Herringbone structures of 2,7-dihalogenated acridine tailored by halogen–halogen interactions

Pentafluorophenylphosphonic Acid as a New Building Block for Molecular Crystal Fabrication

“…The geometrical parameters of the C–F···H–O interactions (Table S1) are in line with values previously reported for organics . With regard to C 6 F 5 ···C 6 F 5 interactions, these interactions are of two types: C–F···F–C contacts and C–F···π F contacts. ,− The former interactions exist not only between C 6 F 5 fragments located in the same layer but also between C 6 F 5 fragments situated in facing layers. Type I and type II C–F···F–C interactions are both observed (Table S1).…”

“…Type I and type II C–F···F–C interactions are both observed (Table S1). ,− Interestingly, it must be pointed out that intermolecular interactions involving fluorine atoms, especially those of the F···F type, are more repulsive than attractive in nature, and this issue has been discussed in detail in two recent publications. , With regard to C–F···π F contacts, these interactions seem to be weak (Table S1). Certainly, they are much weaker than those observed in the structure of the anhydrous form of C 6 F 5 PO 3 H 2 , for which a C–F···Cg distance of 3.279 Å is measured with a C–F···Cg angle of 135.23° …”

Triangular Interchalcogen Interactions: A Joint Crystallographic Data Analysis and Theoretical Study

“…Intermolecular X···X interactions have been extensively studied from both experimental and theoretical points of view. − It is well known that there are two main types of X···X interactions: dispersion interaction is the dominant factor in type I, while type II stems primarily from electrostatics. , Of particular attention is the fact that the unique triangular X 3 synthons containing three type II X···X contacts have been observed in a variety of halogenated molecular crystals. , Furthermore, such triangular windmill structures were also detected in the self-assemblies of fully halogenated aromatic molecules on metal surfaces. − Density functional theory (DFT) calculations on model systems unraveled that windmill X 3 interactions follow the strength trend of conventional halogen bonds (Cl < Br < I) and display no or weak cooperativity. ,− However, to the best of our knowledge, analogous triangular Ch 3 motifs, which consist of three Ch···Ch contacts, remain completely unexplored to date. Undoubtedly, the Ch 3 motifs should exhibit quite different features with respect to the well-studied X 3 patterns, as a result of the divalent nature of chalcogen atoms.…”