Controlling the conformation changes associated to electron transfer steps through chemical substitution: Intriguing redox behavior of substituted vinylogous TTF
Controlling the conformation changes associated to electron transfer steps through chemical substitution: Intriguing redox behavior of substituted vinylogous TTF
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DOI：
10.1021/jp001326x
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发表时间：
2000-11-02
影响因子：
2.9
通讯作者：
Tallec, A
中科院分区：
文献类型：
--
作者：
Bellec, N;Boubekeur, K;Tallec, A
在乙腈和二氯甲烷中研究了一系列四氢呋喃的氧化反应。根据取代基和溶剂的不同，观察到两个单电子转移或一个双电子过程。密度泛函模拟计算和对电化学行为的详细分析表明，短链TTF薄膜的异常氧化还原行为是由于电子转移引起的构象变化所致。闪光光解和光谱电化学实验也证实了这一结论。通过微调分子结构和取代基的选择，可以控制不同氧化还原物种的相对稳定性。一方面，这导致第二次电子转移比第一次电子转移容易得多的情况。在醚端观察到相反的情况，与没有空间位阻的类似TTF相比，第一和第二氧化电位之间的间隔有很大的增加。内球重组能保持不高(0.35-0.45 eV)，允许在电子转移过程中不同构象之间快速通过。
Oxidation of a series of TTF vinylogues has been investigated in acetonitrile and dichloromethane. Depending on the substituent and the solvent, two single-electron transfers or one two-electron process was observed. Density functional modeling calculations and detailed analysis of the electrochemical behavior show that the unusual redox behavior for short-length TTF vinylogues is due to substantial conformation changes concerted with the electron transfers. Flash photolysis and spectroelectrochemistry experiments were also performed to confirm this conclusion. Through fine-tuning of the molecule structure and substituent choice, it is possible to control the relative stabilities of the different redox species. At one end, this leads to situations where the second electron transfer is much easier than the first one. At the ether end, opposite situations are observed with a large increase of the separation between the first and second oxidation potentials by comparison to similar TTF without steric hindrance. The inner sphere reorganization energies remain modest (0.35-0.45 eV), allowing a fast passage between the different conformations during the electron transfers.