Spin Polarization Effect in Organic High-Spin Molecules, as Studied By Single Crystal ESR and1H-ENDOR Spectroscopies

Abstract

Abstract Single crystal ESR of ground-state triplet molecules, p-and m-benzoyldiphenylmethylene (p- and m-BDPM), was measured. From the angular dependence of the spectra the fine structure parameters were determined to be D = +0.327 cm and E = -0.0056 cm for p-BDPM and D = ±0.428 cm−1 and E = ±O. 051 cm−1 for m-BDPM, respectively. It was shown that the effect of the benzoyl group on the spin alignment of the diphenylmethylene (DPM) unit is larger for the para position than for the meta position. Furthermore, in order to examine the effect by the introduction of the p-benzoyl group on the π-spin densities of the DPM unit, single crystal H-ENDOR (Electron Nuclear Double Resonance) measurements of p-BDPM were performed. The H-hyperfine couplings observed showed that relative to unsubstituted diphenylmethylene (DPM) the p-benzoyl substitution increased the absolute value of all the π-spin densities on the phenyl rings of the DPM unit. This result is attributable to the spin polarization enhancement induced by...