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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Contrasting Photoinduced Electron-Transfer Properties of Two Closely Related, Rigidly Linked Porphyrin-Quinone Dyads
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Contrasting Photoinduced Electron-Transfer Properties of Two Closely Related, Rigidly Linked Porphyrin-Quinone Dyads

机译：两种紧密相关，刚性连接的卟啉-醌二元系的对比光诱导电子转移性质

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摘要

Two closely related,rigidly linked porphyrin-naphtoquinone dyads have been prepared and studied using time-resolved fluorescence and absorption methods. Dyad 1, whose quinone carbonyl groups are relatively close to the porphyrin macrocycle, exhibits photoinduced electron-transfer rate constants that are virtually independent of solvent dielectric constant and temperature within the range 77-295 K. Dyad 2, which has a similar donor-acceptor linkage but whose quinone carbonyl groups are ～2 A farther from the porphyrin, features photoinduced electron-transfer rate constants that decrease with decreasing solvent dielectric constant. Electron transfer in this molecule ceases at low temperatures. Photoinduced electron transfer in dyad 2 exhibits the usual dependence on free energy change and solvent reorganization observed in many similar porphyrin-quinone systems. The behavior of 1 may be attributed at least in part to the smaller separation of the porphyrin radical cation and the quinone radical anion, which leads to nearly barrierless electron transfer and makes transfer less susceptible to effects due to changes in solvent dielectric properties and temperature. Charge recombination rates in the dyads are substantially slower than charge separation rates, unlike those of many porphyrin-quinone systems. This suggests that these molecules might be useful as components of more complex molecular devices.
机译：使用时间分辨荧光和吸收方法，制备并研究了两个紧密相关的，刚性连接的卟啉-萘醌二联体。醌羰基相对靠近卟啉大环的Dyad 1表现出光诱导的电子传输速率常数，该常数与溶剂介电常数和温度在77-295 K范围内基本无关。Dyad 2具有相似的供体受体键合，但醌羰基距离卟啉约2 A的特征是光诱导的电子传输速率常数随溶剂介电常数的降低而降低。该分子中的电子转移在低温下停止。在二元体2中的光诱导电子转移表现出对自由能变化和在许多类似的卟啉-醌系统中观察到的溶剂重组的通常依赖性。 1的行为至少可以部分归因于卟啉自由基阳离子和醌自由基阴离子的较小分离，这导致几乎无障碍的电子转移，并使转移不易受到溶剂介电性质和温度变化的影响。与许多卟啉-醌系统不同，二元组中的电荷重组速率比电荷分离速率要慢得多。这表明这些分子可用作更复杂的分子装置的组成部分。

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