Spin Polarization Conservation during Triplet-Triplet Energy Transfer in Fluid Solution As Studied by Time-Resolved ESR Spectroscopy

Electron spin polarization of pyridinyl radicals generated from the photosensitized dissociation of the dimers was studied. Addition of triplet sensitizer to the dimer solution induced drastic change in the CIDEP spectrum. Examinations of the dependence of spectral change on the T₁state energy level and the spin alignment in the T₁sublevels of sensitizers lead to the conclusion that energy transfer between the pyridinyl dimer and the sensitizer occurred and that the spin polarization was conserved during the process. From a series of triplet donors, nonphosphorescent T₁states of two types of pyridinyl dimers were estimated to be 2.43 eV for the 2, 2'-dimer of 1-methyl-4-tert-butylpyridinyl and 2.65 eV for the 4, 4'-dimer of 1-methylpyridinyl.