Predicting the halogen‐n (n = 3–6) synthons to form the “windmill” pattern bonding based on the halogen‐bonded interactions

The “windmill” pattern cyclic halogen polymers (XBr)3 (X = Cl, Br, I) and (BrY)n (n = 3–6, Y = Cl, Br, I) have been investigated using the density functional theory. Due to the anisotropic distribution of its electron density, the halogen atom can form halogen‐bonded interactions by functioning as both electron donor sites and electron acceptor sites. For (XBr)3 (X = Cl, Br, I) trimers, the Cl···Cl interaction is the weakest, and the I···I interaction is the strongest. For (BrY)n (n = 3–6, Y = Cl, Br, I), the Br···Br halogen bonds are the strongest in (BrY)4 tetramers. We predict that the iodine‐4 synthon may allow creation of a self‐assembled island during crystal growth. The angle formed by the electron‐depleted sigma‐hole, the halogen atom and the electron‐rich equatorial belt perpendicular to the bond direction, together with the halogen‐bond angle, can be used to explain the geometries and strength of the halogen‐bond interactions. © 2018 Wiley Periodicals, Inc. M06‐2X calculations with def2‐TZVPD basis set was used to investigate the halogen‐n (n = 3–6) synthons to form the “windmill” pattern bonding.