Gas-Phase Infrared Spectra of Vinyl Selenol and Vinyl Tellurol

摘要

The infrared spectra (3500-500 cm~(-1)) of gaseous vinyl selenol and tellurol have been recorded at 0.1cm~(-1)resolution. For the latter spectra were obtained at room temperature, but for the former a temperatureof -40 °C was required because of the chemical instability of vinyl selenol at room temperature. To compensatethe very weak vapor pressure of vinyl tellurol at room temperature, a long optical path up to 136 m wasnecessary to record its spectrum. B3LYP density functional theory (DFT) calculations have been performedto assign the different absorption bands. Since an unambiguous assignment of the absorption bands requiresa precise knowledge on the relative abundance of the syn and gauche rotamers of these compounds, theirrelative energies and their anharmonic vibrational frequencies were obtained using a very extended Def2-QZVP basis set. Two rotamers, the syn, which is planar, and a nonplanar gauche, were found to be localminima for both compounds. The gauche rotamer presents two degenerate conformers, which differ by theposition of the SeH (TeH) hydrogen atom above or below the molecular plane. Our theoretical results are ingood agreement with the main features of the experimental spectra. Fundamental bands and some combinationbands of vinyl selenol and vinyl tellurol were assigned and compared with those of vinyl alcohol and vinylthiol, whose spectra had been reported previously in the literature.