Magnetic Resonance Studies of Biradicals. III. Verdazyl Mono- and Biradicals

Abstract

We have taken the NMR and ESR spectra of a series of verdazyl mono and biradicals. The susceptibility of each of the compounds was also measured. Zero field splitting parameters were determined from the ESR spectra while electron–nuclei coupling constants were determined from the NMR spectra. The coupling constants of nuclei contained in rings connecting the two monoradical halves proved to be the average of couplings from protons in corresponding positions in the monoradical while the coupling constants for nuclei in other parts of the molecules were one-half of the monoradicals couplings. The relative magnitudes of the various coupling constants were predicted by a simple perturbation calculation and by semiempirical MO calculations.