Tunable Interaction Strength and Nature of the S···Br Halogen Bonds in [(Thione)Br 2 ] 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)Br-2].0.5CH(2)Cl(2) (1), [(2(3H)-benzothiazolethione)Br-2] (2), and [(2-benzimidazolethione)Br].[Br-3] (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 R-BrS = 0.64) and 2 (-116 kJ mol(-1), and R-BrS = 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 R-BrS = 0.60).