The intermolecular stretching vibration of complexes between several Schiff bases and phenols is observed between 160 and 100 cm−1in cyclohexane. The intermolecular force constant calculated by the Lippincott-Schroeder function is intermediate between that calculated from the OH…N part of the molecule and that incorporating the whole masses of the interacting molecules. The far infrared spectrum of the 2,3,5,6-tetrachlorophenol complex where proton transfer takes place is also discussed.