Vibrational spectra of tris(acetylacetonato)chromium(III)

Abstract

The molecular structure and vibrational spectra of tris(acetylacetonato)chromium(III), Cr (AA)3, its mono-deuterated, Cr (DAA)3, and per-deuterated analogous, Cr(D7AA)3, were investigated using density functional theory (DFT) calculations. The geometry of the titled compound was fully optimized at the B3LYP level using 6-311 + G* and 6-31G** basis sets. The harmonic vibrational frequencies were obtained at the B3LYP/6-311 + G** level. Raman scattering activities were calculated at the B3LYP/6-31G** level. The calculated frequencies are compared with the experimental IR and Raman spectra. All of the measured IR and Raman bands were interpreted in terms of the calculated vibrational modes and isotopic frequency shifts. The scaled theoretical frequencies and the structural parameters are in excellent agreement with the experimental data. Analysis of the vibrational spectra indicates a strong coupling between the chelated ring modes. Several bands at 933, 680, 611, 594, 495, 250, 224, and 179 cm−1 are found to be engaged in Cr–O vibrational movements. The IR bands at 611 and 594 cm−1 are attributed to the asymmetric Cr–O stretching and the very strong Raman band at 460 cm−1 is assigned to the totally symmetric Cr–O stretching mode (a1 species).