The electron-spin magnetic moments (g-factors) of C2?, N2?, O2?, and F2? and corresponding M+X2? radicals (M=alkali metal)

Abstract

Trends in the electron-spin magnetic moments (g factors) of the anions C2−, N2−, O2−, and F2− as stabilized in MX2 radicals (M=alkali metal) are discussed on the basis of rules governing the magnetic coupling and MO theory. These expectations are compared with experimental data and our own ab initio results for M=Li, Na. For the σ-radicals MC2 and MF2, the component Δg‖ (parallel to the XX bond) is expected to be slightly negative, while the corresponding in-plane [Δg⟂(i)] and out-of-plane [Δg⟂(o)] perpendicular components are of a few thousand ppm (ppm=10−6). For the π-radicals MN2 and MO2, Δg‖ is of large magnitude but the Δg⟂ components are small. Both calculated and experimental g-shifts for MN2, MO2, and MF2 agree with the predicted trends, whereas those for MC2 (ground state) do not. However, good agreement of theoretical with experimental results is obtained when one considers the excited state 12B1 of MC2 as carrier of the g shifts, rather than the X2A1 state. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 76: 447–457, 20000