ИСТИНА

Vibrational spectroscopy of tolane (diphenylacetylene), which has 66 normal modes, has been advanced. Anharmonic wavenumber predictions were made with the quartic potential energy surface obtained with B3LYP/cc-pVTZ model and the second-order perturbation theory (VPT2). Infrared (IR) intensity and Raman activities were computed at the harmonic level. The IR spectrum of the crystal and Raman spectra of the liquid and the crystal tolane were recorded again. The lingering problem of an excess of polarized Raman bands at wavenumbers appropriate for fundamentals, other then ag modes, has now been attributed to Coriolis coupling within modes of g symmetry species. Consequently, D2h point symmetry group has been confirmed for a planar tolane molecule. Assignments for almost all of the fundamentals of tolane are now secure. Remaining unassigned fundamentals are: n34 and n35, which, as au symmetry species, have IR- and Raman-inactive transitions, and n59(b2u), which is predicted to have a very low wavenumber.