Femtosecond Laser Photolysis Studies on Temperature Dependence of Cyclization and Cycloreversion Reactions of a Photochromic Diarylethene Derivative
Femtosecond Laser Photolysis Studies on Temperature Dependence of Cyclization and Cycloreversion Reactions of a Photochromic Diarylethene Derivative
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DOI：
10.1021/jp2107632
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发表时间：
2012-02-23
影响因子：
3.7
通讯作者：
Miyasaka, Hiroshi
中科院分区：
文献类型：
--
作者：
Ishibashi, Yukihide;Umesato, Toshiyuki;Miyasaka, Hiroshi
采用稳态光谱和飞秒激光光解方法研究了光致变色二芳基乙烯衍生物1，2-双（2-甲基-3-苯并噻吩基）全氟环戊烯（BT）的环化和环化反转过程的温度依赖性.稳态测量结果表明，在253-343 K范围内，环化反应的量子产率和有利于环化反应的C-2 v对称性构象（反平行，AP构象）的比例与温度无关.这些结果表明，开环异构体中的AP构象在激发态下的环化反应没有明显的温度依赖性，并建议，开环异构体中的激发AP构象的命运，如环化或失活到基态，是在圆锥交叉点确定。另一方面，环化逆转反应是依赖于温度;随着温度的升高，反应的量子产率增加，同时减少的闭环异构体的激发态的寿命。根据反应曲线的绝热能面，推断出S-1态的快速失活是在与通向锥形交叉点的活化途径竞争的情况下发生的，在锥形交叉点处发生了环化反转.
Temperature dependencies of cyclization and cycloreversion processes of a photochromic diarylethene derivative, 1,2-bis(2-methyl-3-benzothienyl)perfluorocyclopentene (BT), were investigated by steady-state spectroscopy and femtosecond laser photolysis methods. Steady-state measurements revealed that the cyclization reaction quantum yield and the fraction of the conformer with C-2v symmetry favorable for the cyclization (antiparallel, AP conformer) were independent of temperature in the range of 253-343 K. These results indicated that the cyclization reaction of the AP conformer in the open-ring isomer in the excited state had no apparent temperature dependence and suggested that the fate of the excited AP conformer in the open-ring isomer, such as cyclization or deactivation to the ground state, was determined at the conical intersection. On the other hand, the cycloreversion reaction was dependent on the temperature; the reaction quantum yield increased together with a decrease in the lifetime of the excited state of the closed-ring isomer with increasing temperature. On the basis of the adiabatic energy surface for the reaction profiles, it was deduced that the rapid deactivation into the ground state took place in the S-1 state in competition with the activated pathways leading to the conical intersection where the cycloreversion occurred.