Photoexcited triplet states of UV-B absorbers: ethylhexyl triazone and diethylhexylbutamido triazone

作者：Tsuchiya Takumi; Kikuchi Azusa^*; Oguchi Fujiyama Nozomi; Miyazawa Kazuyuki; Yagi Mikio

来源：Photochemical and Photobiological Sciences, 2015, 14(4): 807-814.

DOI：10.1039/c4pp00373j

The excited states of UV-B absorbers, ethylhexyl triazone (EHT) and diethylhexylbutamido triazone (DBT), have been studied through measurements of UV absorption, fluorescence, phosphorescence, triplet-triplet absorption and electron paramagnetic resonance spectra in ethanol. The energy levels of the lowest excited singlet (S-1) and triplet (T-1) states and quantum yields of fluorescence and phosphorescence of EHT and DBT were determined. In ethanol at 77 K, the deactivation process of EHT and DBT is predominantly fluorescence, however, a significant portion of the S-1 molecules undergoes intersystem crossing to the T-1 state. The observed phosphorescence spectra, T-1 lifetimes and zero-field splitting parameters suggest that the T-1 state of EHT can be assigned to a locally excited (3)pi pi* state within p-(N-methylamino)-benzoic acid, while the T-1 state of DBT can be assigned to a locally excited (3)pi pi* state within p-(N-methylamino)benzoic acid or p-amino-N-methylbenzamide. The quantum yields of singlet oxygen generation by EHT and DBT were determined by time-resolved near-IR phosphorescence measurements in ethanol at room temperature. EHT and DBT did not exhibit significantly antioxidative properties by quenching singlet oxygen, in contrast to the study by Lhiaubet-Vallet et al.

• 出版日期2015