Direct Probing of Photoinduced Electron Transfer in a Self-Assembled Biomimetic [2Fe2S]-Hydrogenase Complex Using Ultrafast Vibrational Spectroscopy
Direct Probing of Photoinduced Electron Transfer in a Self-Assembled Biomimetic [2Fe2S]-Hydrogenase Complex Using Ultrafast Vibrational Spectroscopy
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DOI：
10.1021/ic500777d
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发表时间：
2014-05-19
影响因子：
4.6
通讯作者：
Reek, Joost N. H.
中科院分区：
文献类型：
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作者：
Li, Ping;Amirjalayer, Saeed;Reek, Joost N. H.
合成了吡啶基功能化二硫代二铁配合物[mu-(4-pyCH(2)-NMI- s -2)Fe-2(CO)(6)] （3, py =吡啶（配体），NMI =萘单亚胺），并对其进行了表征。在四苯基卟啉锌（ZnTPP）存在下，吡啶基氮与卟啉锌中心配位，在CH2Cl2中容易形成自组装的3中心点ZnTPP配合物。利用飞秒时间分辨红外光谱（TRIR）监测nu（C O）和nu(C O)（NMI）光谱变化，实时观察了从受激ZnTPP到超分子复合物3的超快光致电子转移。通过对比时间分辨红外光谱和可逆电化学还原产生的3（中心点-）的常规红外光谱，我们证实了光诱导电荷分离产生了单还原物质。电荷分离和电荷重组过程的寿命分别为tau(CS) = 40 +/- 3ps和tau(CR) = 205 +/- 14ps。电荷重组比类似的共价配合物慢得多，证明了超分子方法在延长光催化配合物中电荷分离状态的寿命方面的潜力。观察到的振动频移为Fe2S2配合物不同部位的电子自旋密度的离域提供了一个非常敏感的探针。TR和电化学IR谱、电子顺磁共振谱和密度泛函理论计算均表明，3（中心点-）的自旋密度在双铁核和NMI桥上是离域的。这种离域解释了为什么该配合物具有非常有效的光诱导电子转移，但其催化双氢产量却很低。超快卟啉- nmi - s -2 Fe-2(CO)(6)光诱导电子转移是飞秒TRIR光谱研究超分子fe2s2 -氢化酶模型的第一个例子。我们的研究结果表明，TRIR光谱是研究潜在的产氢催化配合物中光致电子转移的有力工具，并可以通过合理的方法优化其性能。
A pyridyl-functionalized diiron dithiolate complex, [mu-(4-pyCH(2)-NMI-S-2)Fe-2(CO)(6)] (3, py = pyridine (ligand), NMI = naphthalene monoimide) was synthesized and fully characterized. In the presence of zinc tetraphenylporphyrin (ZnTPP), a self-assembled 3 center dot ZnTPP complex was readily formed in CH2Cl2 by the coordination of the pyridyl nitrogen to the porphyrin zinc center. Ultrafast photoinduced electron transfer from excited ZnTPP to complex 3 in the supramolecular assembly was observed in real time by monitoring the nu(C O) and nu(C O)(NMI) spectral changes with femtosecond time-resolved infrared (TRIR) spectroscopy. We have confirmed that photoinduced charge separation produced the monoreduced species by comparing the time-resolved IR spectra with the conventional IR spectra of 3(center dot-) generated by reversible electrochemical reduction. The lifetimes for the charge separation and charge recombination processes were found to be tau(CS) = 40 +/- 3 ps and tau(CR) = 205 +/- 14 ps, respectively. The charge recombination is much slower than that in an analogous covalent complex, demonstrating the potential of a supramolecular approach to extend the lifetime of the charge-separated state in photocatalytic complexes. The observed vibrational frequency shifts provide a very sensitive probe of the delocalization of the electron-spin density over the different parts of the Fe2S2 complex. The TR and spectro-electrochemical IR spectra, electron paramagnetic resonance spectra, and density functional theory calculations all show that the spin density in 3(center dot-) is delocalized over the diiron core and the NMI bridge. This delocalization explains why the complex exhibits low catalytic dihydrogen production even though it features a very efficient photoinduced electron transfer. The ultrafast porphyrin-to-NMI-S-2 Fe-2(CO)(6) photoinduced electron transfer is the first reported example of a suprarnolecular Fe2S2-hydrogenase model studied by femtosecond TRIR spectroscopy. Our results show that TRIR spectroscopy is a powerful tool to investigate photoinduced electron transfer in potential dihydrogen-producing catalytic complexes, and that way to optimize their performance by rational approaches.