Symmetrical Noncovalent Interactions Br center dot center dot center dot Br Observed in Crystal Structure of Exotic Primary Peroxide

4-Bromobenzamidrazone reacts with cyclopentanone giving 3-(4-bromophenyl)-5-(4-peroxobutyl)-1,2,4-triazole, which precipitated as pale-yellow crystals during the reaction. The intermolecular noncovalent interactions BrBr in the single-crystal XRD structure of the peroxo compound were studied theoretically using quantum chemical calculations (omega B97XD/x2c-TZVPPall) and quantum theory of atoms in molecules (QTAIM) analysis. These attractive intermolecular noncovalent interactions BrBr is type I halogenhalogen contacts and their estimated energy is 2.2-2.5 kcal/mol. These weak interactions are suggested to be one of the driving forces (albeit surely not the main one) for crystallization of the peroxo compound during the reaction and thus its stabilization in the solid state.