Photoinduced electron transfer in a charge-transfer complex formed between corannulene and Li+@C60 by concave-convex π-π interactions.
Photoinduced electron transfer in a charge-transfer complex formed between corannulene and Li+@C60 by concave-convex π-π interactions.
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DOI：
10.1021/ja505391x
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发表时间：
2014-09
影响因子：
15
通讯作者：
Mihoko Yamada;K. Ohkubo;M. Shionoya;S. Fukuzumi
中科院分区：
文献类型：
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作者：
Mihoko Yamada;K. Ohkubo;M. Shionoya;S. Fukuzumi
298 K时，在苯甲腈溶液中，角轮烯（C20 H10）与锂离子包封的[60]富勒烯（Li（+）@C60）通过凹凸π-π电荷转移相互作用形成电荷转移络合物，其结合常数KG = 1.9 × 10 ~（-1），并在近红外区有较宽的电荷转移吸收.飞秒激光激发C20 H10/Li（+）@C60 CT复合物产生单重态电荷分离（CS）态（1）（C20 H10（·+）/Li（+）@C60（·-）），其衰变寿命为1.4ns。纳秒激光激发Li（+）@C60导致从C20 H10到Li（+）@C60的三重激发态[（3）（Li（+）@C60）*]的分子间电子转移（ET），产生三重CS态（3）（C20 H10（·+）/Li（+）@C60（·-））。根据EPR测量在4 K下观察到的零场分裂模式，三重态CS中两个电子自旋之间的距离估计为10 μ m。三重态CS通过分子内背电子转移（BET）衰变到基态。在298 K时，在苯甲腈中的CS寿命为240 μs。由BET反应速率常数的温度依赖性，得到了重组能（λ = 1.04 eV）和电子耦合项（V = 0.0080 cm（-1））。三重态CS的长寿命是由于自旋禁戒的BET过程和较小的V值。
A charge-transfer (CT) complex was formed between corannulene (C20H10) and lithium ion-encapsulated [60]fullerene (Li(+)@C60) with the binding constant KG = 1.9 × 10 M(-1) by concave-convex π-π CT interactions in benzonitrile at 298 K, exhibiting a broad CT absorption extended to the NIR region. Femotosecond laser excitation of the C20H10/Li(+)@C60 CT complex resulted in the singlet charge-separated (CS) state, (1)(C20H10(•+)/Li(+)@C60(•-)), which decayed with the lifetime of 1.4 ns. Nanosecond laser excitation of Li(+)@C60 resulted in intermolecular electron transfer (ET) from C20H10 to the triplet excited state of Li(+)@C60 [(3)(Li(+)@C60)*] to produce the triplet CS state (3)(C20H10(•+)/Li(+)@C60(•-)). The distance between two electron spins in the triplet CS state was estimated to be 10 Å from the zero-field splitting pattern observed by EPR measurements at 4 K. The triplet CS state decayed to the ground state via intramolecular back electron transfer (BET). The CS lifetime was determined to be 240 μs in benzonitrile at 298 K. The temperature dependence of the rate constant of BET afforded the reorganization energy (λ = 1.04 eV) and the electronic coupling term (V = 0.0080 cm(-1)). The long lifetime of triplet CS state results from the spin-forbidden BET process and a small V value.