Excited doublet states of electrochemically generated aromatic imide and diimide radical anions
Excited doublet states of electrochemically generated aromatic imide and diimide radical anions
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DOI：
10.1021/jp000706f
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发表时间：
2000-07-20
影响因子：
2.9
通讯作者：
Wasielewski, MR
中科院分区：
文献类型：
--
作者：
Gosztola, D;Niemczyk, MP;Wasielewski, MR
芳香二酰亚胺的阴离子自由基参与了多种光化学电子转移反应。这些自由基阴离子的光激发产生强有力的还原物种。然而，这些有机自由基阴离子的π * 激发双重态的性质仍然模糊不清。本文研究了三种π系统逐渐增大的芳香酰亚胺的自由基阴离子，（2，5-二叔丁基苯基）邻苯二甲酰亚胺，2，N-（2，5-二叔丁基苯基）-1，8-萘二甲酰亚胺，2和N-（2，5-二叔丁基苯基）二萘嵌苯-3，4-二甲酰亚胺，3，以及三种相应的芳族二酰亚胺，N，N '-双（3，5-二叔丁基苯基）均苯四酸酰亚胺，4a，N，N '-双（2，5-二叔丁基苯基）-萘-1，8：4，5-四羧基二酰亚胺，5a和N，N'-双（2，5-二叔丁基苯基）苝-3，4：9，10-四羧基二酰亚胺，6是通过在光学透明的薄层电化学电池中对中性分子进行电化学还原而产生的。这些酰亚胺和二酰亚胺的自由基阴离子都表现出强烈的可见光和较弱的近红外吸收带，对应于它们的D-0 -> D-n跃迁。激发态的自由基阴离子产生的亚皮秒激发到这些吸收带。激发1（.-）和2（.-）导致这些自由基阴离子的分解，而激发3（.-）- 6（.-）得到了它们的D-1 → D-n跃迁的瞬态谱和D-1的寿命。3（. -）-3（. -）-3（.-）-3（.-）-3（.-）6（.-）都小于600 ps，并随着Do-DI能隙的增加而增加。这些结果施加的设计限制，这些激发的自由基阴离子作为电子供体的电子转移系统，针对分子电子学和太阳能转换的使用。
The radical anions of aromatic diimides have been implicated recently ill a wide variety of photochemical electron transfer reactions. Photoexcitation of these radical anions produces powerfully reducing species. Yet, the properties of the pi* excited doublet states of these organic radical anions remain obscure. The radical anions of three aromatic imides with increasingly larger pi systems, N-(2,5-di-tert-butylphenyl)phthalimide, 2, N-(2,5-di-tert-butylphenyl)-1,8-naphthalimide, 2, and N-(2,5-di-tert-butylphenyl)perylene-3,4-dicarboximide, 3, as well as the three corresponding aromatic diimides, N,N'-bis(3,5-di-tert-butylphenyl)pyromellitimide, 4a, N,N'-bis(2,5-di-tert-butylphenyl)-naphthalene-1,8:4,5-tetracarboxydiimide, 5a, and N,N'-bis(2,5-di-tert-butylphenyl)perylene-3,4: 9,10-tetracarboxydiimide, 6, were produced by electrochemical reduction of the neutral molecules in an optically transparent thin layer electrochemical cell. The radical anions of these imides and diimides all exhibit intense visible and weaker near-IR absorption bands corresponding to their D-0 --> D-n transitions. Excited states of the radical anions were generated by subpicosecond excitation into these absorption bands. Excitation of 1(.-) and 2(.-) resulted in decomposition of these radical anions, whereas excitation of 3(.-)-6(.-) yielded transient spectra of their D-1 --> D-n transitions and the lifetimes of D-1. The lifetimes of the D-1 excited states of the radical anions of 3(.-)-6(.-) are all less than 600 ps and increase as the Do-DI energy gap increases. These results impose design constraints on the use of these excited radical anions as electron donors in electron-transfer systems targeted toward molecular electronics and solar energy conversion.