High-Spin Multiplet Endor and Triple Resonance: Its Application to a Model Compound for Organic Ferrimagnets

Abstract

We have applied single-crystal ENDOR and TRIPLE resonance spectroscopies to the first organic high-spin molecule, m-phenylenebis(phenyl- methylene), 1 in its quintet ground state, establishing high-spin multiplet ENDOR and TRIPLE resonance spectroscopies. Both the magnitude and absolute sign of all the proton hyperfine coupling constants have been determined from the ¹H-ENDOR/TRIPLE data, yielding crucial information on the spin- density distribution in its pi-electron network. We have designed and synthesized a model compound, 2 for the units of organic ferrimagnets which possesses antiferromagnetically-exchange coupled heterospins. The high-spin multiplet ¹H-(or ¹³C-) ENDOR and TRIPLE resonance of the heterospin system have demonstrated the salient features of its spin structure which can be characterized in terms of unusually large negative spin polarization.