The molecular interaction in the binary mixture of 3-phenoxybenzaldhyde (3Phbz) and 4-ethoxybenzaldehyde (4Etob) was analysed in four different solvents. The concentration dependence of vibrational relaxation of the C=O stretching band of 3Phbz in different solvents was investigated by varying the concentration of the solute molecule in the solvents by performing Raman spectroscopic measurements. The self-associated nature and the formation of hydrogen-bonded complexes in the solute molecule, 4Etob, were considered to analyse the wavenumber separation between the peaks of hydrogen-bonded and free carbonyl groups. Copyright (C) 2009 John Wiley & Sons, Ltd.