We report an experimental study of the band shapes and relative IR intensities for the stretching ν1 and librational νL modes of the HF subunit in complexes with OC and HCN. The ratio of the transition dipole moments for the ν1 and νL bands is found to be close to unity. The relative intensities of the stretching and librational modes in typical H-bonded species (CH3) 2CO...HF and (CH3)2O...HF are also measured for comparison. A multidimensional quantum mechanical problem of the relative motion of monomers in complexes is solved using model intermolecular interaction potentials and the wave functions expanded in products of 1D-basis functions. Classification of the states of relative motions of monomers is made by considering various cuts through the wave functions. Motions involving different degrees of freedom are shown to be strongly coupled. The frequencies and transition probabilities of the low-frequency modes are computed. The vibrationally averaged electro-optic parameters of complexes evaluated in the framework of the electrostatic induction model are in satisfactory agreement with the experimental data. ©2004 Copyright SPIE - The International Society for Optical Engineering.