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

For the H 2 COH 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, H 2 COH (σ 2 π 2 n 2 π*) is of C 1 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 1 3 A‘‘ of the cation). The π* → 3s state (adiabatically at T e ≈ 3.23 eV, calculated) is placed about 1 eV lower than previously assumed. Experimental T 0 's of 4.34 and 5.09 eV are respectively reassigned to π* → 3p z and π* → 3p x (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 H 2 COH 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 Δ g are due to σ → π* and n → π*. At the ROHF level, Δ g av = g av − g e 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 H 2 COH in solution find Δ g av ≈ 1000 ppm.