Papadopoulos Ilias, Gutiérrez-Moreno David, Bo Yifan, Casillas Rubén, Greißel Phillip M, Clark Timothy, Fernández-Lázaro Fernando, Guldi Dirk M
Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-University Erlangen-Nuremberg, Egerlandstraße 3, 91058 Erlangen, Germany.
Área de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Avda. de la Universidad s/n, 03203 Elche, Spain.
Nanoscale. 2022 Mar 31;14(13):5194-5203. doi: 10.1039/d1nr08523a.
We used a systematic approach to shed light on the inherent differences in perylenes, namely monoimides diimides, including coplanarity and dipole moment, and their impact on singlet fission (SF) by designing, synthesizing, and probing a full fledged series of phenylene- and naphthalene-linked dimers. Next to changing the functionality of the perylene core, we probed the effect of the spacers and their varying degrees of rotational freedom, molecular electrostatic potentials, and intramolecular interactions on the SF-mechanism and -efficiencies. An arsenal of spectroscopic techniques revealed that for perylene-monoimides, a strong charge-transfer mixing with the singlet and triplet excited states restricts SF and yields low triplet quantum yields. This is accompanied by an up-conversion channel that includes geminate triplet-triplet recombination. Using perylene-diimides alters the SF-mechanism by populating a charge-separated-state intermediate, which either favors or shuts-down SF. Napthylene-spacers bring about higher triplet quantum yields and overall better SF-performance for all perylene-monoimides and perylene-diimides. The key to better SF-performance is rotational freedom because it facilitates the overall excited-state polarization and amplifies intramolecular interactions between chromophores.
我们采用了一种系统的方法来揭示苝类化合物（即单酰亚胺和二酰亚胺）的内在差异，包括共面性和偶极矩，以及它们通过设计、合成和探测一系列完整的亚苯基和萘基连接的二聚体对单线态裂变（SF）的影响。除了改变苝核的功能外，我们还探究了间隔基及其不同程度的旋转自由度、分子静电势和分子内相互作用对SF机制和效率的影响。一系列光谱技术表明，对于苝单酰亚胺，与单重态和三重态激发态的强电荷转移混合限制了SF并产生低三重态量子产率。这伴随着一个包括双生三重态-三重态复合的上转换通道。使用苝二酰亚胺通过填充电荷分离态中间体来改变SF机制，该中间体要么促进要么关闭SF。萘间隔基为所有苝单酰亚胺和苝二酰亚胺带来更高的三重态量子产率和总体更好的SF性能。更好的SF性能的关键是旋转自由度，因为它促进了整体激发态极化并增强了发色团之间的分子内相互作用。
