Determination of electron-transfer reorganization energy in nanometer-separated radical ion pair by time-resolved EPR spectroscopy.
Determination of electron-transfer reorganization energy in nanometer-separated radical ion pair by time-resolved EPR spectroscopy.
复制标题
通过时间分辨 EPR 光谱测定纳米分离自由基离子对中的电子转移重组能。
DOI：
10.1021/ja015752n
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发表时间：
2001
影响因子：
15
通讯作者：
S. Tero
中科院分区：
文献类型：
--
作者：
Y. Kobori;T. Yago;K. Akiyama;S. Tero
重组能（λ）对电子给体（D）和受体（A）分子之间的电子转移（ET）反应的效率起着重要的控制作用，正如Marcus理论所预测的那样。1对于溶剂分离自由基离子对（RIP）的电荷复合（CR）反应，通过拟合瞬态吸收光谱得到的CR反应速率与能隙（-ΔGCR）关系的Marcus图，估算了溶剂重组能（λS）和溶质分子内重组能（λV）。2. DA体系的特征λ值对了解ET过程中溶质-溶剂相互作用具有重要意义。迄今为止，还没有研究确定了灵活的纳米分离的双分子ET系统中的单个λ值。在这篇通讯中，我们精确地确定了三重态前体光致双分子电荷分离（CS）产生的1，2，4-三甲氧基苯（TMB）阳离子和杜醌（DQ）阴离子RIP在0.1.2 nm处分离的λ值，通过观察极性溶剂中时间分辨电子顺磁共振（TREPR）谱的温度依赖性，确定了λ（）λS+ λV），探讨了RIP中单重态-三重态能量分裂（J）相互作用产生的化学诱导动态电子极化（CIDEP）3，4。最近，已经清楚地表明，在RIP中的J是由电荷转移相互作用（JCT），这是由电子耦合（V）扰动从电荷重组DA配置创建。5-7自由基对机理（RPM）CIDEP是由扩散分离过程中的单重态-三重态（ST 0）混合和随后可能在RIP中的重新相遇产生的。3、4 RPM偏振图案提供了在柔性分离中心处的J的符号的信息。
The reorganization energy (λ) plays an important role to control the efficiency of the electron transfer (ET) reaction between the electron donor (D) and acceptor (A) molecules, as predicted by Marcus theory. 1 As for the charge-recombination (CR) reactions of the solvent-separated radical ion pairs (RIP), the solvent reorganization (λS) and the solute intramolecular reorganization energies (λV) have been estimated by fitting the Marcus plots of the energy gap (-ΔGCR) dependences of the CR rates, which have been obtained by the transient absorption spectroscopy. 2 The characteristic λ value for the indiVidual DA system is quite significant to understand the solute-solvent interaction in the ET process. Thus far, no studies have determined the individual λ value in the flexibly nanometer-separated bimolecular ET systems. In this Communication, we have precisely determined the λ values for 1, 2, 4-trimethoxybenzene (TMB) cation and duroquinone (DQ) anion RIP separated at∼ 1.2 nm produced from the triplet precursor photoinduced bimolecular charge separation (CS), by observing the temperature dependence of the time-resolved electron paramagnetic resonance (TREPR) spectra in polar solvents.For the purpose of the determination of the λ () λS+ λV), we probed the chemically induced dynamic electron polarization (CIDEP) 3, 4 produced through the interaction of the singlet-triplet energy splitting (J) in the RIP. Recently, it has clearly been demonstrated that the J in the RIPs is governed by the chargetransfer interaction (JCT), which is created by the electronic coupling (V) perturbation from the charge-recombined DA configurations. 5-7 The radical pair mechanism (RPM) CIDEP is generated by the singlet-triplet (ST 0) mixing during the diffusive separation and by the possible subsequent reencounter in the RIPs. 3, 4 The RPM polarization pattern provides the information of the sign of the J at the flexibly separated center-