Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA, Japan Science and Technology (JST) , Suita, Osaka 565-0871, Japan.
J Am Chem Soc. 2014 Sep 24;136(38):13240-8. doi: 10.1021/ja505391x. Epub 2014 Sep 15.
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.
在 298 K 的苯腈中，通过凹-凸 π-π CT 相互作用，蔻烷（C20H10）与锂离子包封的 [60] fullerene（Li(+)@C60）之间形成了一个电荷转移（CT）复合物，其结合常数 KG = 1.9×10 M(-1)，呈现出扩展到近红外区域的宽 CT 吸收。飞秒激光激发 C20H10/Li(+)@C60 CT 复合物导致单重态电荷分离（CS）态，（1）（C20H10(•+)/Li(+)@C60(•-))，其衰减寿命为 1.4 ns。纳秒激光激发 Li(+)@C60 导致从 C20H10 到 Li(+)@C60 的三重激发态的分子间电子转移（ET），产生三重 CS 态（3）（C20H10(•+)/Li(+)@C60(•-))。通过在 4 K 下进行电子顺磁共振（EPR）测量观察到的零场分裂模式，估计三重 CS 态中两个电子自旋之间的距离为 10 Å。三重 CS 态通过分子内反向电子转移（BET）衰减到基态。在 298 K 的苯腈中，CS 寿命确定为 240 μs。BET 速率常数的温度依赖性提供了重组能（λ=1.04 eV）和电子耦合项（V=0.0080 cm(-1))。三重 CS 态的长寿命源于自旋禁阻 BET 过程和小 V 值。
