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Influence of Solvent Relaxation on Ultrafast Excited-State Proton Transfer to Solvent
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2017-09-08 00:00:00 , DOI: 10.1021/acs.jpclett.7b01956
Tatu Kumpulainen 1 , Arnulf Rosspeintner 1 , Bogdan Dereka 1 , Eric Vauthey 1
Affiliation  

A thorough understanding of the microscopic mechanism of excited-state proton transfer (ESPT) and the influence of the solvent environment on its dynamics are of great fundamental interest. We present here a detailed investigation of an ESPT to solvent (DMSO) using time-resolved broadband fluorescence and transient absorption spectroscopies. All excited-state species are resolved spectrally and kinetically using a global target analysis based on the two-step Eigen-Weller model. Reversibility of the initial short-range proton transfer producing excited contact ion pairs (CIP*) is observed unambiguously in fluorescence and must be explicitly considered to obtain the individual rate constants. Close inspection of the early dynamics suggests that the relative populations of the protonated form (ROH*) and CIP* are governed by solvent relaxation that influences the relative energies of the excited states. This constitutes a breakdown of the Eigen-Weller model, although the overall agreement between the data and the analysis using classical rate equations is excellent.

中文翻译:

溶剂弛豫对超快激发态质子转移至溶剂的影响

对激发态质子转移(ESPT)的微观机理以及溶剂环境对其动力学的影响的透彻理解具有重大的根本意义。我们在这里介绍使用时间分辨宽带荧光和瞬态吸收光谱法对溶剂(DMSO)进行ESPT的详细研究。使用基于两步Eigen-Weller模型的全局目标分析,可以在光谱和动力学上解析所有激发态物种。在荧光中可以清晰地观察到产生近距离质子转移产生激发接触离子对(CIP *)的可逆性,必须明确考虑其可逆性以获得单独的速率常数。对早期动力学的仔细检查表明,质子化形式(ROH *)和CIP *的相对种群受溶剂弛豫支配,溶剂弛豫影响了激发态的相对能量。这构成了Eigen-Weller模型的细目,尽管数据与使用经典速率方程式进行的分析之间的总体一致性非常好。
更新日期:2017-09-08
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