13C HYPERFINE INTERACTIONS IN TEREPHTHALATE TRIANION RADICAL

Article abstract of DOI:10.1021/j100324a021

Sufficiently high concentrations of terephthalate radical trianion can be produced by reduction of terephthalate with acetone ketyl radical anion in in situ radiolysis experiments that ESR spectra of the radicals containing ¹³C at natural abundance levels can be recorded readily.The ¹³C hyperfine constant for the carbon atoms at the four equivalent ring positions is (-)1.46 G.Hyperfine constants of 1.37 and 4.64 G are observed for the other two pairs of equivalent carbon atoms with the smaller value found to apply to the carboxylcarbons from studies of a sample with the carboxyl group enriched in ¹³C.Application of the Karplus-Fraenkel relation indicates that there is an unpaired spin population of <*>0.26 on each of the ring carbon atoms adjacent to the carboxyl groups.This high-spin population is reflected in somewhat broadened lines of the radicals with ¹³C at these ring positions.The signals of this radical saturate relatively easily, indicating a longitudinal relaxation period considerably longer than for most transient radicals.