Quantum Mechanical Study on the Blue‐Shifting Hydrogen‐Bond between 3‐Aminophenol and CHX3 (X ═ F, Cl)

Intermolecular bonding between 3‐aminophenol and two halomethanes, namely fluoroform and chloroform, was quantum mechanically investigated. Several low‐energy structures are found, and all geometries within 1 kcal/mol show π‐hydrogen bonds between the aromatic ring and the hydrogen atom of the halomethane. The C—H stretching frequency of halomethane involved in the π‐hydrogen bond is blue‐shifted, and the amount of blue shift is the largest with the most stable isomer and decreases with decreasing stability. Binding energy, infrared intensity, and dipole moment as a function of relative stability are also reported. This study forms another example of a blue‐shifting hydrogen bond, or an anti‐hydrogen bond.