Hydrogen- and halogen-bonding-directed trimeric supramolecular motifs in dihalogenated 1,2,4-triazoles

Hydrogen-bonding and halogen-bonding interactions are important noncovalent interactions that play a significant role in the crystal structure of organic molecules. An in-depth analysis is given of the crystal packing of two previously reported crystal structures of dihalogenated 1,2,4-triazole derivatives, namely 3,5-di­chloro-1H-1,2,4-triazole and 3,5-di­bromo-1H-1,2,4-triazole. This work provides insights into the complex interplay of hydrogen-bonding and halogen-bonding interactions resulting in the formation of multiple trimeric motifs in the crystal structure of 1,2,4-triazole derivatives. Analysis of the crystal packing of these isostructural crystal structures revealed that the molecular arrangement in these molecules is primarily stabilized by the formation of different trimeric motifs stabilized by N—HN hydrogen bonds, N—HX (X = Cl/Br) halogen bonds and C—XX halogen-bonding interactions. Computational studies further revealed that all these trimers are energetically stable. A crystallographic database search further reveals that while the cyclic trimers reported in this study are present in other molecules, structures analyzed in this study are the sole instances where all are present simultaneously.