Applications to Molecular Science

CW-ESR spectroscopy combined with matrix isolation method and ionizing radiation is applied to investigate structure and reactions of intermediate radicals in low temperature solid matrices. ESR parameters are predicted with considerable precision by computations, affording a valuable bridge between experiment and theory. Cyclic-CnF2n- radicals (n = 3-5) have a planar structure with an entirely delocalized singly occupied MO. Unsaturated CnF2n-2- radicals have a distorted pyramidal structure occurring by mixing the pi* and sigma* orbitals. The acetylene anion has a trans-bent structure. Structural distortion occurs in methane cation from original T-d to C-2v symmetry due to the Jahn-Teller effect. A similar symmetry lowering from D-3h to C-2v is discussed for the trimethylenemethane cation. High-resolution ESR spectra of D-labelled methyl radicals in solid Ar are discussed in terms of nuclear spin-rotation couplings. The formation of "H---CH3" radical pairs and of a "H---H-2" complex" in solid Ar is presented. The structure of [H-2(H-2)H-2](+) formed in para-H-2 is discussed based on the ESR spectra of D-substituted samples and on computations.