NOVEL ORGANIC IONS OF HIGH-SPIN STATES .2. DETERMINATION OF THE SPIN MULTIPLICITY OF THE GROUND-STATE AND H-1-ENDOR STUDY OF THE MONOANION OF META-PHENYLENEBIS(PHENYLMETHYLENE)

ESR and H-1-ENDOR measurements of the title anion were performed at temperatures below 4 K. From the temperature dependence of the intensity of the ESR signal the spin multiplicity of the anion in the ground state was concluded to be quartet. The H-1-ENDOR measurement was carried out for the randomly oriented sample by monitoring the X- and Y-axis canonical peaks and the off-axis extra line. From the hyperfine coupling constants (hfcc) of the protons and the divalent C-13 atoms it was concluded that the excess electron in the anion occupies one of the two nonbonding pi-orbitals. The molecular conformation of the anion was suggested to be trans-trans in contrast to cis-trans for the neutral m-phenylenebis(phenylmethylene).