苝酰肼和苝酰亚胺分子内电子转移控制的时间分辨光谱比较研究
Control of Intramolecular Electron Transfer in Perylene Dihydrazides and Perylene Diimides: A Comparative Study by Time-Resolved Spectroscopy
摘要：
分子给体-受体染料体系中的电子转移（ET）是有机半导体中电荷输运的关键。经典的，ET率应减少与增加供体-受体的距离，而微观机制是更复杂的，并显示出复杂的依赖于激发条件。在本文中，我们介绍了高溶解性的N，N '-二烷基二酰肼（PDH）-二萘嵌苯染料与二烷基氨基-NR $_2$供体功能直接键合到它们的两个酰亚胺氮原子。我们比较了PDH的电子转移动力学与一组经典的N，N '-双烷基二萘嵌苯二酰亚胺（PDI）配备了一个-NR $_2$供体连接到PDI受体核心通过不同数量的亚烷基-（CH $_2$）-间隔基团，因此在明显不同的距离。我们的研究对象的特殊物理化学设计特征包括：i）胺部分作为供体基团以最小化自旋-轨道耦合; ii）仅在两个酰亚胺位置处取代以避免对HOMO和LUMO能级的重大影响以及PDI主链的扭曲; iii）通过非共辄亚烷基控制供体-受体分离以排除由于离域$π$电子系统引起的任何额外影响。所有材料都表现出非单指数的光致发光衰减动力学。的速率方程分析支持的电化学和绝对光致发光效率的测量产生的证据有效的系统间交叉没有重元素，并揭示了整个分子内界面的电荷转移效率强烈依赖于过剩的激发能。
英文摘要：
Electron transfer (ET) in molecular donor-acceptor dye systems is crucial for charge transport in organic semiconductors. Classically, ET rates should decrease with increasing donor-acceptor distance while the microscopic mechanism is more complex and shows intricate dependencies on the excitation conditions. In this paper, we introduce highly soluble N,N'-dialkyl perylene dihydrazides (PDH) - perylene dyes with a dialkylamino -NR$_2$ donor functionality directly bonded to both of their imide nitrogen atoms. We compare the PDH electron-transfer dynamics with a group of classical N,N'-bisalkylperylene diimides (PDI) equipped with a -NR$_2$ donor linked to the PDI acceptor core via a varying number of alkylene -(CH$_2$)- spacer groups, thus at distinctively different distance. Special physicochemical design features of our study objects include: i) amine moieties as donor group to minimize spin-orbit coupling; ii) substitution solely at both imide positions to avoid major impact on HOMO and LUMO levels and distortions of the PDI backbone; iii) control of donor-acceptor separation by non-conjugated alkylene groups to exclude any additional effects due to delocalized $π$ electron systems. All materials show non-single-exponential photoluminescence decay dynamics. A rate equation analysis supported by electrochemical and absolute photoluminescence efficiency measurements yields evidence for efficient intersystem-crossing without heavy elements and reveals that the charge-transfer efficiency across the intramolecular interface strongly depends on the surplus excitation energy.
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