Ultrafast dynamics of UV-excited trans- and cis-ferulic acid in aqueous solutions,Physical Chemistry Chemical Physics

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Ultrafast dynamics of UV-excited trans- and cis-ferulic acid in aqueous solutions
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2017-11-02 00:00:00 , DOI: 10.1039/c7cp05301k
Shuangqing Wang _{1,

2,

3,

4} , Sebastian Schatz _{1,

2,

3,

4} , Mayra C. Stuhldreier _{1,

2,

3,

4} , Hendrik Böhnke _{1,

2,

3,

4} , Joss Wiese _{1,

2,

3,

4} , Carsten Schröder _{1,

2,

3,

4} , Tim Raeker _{1,

2,

3,

4} , Bernd Hartke _{1,

2,

3,

4} , Julia K. Keppler _{2,

4,

5,

6} , Karin Schwarz _{2,

4,

5,

6} , Falk Renth _{1,

2,

3,

4} , Friedrich Temps _{1,

2,

3,

4}

Affiliation

The ultrafast UV-induced processes of the neutral, anionic and dianionic forms of trans- and cis-ferulic acid (FA) in aqueous solution were studied by static and femtosecond time-resolved emission and absorption spectroscopy combined with quantum chemical calculations. In all cases, initial excitation populates the first ¹ππ* state. For the dianionic cis-isomer cFA²⁻, electronic deactivation takes place with a time constant of only 1.4 ps, whereas in all other cases, excited-state deactivation happens more than ten times slower, on a time scale of ≈20 ps. The data suggest sequential de-excitation pathways, where initial sub-picosecond solvent rearrangement and structural changes are followed by internal conversion to an intermediate excited electronic state from which deactivation to the ground state proceeds. Considering the time scales, barrierless excited-state pathways are suggested only in the case of cFA²⁻, where the observed formation of the isomerisation photoproduct tFA²⁻ provides clear evidence for a cis ⇄ trans isomerisation coordinate. In the other cases, pathways with an excited-state energy barrier, presumably along the same coordinate, are likely, given the longer excited-state lifetimes.

中文翻译：

的超快动力学UV激发反式-和CIS在水溶液中-ferulic酸

的中性，阴离子和二价阴离子形式的超快UV诱导的程序反式-和CIS在水溶液-ferulic酸（FA）通过静态和飞秒时间分辨发射和吸收光谱与量子化学计算相结合研究。在所有情况下，初始励磁填充第一^1个ππ*状态。对于双阴离子顺式异构体cFA ^2-，电子失活仅以1.4 ps的时间常数发生，而在所有其他情况下，激发态失活发生的速度要慢20倍以上，约20 ps。数据表明了顺序的去激励途径，其中最初的亚皮秒级溶剂重排和结构变化之后是内部转化为中间激发的电子态，然后从该状态开始失活为基态。考虑到时间尺度上，barrierless激发态途径建议仅在CFA中的情况下^2-，其中所述异构化光化产物TFA的观察形成^2-提供明确的证据为顺⇄反异构化坐标。在其他情况下，考虑到更长的激发态寿命，可能存在具有激发态能垒的路径，大概沿着相同的坐标。

更新日期：2017-11-22

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