ESR Study of ·CF2COO− Radicals in Irradiated Single Crystals of Sodium Chlorodifluoroacetate

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Abstract
Electron spin resonance studies have been made of the radicals produced by electron irradiation of sodium chlorodifluoroacetate at room temperature. Three sets of · CF 2 COO − radicals are observed, each with a somewhat different conformation or local environment in the crystal lattice, but each with nearly the same principal values of the hyperfine splittingtensor for the two equivalent α‐fluorine atoms. One radical occupies two sets of nonequivalent positions characteristic of the space group. A second radical also shows site splitting in the ESR spectrum, but the maximum separation is only about 14 G since the maximum principal component of the hyperfine splittingtensor lies nearly parallel to the a axis of the monoclinic unit cell and one of the smaller principal values is nearly parallel to b. A third radical has its maximum principal hyperfine splitting direction perpendicular to b and minimum value parallel to b so that no site splitting is observed; however, triplet superhyperfine structure from interaction with two equivalent nuclei of spin one‐half is present. The hyperfine coupling tensors have been evaluated and the structures of the radicals discussed. The radicals undergo some reorientation in the lattice on cooling from 300 to 77°K. Incomplete data for · , 13 CF 2 COO − indicate that these radicals are probably nonplanar with the unpaired electron in an orbital with some s character. Exposure to air or gaseous oxygen converts all these to peroxide radicals, each of which gives only a single ESR line.