Experimental (FT-IR and FT-RS) and theoretical (QC-DFT) studies of vibrational modes and molecular structure of new low-temperature phases of [Ru(NH3)6](BF4)3 and [Ru(NH3)6](ClO4)3

Vibrational spectra of [Ru(NH3)6](BF4)3 and [Ru(NH3)6](ClO4)3 in their novel low-temperature solid phases were recorded using FT-IR and FT-RS. Quantum chemical calculations of molecular structure and vibrational modes were made separately for BF4-,ClO4-and[Ru(NH3)6]3+ ions. The harmonic vibrational frequencies and the related IR and RS bands intensities and activities, respectively, were simulated at the B3LYP/6-311+G(d) and B3LYP/LANL2TZ(f)/6-311+G(d,p) levels of the DFT. Full interpretation of the vibrational spectra has been carried out with the aid of the normal coordinate analysis. The assignments of the vibrational modes were based on the potential energy distribution data, using the MOLVIB program. The calculated Ru–N stretching frequencies are too low, in comparison to experiment, which indicates that B3LYP method underestimates the Ru–N bond strength. Some values of calculated and measured (obtained from X-ray) bond lengths and angles were also compared. Conclusions about possible interactions inside and between the complex ions were drawn.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We present the vibrational spectra of novel phases of ruthenium(III) complexes. ► The vibrational assignments have been made on the basis of the NCA. ► We draw conclusions about the interactions between the ions in both compounds. ► We compare the interatomic distances in [Ru(NH3)6](BF4)3 with the computed values.