We report application of nuclear inelastic scattering (NIS) spectroscopy to the compound tris(acetylacetonate)iron(III), [Fe(III)(acac)(3)] enriched in (57)Fe. Experimental results are compared with the simulated spectrum based on the normal mode analysis of the isolated [(57)Fe(III)(acac)(3)] molecule using DFT calculations. Good agreement between the peak positions and intensities of the simulated and experimental spectra enables complete and reliable assignment of the Fe-selective vibrational modes. It is concluded that in the solid state E modes are enhanced by coupling with the lattice modes. Additionally, infrared and Raman spectra of [Fe(III)(acac)(3)] are calculated from DFT and compared with experiment thus demonstrating the complementarity of these three vibrational spectroscopic techniques. (C) 2011 Elsevier B.V. All rights reserved.