Molecular-wire behaviour in p-phenylenevinylene oligomers
Molecular-wire behaviour in p-phenylenevinylene oligomers
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DOI：
10.1038/23912
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发表时间：
1998-11-05
期刊：
影响因子：
64.8
通讯作者：
Wasielewski, MR
中科院分区：
文献类型：
--
作者：
Davis, WB;Svec, WA;Wasielewski, MR
电子通过分子“桥”从电子供体分子转移到电子受体分子是许多生物和化学系统的一个特征。众所周知，供体-桥-受体 (DBA) 系统中桥组件的电子结构在决定电子转移的难易程度方面发挥着关键作用(1,2)。在大多数 DBA 系统中，电子转移发生的速率与供体-受体距离（有效地与桥分子的长度）呈指数关系。但理论预测存在距离依赖性可能非常弱的状态，桥分子本质上充当不相干的分子线(3-6)。在这里，我们展示了如何通过分子设计来实现这些机制。我们合成了一系列结构明确的 DBA 分子，其中并四苯作为供体，均苯四酰亚胺作为受体，通过不同长度的对亚苯基亚乙烯基低聚物连接。该系列中的光诱导电子转移对于高达 40 埃的供体-受体分离表现出非常弱的距离依赖性，速率常数为 10(11) s(-1) 量级。这些发现证明了供体和桥元件之间能量匹配对于实现分子线行为的重要性。
Electron transfer from electron-donor to electron-acceptor molecules via a molecular 'bridge' is a feature of many biological and chemical systems. The electronic structure of the bridge component in donor-bridge-acceptor (DBA) systems is known to play a critical role in determining the ease of electron transfer(1,2). In most DBA systems, the rate at which electron transfer occurs scales exponentially with the donor-acceptor distance-effectively the length of the bridge molecule. But theory predicts that regimes exist wherein the distance dependence may be very weak, the bridge molecules essentially acting as incoherent molecular wires(3-6). Here we show how these regimes can be accessed by molecular design. We have synthesized a series of structurally well-defined DBA molecules that incorporate tetracene as the donor and pyromellitimide as the acceptor, linked by p-phenylenevinylene oligomers of various lengths. Photoinduced electron transfer in this series exhibits very weak distance dependence for donor-acceptor separations as large as 40 Angstrom, with rate constants of the order of 10(11) s(-1). These findings demonstrate the importance of energy matching between the donor and bridge components for achieving molecular-wire behaviour.