The structure, properties, and nature of C–Br⋯F halogen bond involving HArF: Substitution, hybridization, and nonadditivity

Quantum chemical calculations have been performed to investigate the halogen bond of HArF with some brominated hydrocarbons at the MP2/aug-cc-pVTZ level. The C–Br bond in F3CBr–FArH complex is contracted, while it is elongated in other halogen-bonded complexes. However, the C–Br stretch vibration has a small red shift in all complexes. The strength of halogen bond becomes stronger in order of C sp 3 – Br < C sp 2 – Br < C sp – Br . The substitution position in CH2CHBr has a prominent effect on the strength of halogen bond. With the number of F atom in CH2CHBr, the halogen bond is stronger and a negative nonadditivity is present for F substitution. The average contribution of each F atom to the interaction energy of halogen bond is estimated to be −4 kJ/mol. Additionally, two hydrogen-bonded complexes of BrCCH–FArH and HCCBr-pi-HArF have also been studied. These complexes have been analyzed with the electrostatic potentials and NBO theory.