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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Distance Dependence of Photoinduced Electron Transfer in Metalloporphyrin Dimers
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Distance Dependence of Photoinduced Electron Transfer in Metalloporphyrin Dimers

机译：金属卟啉二聚体中光诱导电子转移的距离依赖性

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摘要

To study the dynamics and mechanism of intramolecular photoinduced electron transfer (PET) reactions, a series of (Zn~(II)-Fe~(III)) meso-tetraarylmetalloporphyrin dimers were synthesized and the kinetics of their PET reactivity was measured. Molecular building blocks were prepared by selective nucleophilic aromatic substitution of a para fluorine on tetraarylporphyrins containing a single pentafluorophenyl group. This synthetic approach allows a wide variety of systematic modifications such as type and length of spacer, metal center, and redox-potential difference between donor and acceptor. The edge-to-edge distance between the two porphyrins varies from 14.4 to 27.3 A. Into a symmetric dimer, with two identical porphyrins covalently linked by a rigid partly saturated bridge, one zinc(II) and one iron(III) can be inserted. From measurements of fluorescence lifetimes the rate constants for PET from the electronically excited state of the zinc porphyrin to the bis(imidazole)iron porphyrin cation were evaluated. The electron-transfer rate decreases by a factor of only 165 when the distance increases by 13 A. This small decrease is indicative of a surprisingly weak attenuation of the electronic coupling with distance.
机译：为了研究分子内光致电子转移（PET）反应的动力学和机理，合成了一系列（Zn〜（II）-Fe〜（III））内消旋四芳基金属卟啉二聚体，并测量了它们的PET反应动力学。通过在包含单个五氟苯基的四芳基卟啉上对氟的选择性亲核芳族取代制备分子构件。这种合成方法可进行多种系统修饰，例如间隔基的类型和长度，金属中心以及施主与受主之间的氧化还原电位差。两种卟啉之间的边到边距离在14.4至27.3 A之间变化。通过对称的二聚体，通过刚性的部分饱和桥共价连接两个相同的卟啉，可以插入一个锌（II）和一个铁（III）。 。通过测量荧光寿命，评估了从卟啉锌的电子激发态到双（咪唑）铁卟啉阳离子的PET的速率常数。当距离增加13 A时，电子传输速率仅减小165倍。这种小的减小表明电子耦合随距离的衰减非常弱。

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