ESR spectra and structure of the perchloryl fluoride radical anion (FClO3-): a 33 valence electron radical with C3v symmetry

Abstract

The isotropic and anisotropic ESR spectra of FClO/sub 3//sup -/ have been observed, the former in the SF/sub 6/ matrix and the latter in both the FClO/sub 3/ and (CH/sub 3/)/sub 4/Si matrices. The isotropic hyperfine coupling constants derived from the anisotropic parameters agree with the values (/sup 35/a = 656 MHz, /sup 37/a = 546 MHz, /sup 19/a = 726 MHz) obtained from the isotropic spectrum. Moreover, the analysis of the anisotropic spectrum reveals that the chlorine and fluorine hyperfine tensors have cylindrical symmetry with their largest principal values lying along the same principal axis. This result rules out a trigonal-bipyramidal structure for this 33 valence electron radical but is entirely consistent with a C/sub 3/V structure in which the Cl-F bond represents the symmetry axis (z). Most of the spin density is concentrated in the antibonding sigma/sub Cl-F/* orbital which is composed of the 3s and 3p/sub z/ orbitals of chlorine (p/sub 3s/ = 0.14, p/sub 3p/ = 0.40) in combination with the 2p/sub z/ orbital of fluorine (p = 0.35). These results are in qualitative agreement with CNDO/2 calculations which also show that the Cl-F bond is longer in the radical anion than in the parent molecule.more » As expected from a consideration of its electronic structure, FClO/sub 3//sup -/ dissociates to give the neutral ClO/sub 3/ radical which has been detected in the SF/sub 6/ matrix.« less