Methylene imino radical H2CN•: matrix isolation ESR and density functional theory study

Abstract

Methylene imino radical H2CN, and its C-13 isotopic isomer were generated in argon matrices and their ESR spectra were observed. The g tensor and the proton, C-13, and N-14 hyperfine coupling (hfc) tensors of the radical were determined. The experimentally determined g tensor and the hfc tensors were initially analysed in terms of the singly occupied molecular orbital (SOMO) as predicted by semi-empirical INDO calculations. Finally the hfc tensors were calculated by gradient corrected density functional theory (DFT), using both the INDO and DFT optimized geometries, as well as a model of H2CN embedded in 6 argon atoms (fully optimized). The calculated isotropic component of the hydrogen hfc tensor and the anisotropic components of all the tensors are in very nice agreement with the observed data whereas the isotropic components for the nitrogen and carbon show larger deviation, as previously noted. The effects of the Ar matrix are minor.