CMM-RS Potential for Characterization of the Properties of the Halogen-Bonded OC–Cl2 Complex, and a Comparison with Hydrogen-Bonded OC–HCl

Abstract

Transitions associated with the vibrations ν₁, ν₁ + ν(b)¹, ν₁ + ν₅¹, and ν₁ + ν₅¹ - ν₅¹ of the complex OC···Cl₂ have been rovibrationally analyzed for several isotopologues involving isotopic substitutions in Cl₂. Spectra were recorded using a recently constructed near-infrared (4.34 to 4.56 μm), quantum-cascade laser spectrometer with cw supersonic slit jet expansion. Spectral analysis allowed precise determination of the ν₅¹ intermolecular vibration of OC-³⁵Cl₂ to be 25.977637(80) cm⁻¹. These results were incorporated with other previously determined data into a spectroscopic database for generation of a five-dimensional morphed potential energy surface. This compound-model morphed potential with radial shifting (CMM-RS) was then used to make more accurate predictions of properties of the OC-³⁵Cl₂ complex including D(e) = 544(5) cm⁻¹, D₀ = 397(5) cm⁻¹, ν₃ = 56.43(4) cm⁻¹, and ν(b)¹ = 85.43(4) cm⁻¹. The CMM-RS potential determined for OC-Cl₂ was also used to compare quantitatively many of the inherent properties of this non-covalent halogen bonded complex with those of the closely related hydrogen-bonded complex OC-HCl, which has a similar dissociation energy D₀. We found that in the ground state, the CO bending amplitude is larger in OC-Cl₂ than in OC-HCl.