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.
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