Fifteen Solid Solutions of Four Thioxanthone Halogen Derivatives: Structures, Miscibility Limits, and Luminescence

We present an experimental study of solid-form landscape and binary solid-solution formation between structurally similar organic compounds differing by halogen substituents, namely, 2-fluorothioxanthone, 2-chlorothioxanthone, 2-bromothioxanthone, and 2-iodothioxanthone. The pure compounds form six different crystal packings, some of which are common for two different halogen derivatives. All forms are structurally characterized. A total of 15 binary solid solutions have been discovered, and their miscibility limits as well as luminescence properties have been studied. Certain trends are discussed regarding the ease of solid-solution formation in systems with and without halogen bonding. As far as luminescence is concerned, some solid solutions display a pronounced luminescence color change depending on composition, while for other solid solutions existing in a large composition range, the luminescence color does not change significantly.