Femtosecond infrared transient grating and three pulse photon-echo experiments have been performed to investigate the vibrational dynamics of the CN stretching mode of Fe(CN)(6)(4-) in H2O. From the transient grating measurements, it was found that the vibrational population relaxation in H2O occurs about six times faster than that in D2O. This reflects the strong coupling to solvent modes for the vibrational relaxation. On the other hand, the photon-echo experiments have shown that the time-scales of the spectral diffusion processes are similar in H2O and D2O. (C) 2004 Elsevier B.V. All rights reserved.