Ultrafast dynamics of nonequilibrium electron transfer in photoinduced redox cycle: solvent mediation and conformation flexibility.
Ultrafast dynamics of nonequilibrium electron transfer in photoinduced redox cycle: solvent mediation and conformation flexibility.
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DOI：
10.1021/jp304518f
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发表时间：
2012-08-02
影响因子：
3.3
通讯作者：
Zhong, Dongping
中科院分区：
文献类型：
--
作者：
Kao, Ya-Ting;Guo, Xunmin;Yang, Yi;Liu, Zheyun;Hassanali, Ali;Song, Qin-Hua;Wang, Lijuan;Zhong, Dongping
在此，我们报告了在三种不同溶剂（水、乙腈和二氧环）中，由n-乙酰色氨酸甲基lester作为电子供体和胸腺嘧啶作为电子受体组成的共价连接的柔性系统中光诱导电子转移（ET）氧化还原循环的系统表征。在飞秒分辨率下，我们通过跟踪从反应物到中间体，最后到产物的完整反应演变，确定了所有ET的时间尺度，向前和向后。令人惊讶的是，我们在水中观察到两种截然不同的ET动力学，对应于0.7 ps时超快ET的堆叠结构和4.5 ps时反向ET的堆叠结构，以及322 ps时ET的部分折叠C-clamp构象，但反向ET在17 ps时。在乙腈和二氧环中，ET分别在470和1068 ps和110和94 ps时只观察到C-clamp构象。这些在几百皮秒内相对缓慢的ET动力学都表现出明显的构象非均质性，并遵循拉伸衰减行为。通过测定正向和反向蒸散速率，我们推导出溶剂重组能和耦合常数。重要的是，我们发现嵌入C-clamp结构缝隙中的溶剂分子介导电子转移，隧穿参数（β）为1.0-1.4 Å−1，产物中的高频振动模式与回ET过程耦合，导致数十皮秒内的超快回ET动力学。这些发现提供了非平衡ET动力学的机理见解，由构象灵活性调节，由独特的溶剂构型介导，并由振动耦合加速。
We report here our systematic characterization of a photoinduced electron-transfer (ET) redox cycle in a covalently linked donor-spacer-acceptor flexible system, consisting of N-acetyl-tryptophan methylester as electron donor and thymine as electron acceptor in three distinct solvents of water, acetonitrile and dioxane. With femtosecond resolution, we determined all the ET time scales, forward and backward, by following the complete reaction evolution from reactants, to intermediates and finally to products. Surprisingly, we observed two distinct ET dynamics in water, corresponding to a stacked configuration with ultrafast ET in 0.7 ps and back ET in 4.5 ps and a partially folded C-clamp conformation with ET in 322 ps but back ET in 17 ps. In acetonitrile and dioxane, only the C-clamp conformations were observed with ET in 470 and 1068 ps and back ET in 110 and 94 ps, respectively. These relatively slow ET dynamics in hundreds of picoseconds all showed significant conformation heterogeneity and followed a stretched decay behavior. With both forward and back ET rates determined, we derived solvent reorganization energies and coupling constants. Significantly, we found that solvent molecules intercalated in the cleft of the C-clamp structure mediate electron transfer with a tunneling parameter (β) of 1.0–1.4 Å−1 and the high-frequency vibration modes in the product(s) couple with the back ET process, leading to the ultrafast back ET dynamics in tens of picoseconds. These findings provide mechanistic insights of nonequilibrium ET dynamics modulated by conformation flexibility, mediated by unique solvent configuration, and accelerated by vibrational coupling.
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影响因子：
15
作者：
Chang, Chih-Wei;He, Ting-Fang;Guo, Lijun;Stevens, Jeffrey A.;Li, Tanping;Wang, Lijuan;Zhong, Dongping
通讯作者：
Zhong, Dongping
影响因子：
3.3
作者：
KIM, ST;HARTMAN, RF;ROSE, SD
通讯作者：
ROSE, SD
肽和氨基酸类似物中酪氨酸苯氧基和色氨酸吲哚基的电化学性质
影响因子：
--
作者：
DEFELIPPIS, MR;MURTHY, CP;KLAPPER, MH
通讯作者：
KLAPPER, MH
影响因子：
--
作者：
FINCKH, P;HEITELE, H;MICHELBEYERLE, ME
通讯作者：
MICHELBEYERLE, ME
影响因子：
15
作者：
Kao, Ya-Ting;Tan, Chuang;Zhong, Dongping
通讯作者：
Zhong, Dongping