Fully conjugated macrocycles composed of thiophenes, acetylenes, and ethylenes
Fully conjugated macrocycles composed of thiophenes, acetylenes, and ethylenes
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DOI：
10.1351/pac-con-09-11-01
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发表时间：
2010-03
影响因子：
1.8
通讯作者：
M. Iyoda
中科院分区：
文献类型：
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作者：
M. Iyoda
以改进的McMurry偶联反应为关键步骤，合成了24 ~ 180π电子体系的全共轭π-扩展大环寡硫吩。以噻吩和乙炔为原料，采用溴化-脱氢溴化和双消除法制备了环[n]（2,5-噻吩-乙炔）。x射线分析显示，具有24π、60π和72π体系的大环寡硫吩具有独特的分子和填充结构，反映了具有中到大内腔的平面环状框架。所有巨环都表现出多步可逆氧化还原行为，具有相当低的首次氧化电位，反映了它们的循环共轭性。碘掺杂的大环由于其π-给体性质和π -π堆积能力形成半导体。有趣的是，90π、108π和120π体系在固态下自聚集形成红色纳米纤维或花瓣结构，而150π到180π体系形成红色纳米颗粒。通过扫描电子显微镜（SEM）和原子力显微镜（AFM）分析，确定了纤维聚集体和颗粒的结构。此外，对72π、108π、144π和180π体系的双光子特性研究表明，π共轭系数的增加导致双光子吸收截面的增加，在可见光谱区域的幅度高达10万GM。
Fully conjugated π-expanded macrocyclic oligothiophenes with 24π to 180π electron systems have been synthesized using a modified McMurry coupling reaction as the key step. For the synthesis of cyclo[n](2,5-thienylene-ethynylene)s composed of thiophenes and acetylenes, bromination-dehydrobromination and double elimination procedure were employed. X-ray analyses of macrocyclic oligothiophenes with 24π, 60π, and 72π systems revealed unique molecular and packing structures, reflecting planar cyclic frameworks with medium to large inner cavities. All the giant macrocycles exhibit multistep reversible redox behavior with a fairly low first-oxidation potentials, reflecting their cyclic conjugation. The doping of macrocycles with iodine forms semiconductors owing to their π-donor properties and π–π stacking ability. Interestingly, 90π, 108π, and 120π systems self-aggregate in the solid state to form red nanofibers or petal structure, whereas 150π to 180π systems form red nanoparticles. The structures of fibrous aggregates and particles have been established by scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses. Furthermore, two-photon properties of 72π, 108π, 144π, and 180π systems show that the increasing π-conjugation leads to an increase in the two-photon absorption cross-section with magnitudes as high as 100 000 GM in the visible spectral region.