Structural and Vibrational Properties of Iodopentafluorobenzene: A Combined Raman and Infrared Spectral and Theoretical Study

A combined study of the vibrational spectroscopy of iodopentafluorobenzene by new Raman and Fourier transform infrared (FTIR) spectroscopies, over the spectral range 300 to 3200 cm–1 (Raman) and 50 to 3400 cm–1 (FTIR), with a state-of-the-art theoretical investigation is reported. This has enabled reliable identification of numerous fundamental, overtone, and combination band transitions in unprecedented detail. The theoretical analysis, beyond the double-harmonic approximation, is based on generalized second-order vibrational perturbation theory (GVPT2) with a hybrid coupled cluster/density functional theory (CC/DFT) approach. Anharmonic contributions to structural parameters, rotational constants, vibrational frequencies, and spectral intensities are incorporated. The procedures, of general applicability, enable rigorous comparison of theoretical methods with experimental results in vibrational spectroscopy.