Stability, Properties, and Electronic g Tensors of the H2COH Radical

Abstract

For the H2COH radical, properties such as geometries, frequencies, electric and magnetic dipole moments, electronic and ionization spectra, etc., were investigated at the ab initio level (second-order Møeller−Plesset and multireference configuration interaction (MRD-CI) methods). At equilibrium, H2COH (σ2π2n2π*) is of C1 symmetry. The inversion and rotation conformations are about 1 and 5 kcal/mol less stable. The MRD-CI vertical ionization potentials (eV) lie at 7.89 (π* → ∞) and 12.91 (n → ∞, into 13A‘‘ of the cation). The π* → 3s state (adiabatically at Te ≈ 3.23 eV, calculated) is placed about 1 eV lower than previously assumed. Experimental T0's of 4.34 and 5.09 eV are respectively reassigned to π* → 3pz and π* → 3px (perpendicular and parallel bands relative to the CO bond). At the equilibrium geometry, the valence states lie at 6.46 (n → π*), 7.30 (π → π*), and 8.40 eV (σ → π*); i.e., the latter lies in the ionization continuum. The direction of the electric dipole moment of H2COH is mainly governed by the OH bond. The electron-spin magnetic moment (g factor) was evaluated via a perturbative approach complete to second order, using a Breit−Pauli Hamiltonian. The largest second-order contributions to Δg are due to σ → π* and n → π*. At the ROHF level, Δgav = gav − ge is ∼500 ppm for both the equilibrium and inversion conformations and near 300 ppm for the rotation geometry. Correlated values are estimated to be ∼150 ppm higher. Experimental studies for H2COH in solution find Δgav ≈ 1000 ppm.