Cooperativity of Halogen- and Chalcogen-Bonding Interactions in the Self-Assembly of 4-Iodoethynyl- and 4,7-Bis(iodoethynyl)benzo-2,1,3-chalcogenadiazoles: Crystal Structures, Hirshfeld Surface Analyses, and Crystal Lattice Energy Calculations

Abstract

Several new 4-iodoethynyl- and 4,7-bis(iodoethynyl)benzo-2,1,3-chalcogenadiazoles were prepared, and a comprehensive analysis of the most prominent secondary bonding interactions responsible for the crystal self-assembly was performed using X-ray diffraction. The presence of both the iodoethynyl and chalcogenadiazole moieties allows an evaluation of the preference of these molecules to aggregate through either chalcogen- or halogen-bonding interactions in the solid state. The crystal structures of the compounds revealed that their solid-state arrangements are influenced by the nature of the chalcogen atom: for the crystals of the thiadiazoles studied, the C-I···N halogen bonds were preferred, whereas in the corresponding 2,1,3-selenadiazole derivatives, the self-complementary [Se···N]2 supramolecular synthons together with the C-I···N halogen-bonding interactions determined the molecular self-assembly. Furthermore, in the case of the bis(iodoethynyl) derivative the crystal structure was additionally influenced by the C-I···π(ethynyl) halogen bond. Hirshfeld surface and 2D fingerprint plot analyses were used to demonstrate the intermolecular interactions and intercontact distributions. Also, the total lattice energies were calculated using the CRYSTAL09 and CrystalExplorer programs. They both indicated intermolecular π···πinteractions as the forces of substantial contribution to the total lattice energies.