Extended Quinolizinium-Fused Corannulene Derivatives: Synthesis and Properties

Reported here is
the design and synthesis of a novel class of extended
quinolizinium-fused corannulene derivatives with curved geometry.
These intriguing molecules were synthesized through a rationally designed
synthetic strategy, utilizing double Skraup–Doebner–Von
Miller quinoline synthesis and a rhodium-catalyzed C–H activation/annulation
(CHAA) as the key steps. Single-crystal X-ray analysis revealed a
bowl depth of 1.28–1.50 Å and a unique “windmill-like”
shape packing of 12a(2PF6–) due to the curvature and
incorporation of two aminium ions. All of the newly reported curved
salts exhibit green to orange fluorescence with enhanced quantum yields
(Φf = 9–13%) and improved dispersibility compared
to the pristine corannulene (Φf = 1%). The reduced
optical energy gap and lower energy frontier orbital found by doping
extended corannulene systems with nitrogen cations was investigated
by UV–vis, fluorescence, and theoretical calculations. Electrochemical
measurements reveal a greater electron-accepting behavior compared
with that of their pyridine analogues. The successful synthesis, isolation,
and evaluation of these curved salts provide a fresh perspective and
opportunity for the design of cationic nitrogen-doped curved aromatic
hydrocarbon-based materials.

本文报道了一类具有曲面几何结构的新型扩展型喹啉鎓稠合碗烯（corannulene）衍生物的设计与合成。这类引人关注的分子通过合理设计的合成策略制备得到，核心步骤包括双分子斯克劳普-多布纳-冯·米勒喹啉合成反应以及铑催化的C-H活化/环化（CHAA）反应。单晶X射线衍射分析结果显示，该类衍生物的碗状深度为1.28~1.50埃；由于其曲面结构与两个氨基正离子的引入，12a(2PF6–)呈现出独特的“风车状”堆积形貌。所有新报道的这类曲面盐类均表现出绿色至橙色的荧光，相较于原始碗烯（Φf=1%），其量子产率提升至9%~13%，且分散性得到显著改善。通过紫外-可见光谱、荧光光谱及理论计算，研究了氮正离子掺杂扩展型碗烯体系所导致的光学带隙降低与前线轨道能级下降现象。电化学测试结果表明，相较于其吡啶类似物，该类化合物展现出更强的电子接受特性。这类曲面盐类的成功合成、分离提纯与性能表征，为阳离子型氮掺杂曲面芳香烃基功能材料的设计提供了全新的思路与发展机遇。