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 (${\nu }_2$) are 492 cm${}^{-1}$ for OCP${}^{-}$ and 362 cm${}^{-1}$ for SCP${}^{-}$. Due to strong coupling, the stretching motions of SCP${}^{-}$ are best described as pseudo-symmetric (${\nu }_1$) and pseudo-antisymmetric (${\nu }_3$) stretches that we estimate to be 588 cm${}^{-1}$ and 1367 cm${}^{-1}$, respectively. For OCP${}^{-}$, our best predictions are 792 cm${}^{-1}$ for ${\nu }_1$ and 1795 cm${}^{-1}$ for ${\nu }_3$, 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.

GRAPHICAL ABSTRACT

Keywords:

• 2-phosphaethynolate anion (OCP${}^{-}$)
• 2-phosphaethynthiolate anion (SCP${}^{-}$)
• anharmonic fundamental vibrational frequencies
• second-order vibrational perturbation theory (VPT2)
• vibrational configuration interaction (VCI) theory

Acknowledgments

This work is dedicated to Professor John F. Stanton on the occasion of his 60th birthday. The Mississippi Center for Supercomputing Research (MCSR) is acknowledged for a generous allocation of time on their computational resources. KRB would also like to thank Dr. Thomas Sexton and Dr. Shane Autry at the University of Mississippi for many helpful discussions and their technical expertise.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This material is based upon work supported by the National Science Foundation under grant numbers CHE-1664998,CHE-1757888.