Dual-frequency 2D IR heterodyned photon echo experiments with independently tunable mid-IR pulses are presented. Two-dimensional IR spectra acquired using three pulses in a sequence of 3, 3 and 6 mum allow observation of NH and CO stretching mode interactions. Intermolecular hydrogen bonding between NH and CO groups is characterized via observation of interaction of the NH and CO vibrational modes. Structural and dynamical parameters determined include the cross anharmonicity, angular constraints, and a correlation factor for the frequency distributions. (C) 2004 Published by Elsevier B.V.