High Fluorescence Efficiencies and Large Stokes Shifts of Folded Fluorophores Consisting of a Pair of Alkenyl-Tethered, π‑Stacked Oligo‑<i>p</i>‑phenylenes

A series of pure hydrocarbon fluorophores containing a pair of π-stacked oligo-p-phenylenes have been synthesized and analyzed by NMR and X-ray crystallography. They show good fluorescence in solutions and enhanced fluorescence in the aggregated state. Large Stokes shifts (up to 214 nm) have been achieved in these folded fluorophores in virtue of intramolecular energy transfer, and balanced structural rigidity and flexibility. These folded fluorophores provide perfect models for understanding the energy and charge transfer process in π-stacked systems.本研究合成了一系列含有一对π堆积（π-stacked）低聚对亚苯基（oligo-p-phenylenes）的纯烃类荧光团（fluorophores），并通过核磁共振波谱法（NMR）与X射线晶体学（X-ray crystallography）对其进行了表征分析。该类荧光团在溶液中展现出良好的荧光性能，在聚集态下荧光强度得到进一步增强。得益于分子内能量转移以及结构刚性与柔性的平衡，这类折叠型荧光团实现了大斯托克斯位移（Stokes shift，最大可达214 nm）。上述折叠型荧光团为理解π堆积体系中的能量与电荷转移过程提供了理想模型。