A Research Paper Published in Crystal Growth & Design

In the majority of everyday crystallographic studies, structural disorder is viewed as an undesirable nuisance, which merely complicates refinement and interpretation of the structural model. However, disorder in crystal structures can have a great effect on the properties of the bulk material, and its study therefore is crucial for elucidating the interconnections between the microscopic structure and macroscopic properties of solid materials. This paper demonstrates how structural disorder can be controlled by the presence of halogen bond.

In a series of nine cocrystals of m-halogenobenzoic acids with m-halogenopyridines (halogen being Cl, Br or I), five crystals have been shown to crystalize with the acid—pyridine complexes in orientational disorder over inversion centers, while four have ordered structures. The four ordered structures all comprise I∙∙∙O halogen bond, which is impossible (or at least absent) in the disordered structures. Thus it has been demonstrated that the presence of I···O halogen bonds is a prerequisite for ordering of structures in the cocrystals of m-halogenobenzoic acids with m-halogenopyridines. The paper also presents an attempted to elucidation of the nature of disorder in the five disordered structures using a combined X-ray diffraction, solid-state NMR and computational approach, and discusses the effects of the structural features on thermal properties of the crystalline materials.

The research was performed as a part of the research project New building blocks for the supramolecular design of complex multi-component molecular crystals based on halogen bonds (HaloBond IP-2019-04-1868) funded by the Croatian Science Foundation.