Spin-state dynamics of the triplet-exciton in TAB revealed by TREPR spectroscopy To elucidate the accelerated and deaccelerated 𝑘 ((# s in TAB at the molecular level , we performed TREPR measurements of the PtOEP/TAB and PtOEP/DPA systems. PtOEP and either TAB or DPA were dissolved in solvents with different viscosities prepared by mixing low viscosity toluene and high viscosity liquid paraffin in various mixing ratios. The sample solutions were degassed and sealed in 5 mm quartz EPR tubes. As in the time-resolved emission measurements, a Nd:YAG laser at 532 nm was used for light excitation. Importantly, the triplet state of PtOEP is not detected in the Xband (~ 9.5 GHz) EPR used in this study because of its large zerofield splitting (ZFS) interaction.