SPIN ALIGNMENT BETWEEN THE TRIPLET EXCITED STATE OF PHENYLANTHRACENE AND THE DANGLING VERDAZYL RADICAL AS STUDIED BY TIME-RESOLVED ELECTRON SPIN RESONANCE

Abstract

The photo-excited quartet (S=3/2) high spin state of a radical-excited triplet pair of a novel compound, phenylanthracene-verdazyl radical, was detected by time-resolved electron spin resonance (TRESR) technique. The TRESR spectrum was well analyzed by the ordinary spin Hamiltonian with the Zeeman and fine-structure terms. The g value, fine-structure splitting, and relative population of the Ms sublevels have been determined to be g=2.0043, D=0.0230 cm -1, E=0.0 cm -1 and P1/2′=P-12′=0.5 and P3/2′=P-3/2′=0.0, respectively, by the spectral simulation. The direct observation of the excited quartet state shows tha the photo-induced intramolecular spin alignment is realized between the excited triplet state (S=1) of the phenylanthracene moiety and the doublet spin (S=1/2) of the dangling verdazyl radical.