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首页> 外文期刊>Chemistry: A European journal >Supramolecular Tetrad Featuring Covalently Linked Bis(porphyrin)-Phthalocyanine Coordinated to Fullerene: Construction and Photochemical Studies
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Supramolecular Tetrad Featuring Covalently Linked Bis(porphyrin)-Phthalocyanine Coordinated to Fullerene: Construction and Photochemical Studies

机译：共价连接双（卟啉）-酞菁与富勒烯配位的超分子四联体：结构和光化学研究

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摘要

A multimodular donor-acceptor tetrad featuring a bis(zinc porphyrin)-(zinc phthalocyanine) ((ZnP-ZnP)-ZnPc) triad and bis-pyridine-functionalized fullerene was assembled by a "two-point" binding strategy, and investigated as a charge-separating photosynthetic antenna-reaction center mimic. The spectral and computational studies suggested that the mode of binding of the bis-pyridine-functionalized fullerene involves either one of the zinc porphyrin and zinc phthalocyanine (Pc) entities of the triad or both zinc porphyrin entities leaving ZnPc unbound. The binding constant evaluated by constructing a Benesi-Hildebrand plot by using the optical data was found to be 1.17× 10~5m~(-1), whereas a plot of "mole-ratio" method revealed a 1:1 stoichiometry for the supramolecular tetrad. The mode of binding was further supported by differential pulse voltammetry studies, in which redox modulation of both zinc porphyrin and zinc phthalocyanine entities was observed. The geometry of the tetrad was deduced by B3LYP/6-31G* optimization, whereas the energy levels for different photochemical events was established by using data from the optical absorption and emission, and electrochemical studies. Excitation of the zinc porphyrin entity of the triad and tetrad revealed ultrafast singlet-singlet energy transfer to the appended zinc phthalocyanine. The estimated rate of energy transfer (k_(ENT)) in the case of the triad was found to be 7.5× 10~(110 s~(-1) in toluene and 6.3×10~(11) s~(-1) in o-dichlorobenzene, respectively. As was predicted from the energy levels, photoinduced electron transfer from the energy-transfer product, that is, singlet-excited zinc phthalocyanine to fullerene was verified from the femtosecond-transient spectral studies, both in o-dichlorobenzene and toluene. Transient bands corresponding to ZnPc~(·+) in the 850 nm range and C_(60)~(·-) in the 1020 nm range were clearly observed. The rate of charge separation, k_(CS), and rate of charge recombination, k_(CR), for the (ZnP-ZnP)-ZnPc~(·+):Py_2C_(60)~(·-) radical ion pair (from the time profile of 849 nm peak) were found to be 2.20×10~(11) and 6.10×10~8 s~(-1) in toluene, and 6.82×10~(11) and 1.20×10~9 s~(-1) in o-dichlorobenzene, respectively. These results revealed efficient energy transfer followed by charge separation in the newly assembled supramolecular tetrad.
机译：通过“两点”结合策略组装了具有双（卟啉锌）-（酞菁锌）（（ZnP-ZnP）-ZnPc）三单元和双吡啶官能化富勒烯的多模块供体-受体四联体，并进行了研究电荷分离的光合天线反应中心模拟物。光谱和计算研究表明，双吡啶官能化的富勒烯的结合模式涉及三合一的锌卟啉和酞菁锌（Pc）实体之一，或两个锌卟啉实体均未结合。通过利用光学数据构建Benesi-Hildebrand图评估的结合常数被发现为1.17×10〜5m〜（-1），而“摩尔比”法的图显示超分子的化学计量为1：1。四元组差分脉冲伏安法研究进一步支持了结合方式，其中观察到了卟啉锌和酞菁锌实体的氧化还原调节。通过B3LYP / 6-31G *优化推导了四联体的几何形状，而通过使用来自光吸收和发射以及电化学研究的数据，确定了不同光化学事件的能级。三元组和四元组的锌卟啉实体的激发表明超快的单重态单重态能量转移到所附的酞菁锌上。在三元组的情况下，估计的能量转移速率（k_（ENT））在甲苯中为7.5×10〜（110 s〜（-1），在甲苯中为6.3×10〜（11）s〜（-1）。从能级预测，从飞秒瞬态光谱研究中证实了从飞秒瞬态光谱研究中证实了光能电子从能量转移产物即单重态激发的酞菁锌向富勒烯的光转移。清楚地观察到在850 nm范围内的ZnPc〜（·+）和在1020 nm范围内的C_（60）〜（·-）的瞬态谱带，电荷分离率，k_（CS）和速率发现（ZnP-ZnP）-ZnPc〜（·+）：Py_2C_（60）〜（·-）自由基离子对的电荷重组k_（CR）（从849 nm峰的时间曲线来看）为在甲苯中分别为2.20×10〜（11）和6.10×10〜8 s〜（-1），在邻二氯苯中分别为6.82×10〜（11）和1.20×10〜9 s〜（-1）。结果表明在新组装的超分子中有效的能量转移和电荷分离四分体

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