Tunable Interaction Strength and Nature of the S···Br Halogen Bonds in [(Thione)Br₂] Systems

The strength and nature of the S···Br and Br···Br interactions were systematically tuned by altering the electron donor properties of the thione group. Three new halogen-bonded compounds, [(N-methylbenzothiazole-2-thione)­Br2]·0.5CH2Cl2 (1), [(2­(3H)-benzothiazolethione)­Br2] (2), and [(2-benzimidazolethione)­Br]·[Br3] (3), were synthesized and studied structurally by using X-ray crystallography and computationally by using charge density analysis based on QTAIM calculations. Analysis of the interaction strength indicated a formation of surprisingly strong S···Br halogen bonds in 1 (−104 kJ mol–1, and RBrS = 0.64) and 2 (−116 kJ mol–1, and RBrS = 0.63) with a substantial covalent contribution. The strong electron donor character of the thione ligand in 3 induced a heterolytic cleavage of the dibromine molecule and a change in the S···Br interaction nature to form a covalent bond with a high interaction energy (−147 kJ mol–1, and RBrS = 0.60).