Fundamental vibrational frequencies of isolated 2-phosphaethynolate and 2-phosphaethynthiolate anions: OCP– and SCP–

Abstract

Both second-order vibrational perturbation theory (VPT2) and vibrational configuration interaction (VCI) theory have been employed to compute the fundamental vibrational frequencies of the isolated 2-phosphaethynolate and 2-phosphaethynthiolate anions (OCP and SCP) near the CCSD(T) complete basis set (CBS) limit. Our best estimates of the fundamental frequency associated with the doubly degenerate bending mode of these linear triatomic ions () are 492 cm for OCP and 362 cm for SCP. Due to strong coupling, the stretching motions of SCP are best described as pseudo-symmetric () and pseudo-antisymmetric () stretches that we estimate to be 588 cm and 1367 cm, respectively. For OCP, our best predictions are 792 cm for and 1795 cm for , with the latter having predominantly CO stretching character. In the absence of experimental gas-phase vibrational spectra for these species, these computed anharmonic frequencies provide important reference values to help quantify spectroscopic perturbations induced by environmental effects such as those from solvents or counter ions.