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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Fast Triplet Formation via Singlet Exciton Fission in a Covalent Perylenediimide-beta-apocarotene Dyad Aggregate
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Fast Triplet Formation via Singlet Exciton Fission in a Covalent Perylenediimide-beta-apocarotene Dyad Aggregate

机译：通过单重态裂变在共价Per二酰亚胺-β-apocar​​otenedyad聚集体中快速三重态形成。

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摘要

A covalent dyad was synthesized in which perylene-3,4,:9:10-bis(dicarboximide) (PDI) is linked to beta-apocarotene (Car) using a biphenyl spacer. The dyad is monomeric in toluene and forms a solution aggregate in methylcyclohexane (MCH). Using femtosecond transient absorption (fsTA) spectroscopy, the monomeric dyad and its aggregates were studied both in solution and in thin films. In toluene, photoexcitation at 530 nm preferentially excites PDI, and the dyad undergoes charge separation in tau = 1.7 ps and recombination in tau = 1.6 ns. In MCH and in thin solid films, 530 nm excitation of the PDI-Car aggregate also results in charge transfer that competes with energy transfer from (1)*PDI to Car and with an additional process, rapid Car triplet formation in <50 ps. Car triplet formation is only observed in the aggregated PDI-Car dyad and is attributed to singlet exciton fission (SF) within the aggregated PDI, followed by rapid triplet energy transfer from (3)*PDI to the carotenoid. SF from beta-apocarotene aggregation is ruled out by direct excitation of Car films at 414 nm, where no triplet formation is observed. Time-resolved electron paramagnetic resonance measurements on aggregated PDI-Car show the formation of (3)*Car with a spin-polarization pattern that rules out radical-pair intersystem crossing as the mechanism of triplet formation as well.
机译：合成了一个共价二元体，其中使用联苯间隔基将per-3,4，：9：10-双（二甲叉酰亚胺）（PDI）连接到β-环戊烯（Car）。二元体在甲苯中为单体，并在甲基环己烷（MCH）中形成溶液聚集体。使用飞秒瞬态吸收（fsTA）光谱，研究了溶液和薄膜中的单体二分体及其聚集体。在甲苯中，在530 nm处的光激发会优先激发PDI，并且二分体在tau = 1.7 ps时经历电荷分离，在tau = 1.6 ns时发生重组。在MCH和固态薄膜中，PDI-Car聚集体的530 nm激发还导致电荷转移，该电荷转移与（1）* PDI到Car的能量转移竞争，并且需要额外的过程，在<50 ps内快速形成Car三重态。仅在聚集的PDI-Car dyad中观察到汽车三重态的形成，这归因于聚集的PDI中的单重态激子裂变（SF），随后是三重态能量从（3）* PDI迅速转移至类胡萝卜素。通过在414 nm处直接激发Car膜，排除了β-apocar​​otene聚集产生的SF，其中未观察到三重峰的形成。在聚集的PDI-Car上进行时间分辨的电子顺磁共振测量表明，（3）* Car的形成具有自旋极化模式，该模式也排除了自由基对之间的系统交叉也是三重态形成的机制。

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