Infrared Spectra of Chlorinated Ethylene Cations:  C₂Cl₄⁺, C₂HCl₃⁺, 1,1-C₂H₂Cl₂⁺, and trans-C₂H₂Cl₂⁺ in Solid Argon

Abstract

Infrared spectra of chlorinated ethylene cations: C2Cl4+, C2HCl3+, 1,1-C2H2Cl2+, and trans-C2H2Cl2+ isolated in solid argon are presented. These cations were produced by co-deposition of chlorinated ethylene/Ar mixtures with high-frequency-discharged Ar at 4 K. Photosensitive absorptions are assigned to different vibrational modes of the cations on the basis of observed chlorine isotopic shifts and quantum chemical frequency calculations. With the removal of one electron from the HOMO of chlorinated ethylene neutrals that is C=C bonding and C-Cl antibonding in character, the observed C-Cl stretching vibrational frequencies of the cations are blue-shifted relative to those of the chlorinated ethylene neutrals. The results also show that the cations can be regarded as "isolated" with the vibrational frequencies only slightly shifted when compared to the available gas-phase values.

The photoelectron spectroscopy of the dichloroethylenes: the geminal isomer 1,1-Cl2C2H2. An experimental and quantum chemical study

“…The data analysis leads to ω=1347±8 cm −1 (0.167±0.001 eV) and ωx=3.9±1.1 cm −1 (0.48±0.14 meV). This wavenumber is in good agreement with the predicted anharmonic value [7].…”

“…The corresponding wavenumbers are listed in table 2. The present theoretical results can only be compared to those obtained by Zhou et al [7] and Takeshita [27]. This latter author reported on the ab initio calculated photoelectron spectrum of the three dichloroethylene isomers [27].…”

“…Surprisingly, this vibration has not been observed by infrared spectroscopy of + -1, 1 C H Cl 2 2 2 trapped in a solid Argon matrix [7]. In previous quantum chemical calculations, the harmonic wavenumber of 1366.1 cm −1 and the anharmonic value of 1340.6 cm −1 were predicted [7]. In the present work, the calculated wavenumbers that can be related to a C=C stretching are equal to ω 2 =1499 (1477) cm −1 and ω 3 =1364 (1330) cm −1 at the M06-2X (B3LYP) level (see table 2).…”

“…1290 cm −1 [4], 1320 cm −1 [3] or 0.16 eV (1290 cm −1 ) [2]. Surprisingly, this vibration has not been observed by infrared spectroscopy of + -1, 1 C H Cl 2 2 2 trapped in a solid Argon matrix [7]. In previous quantum chemical calculations, the harmonic wavenumber of 1366.1 cm −1 and the anharmonic value of 1340.6 cm −1 were predicted [7].…”

“…Quantum chemical calculations at different levels were applied to assign the photoelectron bands. At about the same time Zhou et al [7] measured the infrared spectra of the dichloroethylene molecular ions trapped in a solid Argon matrix at 4 K. The + -1,1 C H Cl 2 2 2 and trans-1,2-C 2 H 2 Cl 2 + IR spectra have been reported.…”