The structure, properties, and nature of HArF‐HOX (X = F, Cl, Br) complex: An ab initio study and an unusual short hydrogen bond

Abstract

The structure and properties (geometric, energetic, electronic, spectroscopic, and thermodynamic properties) of HArF-HOX (X = F, Cl, Br) complex have been investigated at the MP2/aug-cc-pVTZ level. Three types of complexes are formed through a hydrogen bond or a halogen bond. The HArF-HOX complex is the most stable, followed by the FArH-OHX complex, and the HArF-XOH complex is the most unstable. The binding distance in FArH-OHX complex is very short (1.1-1.7 Å) and is smaller than that in HArF-HOX complex. However, the interaction strength in the former is weaker than that in the latter. Thus, an unusual short hydrogen bond is present in FArH-OHX complex. The associated H-Ar bond exhibits a red shift, whereas the distant one gives a blue shift. A similar result is also found for the O-H and O-X bonds. The isotropic chemical shift is negative for the associated hydrogen atom but is positive for the associated halogen atom. However, a reverse result is found for the anisotropic chemical shift. The analyses of natural bond orbital and atoms in molecules have been performed for these complexes to understand the nature and properties of hydrogen and halogen bonds.