Solvent-Templated Folding of Perylene Bisimide Macrocycles into Coiled Double-String Ropes with Solvent-Sensitive Optical Signatures.
Solvent-Templated Folding of Perylene Bisimide Macrocycles into Coiled Double-String Ropes with Solvent-Sensitive Optical Signatures.
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DOI：
10.1021/jacs.6b11973
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发表时间：
2017-01
影响因子：
15
通讯作者：
P. Spenst;Ryan M. Young;B. Phelan;M. Keller;J. Dostál;T. Brixner;M. Wasielewski;F. Würthner
中科院分区：
文献类型：
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作者：
P. Spenst;Ryan M. Young;B. Phelan;M. Keller;J. Dostál;T. Brixner;M. Wasielewski;F. Würthner
采用一锅法合成了一系列含2 ~ 9个苝酰亚胺（PBI）生色团的半刚性PBI大环化合物，并通过荧光光谱、稳态吸收光谱、瞬态吸收光谱和飞秒受激拉曼光谱对其物理性质进行了表征.这些大环化合物表现出溶剂依赖的构象平衡和激发态性质。在二氯甲烷中，大环占主导地位的宽拉伸构象和光激发后表现出破坏电荷分离，然后由电荷重组到三重态，光敏单线态氧的形成。与此相反，在芳香族溶剂中折叠的大环与一个独特的奇偶效应的PBI发色团单位的数量观察到在稳态和时间分辨吸收和荧光光谱，以及飞秒受激拉曼光谱。这些独特的光学性质是由于偶数元大环在芳香族溶剂中折叠成激子-振动耦合的二聚体对。在各种芳香族溶剂中的研究表明，这些溶剂嵌入PBI二聚体对之间，并相应地模板的偶数元PBI大环折叠成绳状折叠构象，从而引起溶剂特异性激子振动耦合的紫外-可见吸收光谱。由于溶剂分子嵌入盘绕的双绳结构中，对于两个最低能量的激子振动带观察到高度溶剂比强度比，从而能够简单地基于测量的吸收光谱来分配相应的溶剂四聚体大环。
A series of semirigid perylene bisimide (PBI) macrocycles with varied ring size containing two to nine PBI chromophores were synthesized in a one-pot reaction and their photophysical properties characterized by fluorescence, steady-state, and transient absorption spectroscopy as well as femtosecond stimulated Raman spectroscopy. These macrocycles show solvent-dependent conformational equilibria and excited-state properties. In dichloromethane, the macrocycles prevail in wide-stretched conformations and upon photoexcitation exhibit symmetry-breaking charge separation followed by charge recombination to triplet states, which photosensitize singlet oxygen formation. In contrast, in aromatic solvents folding of the macrocycles with a distinct odd-even effect regarding the number of PBI chromophore units was observed in steady-state and time-resolved absorption and fluorescence spectroscopy as well as femtosecond stimulated Raman spectroscopy. These distinctive optical properties are attributable to the folding of the even-membered macrocycles into exciton-vibrational coupled dimer pairs in aromatic solvents. Studies in a variety of aromatic solvents indicate that these solvents embed between PBI dimer pairs and accordingly template the folding of even-membered PBI macrocycles into ropelike folded conformations that give rise to solvent-specific exciton-vibrational couplings in UV-vis absorption spectra. As a consequence of the embedding of solvent molecules in the coiled double-string rope architecture, highly solvent specific intensity ratios are observed for the two lowest-energy exciton-vibrational bands, enabling assignment of the respective solvent simply based on the absorption spectra measured for the tetramer macrocycle.