Fluorosumanenes as building blocks for organic crystalline dielectrics
Fluorosumanenes as building blocks for organic crystalline dielectrics
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DOI：
10.1515/pac-2023-0211
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发表时间：
2023-04
影响因子：
1.8
通讯作者：
Y. Yakiyama;Minghong Li;H. Sakurai
中科院分区：
文献类型：
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作者：
Y. Yakiyama;Minghong Li;H. Sakurai
摘要 有机晶体介电材料是材料化学领域颇具吸引力的研究对象。在他们的设计策略中，需要外部介电场引起的分子运动来最大化材料中的极化效应，以实现大介电常数。特别是，已知弯曲π芳香族化合物（例如C60）及其超分子配合物的分子运动在固态下表现出特征平滑性。在此背景下，我们重点研究了具有代表性的巴基碗之一苏曼烯（Sum）在其曲线与曲线接触的柱状结构中的面内运动，作为介电响应出现的新运动平台。新设计和合成的氟化苏马烯，1,1-二氟苏马烯（F2-Sum），在原始苏马烯的同一苄基碳上拥有两个氟原子，沿面内方向显示出较大的偶极矩。热分析、变温 X 射线衍射和红外测量表明 F2-Sum 存在面内运动，尽管不涉及明显的相变。 F2-Sum 的这种热特性在单晶态下实现了具有德拜型介电弛豫的各向异性介电响应。进一步尝试以不同的混合比例形成Sum和F2-Sum的固溶体，实现了介电性能的调节。
Abstract Organic crystalline dielectric materials are attractive target in the field of materials chemistry. In their designing strategy, the molecular motion induced by the external dielectric field is required to maximize the polarization effect in the materials to realize a large dielectric constant. Especially, the molecular motion of curved-π aromatics such as C60 and their supramolecular complexes are the known to show characteristic smoothness in the solid state. In this context, we focused on the in-plane motion of the one of the representative buckybowl, sumanene (Sum) in its curve-to-curve-contacted columnar structure as the new platform of the motion for the emergence of dielectric response. The newly designed and synthesized fluorinated sumanene, 1,1-difluorosumanene (F2-Sum), which possesses two fluorine atoms on the same benzylic carbon of pristine sumanene showed a large dipole moment along the in-plane direction. Thermal analyses, variable temperature X-ray diffraction and IR measurements indicated the presence of in-plane motion of F2-Sum although no clear phase transition was involved. This thermal property of F2-Sum realized an anisotropic dielectric response with a Debye-type dielectric relaxation in the single crystalline state. Further trials to form the solid solution of Sum and F2-Sum in various mixing ratio realized the tuning of the dielectric property.