Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol.334, 131-138, 1999
Preparation and exchange interaction of DPPH-derived polyradicals
A series of 1,1'-(benzene-1,3-diyl)bis(1-phenyl-2-picrylhydrazine) derivatives was prepared and oxidized to generate the corresponding bis-DPPH diradicals. No triplet species was observed for the parent compound in the ESR. Incorporation of substituents in both the central benzene ring and the N-phenyl groups resulted in the detection of triplet diradicals. Especially, the diradical with Me and t-Bu groups on the central benzene and the N-phenyl rings, respectively, was successfully purified and isolated at 0 degreesC as a purple solid. Temperature-dependence of the intensity of the ESR signal showed that the isolated radical had a triplet ground state.