PUB - Publikationen an der Universität Bielefeld

The in situ low-temperature (co)crystallization of liquids and gases, followed by a detailed structural study, represents an approach to engineer and discover novel materials that are not formed under ambient conditions. Single-crystal X-ray diffraction revealed dimorphism along with a hierarchy of particular interactions in pentafluoroiodobenzene, C6F5I(1), and its benzene cocrystal (C6F5I)(2)center dot C6H6 (2). There are four polymorphs, two of 1, 1-I and 1-II, and two of 2, 2-I and 2-II, and they all are principally dominated by I center dot center dot center dot F and F center dot center dot center dot F halogen interactions. The nature and the contribution of different interactions were identified as important factors responsible for the polymorphic behavior of the studied systems. The only attractive interactions between C6F5I and C6H6 molecules in both polymorphs of 2 are F center dot center dot center dot H contacts, whereas sigma-hole C-X center dot center dot center dot pi C6H6-type interactions are absent. A reversible polymorphic phase transition in 2 is associated with the formation of new contacts, including relatively long pi-hole center dot center dot center dot pi (C-C6F5I center dot center dot center dot C-C6H6) interactions.