Relation Between Bond Angle and Carbon-Oxygen Stretching Frequencies in CO2-Containing Compounds

Madison M Foreman; John F Stanton; J Mathias Weber

doi:10.1021/acs.jpca.3c05082

Relation Between Bond Angle and Carbon-Oxygen Stretching Frequencies in CO₂-Containing Compounds

J Phys Chem A. 2023 Nov 23;127(46):9717-9722. doi: 10.1021/acs.jpca.3c05082. Epub 2023 Nov 9.

Authors

Madison M Foreman¹, John F Stanton², J Mathias Weber¹

Affiliations

¹ JILA and Department of Chemistry, University of Colorado-Boulder, 440 UCB, Boulder, Colorado 80309-0440, United States.
² Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States.

PMID: 37944122
DOI: 10.1021/acs.jpca.3c05082

Abstract

The symmetric (ν_s) and antisymmetric (ν_as) O-C-O stretching modes of CO₂-containing compounds encode structural information that can be difficult to decipher, due to the sensitivity of these spectral features to small shifts in charge distribution and structure, as well as the anharmonicities of these two vibrational modes. In this work, we discuss the relation between the frequency of these modes and the geometry of the O-C-O group, showing that the splitting between ν_s and ν_as (Δν_as-s = ν_as - ν_s) can be predicted based only on the O-C-O bond angle obtained from quantum chemical calculations with reasonable accuracy (±46 cm^-1, R² = 0.994). The relationship is shown to hold for the infrared spectra of a variety of CO₂-containing molecules measured in vacuo. The origins of this model are discussed in the framework of elementary mode analysis.