Effect of molecular dimension on the rate of return electron transfer within photoproduced geminate radical ion pairs
Effect of molecular dimension on the rate of return electron transfer within photoproduced geminate radical ion pairs
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分子尺寸对光生双自由基离子对内电子转移返回率的影响
DOI：
10.1021/ja00214a068
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发表时间：
1988
影响因子：
15
通讯作者：
S. Farid
中科院分区：
文献类型：
--
作者：
I. Gould;J. Moser;D. Ege;S. Farid
A+ D Δ E ′/D*+-* Δ E ′ + D-+（1）已经表明，随着离子对的能量含量（Emd-E ′）增加而减小28，并且这种行为表示马库斯“反转区域”的清楚示例。[3]我们现在提供的数据表明，除了这种自由能依赖性之外，k^ t还依赖于自由基配对的分子尺寸。9，10-二氰基蒽（DCA）或2，6，9，10-四氰基蒽（TCA）的自由基阴离子，萘（Ia）、2-甲基萘（Ib）、2，6-二甲基萘（Ic）、联苯（2a）、3，3 ′-二甲基联苯（2b）、4，4 ′-二甲基联苯（2c）和芴（3）的自由基阳离子对，和表I中总结的取代苯进行了研究。实验过程与文献2a中所述相同，其中使用4，4-二甲氧基二苯乙烯（DMS）作为监测剂来拦截逸出成对的自由基阳离子。4，5（2）（a）Gould，I.的R.; Ege，D.; Mattes，S. L.的; Farid，S. J. Am. 1987，109，3794中所述。(b)Mattes，S. L.的; Farid，S.美国化学会杂志，化学通讯1980年，126。(c)Mattes，S. L.的;法里德，S。J. Am. 1983，105，1386中所述。(d)Mattes，S. L.的;法里德，S。J. Am. 1986，108，7356中所述。（3）（a）Marcus，R. A. J. Chem.Phys.1956，24，966。(b)马库斯河A.阿穆Rev. Phys. Chem. 1964，15，155。(4)k^的值是由分离自由基离子形成的量子产率确定的（参考文献5），假设它仅由k^ t和自由基离子从成对离子对中分离形成分离自由基离子的速率（k^）确定。在这项工作中，k^ p被取为5 × 108 s-1，对于所有研究的根对（参考文献2a）。
A+ D A*'/D*+—* A*'+ D-+(1) have shown that decreases as the energy content of the ion pair (Emd~£™*) increases28 and that this behavior represents a clear example of the Marcus “inverted region”. 3 We now present data which demonstrate that in addition to this free-energy dependence, k^ t depends upon themolecular dimensions of the radical pair partners. Radical ion pairs of the radical anions of9, 10-dicyanoanthracene (DCA) or 2, 6, 9, 10-tetracyanoanthracene (TCA), the radical cations of naphthalene (la), 2-methyl-naphthalene (lb), 2, 6-dimethylnaphthalene (lc), biphenyl (2a), 3, 3'-dimethylbiphenyl (2b), 4, 4'-dimethylbiphenyl (2c), and fluorene (3), and the substituted benzenes summarized in Chart I were studied. The experimental procedure was the same as that described in ref 2a, in which 4, 4,-dimethoxystilbene (DMS) was used as a monitor to intercept the radical cations which escape the geminate pair. 4, 5 (2)(a) Gould, I. R.; Ege, D.; Mattes, S. L.; Farid, S. J. Am. Chem. Soc. 1987, 109, 3794.(b) Mattes, S. L.; Farid, S. J. Chem. Soc., Chem. Commun. 1980, 126.(c) Mattes, S. L.; Farid, S. J. Am. Chem. Soc. 1983, 105, 1386.(d) Mattes, S. L.; Farid, S. J. Am. Chem. Soc. 1986, 108, 7356.(3)(a) Marcus, R. A. J. Chem. Phys. 1956, 24, 966.(b) Marcus, R. A. Amu. Rev. Phys. Chem. 1964, 15, 155.(4) The values of k^ were determined from quantum yields of separated radical ion formation (, ref 5) by assuming that is determined only by k^ t and the rate of separation (k^) of radical ions from the geminate pair to form separated radical ions. In this work k^ p is taken to be 5 X 108 s'1 for all of the radicalion pairs studied (ref 2a).