl)Quinacridone: Structures and Solid-State Luminescence Properties

The single crystal X-ray structures of four polymorphs and two pseudopolymorphs of N,N-di(n-butyl)quinacridone (DBQA) are investigated. Polymorphs A, B, and C crystallize in monoclinic systems, and polymorph D, pseudopolymorphs E and F crystallize in triclinic systems. Four polymorphs and two pseudopolymorphs show different characteristics of molecular structures and packing arrangements. The six crystalline phases show slight differences in the quinacridone (QA) core structures and the orientations of the n-butyl chains. Noncovalent intermolecular interactions such as C−H···O hydrogen bonds and π···π stacking interactions are different for the six crystals. The emission properties of the polymorphs and pseudopolymorphs in the solid state have been reported. All the polymorphs and the pseudopolymorphs exhibit solid-state photoluminescence. The crystal phases with stronger π···π interactions show the emission maximum at a longer wavelength region, while that with relatively weaker π···π interactions exhibit an emission maximum at a shorter wavelength region. From the X-ray single-crystal analysis, we can conclude that the molecular packing structure is the critical element that determines the solid-state emission characteristics.