NONRADIATIVE DECAY ROUTE OF CINNAMATE DERIVATIVES STUDIED BY FREQUENCY AND TIME DOMAIN LASER SPECTROSCOPY IN THE GAS PHASE, MATRIX ISOLATION FTIR SPECTROSCOPY AND QUANTUM CHEMICAL CALCULATIONS

The nonraddiative dececy route involving trans $rightarrow$ cis photo-isomerization from the S$_1$ ($pi$$pi$*) state has been investigated for several trans-cinnamate derivatives, which are known as sunscreen reagents. We examined two types of substitution effects._x000d_ _x000d_ One is structural isomer such as ortho-, meta-, and para-hydroxy-methylcinnmate (o-, m-, p-HMC). The S$_1$ lifetime of p-HMC is less than 8 ps at zero-point level, and it undergoes rapid S$_1$ $rightarrow$ $^1$n$pi$* $rightarrow$ T$_1$ decay via multiple conical intersections. Finally, the trans $rightarrow$ cis isomerization proceeds in the T$_1$ state. On the other hand, both o- and m-HMC show very slow decay. Their S$_1$ lifetimes are in the order of 100 ps even at the excess energy of 2000-3000 wn. _x000d_ _x000d_ The other is the effect of the complexity of ester group in para-subsitituted species, such as para-methoxy-methyl, -ethyl and -2ethylhexyl cinnamate (p-MMC, p-MEC, p-M2EHC). p-MMC and p-MEC show sharp S$_0$ $rightarrow$ S$_1$ ($pi$$pi$*) vibronic bands, while p-M2EHC shows only broad structureless feature even under the jet-cooled condition. In addition, we found that the S$_0$ $rightarrow$ $^1$n$pi$* absorption appears at 1000 wn below the S$_0$ $rightarrow$ S$_1$ ($pi$$pi$*) transition in p-MEC and p-M2EHC, but not in p-MMC. Thus, the complexity of the ester group is very important for the appearance of the $^1$n$pi$* state

ピコ秒時間分解IR-UVポンプ-プローブ法によるベンゼンダイマーの振動緩和の研究 : サイト特異的な振動緩和の発見

第4回分子科学討論会, 2010年9月14日-17日, 大阪大学豊中キャンパス(大阪), 1A1

レーザー分光を用いた超音速ジェット中のBenzo-18-crown-6-etherとDibenzo-18-crown-6-etherのコンフォマーと水和構造の研究

第1回分子科学討論会, 2007年9月17日-20日, 東北大学川内北キャンパス(仙台), 3B1