Electron spin resonance and the structure of inorganic radicals.

The theory of electron spin resonance is developed in Part I so that the parameters which occur in the spin-Hamiltonian can be related to the structure of the oxides and oxy-ions of the non-metals discussed in Part II. Spectra of various ?-irradiated phosphates show that hydrogen atoms are trapped, often at elevated temperatures. A model of the trapping site is suggested which accounts for the observed hyperfine and g-tensors, and the dependence of the stability on the basicity of the anion present. Spectra of NO2, NO2-2 and NO2-3 are discussed and structural information derived. The structure and reactivity of CO-2 is compared to that of nitrogen dioxide. The oxy-ions PO2-3 and HPO-2 are investigated and their structure discussed. The large proton splitting in the latter is interpreted in terms of two bond angle dependent mechanisms. A number of spectra are tentatively ascribed to PO2-4 and P2O3-4. The structure of SO-2 is discussed. SO-4 was observed in both ?-and ultra-violet irradiated potassium persulphate; in the latter the spectra is accounted for by a pairwise trapping of the radicals, and a machanism which explains both this and the thermal and optical bleaching cycles is suggested. The oxy-ions SeO-2, SeO-3, and SeO-4 are discussed. The possibility of d-orbital involvement in SeO-2 is considered together with its effect on the g-tensor. The monoxide, dioxide, and trioxide of chlorine are discussed. The large line-widths observed for the dioxide are ascribed to a gas-like behaviour in some non-interacting solvents. Phosphorus tetrafluoride was investigated. The molecule is a distorted tetrahedron which inverts rapidly at room temperature. The shape and structure is compared to that of transition metal complexes. The dependence of electron population, bond angles and reactivity on electronegativity is reviewed and is seen to accord with expectation. The effect of d-orbitals and distortions is discussed.