title: Solvent Viscosity Effect on Triplet-Triplet Pair in Triplet Fusion.
abstract: The effect of the solvent viscosity dependence of time-resolved magnetoluminescence (ML) on the delayed fluorescence of 9,10-diphenylanthracene (DPA) sensitized by platinum octaethylporphyrin has clarified the structure and dynamics of the triplet-triplet pair (TT), i.e., the transition state of triplet fusion. Phase inversion of the ML effect with time provides evidence for the recycle dynamics of the excited triplet state for DPA in triplet fusion. The electron spin-relaxation by random molecular rotation causes intersystem crossing among the different spin states of the triplet-triplet pair and allows the (3,5)TT to engage in triplet fusion. Therefore, slow-down of the molecular diffusion by an increase in the solvent viscosity can enhance the triplet fusion yield. However, the reduction of the ML effect observed in quite high viscosity solvents suggests that the substantially slow rotational motion decreases the triplet fusion yield due to steric factors in electron exchange from the triplet-triplet pair.
authors.affiliation: Graduate School of Science and Technology, Niigata University , 2-8050 Ikarashi, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Kana
authors.initials: K
authors.lastname: Yokoyama
authors.affiliation: Advanced Instrumental Analysis Center, Shizuoka Institute of Science and Technology , 2200-2 Toyosawa, Fukuroi 437-8555, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Wakikawa
authors.affiliation: Graduate School of Science and Technology, Niigata University , 2-8050 Ikarashi, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Miura
authors.affiliation: Institute of Education, Shinshu University , 6-Ro Nishinagano, Nagano 380-8544, Japan.
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Fujimori
authors.affiliation: Institute of Education, Shinshu University , 6-Ro Nishinagano, Nagano 380-8544, Japan.
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Ito
authors.affiliation: Graduate School of Science and Technology, Niigata University , 2-8050 Ikarashi, Nishi-ku, Niigata 950-2181, Japan.|Core Research for Evolutionary Science and Technology, Japan Science and Technology Agency , 4-1-8 Honcho, Kawaguchi 332-0012, Japan.|Center for Instrumental Analysis, Niigata University , 2-8050 Ikarashi, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Tadaaki
authors.initials: T
authors.lastname: Ikoma