How Do Amides Affect the Electronic Properties of Pyrene?
How Do Amides Affect the Electronic Properties of Pyrene?
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DOI：
10.1021/acsomega.8b01581
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发表时间：
2018-10-01
期刊：
影响因子：
4.1
通讯作者：
Vullev, Valentine, I
中科院分区：
文献类型：
--
作者：
Espinoza, Eli M.;Clark, John A.;Vullev, Valentine, I
酰胺连接体是生物分子的复杂组成部分，其电子性质提供了大量未探索的可能性。在这里，我们演示了如何将酰胺连接到芘发色团的不同模式影响发色团的电化学和光学性质。因此，尽管它们引起最小的光谱位移，酰胺取代基可以改善芘的电子接受或电子供给能力。具体而言，酰胺取向的反转使还原电位移动200 mV。这些趋势表明，虽然酰胺影响到类似程度的芘的基态和单重激发态的能量，其自由基离子的双重态的影响是明显不同的。这种行为反映了酰胺取代基的共振效应的异常强的取向依赖性，这应该扩展到酰胺取代基上的其他类型的发色团一般。这些结果代表了一个例子，其中Hammett σ常数未能预测取代基对电化学性质的影响。另一方面，Swain-Lupton参数被发现是在良好的协议与观察到的趋势。芘衍生物及其组分的前沿轨道的检查揭示了观察到的酰胺对这种多环芳烃的电子性质的影响的根本原因，并指出了电子和能量转换系统的关键分子设计策略。
The electronic properties of amide linkers, which are intricate components of biomolecules, offer a wealth of unexplored possibilities. Herein, we demonstrate how the different modes of attaching an amide to a pyrene chromophore affect the electrochemical and optical properties of the chromophore. Thus, although they cause minimal spectral shifts, amide substituents can improve either the electron-accepting or electron-donating capabilities of pyrene. Specifically, inversion of the amide orientation shifts the reduction potentials by 200 mV. These trends indicate that, although amides affect to a similar extent the energies of the ground and singlet excited states of pyrene, the effects on the doublet states of its radical ions are distinctly different. This behavior reflects the unusually strong orientation dependence of the resonance effects of amide substituents, which should extend to amide substituents on other types of chromophores in general. These results represent an example where the Hammett sigma constants fail to predict substituent effects on electrochemical properties. On the other hand, Swain-Lupton parameters are found to be in good agreement with the observed trends. Examination of the frontier orbitals of the pyrene derivatives and their components reveals the underlying reason for the observed amide effects on the electronic properties of this polycyclic aromatic hydrocarbon and points to key molecular-design strategies for electronic and energy-conversion systems.