Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor
Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor
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选择一边：结合电子供体的不对称电子接受环烷中不寻常的超快电荷转移途径
DOI：
10.1039/c8sc05514a
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发表时间：
2019
期刊：
影响因子：
8.4
通讯作者：
Wasielewski, Michael R.
中科院分区：
文献类型：
--
作者：
Zhou, Jiawang;Wu, Yilei;Roy, Indranil;Samanta, Avik;Stoddart, J. Fraser;Young, Ryan M.;Wasielewski, Michael R.
构建用于太阳能转换和量子信息科学的功能分子系统需要对供体-桥-受体（D-B-A）系统中的电子转移以及受体-供体-受体（a - d - a）和受体-供体-受体‘ （a - d - a ’）系统中的竞争反应途径有基本的了解。在这里，我们提出了一种超分子复合物，包括具有苯基延伸紫素（ExV2+）和双吡啶基噻唑噻唑（TTz2+）电子受体的四聚环烷，通过两个对二甲苯连接剂（TTzExVBox4+）双连接，它很容易在其腔中（Per∧TTzExVBox4+）包含苝（Per）客体，以建立a - d - a’系统，其中ExV2+和TTz2+单元作为具有不同还原电位的竞争电子受体。Per客体的光激发在< 1ps内产生TTz+˙-Per +˙-ExV2 +和TTz2+ -Per +˙-ExV +˙，而TTz2+ -Per +˙-ExV +˙的反向电子传递是通过不寻常的顺序TTz2+ -Per +˙-ExV +→TTz+˙-Per +˙-ExV2 +→TTz2+ -Per -ExV2 +进行的。此外，TTz2+的选择性化学还原得到Per´TTzExVBox3+˙，将复合物转变为D-B-A系统，其中TTz+˙光激发导致反应顺序为2*TTz+˙-Per-ExV2 +→TTz2+ -Per-ExV +˙→TTz+˙-Per-ExV2 +。无论桥分子是Per+˙还是Per， TTz2+ -Per +˙-ExV +˙→TTz+˙-Per +˙-ExV2 +和TTz2+ -Per -ExV +˙→TTz+˙-Per -ExV2 +两个反应都以（16±1 ps）−1的速率常数发生。这些结果是用超交换机制来解释的，在这种机制中，苝的离子态在每种情况下都充当虚态，并为研究D-B-A体系中桥能量学的影响提供了一个新的超分子平台。
Constructing functional molecular systems for solar energy conversion and quantum information science requires a fundamental understanding of electron transfer in donor–bridge–acceptor (D–B–A) systems as well as competitive reaction pathways in acceptor–donor–acceptor (A–D–A) and acceptor–donor–acceptor′ (A–D–A′) systems. Herein we present a supramolecular complex comprising a tetracationic cyclophane having both phenyl-extended viologen (ExV2+) and dipyridylthiazolothiazole (TTz2+) electron acceptors doubly-linked by means of two p-xylylene linkers (TTzExVBox4+), which readily incorporates a perylene (Per) guest in its cavity (Per ⊂ TTzExVBox4+) to establish an A–D–A′ system, in which the ExV2+ and TTz2+ units serve as competing electron acceptors with different reduction potentials. Photoexcitation of the Per guest yields both TTz+˙–Per+˙–ExV2+ and TTz2+–Per+˙–ExV+˙ in <1 ps, while back electron transfer in TTz2+–Per+˙–ExV+˙ proceeds via the unusual sequence TTz2+–Per+˙–ExV+˙ → TTz+˙–Per+˙–ExV2+ → TTz2+–Per–ExV2+. In addition, selective chemical reduction of TTz2+ gives Per ⊂ TTzExVBox3+˙, turning the complex into a D–B–A system in which photoexcitation of TTz+˙ results in the reaction sequence 2*TTz+˙–Per–ExV2+ → TTz2+–Per–ExV+˙ → TTz+˙–Per–ExV2+. Both reactions TTz2+–Per+˙–ExV+˙ → TTz+˙–Per+˙–ExV2+ and TTz2+–Per–ExV+˙ → TTz+˙–Per–ExV2+ occur with a (16 ± 1 ps)−1 rate constant irrespective of whether the bridge molecule is Per+˙ or Per. These results are explained using the superexchange mechanism in which the ionic states of the perylene guest serve as virtual states in each case and demonstrate a novel supramolecular platform for studying the effects of bridge energetics within D–B–A systems.