Studies on the σ-hole bonds (halogen, chalcogen, pnicogen and carbon bonds) based on the orientation of crystal structure

The 4,7-dibromo-5,6-dinitro-2,1,3-benzothiadiazole (DDBT) crystal has two polymorphic forms [ 1], where the close contacts between two electronegative atoms are identified and studied through Hirshfeld surface analysis. Br-Br and O-O cut-off distances are addressed and analysed. The sigma-hole of bromine, sulphur, oxygen atoms and p-hole of carbon and nitrogen atoms were subjected to study using molecular electrostatic potential map and 3D-deformation density map. Sixteen types of dimers from the two forms of crystal structure (6 for form I and 10 for form II) were studied using the charge transfer properties and interaction energies and made detailed analysis of halogen bond (Br-N), dihalogen bond (Br-Br), chalcogen bond (O-Br and S-Br), dichalcogen bond (S-O, O-S and O-O), pnicogen bond (N-O) and carbon bond (C-O and C-Br) interactions. The impact of orientations is discussed to define the type of interaction and its strength through charge transfer mechanism. The contribution of bond angle values for the sigma-hole and p-hole bonds are discussed. Utilisation of sigma-hole in smaller bond angle values (above 30 degrees) of vertical bar theta(1) - theta(2)vertical bar existing in type II halogen-halogen bond have been examined in the two forms. [GRAPHICS] .