• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ultrafast Electronic Relaxation and Hydrogen-Bond-Formation/Dissociation Dynamics of Photoexcited All-trans Retinal in Protic Solvents
【24h】

Ultrafast Electronic Relaxation and Hydrogen-Bond-Formation/Dissociation Dynamics of Photoexcited All-trans Retinal in Protic Solvents

机译：超快电子弛豫和质子溶剂中光激发全反式视网膜的氢键形成/离解动力学

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The ultrafast electronic relaxation and the hydrogen-bond-formation/dissociation dynamics of photoexcited all-trans retinal in 1-butanol/cyclohexane mixed solvents have been studied by femtosecond time-resolved visible absorption spectroscopy. Four transient absorption bands, which can be assigned to the S_3, S_2, S_1, and T_1 states, were observed in neat cyclohexane. The shapes and the dynamics of these absorption bands agree very well with those reported previously for all-trans retinal in hexane. In contrast, only three transient absorption bands, which can be assigned to the S_3, S_2, and T_1 states, were identified in the mixed solvents. The band assigned to the S_2 state showed a time-dependent peak shift, which is attributed to solvent reorganization on a picosecond time scale. A kinetic analysis of the three transient absorption bands has led to the conclusion that no state-ordering change of the (n, π~*) and (π, π~*) states takes place in the excited singlet manifold upon hydrogen-bond formation. The 1-butanol concentration dependence of the absorption spectra shows that the free and hydrogen-bonded species coexist in the S_3 and T_1 states, but that all of the retinal molecules are hydrogen-bonded in the S_2 state. These observations indicate that an ultrafast hydrogen-bond-formation reaction takes place during or just after the S_3 → S_2 internal conversion and is complete within a time scale much shorter than the S_2 lifetime. Dissociation of the hydrogen bonding is most likely to take place during or after the S_1 → T_1 intersystem crossing and is complete within a time scale much shorter than the T_1 lifetime. The observed longer lifetime of the hydrogen-bonded S_2 state is consistent with the higher isomerization quantum yield in protic solvents than in aprotic nonpolar solvents.
机译：飞秒时间分辨可见吸收光谱研究了光激发全反式视网膜在1-丁醇/环己烷混合溶剂中的超快电子弛豫和氢键形成/离解动力学。在纯环己烷中观察到四个瞬态吸收带，可以分配给S_3，S_2，S_1和T_1状态。这些吸收带的形状和动力学与先前报道的在己烷中的全反式视网膜非常吻合。相比之下，在混合溶剂中仅识别出三个可以指定为S_3，S_2和T_1状态的瞬态吸收带。分配给S_2状态的谱带显示出随时间变化的峰位移，这归因于皮秒级的溶剂重组。对三个瞬态吸收带的动力学分析得出的结论是，在形成氢键的激发单重态歧管中，（n，π〜*）和（π，π〜*）状态没有发生状态有序变化。吸收光谱的1-丁醇浓度依赖性表明，游离和氢键结合的物种共存于S_3和T_1状态，但所有视网膜分子均以S_2状态氢键合。这些观察结果表明，超快氢键形成反应发生在S_3→S_2内部转化过程中或之后，并且在比S_2寿命短得多的时间范围内完成。氢键的解离最有可能发生在S_1→T_1系统间穿越期间或之后，并且在比T_1寿命短得多的时间范围内完成。在质子溶剂中观察到的更长的氢键合S_2态寿命与非质子非极性溶剂中更高的异构化量子产率一致。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号