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

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 CC 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.