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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Photoinduced Electron-Transfer Processes between [C60]Fullerene and Triphenylamine Moieties Tethered by Rotaxane Structures.Through-Space Electron Transfer via Excited Triplet States of [60]Fullerene
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Photoinduced Electron-Transfer Processes between [C60]Fullerene and Triphenylamine Moieties Tethered by Rotaxane Structures.Through-Space Electron Transfer via Excited Triplet States of [60]Fullerene

机译：轮烷结构束缚的[C60]富勒烯与三苯胺部分之间的光诱导电子转移过程。通过[60]富勒烯的激发三重态通过空间电子转移

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摘要

Two rotaxanes tethering [60]fullerene (C_60) and triphenylamine (TPA) moieties were synthesized in good yields by the urethane end-capping method using a crown ether-secondary amine motif.In these rotaxanes,the C_60 group serving as electron acceptor is attached to the crown ether wheel through which the axle with a TPA group acting as electron donor on its terminal penetrates.One rotaxane has an ammonium moiety,whereas the other has a neutral amide moiety in the center of the axle.The corresponding reference compounds without rotaxane structures were also prepared.The intra-rotaxane photoinduced electron-transfer processes of C-60 and TPA have been investigated by time-resolved transient absorption and fluorescence measurements with changing solvent polarity and temperature.Nanosecond transient absorption measurements of these rotaxanes demonstrated that the long-lived charge-separated state (C_60~(-),TPA~(+))_(rotaxane) is formed via the excited triplet state of C_(60)~(3C_60~*) in polar solvents.The rate constants for the charge separation process were in the range of (5-8) x 10~7 s~(-1),while the rate constants of charge recombination were in the range of (3-6) x 10~6 s~(-1),corresponding to the lifetimes of the charge-separated states of 170-300 ns.Both rate constants depended on rotaxane structure,solvent polarity,and temperature.The activation free energy changes of charge separation and recombination processes were evaluated to be 0.01-0.03 and 0.03-0.06 eV by temperature dependences,respectively.Such low activation energies may be related to through-space electron transfer in these rotaxanes.On the other hand,in a covalently connected TPA-C_60 dyad,fast charge separation from the excited singlet state and fast charge recombination were observed through bonds in polar solvents.
机译：使用冠醚-仲胺基序通过氨基甲酸酯封端法以高收率合成了两个拴住[60]富勒烯（C_60）和三苯胺（TPA）部分的轮烷。在这些轮烷中，连接了C_60基团作为电子受体与冠醚轮相连，具有TPA基团作为末端电子供体的车轴穿过该冠轮。一个轮烷具有一个铵部分，另一个轮轴具有一个中性酰胺部分。通过时间分辨瞬态吸收和荧光测量（随溶剂极性和温度的变化）研究了轮烷内部C-60和TPA的光诱导电子转移过程。这些轮烷的纳秒瞬态吸收测量表明p中C_（60）〜（3C_60〜*）的三重激发态形成了活体电荷分离态（C_60〜（-），TPA〜（+））_（轮烷）电荷分离过程的速率常数在（5-8）x 10〜7 s〜（-1）的范围内，而电荷重组的速率常数在（3-6）x的范围内10〜6 s〜（-1），对应于170-300 ns电荷分离态的寿命。速率常数均取决于轮烷结构，溶剂极性和温度。电荷分离和复合的活化能自由变化通过温度依赖性将这些过程分别评估为0.01-0.03和0.03-0.06 eV。如此低的活化能可能与这些轮烷中的空间电子转移有关。另一方面，在共价连接的TPA-C_60 dyad中，通过极性溶剂中的键观察到从激发单重态快速分离电荷和快速重组。

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