Intermolecular interactions and structural dichotomy in 1,3,2,4-benzodithiadiazine crystals

The intermolecular interactions and structural dichotomy in 1,3,2,4-benzodithiadiazine crystals ( 1 ) (the heterocycle is planar for one derivative, but bent for another) were studied in terms of topological analysis of electron density (ED) using QTAIM theory and crystal packing modeling in an OPiX approximation. The intermolecular interactions in crystals 1 can be detected and quantified by means of the critical points (CPs) of ED with (3, −1). The total value of ED at all CPs of a molecule can be correlated with the torsion angle that defines the bending of its heterocycle; the larger the total ED at intermolecular CPs, the smaller the bending of the heterocycle. Thus, under the conditions of weak intermolecular interactions in crystal, molecules 1 preserve the bent conformations typical of the gas phase; strong intermolecular interactions lead to planar conformations.