Matrix Infrared Spectra and Density Functional Calculations of CH2Cl–Cl and CH2Br–Br Produced by Laser‐ablated Metal Plume Irradiation

摘要

CH2Cla??Cl and CH2Bra??Br, photoisomers of CH2Cl2 and CH2Br2 , were identified in the matrix IR spectra from the precursors exposed to plume radiation of a lasera??ablated transition metal. On the other hand, the corresponding photoisomers of CH2F2 and CH2FCl (CH2Fa??F, CH2Fa??Cl, and CH2Cla??F) were not observed because of their instabilities. The C?￡?X bond of the product is unusually strong, leading to a high C?￡?X stretching frequency. Natural bond orbital (NBO) analysis reveals that it is a true carbona??halogen double bond; in contrast, the X?￡?X bond is largely ionic (H2C?￡?X?′+ a??a??a??X?′a?? ), similar to the previously studied analogs from tria?? and tetrahalomethanes. Intrinsic reaction coordinate (IRC) computation reproduces the smooth interconversion between the precursor and the energetically higher photoisomer, consistent with the disappearance of the product during visible photolysis.