Triangular Halogen Bond and Hydrogen Bond Supramolecular Complex Consisting of Carbon Tetrabromide, Halide, and Solvent Molecule: A Theoretical and Spectroscopic Study

The theoretical calculation and spectroscopic experiments indicate a kind of triangu-lar three bonding supramolecular complexes CBr₄…X^-…H-C, which consist of carbon tetrabromide, halide, and protic solvent molecule (referring to dichloromethane, chloro-form and acetonitrile), can be formed in solution. The strength of halogen and hydro-gen bonds in the triangular complexes using halide as common acceptor obeys the order of iodide>bromide>chloride. The halogen and hydrogen bonds work weak-cooperatively. Charge transfer bands of halogen bonding complexes between CBr4 and halide are observed in UV-Vis absorption spectroscopy in three solvents, and then the stoichiometry of 1:1, for-mation constants K and molar extinction coefficients ? of the halogen bonding complexes are obtained by Benesi-Hildebrand method. The K and ? show a dependence on the solvent dielectric constant and, on the whole, obey an order of iodide>bromide>chloride in the samesolvents. Furthermore, the C-H vibrational frequencies of solvent molecules vary obviously with the addition of halide, which indicates the C-H…X^- interaction. The experimental data indicate that the halogen bond and hydrogen bond coexist by sharing a common halide acceptor as predicted by calculation.